models.py

import datetime
import itertools
import logging
import re
from collections import Counter, defaultdict
from urllib.parse import urljoin
from uuid import uuid4

import pytz
import requests
import waffle  # lint-amnesty, pylint: disable=invalid-django-waffle-import
from config_models.models import ConfigurationModel
from django.conf import settings
from django.contrib.auth import get_user_model
from django.core.exceptions import ObjectDoesNotExist, ValidationError
from django.core.validators import FileExtensionValidator, MaxValueValidator, MinValueValidator, RegexValidator
from django.db import IntegrityError, models, transaction
from django.db.models import F, Q, UniqueConstraint
from django.db.models.query import Prefetch
from django.utils.functional import cached_property
from django.utils.translation import gettext_lazy as _
from django_celery_results.models import TaskResult
from django_countries import countries as COUNTRIES
from django_elasticsearch_dsl.registries import registry
from django_extensions.db.fields import AutoSlugField
from django_extensions.db.models import TimeStampedModel
from edx_django_utils.cache import RequestCache, get_cache_key
from elasticsearch.exceptions import RequestError
from elasticsearch_dsl.query import Q as ESDSLQ
from localflavor.us.us_states import CONTIGUOUS_STATES
from model_utils import FieldTracker
from multi_email_field.fields import MultiEmailField
from multiselectfield import MultiSelectField
from opaque_keys.edx.keys import CourseKey
from parler.models import TranslatableModel, TranslatedFieldsModel
from simple_history.models import HistoricalRecords
from slugify import slugify as uslugify
from solo.models import SingletonModel
from sortedm2m.fields import SortedManyToManyField
from stdimage.models import StdImageField
from taggit_autosuggest.managers import TaggableManager
from taxonomy.signals.signals import UPDATE_PROGRAM_SKILLS

from course_discovery.apps.core.models import Currency, Partner, User
from course_discovery.apps.course_metadata import emails
from course_discovery.apps.course_metadata.choices import (
    BulkOperationStatus, BulkOperationType, CertificateType, CourseLength, CourseRunPacing, CourseRunRestrictionType,
    CourseRunStatus, ExternalCourseMarketingType, ExternalProductStatus, PathwayStatus, PayeeType, ProgramStatus,
    ReportingType
)
from course_discovery.apps.course_metadata.constants import SUBDIRECTORY_SLUG_FORMAT_REGEX, PathwayType
from course_discovery.apps.course_metadata.fields import AutoSlugWithSlashesField, HtmlField, NullHtmlField
from course_discovery.apps.course_metadata.managers import DraftManager
from course_discovery.apps.course_metadata.people import MarketingSitePeople
from course_discovery.apps.course_metadata.publishers import (
    CourseRunMarketingSitePublisher, ProgramMarketingSitePublisher
)
from course_discovery.apps.course_metadata.query import CourseQuerySet, CourseRunQuerySet, ProgramQuerySet
from course_discovery.apps.course_metadata.toggles import (
    IS_COURSE_RUN_FOR_DUMMY_SKU_GENERATION, IS_SUBDIRECTORY_SLUG_FORMAT_ENABLED,
    IS_SUBDIRECTORY_SLUG_FORMAT_FOR_BOOTCAMP_ENABLED, IS_SUBDIRECTORY_SLUG_FORMAT_FOR_EXEC_ED_ENABLED
)
from course_discovery.apps.course_metadata.utils import (
    UploadToFieldNamePath, bulk_operation_upload_to_path, clean_query, clear_slug_request_cache_for_course,
    custom_render_variations, generate_sku, get_course_run_statuses, get_slug_for_course, is_ocm_course,
    push_to_ecommerce_for_course_run, push_tracks_to_lms_for_course_run, set_official_state, subtract_deadline_delta,
    validate_ai_languages
)
from course_discovery.apps.ietf_language_tags.models import LanguageTag
from course_discovery.apps.ietf_language_tags.utils import serialize_language
from course_discovery.apps.publisher.utils import VALID_CHARS_IN_COURSE_NUM_AND_ORG_KEY

logger = logging.getLogger(__name__)


class ManageHistoryMixin(models.Model):
    """
    Manages the history creation of the models based on the actual changes rather than saving without changes.
    """

    def has_model_changed(self, external_keys=None, excluded_fields=None):
        """
        Returns True if the model has changed, False otherwise.
        Args:
        external_keys (list): Names of the Foreign Keys to check
        excluded_fields (list): Names of fields to exclude

        Returns:
        Boolean indicating if model or associated keys have changed.
        """
        external_keys = external_keys if external_keys else []
        excluded_fields = excluded_fields if excluded_fields else []
        changed = self.field_tracker.changed()
        for field in excluded_fields:
            changed.pop(field, None)

        return len(changed) or any(
            item.has_changed for item in external_keys if hasattr(item, 'has_changed')
        )

    def save(self, *args, **kwargs):
        """
        Sets the parameter 'skip_history_on_save' if the object is not changed. This is only applicable for already
        created object. Any new object will always have a history entry. This is added to avoid the changes
        introduced in django-simple-history in https://github.com/jazzband/django-simple-history/pull/1262.
        """
        if not self.has_changed and self.pk:
            setattr(self, 'skip_history_when_saving', True)  # pylint: disable=literal-used-as-attribute

        super().save(*args, **kwargs)

        if hasattr(self, 'skip_history_when_saving'):
            delattr(self, 'skip_history_when_saving')  # pylint: disable=literal-used-as-attribute

    class Meta:
        abstract = True


class DraftModelMixin(models.Model):
    """
    Defines a draft boolean field and an object manager to make supporting drafts more transparent.

    This defines two managers. The 'everything' manager will return all rows. The 'objects' manager will exclude
    draft versions by default unless you also define the 'objects' manager.

    Remember to add 'draft' to your unique_together clauses.

    Django doesn't allow real model mixins, but since everything has to inherit from models.Model, we shouldn't be
    stepping on anyone's toes. This is the best advice I could find (at time of writing for Django 1.11).

    .. no_pii:
    """
    draft = models.BooleanField(default=False, help_text='Is this a draft version?')
    draft_version = models.OneToOneField('self', models.SET_NULL, null=True, blank=True,
                                         related_name='_official_version', limit_choices_to={'draft': True})

    everything = models.Manager()
    objects = DraftManager()

    @property
    def official_version(self):
        """
        Related name fields will return an exception when there is no connection.  In that case we want to return None
        Returns:
            None: if there is no Official Version
        """
        try:
            return self._official_version
        except ObjectDoesNotExist:
            return None

    class Meta:
        abstract = True


class CachedMixin:
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._cache = dict(self.__dict__)

    def refresh_from_db(self, using=None, fields=None, **kwargs):
        super().refresh_from_db(using, fields, **kwargs)
        self.__dict__.pop('_cache', None)
        self._cache = dict(self.__dict__)

    def save(self, **kwargs):
        super().save(**kwargs)
        self.__dict__.pop('_cache', None)
        self._cache = dict(self.__dict__)

    def did_change(self, field):
        return field in self.__dict__ and (field not in self._cache or getattr(self, field) != self._cache[field])


class AbstractNamedModel(TimeStampedModel):
    """ Abstract base class for models with only a name field. """
    name = models.CharField(max_length=255, unique=True)

    def __str__(self):
        return self.name

    class Meta:
        abstract = True


class AbstractValueModel(TimeStampedModel):
    """ Abstract base class for models with only a value field. """
    value = models.CharField(max_length=255)

    def __str__(self):
        return self.value

    class Meta:
        abstract = True


class AbstractMediaModel(TimeStampedModel):
    """ Abstract base class for media-related (e.g. image, video) models. """
    src = models.URLField(max_length=255, unique=True)
    description = models.CharField(max_length=255, null=True, blank=True)

    def __str__(self):
        return self.src

    class Meta:
        abstract = True


class AbstractTitleDescriptionModel(TimeStampedModel):
    """ Abstract base class for models with a title and description pair. """
    title = models.CharField(max_length=255, blank=True, null=True)
    description = models.TextField(blank=True, null=True)

    def __str__(self):
        if self.title:
            return self.title
        return self.description

    class Meta:
        abstract = True


class AbstractHeadingBlurbModel(TimeStampedModel):
    """ Abstract base class for models with a heading and html blurb pair. """
    heading = models.CharField(max_length=255, blank=True, null=False)
    blurb = NullHtmlField()

    def __str__(self):
        return self.heading if self.heading else f"{self.blurb}"

    class Meta:
        abstract = True


class Organization(ManageHistoryMixin, CachedMixin, TimeStampedModel):
    """ Organization model. """
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    uuid = models.UUIDField(blank=False, null=False, default=uuid4, editable=True, verbose_name=_('UUID'))
    key = models.CharField(max_length=255, help_text=_('Please do not use any spaces or special characters other '
                                                       'than period, underscore or hyphen. This key will be used '
                                                       'in the course\'s course key.'))
    name = models.CharField(max_length=255)
    certificate_name = models.CharField(
        max_length=255, null=True, blank=True, help_text=_('If populated, this field will overwrite name in platform.')
    )
    slug = AutoSlugField(populate_from='key', editable=False, slugify_function=uslugify)
    description = models.TextField(null=True, blank=True)
    description_es = models.TextField(
        verbose_name=_('Spanish Description'),
        help_text=_('For seo, this field allows for alternate spanish description to be manually inputted'),
        blank=True,
    )
    homepage_url = models.URLField(max_length=255, null=True, blank=True)
    logo_image = models.ImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='organization/logos'),
        blank=True,
        null=True,
        validators=[FileExtensionValidator(['png'])]
    )
    certificate_logo_image = models.ImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='organization/certificate_logos'),
        blank=True,
        null=True,
        validators=[FileExtensionValidator(['png'])]
    )
    banner_image = models.ImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='organization/banner_images'),
        blank=True,
        null=True,
    )
    salesforce_id = models.CharField(max_length=255, null=True, blank=True)  # Publisher_Organization__c in Salesforce

    tags = TaggableManager(
        blank=True,
        help_text=_('Pick a tag from the suggestions. To make a new tag, add a comma after the tag name.'),
    )
    auto_generate_course_run_keys = models.BooleanField(
        default=True,
        verbose_name=_('Automatically generate course run keys'),
        help_text=_(
            "When this flag is enabled, the key of a new course run will be auto"
            " generated.  When this flag is disabled, the key can be manually set."
        )
    )
    enterprise_subscription_inclusion = models.BooleanField(
        default=False,
        help_text=_('This field signifies if any of this org\'s courses are in the enterprise subscription catalog'),
    )
    organization_hex_color = models.CharField(
        help_text=_("""The 6 character-hex-value of the orgnization theme color,
            all related course under same organization will use this color as theme color.
            (e.g. "#ff0000" which equals red) No need to provide the `#`"""),
        validators=[RegexValidator(
            regex=r'^(([0-9a-fA-F]{2}){3}|([0-9a-fA-F]){3})$',
            message='Hex color must be 3 or 6 A-F or numeric form',
            code='invalid_hex_color'
        )],
        blank=True,
        null=True,
        max_length=6,
    )
    data_modified_timestamp = models.DateTimeField(
        default=None,
        null=True,
        blank=True,
        help_text=_('The timestamp of the last time the organization data was modified.'),
    )
    # Do not record the slug field in the history table because AutoSlugField is not compatible with
    # django-simple-history.  Background: https://github.com/openedx/course-discovery/pull/332
    history = HistoricalRecords(excluded_fields=['slug'])

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed(excluded_fields=['data_modified_timestamp'])

    def clean(self):
        if not VALID_CHARS_IN_COURSE_NUM_AND_ORG_KEY.match(self.key):
            raise ValidationError(_('Please do not use any spaces or special characters other than period, '
                                    'underscore or hyphen in the key field.'))

    class Meta:
        unique_together = (
            ('partner', 'key'),
            ('partner', 'uuid'),
        )
        ordering = ['created']

    def __str__(self):
        if self.name and self.name != self.key:
            return f'{self.key}: {self.name}'
        else:
            return self.key

    @property
    def marketing_url(self):
        if self.slug and self.partner:
            return urljoin(self.partner.marketing_site_url_root, 'school/' + self.slug)

        return None

    @classmethod
    def user_organizations(cls, user):
        return cls.objects.filter(organization_extension__group__in=user.groups.all())

    def update_data_modified_timestamp(self):
        """
        Update the data_modified_timestamp field to the current time if the organization data has changed.
        """
        if not self.data_modified_timestamp or self.has_changed:
            self.data_modified_timestamp = datetime.datetime.now(pytz.UTC)

    def save(self, *args, **kwargs):
        """
        We cache the key here before saving the record so that we can hit the correct
        endpoint in lms.
        """
        key = self._cache['key']
        self.update_data_modified_timestamp()
        super().save(*args, **kwargs)
        key = key or self.key
        partner = self.partner
        data = {
            'name': self.certificate_name or self.name,
            'short_name': self.key,
            'description': self.description,
        }
        logo = self.certificate_logo_image
        if logo:
            base_url = getattr(settings, 'ORG_BASE_LOGO_URL', None)
            logo_url = f'{base_url}{logo}' if base_url else logo.url
            data['logo_url'] = logo_url
        organizations_url = f'{partner.organizations_api_url}organizations/{key}/'
        try:
            partner.oauth_api_client.put(organizations_url, json=data)
        except requests.exceptions.ConnectionError as e:
            logger.error('[%s]: Unable to push organization [%s] to lms.', e, self.uuid)
        except Exception as e:
            raise e


class OrganizationMapping(models.Model):
    """
    Model to map external/third party organization codes to organizations internal to Discovery.
    """
    organization = models.ForeignKey('Organization', models.CASCADE)
    source = models.ForeignKey('Source', models.CASCADE)
    organization_external_key = models.CharField(
        max_length=255,
        help_text=_('Corresponding organization code in an external product source')
    )

    def __str__(self):
        return f'{self.source.name} - {self.organization_external_key} -> {self.organization.name}'

    class Meta:
        """
        Meta options.
        """
        unique_together = ('source', 'organization_external_key')


class Image(AbstractMediaModel):
    """ Image model. """
    height = models.IntegerField(null=True, blank=True)
    width = models.IntegerField(null=True, blank=True)


class Video(ManageHistoryMixin, AbstractMediaModel):
    """ Video model. """
    image = models.ForeignKey(Image, models.CASCADE, null=True, blank=True)

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def __str__(self):
        return f'{self.src}: {self.description}'


class LevelType(TranslatableModel, TimeStampedModel):
    """ LevelType model. """
    # This field determines ordering by which level types are presented in the
    # Publisher tool, by virtue of the order in which the level types are
    # returned by the serializer, and in turn the OPTIONS requests against the
    # course and courserun view sets.
    name = models.CharField(max_length=255)
    sort_value = models.PositiveSmallIntegerField(default=0, db_index=True)

    def __str__(self):
        return self.name_t

    class Meta:
        ordering = ('sort_value',)


class LevelTypeTranslation(TranslatedFieldsModel):
    master = models.ForeignKey(LevelType, models.CASCADE, related_name='translations', null=True)
    name_t = models.CharField('name', max_length=255)

    class Meta:
        unique_together = (('language_code', 'name_t'), ('language_code', 'master'))
        verbose_name = _('LevelType model translations')


class SeatType(TimeStampedModel):
    name = models.CharField(max_length=64)
    slug = AutoSlugField(populate_from='name', slugify_function=uslugify, unique=True)

    def __str__(self):
        return self.name


class ProgramType(TranslatableModel, TimeStampedModel):
    XSERIES = 'xseries'
    MICROMASTERS = 'micromasters'
    PROFESSIONAL_CERTIFICATE = 'professional-certificate'
    PROFESSIONAL_PROGRAM_WL = 'professional-program-wl'
    MASTERS = 'masters'
    BACHELORS = 'bachelors'
    DOCTORATE = 'doctorate'
    LICENSE = 'license'
    CERTIFICATE = 'certificate'
    MICROBACHELORS = 'microbachelors'

    name = models.CharField(max_length=32, blank=False)
    applicable_seat_types = models.ManyToManyField(
        SeatType, help_text=_('Seat types that qualify for completion of programs of this type. Learners completing '
                              'associated courses, but enrolled in other seat types, will NOT have their completion '
                              'of the course counted toward the completion of the program.'),
    )
    logo_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='name', path='media/program_types/logo_images/'),
        blank=True,
        null=True,
        variations={
            'large': (256, 256),
            'medium': (128, 128),
            'small': (64, 64),
            'x-small': (32, 32),
        },
        help_text=_('Please provide an image file with transparent background'),
    )
    slug = AutoSlugField(populate_from='name_t', editable=True, unique=True, slugify_function=uslugify,
                         help_text=_('Leave this field blank to have the value generated automatically.'))
    uuid = models.UUIDField(default=uuid4, editable=False, verbose_name=_('UUID'), unique=True)
    coaching_supported = models.BooleanField(default=False)

    # Do not record the slug field in the history table because AutoSlugField is not compatible with
    # django-simple-history.  Background: https://github.com/openedx/course-discovery/pull/332
    history = HistoricalRecords(excluded_fields=['slug'])

    def __str__(self):
        return self.name_t

    @staticmethod
    def get_program_type_data(pub_course_run, program_model):
        slug = None
        name = None
        program_type = None

        if pub_course_run.is_micromasters:
            slug = ProgramType.MICROMASTERS
            name = pub_course_run.micromasters_name
        elif pub_course_run.is_professional_certificate:
            slug = ProgramType.PROFESSIONAL_CERTIFICATE
            name = pub_course_run.professional_certificate_name
        elif pub_course_run.is_xseries:
            slug = ProgramType.XSERIES
            name = pub_course_run.xseries_name
        if slug:
            program_type = program_model.objects.get(slug=slug)
        return program_type, name

    @classmethod
    def is_enterprise_catalog_program_type(cls, program_type):
        return program_type.slug in [
            cls.XSERIES, cls.MICROMASTERS, cls.PROFESSIONAL_CERTIFICATE, cls.PROFESSIONAL_PROGRAM_WL, cls.MICROBACHELORS
        ]


class Source(TimeStampedModel):
    """
    Source Model to find where a course or program originated from.
    """
    name = models.CharField(max_length=255, help_text=_('Name of the external source.'))
    slug = AutoSlugField(
        populate_from='name', editable=True, slugify_function=uslugify, overwrite_on_add=False,
        help_text=_('Leave this field blank to have the value generated automatically.')
    )
    description = models.CharField(max_length=255, blank=True, help_text=_('Description of the external source.'))
    ofac_restricted_program_types = SortedManyToManyField(
        ProgramType,
        blank=True,
        related_name='ofac_restricted_source',
        help_text=_('Programs of these types will be OFAC restricted')
    )

    def __str__(self):
        return self.name


class ProgramTypeTranslation(TranslatedFieldsModel):
    master = models.ForeignKey(ProgramType, models.CASCADE, related_name='translations', null=True)

    name_t = models.CharField("name", max_length=32, blank=False, null=False)

    class Meta:
        unique_together = (('language_code', 'master'), ('name_t', 'language_code'))
        verbose_name = _('ProgramType model translations')


class Mode(TimeStampedModel):
    """
    This model is similar to the LMS CourseMode model.

    It holds several fields that (one day will) control logic for handling enrollments in this mode.
    Examples of names would be "Verified", "Credit", or "Masters"

    See docs/decisions/0009-LMS-types-in-course-metadata.rst for more information.
    """
    name = models.CharField(max_length=64)
    slug = models.CharField(max_length=64, unique=True)
    is_id_verified = models.BooleanField(default=False, help_text=_('This mode requires ID verification.'))
    is_credit_eligible = models.BooleanField(
        default=False,
        help_text=_('Completion can grant credit toward an organization’s degree.'),
    )
    certificate_type = models.CharField(
        max_length=64, choices=CertificateType.choices, blank=True,
        help_text=_('Certificate type granted if this mode is eligible for a certificate, or blank if not.'),
    )
    payee = models.CharField(
        max_length=64, choices=PayeeType.choices, default='', blank=True,
        help_text=_('Who gets paid for the course? Platform is the site owner, Organization is the school.'),
    )

    history = HistoricalRecords()

    def __str__(self):
        return self.name

    @property
    def is_certificate_eligible(self):
        """
        Returns True if completion can impart any kind of certificate to the learner.
        """
        return bool(self.certificate_type)


class Track(TimeStampedModel):
    """
    This model ties a Mode (an LMS concept) with a SeatType (an E-Commerce concept)

    Basically, a track is all the metadata for a single enrollment type, with both the course logic and product sides.

    See docs/decisions/0009-LMS-types-in-course-metadata.rst for more information.
    """
    seat_type = models.ForeignKey(SeatType, models.CASCADE, null=True, blank=True)
    mode = models.ForeignKey(Mode, models.CASCADE)

    history = HistoricalRecords()

    def __str__(self):
        return self.mode.name


class CourseRunType(TimeStampedModel):
    """
    This model defines the enrollment options (Tracks) for a given course run.

    A single course might have runs with different enrollment options. Like a course that has a
    "Masters, Verified, and Audit" CourseType might contain CourseRunTypes named
    - "Masters, Verified, and Audit" (pointing to three different tracks)
    - "Verified and Audit"
    - "Audit only"
    - "Masters only"

    See docs/decisions/0009-LMS-types-in-course-metadata.rst for more information.
    """
    AUDIT = 'audit'
    VERIFIED_AUDIT = 'verified-audit'
    PROFESSIONAL = 'professional'
    CREDIT_VERIFIED_AUDIT = 'credit-verified-audit'
    HONOR = 'honor'
    VERIFIED_HONOR = 'verified-honor'
    VERIFIED_AUDIT_HONOR = 'verified-audit-honor'
    EMPTY = 'empty'
    PAID_EXECUTIVE_EDUCATION = 'paid-executive-education'
    UNPAID_EXECUTIVE_EDUCATION = 'unpaid-executive-education'
    PAID_BOOTCAMP = 'paid-bootcamp'
    UNPAID_BOOTCAMP = 'unpaid-bootcamp'

    uuid = models.UUIDField(default=uuid4, editable=False, verbose_name=_('UUID'), unique=True)
    name = models.CharField(max_length=64)
    slug = models.CharField(max_length=64, unique=True)
    tracks = models.ManyToManyField(Track)
    is_marketable = models.BooleanField(default=True)

    history = HistoricalRecords()

    def __str__(self):
        return self.name

    @property
    def empty(self):
        """ Empty types are special - they are the default type used when we don't know a real type """
        return self.slug == self.EMPTY


class CourseType(TimeStampedModel):
    """
    This model defines the permissible types of enrollments provided by a whole course.

    It holds a list of permissible entitlement options and a list of permissible CourseRunTypes.

    Examples of names would be "Masters, Verified, and Audit" or "Verified and Audit"
    """
    AUDIT = 'audit'
    VERIFIED_AUDIT = 'verified-audit'
    PROFESSIONAL = 'professional'
    CREDIT_VERIFIED_AUDIT = 'credit-verified-audit'
    EMPTY = 'empty'
    EXECUTIVE_EDUCATION_2U = 'executive-education-2u'
    BOOTCAMP_2U = 'bootcamp-2u'

    uuid = models.UUIDField(default=uuid4, editable=False, verbose_name=_('UUID'), unique=True)
    name = models.CharField(max_length=64)
    slug = models.CharField(max_length=64, unique=True)
    entitlement_types = models.ManyToManyField(SeatType, blank=True)
    course_run_types = SortedManyToManyField(
        CourseRunType, help_text=_('Sets the order for displaying Course Run Types.')
    )
    white_listed_orgs = models.ManyToManyField(Organization, blank=True, help_text=_(
        'Leave this blank to allow all orgs. Otherwise, specifies which orgs can see this course type in Publisher.'
    ))

    history = HistoricalRecords()

    def __str__(self):
        return self.name

    @property
    def empty(self):
        """ Empty types are special - they are the default type used when we don't know a real type """
        return self.slug == self.EMPTY


class Subject(TranslatableModel, TimeStampedModel):
    """ Subject model. """
    uuid = models.UUIDField(blank=False, null=False, default=uuid4, editable=False, verbose_name=_('UUID'))
    banner_image_url = models.URLField(blank=True, null=True)
    card_image_url = models.URLField(blank=True, null=True)
    slug = AutoSlugField(populate_from='name', editable=True, blank=True, slugify_function=uslugify,
                         help_text=_('Leave this field blank to have the value generated automatically.'))

    partner = models.ForeignKey(Partner, models.CASCADE)

    def __str__(self):
        return self.name

    class Meta:
        unique_together = (
            ('partner', 'slug'),
            ('partner', 'uuid'),
        )
        ordering = ['created']

    def validate_unique(self, *args, **kwargs):
        super().validate_unique(*args, **kwargs)
        qs = Subject.objects.filter(partner=self.partner_id)
        if qs.filter(translations__name=self.name).exclude(pk=self.pk).exists():
            raise ValidationError({'name': ['Subject with this Name and Partner already exists', ]})


class SubjectTranslation(TranslatedFieldsModel):
    master = models.ForeignKey(Subject, models.CASCADE, related_name='translations', null=True)

    name = models.CharField(max_length=255, blank=False, null=False)
    subtitle = models.CharField(max_length=255, blank=True, null=True)
    description = models.TextField(blank=True, null=True)

    class Meta:
        unique_together = ('language_code', 'master')
        verbose_name = _('Subject model translations')


class Topic(ManageHistoryMixin, TranslatableModel, TimeStampedModel):
    """ Topic model. """
    uuid = models.UUIDField(blank=False, null=False, default=uuid4, editable=False, verbose_name=_('UUID'))
    banner_image_url = models.URLField(blank=True, null=True)
    slug = AutoSlugField(populate_from='name', editable=True, blank=True, slugify_function=uslugify,
                         help_text=_('Leave this field blank to have the value generated automatically.'))

    partner = models.ForeignKey(Partner, models.CASCADE)

    def __str__(self):
        return self.name

    class Meta:
        unique_together = (
            ('partner', 'slug'),
            ('partner', 'uuid'),
        )
        ordering = ['created']

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def validate_unique(self, *args, **kwargs):
        super().validate_unique(*args, **kwargs)
        qs = Topic.objects.filter(partner=self.partner_id)
        if qs.filter(translations__name=self.name).exclude(pk=self.pk).exists():
            raise ValidationError({'name': ['Topic with this Name and Partner already exists', ]})


class TopicTranslation(TranslatedFieldsModel):
    master = models.ForeignKey(Topic, models.CASCADE, related_name='translations', null=True)

    name = models.CharField(max_length=255, blank=False, null=False)
    subtitle = models.CharField(max_length=255, blank=True, null=True)
    description = models.TextField(blank=True, null=True)
    long_description = models.TextField(blank=True, null=True)

    class Meta:
        unique_together = ('language_code', 'master')
        verbose_name = _('Topic model translations')


class Fact(ManageHistoryMixin, AbstractHeadingBlurbModel):
    """ Fact Model """

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Fact update_product_data_modified_timestamp triggered for {self.pk}."
                f"Updating timestamp for related products."
            )
            Course.everything.filter(additional_metadata__facts__pk=self.pk).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(additional_metadata__facts__pk=self.pk)
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))


class CertificateInfo(ManageHistoryMixin, AbstractHeadingBlurbModel):
    """ Certificate Information Model """

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(f"Changes detected in CertificateInfo {self.pk}, updating related product timestamps")
            Course.everything.filter(additional_metadata__certificate_info__pk=self.pk).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(additional_metadata__certificate_info__pk=self.pk)
            ).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )


class ProductMeta(ManageHistoryMixin, TimeStampedModel):
    """
    Model to contain SEO/Meta information for a product.
    """
    title = models.CharField(
        max_length=200, default='', null=True, blank=True,
        help_text="Product title that will appear in meta tag for search engine ranking"
    )
    description = models.CharField(
        max_length=255, default='', null=True, blank=True,
        help_text="Product description that will appear in meta tag for search engine ranking"
    )
    keywords = TaggableManager(
        blank=True,
        related_name='product_metas',
        help_text=_('SEO Meta tags for Products'),
    )

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"ProductMeta update_product_data_modified_timestamp triggered for {self.pk}."
                f"Updating timestamp for related products."
            )
            Course.everything.filter(additional_metadata__product_meta__pk=self.pk).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(additional_metadata__product_meta__pk=self.pk)
            ).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return self.title


class TaxiForm(ManageHistoryMixin, TimeStampedModel):
    """
    Represents the data needed for a single Taxi (2U form library) lead capture form.
    """
    form_id = models.CharField(
        help_text=_('The ID of the Taxi Form (by 2U) that would be rendered in place of the hubspot capture form'),
        max_length=75,
        blank=True,
        default='',
    )
    grouping = models.CharField(
        help_text=_('The grouping of the Taxi Form (by 2U) that would be rendered instead of the hubspot capture form'),
        max_length=50,
        blank=True,
        default='',
    )
    title = models.CharField(max_length=255, default=None, null=True, blank=True)
    subtitle = models.CharField(max_length=255, default=None, null=True, blank=True)
    post_submit_url = models.URLField(null=True, blank=True)
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"TaxiForm update_product_data_modified_timestamp triggered for {self.form_id}."
                f"Updating data modified timestamp for related products."
            )
            if hasattr(self, 'additional_metadata') and self.additional_metadata:
                self.additional_metadata.related_courses.all().update(
                    data_modified_timestamp=datetime.datetime.now(pytz.UTC)
                )
                Program.objects.filter(
                    courses__in=self.additional_metadata.related_courses.all()
                ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

            if hasattr(self, 'program') and self.program:
                Program.objects.filter(pk=self.program.id).update(
                    data_modified_timestamp=datetime.datetime.now(pytz.UTC)
                )

    def __str__(self):
        return f"{self.title}({self.form_id})"


class AdditionalMetadata(ManageHistoryMixin, TimeStampedModel):
    """
    This model holds 2U related additional fields.
    """

    external_url = models.URLField(
        blank=False, null=False, max_length=511,
        help_text=_('The URL of the paid landing page on external site')
    )
    external_identifier = models.CharField(max_length=255, blank=True, null=False)
    lead_capture_form_url = models.URLField(blank=True, null=False, max_length=511)
    organic_url = models.URLField(
        blank=True, null=False, max_length=511,
        help_text=_('The URL of the organic landing page on external site')
    )
    facts = models.ManyToManyField(
        Fact, blank=True, related_name='related_course_additional_metadata',
    )
    certificate_info = models.ForeignKey(
        CertificateInfo, models.CASCADE, default=None, null=True, blank=True,
        related_name='related_course_additional_metadata',
    )
    start_date = models.DateTimeField(
        default=None, blank=True, null=True,
        help_text=_('The start date of the external course offering for marketing purpose')
    )
    end_date = models.DateTimeField(
        default=None, blank=True, null=True,
        help_text=_('The ends date of the external course offering for marketing purpose')
    )
    registration_deadline = models.DateTimeField(
        default=None, blank=True, null=True,
        help_text=_('The suggested deadline for enrollment for marketing purpose')
    )
    variant_id = models.UUIDField(
        blank=False, null=True, editable=False,
        help_text=_('The identifier for a product variant.')
    )
    course_term_override = models.CharField(
        max_length=20,
        verbose_name=_('Course override'),
        help_text=_('This field allows for override the default course term'),
        blank=True,
        null=True,
        default=None,
    )
    product_meta = models.OneToOneField(
        ProductMeta,
        on_delete=models.DO_NOTHING,
        blank=True,
        null=True,
        default=None,
        related_name="product_additional_metadata"
    )
    taxi_form = models.OneToOneField(
        TaxiForm,
        on_delete=models.DO_NOTHING,
        blank=True,
        null=True,
        default=None,
        related_name='additional_metadata',
    )
    product_status = models.CharField(
        default=ExternalProductStatus.Published, max_length=50, null=False, blank=False,
        choices=ExternalProductStatus.choices
    )
    external_course_marketing_type = models.CharField(
        help_text=_('This field contain external course marketing type specific to product lines'),
        max_length=50,
        blank=True,
        null=True,
        default=None,
        choices=ExternalCourseMarketingType.choices,
    )
    display_on_org_page = models.BooleanField(
        null=False, default=True,
        help_text=_('Determines weather the course should be displayed on the owning organization\'s page')
    )

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        external_keys = [self.product_meta, self.taxi_form]
        return self.has_model_changed(external_keys=external_keys)

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"AdditionalMetadata update_product_data_modified_timestamp triggered for {self.external_identifier}."
                f"Updating data modified timestamp for related products."
            )
            self.related_courses.all().update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=self.related_courses.all()
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

    def __str__(self):
        return f"{self.external_url} - {self.external_identifier}"


class Prerequisite(AbstractNamedModel):
    """ Prerequisite model. """


class ExpectedLearningItem(AbstractValueModel):
    """ ExpectedLearningItem model. """


class JobOutlookItem(AbstractValueModel):
    """ JobOutlookItem model. """


class SyllabusItem(AbstractValueModel):
    """ SyllabusItem model. """
    parent = models.ForeignKey('self', models.CASCADE, blank=True, null=True, related_name='children')


class AdditionalPromoArea(AbstractTitleDescriptionModel):
    """ Additional Promo Area Model """


class Person(TimeStampedModel):
    """ Person model. """
    uuid = models.UUIDField(blank=False, null=False, default=uuid4, editable=False, verbose_name=_('UUID'))
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    salutation = models.CharField(max_length=10, null=True, blank=True)
    given_name = models.CharField(max_length=255)
    family_name = models.CharField(max_length=255, null=True, blank=True)
    bio = NullHtmlField()
    bio_language = models.ForeignKey(LanguageTag, models.CASCADE, null=True, blank=True)
    profile_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/people/profile_images'),
        blank=True,
        null=True,
        variations={
            'medium': (110, 110),
        },
    )
    slug = AutoSlugField(populate_from=('given_name', 'family_name'), editable=True, slugify_function=uslugify)
    email = models.EmailField(null=True, blank=True, max_length=255)
    major_works = HtmlField(
        blank=True,
        help_text=_('A list of major works by this person. Must be valid HTML.'),
    )
    published = models.BooleanField(default=False)

    class Meta:
        unique_together = (
            ('partner', 'uuid'),
        )
        verbose_name_plural = _('People')
        ordering = ['id']

    def __str__(self):
        return self.full_name

    def save(self, *args, **kwargs):
        with transaction.atomic():
            super().save(*args, **kwargs)
            if waffle.switch_is_active('publish_person_to_marketing_site'):
                MarketingSitePeople().update_or_publish_person(self)

        logger.info('Person saved UUID: %s', self.uuid, exc_info=True)

    @property
    def full_name(self):
        if self.family_name:
            full_name = ' '.join((self.given_name, self.family_name,))
            if self.salutation:
                return ' '.join((self.salutation, full_name,))

            return full_name
        else:
            return self.given_name

    @property
    def profile_url(self):
        return self.partner.marketing_site_url_root + 'bio/' + self.slug

    @property
    def get_profile_image_url(self):
        if self.profile_image and hasattr(self.profile_image, 'url'):
            return self.profile_image.url
        return None


class Position(TimeStampedModel):
    """ Position model.

    This model represent's a `Person`'s role at an organization.
    """
    person = models.OneToOneField(Person, models.CASCADE)
    title = models.CharField(max_length=255)
    organization = models.ForeignKey(Organization, models.CASCADE, null=True, blank=True)
    organization_override = models.CharField(max_length=255, null=True, blank=True)

    def __str__(self):
        return f'{self.title} at {self.organization_name}'

    @property
    def organization_name(self):
        name = self.organization_override

        if self.organization and not name:
            name = self.organization.name

        return name


class PkSearchableMixin:
    """
    Represents objects that have a search method to query elasticsearch and load by primary key.
    """

    @classmethod
    def search(cls, query, queryset=None):
        """ Queries the search index.

        Args:
            query (str) -- Elasticsearch querystring (e.g. `title:intro*`)
            queryset (models.QuerySet) -- base queryset to search, defaults to objects.all()

        Returns:
            QuerySet
        """
        query = clean_query(query)

        if queryset is None:
            queryset = cls.objects.all()

        if query == '(*)':
            # Early-exit optimization. Wildcard searching is very expensive in elasticsearch. And since we just
            # want everything, we don't need to actually query elasticsearch at all.
            return queryset

        logger.info(f"Attempting Elasticsearch document search against query: {query}")
        es_document, *_ = registry.get_documents(models=(cls,))
        dsl_query = ESDSLQ('query_string', query=query, analyze_wildcard=True)
        try:
            results = es_document.search().query(dsl_query).execute()
        except RequestError as exp:
            logger.warning('Elasticsearch request is failed. Got exception: %r', exp)
            results = []
        ids = {result.pk for result in results}
        logger.info(f'{len(ids)} records extracted from Elasticsearch query "{query}"')
        filtered_queryset = queryset.filter(pk__in=ids)
        logger.info(f'Filtered queryset of length {len(filtered_queryset)} extracted against query "{query}"')
        return filtered_queryset


class SearchAfterMixin:
    """
    Represents objects to query Elasticsearch with `search_after` pagination and load by primary key.
    """

    @classmethod
    def search(
        cls,
        query,
        queryset=None,
        page_size=settings.ELASTICSEARCH_DSL_QUERYSET_PAGINATION,
        partner=None,
        identifiers=None,
        document=None,
        sort_field="id",
    ):
        """
        Queries the Elasticsearch index with optional pagination using `search_after`.

        Args:
            query (str) -- Elasticsearch querystring (e.g. `title:intro*`)
            queryset (models.QuerySet) -- base queryset to search, defaults to objects.all()
            page_size (int) -- Number of results per page.
            partner (object) -- To be included in the ES query.
            identifiers (object) -- UUID or key of a product.
            document (object) -- ES Document for the given model.
            sort_field (str) -- Field to sort results by. Defaults to 'id'.

        Returns:
            QuerySet
        """
        query = clean_query(query)
        if queryset is None:
            queryset = cls.objects.all()

        if query == '(*)':
            # Early-exit optimization. Wildcard searching is very expensive in elasticsearch. And since we just
            # want everything, we don't need to actually query elasticsearch at all.
            return queryset

        logger.info(f"Attempting Elasticsearch document search against query: {query}")
        es_document = document or next(iter(registry.get_documents(models=(cls,))), None)

        must_queries = [ESDSLQ('query_string', query=query, analyze_wildcard=True)]
        if partner:
            must_queries.append(partner)
        if identifiers:
            must_queries.append(identifiers)

        dsl_query = ESDSLQ('bool', must=must_queries)

        all_ids = set()
        search_after = None

        while True:
            search = (
                es_document.search()
                .query(dsl_query)
                .sort(sort_field)
                .extra(size=page_size)
            )

            search = search.extra(search_after=search_after) if search_after else search

            results = search.execute()

            ids = {result.pk for result in results}
            if not ids:
                logger.info("No more results found.")
                break

            all_ids.update(ids)
            search_after = results[-1].meta.sort if results[-1] else None
            logger.info(f"Fetched {len(ids)} records; total so far: {len(all_ids)}")

        filtered_queryset = queryset.filter(pk__in=all_ids)
        logger.info(f"Filtered queryset of size {len(filtered_queryset)} for query: {query}")
        return filtered_queryset


class Collaborator(TimeStampedModel):
    """
    Collaborator model, defining any collaborators who helped write course content.
    """
    image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/course/collaborator/image'),
        blank=True,
        null=True,
        variations={
            'original': (200, 100),
        },
        help_text=_('Add the collaborator image, please make sure its dimensions are 200x100px')
    )
    name = models.CharField(max_length=255, default='')
    uuid = models.UUIDField(default=uuid4, editable=False, verbose_name=_('UUID'))

    @property
    def image_url(self):
        if self.image and hasattr(self.image, 'url'):
            return self.image.url
        return None

    def __str__(self):
        return f'{self.name}'


class ProductValue(ManageHistoryMixin, TimeStampedModel):
    """
    ProductValue model, with fields related to projected value for a product.
    """
    DEFAULT_VALUE_PER_LEAD = 0
    DEFAULT_VALUE_PER_CLICK = 5

    per_lead_usa = models.IntegerField(
        null=True, blank=True, default=DEFAULT_VALUE_PER_LEAD,
        verbose_name=_('U.S. Value Per Lead'), help_text=_(
            'U.S. value per lead in U.S. dollars.'
        )
    )
    per_lead_international = models.IntegerField(
        null=True, blank=True, default=DEFAULT_VALUE_PER_LEAD,
        verbose_name=_('International Value Per Lead'), help_text=_(
            'International value per lead in U.S. dollars.'
        )
    )
    per_click_usa = models.IntegerField(
        null=True, blank=True, default=DEFAULT_VALUE_PER_CLICK,
        verbose_name=_('U.S. Value Per Click'), help_text=_(
            'U.S. value per click in U.S. dollars.'
        )
    )
    per_click_international = models.IntegerField(
        null=True, blank=True, default=DEFAULT_VALUE_PER_CLICK,
        verbose_name=_('International Value Per Click'), help_text=_(
            'International value per click in U.S. dollars.'
        )
    )
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in ProductValue {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            self.courses.all().update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

            Program.objects.filter(
                courses__in=self.courses.all()
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

            self.programs.all().update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))


class GeoLocation(ManageHistoryMixin, TimeStampedModel):
    """
    Model to keep Geographic location for Products.
    """
    DECIMAL_PLACES = 11
    LAT_MAX_DIGITS = 14
    LNG_MAX_DIGITS = 14

    location_name = models.CharField(
        max_length=128,
        blank=False,
        null=True,
    )

    lat = models.DecimalField(
        max_digits=LAT_MAX_DIGITS,
        decimal_places=DECIMAL_PLACES,
        validators=[MaxValueValidator(90), MinValueValidator(-90)],
        verbose_name=_('Latitude'),
        null=True,
    )
    lng = models.DecimalField(
        max_digits=LNG_MAX_DIGITS,
        decimal_places=DECIMAL_PLACES,
        validators=[MaxValueValidator(180), MinValueValidator(-180)],
        verbose_name=_('Longitude'),
        null=True
    )

    class Meta:
        unique_together = (('lat', 'lng'),)

    def __str__(self):
        return f'{self.location_name}'

    @property
    def coordinates(self):
        if (self.lat is None or self.lng is None):
            return None
        return self.lat, self.lng

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in GeoLocation {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            self.courses.all().update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

            Program.objects.filter(
                courses__in=self.courses.all()
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

            self.programs.all().update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))


class AbstractLocationRestrictionModel(TimeStampedModel):
    ALLOWLIST = 'allowlist'
    BLOCKLIST = 'blocklist'
    RESTRICTION_TYPE_CHOICES = (
        (ALLOWLIST, _('Allowlist')),
        (BLOCKLIST, _('Blocklist'))
    )

    countries = MultiSelectField(choices=COUNTRIES, null=True, blank=True, max_length=len(COUNTRIES))
    states = MultiSelectField(choices=CONTIGUOUS_STATES, null=True, blank=True, max_length=len(CONTIGUOUS_STATES))
    restriction_type = models.CharField(
        max_length=255, choices=RESTRICTION_TYPE_CHOICES, default=ALLOWLIST
    )

    class Meta:
        abstract = True


class CourseLocationRestriction(ManageHistoryMixin, AbstractLocationRestrictionModel):
    """
    Course location restriction model.

    We have to set this as a foreign key field on course rather than a one to one relationship, due to draft courses.
    """
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in CourseLocationRestriction {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            self.courses.all().update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))
            Program.objects.filter(
                courses__in=self.courses.all()
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))


class Course(ManageHistoryMixin, DraftModelMixin, PkSearchableMixin, CachedMixin, TimeStampedModel):
    """ Course model. """
    partner = models.ForeignKey(Partner, models.CASCADE)
    uuid = models.UUIDField(default=uuid4, editable=True, verbose_name=_('UUID'))
    canonical_course_run = models.OneToOneField(
        'course_metadata.CourseRun', models.CASCADE, related_name='canonical_for_course',
        default=None, null=True, blank=True,
    )
    key = models.CharField(max_length=255, db_index=True)
    key_for_reruns = models.CharField(
        max_length=255, blank=True,
        help_text=_('When making reruns for this course, they will use this key instead of the course key.'),
    )
    title = models.CharField(max_length=255, default=None, null=True, blank=True)
    url_slug = AutoSlugField(populate_from='title', editable=True, slugify_function=uslugify, overwrite_on_add=False,
                             help_text=_('Leave this field blank to have the value generated automatically.'))
    short_description = NullHtmlField()
    full_description = NullHtmlField()
    extra_description = models.ForeignKey(
        AdditionalPromoArea, models.CASCADE, default=None, null=True, blank=True, related_name='extra_description',
    )
    additional_metadata = models.ForeignKey(
        AdditionalMetadata, models.CASCADE,
        related_name='related_courses',
        default=None, null=True, blank=True
    )
    course_length = models.CharField(
        max_length=64, choices=CourseLength.choices, blank=True,
        help_text=_('The actual duration of this course as experienced by learners who complete it.'),
    )
    authoring_organizations = SortedManyToManyField(Organization, blank=True, related_name='authored_courses')
    sponsoring_organizations = SortedManyToManyField(Organization, blank=True, related_name='sponsored_courses')
    collaborators = SortedManyToManyField(Collaborator, null=True, blank=True, related_name='courses_collaborated')
    subjects = SortedManyToManyField(Subject, blank=True)
    prerequisites = models.ManyToManyField(Prerequisite, blank=True)
    level_type = models.ForeignKey(LevelType, models.CASCADE, default=None, null=True, blank=True)
    expected_learning_items = SortedManyToManyField(ExpectedLearningItem, blank=True)
    outcome = NullHtmlField()
    prerequisites_raw = NullHtmlField()
    syllabus_raw = NullHtmlField()
    card_image_url = models.URLField(null=True, blank=True)
    image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/course/image'),
        blank=True,
        null=True,
        variations={
            'original': (1134, 675),
            'small': (378, 225)
        },
        help_text=_('Add the course image')
    )
    video = models.ForeignKey(Video, models.CASCADE, default=None, null=True, blank=True)
    faq = NullHtmlField(verbose_name=_('FAQ'))
    learner_testimonials = NullHtmlField()
    enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_('Total number of learners who have enrolled in this course')
    )
    product_source = models.ForeignKey(Source, models.SET_NULL, null=True, blank=True, related_name='courses')
    recent_enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_(
            'Total number of learners who have enrolled in this course in the last 6 months'
        )
    )
    salesforce_id = models.CharField(max_length=255, null=True, blank=True)  # Course__c in Salesforce
    salesforce_case_id = models.CharField(max_length=255, null=True, blank=True)  # Case in Salesforce
    type = models.ForeignKey(CourseType, models.CASCADE, null=True)  # while null IS True, it should always be set

    # Do not record the slug field in the history table because AutoSlugField is not compatible with
    # django-simple-history.  Background: https://github.com/openedx/course-discovery/pull/332
    history = HistoricalRecords(excluded_fields=['url_slug'])

    # TODO Remove this field.
    number = models.CharField(
        max_length=50, null=True, blank=True, help_text=_(
            'Course number format e.g CS002x, BIO1.1x, BIO1.2x'
        )
    )

    topics = TaggableManager(
        blank=True,
        help_text=_('Pick a tag from the suggestions. To make a new tag, add a comma after the tag name.'),
        related_name='course_topics',
    )

    # The 'additional_information' field holds HTML content, but we don't use a NullHtmlField for it, because we don't
    # want to validate its content at all. This is filled in by administrators, not course teams, and may hold special
    # HTML that isn't normally allowed.
    additional_information = models.TextField(blank=True, null=True, default=None,
                                              verbose_name=_('Additional Information'))
    organization_short_code_override = models.CharField(max_length=255, blank=True)
    organization_logo_override = models.ImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='organization/logo_override'),
        blank=True,
        null=True,
        validators=[FileExtensionValidator(['png'])]
    )

    geolocation = models.ForeignKey(
        GeoLocation, models.SET_NULL, related_name='courses', default=None, null=True, blank=True
    )

    location_restriction = models.ForeignKey(
        CourseLocationRestriction, models.SET_NULL, related_name='courses', default=None, null=True, blank=True
    )

    in_year_value = models.ForeignKey(
        ProductValue, models.SET_NULL, related_name='courses', default=None, null=True, blank=True
    )

    data_modified_timestamp = models.DateTimeField(
        default=None, null=True, blank=True, help_text=_('The last time this course was modified in the database.')
    )

    enterprise_subscription_inclusion = models.BooleanField(
        null=True,
        help_text=_('This field signifies if this course is in the enterprise subscription catalog'),
    )

    excluded_from_search = models.BooleanField(
        null=True,
        blank=True,
        default=False,
        verbose_name='Excluded From Search (Algolia Indexing)',
        help_text=_('If checked, this item will not be indexed in Algolia and will not show up in search results.')
    )

    excluded_from_seo = models.BooleanField(
        null=True,
        blank=True,
        default=False,
        verbose_name='Excluded From SEO (noindex tag)',
        help_text=_('If checked, the About Page will have a meta tag with noindex value')
    )

    watchers = MultiEmailField(
        blank=True,
        verbose_name=_("Watchers"),
        help_text=_(
            "The list of email addresses that will be notified if any of the course runs "
            "is published or scheduled."
        )
    )

    # Changing these fields at the course level will not trigger re-reviews
    # on related course runs that are already in the scheduled state
    STATUS_CHANGE_EXEMPT_FIELDS = [
        'additional_metadata',
        'geolocation',
        'in_year_value',
        'location_restriction',
        'watchers'
    ]

    everything = CourseQuerySet.as_manager()
    objects = DraftManager.from_queryset(CourseQuerySet)()

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        excluded_fields = [
            'data_modified_timestamp',
        ]
        return self.has_model_changed(excluded_fields=excluded_fields)

    class Meta:
        unique_together = (
            ('partner', 'uuid', 'draft'),
            ('partner', 'key', 'draft'),
        )
        ordering = ['id']

    def _check_enterprise_subscription_inclusion(self):
        # if false has been passed in, or it's already been set to false
        if not self.is_enterprise_catalog_allowed_course() or \
                self.enterprise_subscription_inclusion is False:
            return False
        for org in self.authoring_organizations.all():
            if not org.enterprise_subscription_inclusion:
                return False
        return True

    def is_enterprise_catalog_allowed_course(self):
        """
        As documented in ADR docs/decisions/0012-enterprise-program-inclusion-boolean.rst, OC course types
        are allowed in Enterprise catalog inclusion. OC types are all course types excluding ExecEd and Bootcamp.
        """
        return not self.is_external_course

    def update_data_modified_timestamp(self):
        """
        Update the data_modified_timestamp field to the current time if the course has changed.
        """
        if not self.data_modified_timestamp:
            # If the course has never been saved, set the data_modified_timestamp to the current time.
            self.data_modified_timestamp = datetime.datetime.now(pytz.UTC)
        elif self.draft and self.has_changed:
            now = datetime.datetime.now(pytz.UTC)
            self.data_modified_timestamp = now
            Program.objects.filter(
                courses__in=Course.everything.filter(key=self.key)
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))

    def set_data_modified_timestamp(self):
        """
        Set the data modified timestamp for both draft & non-draft version of the course.
        """
        Course.everything.filter(key=self.key).update(
            data_modified_timestamp=datetime.datetime.now(pytz.UTC)
        )
        Program.objects.filter(courses__in=Course.everything.filter(key=self.key)).update(
            data_modified_timestamp=datetime.datetime.now(pytz.UTC)
        )
        self.refresh_from_db()

    def save(self, *args, **kwargs):
        """
        There have to be two saves because in order to check for if this is included in the
        subscription catalog, we need the id that is created on save to access the many-to-many fields
        and then need to update the boolean in the record based on conditional logic
        """
        self.update_data_modified_timestamp()
        super().save(*args, **kwargs)
        self.enterprise_subscription_inclusion = self._check_enterprise_subscription_inclusion()
        kwargs['force_insert'] = False
        kwargs['force_update'] = True
        super().save(*args, **kwargs)

        # Course runs calculate enterprise subscription inclusion based off of their parent's status, so we need to
        # force a recalculation
        course_runs = self.course_runs.all()
        for course_run in course_runs:
            course_run.save()

    def __str__(self):
        return f'{self.key}: {self.title}'

    def clean(self):
        # We need to populate the value with 0 - model blank and null definitions are to validate the admin form.
        if self.enrollment_count is None:
            self.enrollment_count = 0
        if self.recent_enrollment_count is None:
            self.recent_enrollment_count = 0

    @property
    def image_url(self):
        if self.image and self.image.name:
            variation_path = self.image.get_variation_name(self.image.name, 'small')
            return self.image.storage.url(variation_path)
        return self.card_image_url

    @property
    def organization_logo_override_url(self):
        if self.organization_logo_override:
            return self.organization_logo_override.url
        return None

    @property
    def is_external_course(self):
        """
        Property to check if the course is an external product type.
        """
        return self.type.slug in [CourseType.EXECUTIVE_EDUCATION_2U, CourseType.BOOTCAMP_2U]

    @property
    def original_image_url(self):
        if self.image:
            return self.image.url
        return None

    @property
    def marketing_url(self):
        url = None
        if self.partner.marketing_site_url_root:
            path = self.get_course_url_path()
            url = urljoin(self.partner.marketing_site_url_root, path)

        return url

    @property
    def preview_url(self):
        """ Returns the preview url for the course. """
        url = None
        if self.partner.marketing_site_url_root and self.active_url_slug:
            path = self.get_course_url_path()
            url = urljoin(self.partner.marketing_site_url_root, f'preview/{path}')

        return url

    @property
    def active_url_slug(self):
        """ Official rows just return whatever slug is active, draft rows will first look for an associated active
         slug and, if they fail to find one, take the slug associated with the official course that has
         is_active_on_draft: True."""
        active_url_cache = RequestCache("active_url_cache")
        cache_key = get_cache_key(course_uuid=self.uuid, draft=self.draft)
        cached_active_url = active_url_cache.get_cached_response(cache_key)
        if cached_active_url.is_found:
            return cached_active_url.value

        # The if clause is simply to prevent N+1 issues
        if hasattr(self, '_prefetched_active_slug') and self._prefetched_active_slug:
            active_url = self._prefetched_active_slug[0]
        else:
            active_url = CourseUrlSlug.objects.filter(course=self, is_active=True).first()

        if not active_url and self.draft and self.official_version:
            # current draft url slug has already been published at least once, so get it from the official course
            active_url = CourseUrlSlug.objects.filter(course=self.official_version, is_active_on_draft=True).first()

        url_slug = getattr(active_url, 'url_slug', None)
        if url_slug:
            active_url_cache.set(cache_key, url_slug)
        return url_slug

    def get_course_url_path(self):
        """
        Returns marketing url path for course based on active url slug
        """
        active_url_slug = self.active_url_slug
        return active_url_slug if active_url_slug and active_url_slug.find('/') != -1 else f'course/{active_url_slug}'

    def course_run_sort(self, course_run):
        """
        Sort course runs by enrollment_start or start, preferring the former

        A missing date is stubbed to max datetime to be sorted last
        """
        date = course_run.enrollment_start or course_run.start
        if date:
            return date
        return datetime.datetime.max.replace(tzinfo=pytz.UTC)

    @property
    def active_course_runs(self):
        """ Returns course runs that have not yet ended and meet the following enrollment criteria:
            - Open for enrollment
            - OR will be open for enrollment in the future
            - OR have no specified enrollment close date (e.g. self-paced courses)

        This is basically a QuerySet version of "all runs where has_enrollment_ended is False"

        Returns:
            QuerySet
        """
        now = datetime.datetime.now(pytz.UTC)
        return self.course_runs.filter(
            Q(end__gt=now) &
            (
                Q(enrollment_end__gt=now) |
                Q(enrollment_end__isnull=True)
            )
        )

    @property
    def end_date(self):
        """
        Returns the "end" date of the course run falling at the last. Every course run has an end date and this property
        returns the max value of those end dates.
        """
        course_runs = self.course_runs.all()
        last_course_run_end = None
        if course_runs:
            try:
                last_course_run_end = max(
                    course_run.end
                    for course_run in course_runs
                    if course_run.end is not None and course_run.status == CourseRunStatus.Published
                )
            except ValueError:
                last_course_run_end = None
        return last_course_run_end

    @property
    def course_ends(self):
        """
        Returns a string depending on if course.end_date falls in past or future. Course.end_date is the "end" date of
        the last course run.
        """
        now = datetime.datetime.now(pytz.UTC)
        if not self.end_date or self.end_date > now:
            return _('Future')
        else:
            return _('Past')

    def languages(self, exclude_inactive_runs=False):
        """
        Returns a set of all languages used in this course.

        Arguments:
            exclude_inactive_runs (bool): whether to exclude inactive runs
        """
        if exclude_inactive_runs:
            return list({
                serialize_language(course_run.language) for course_run in self.course_runs.all()
                if course_run.is_active and course_run.language is not None
            })
        return list({
            serialize_language(course_run.language) for course_run in self.course_runs.all()
            if course_run.language is not None
        })

    def languages_codes(self, exclude_inactive_runs=False):
        """
        Returns a string of languages codes used in this course. The languages codes are separated by comma.
        This property will ignore restricted runs and course runs with no language set.

        Arguments:
            exclude_inactive_runs (bool): whether to exclude inactive runs
        """
        if exclude_inactive_runs:
            language_codes = set(
                course_run.language.code for course_run in self.active_course_runs.filter(
                    language__isnull=False, restricted_run__isnull=True
                )
            )
        else:
            language_codes = set(
                course_run.language.code for course_run in self.course_runs.filter(
                    language__isnull=False, restricted_run__isnull=True
                )
            )

        return ", ".join(sorted(language_codes))

    @property
    def first_enrollable_paid_seat_price(self):
        """
        Sort the course runs with sorted rather than order_by to avoid
        additional calls to the database
        """
        for course_run in sorted(
            self.active_course_runs,
            key=lambda active_course_run: active_course_run.key.lower(),
        ):
            if course_run.has_enrollable_paid_seats():
                return course_run.first_enrollable_paid_seat_price

        return None

    @property
    def course_run_statuses(self):
        """
        Returns all unique course run status values inside this course.

        Note that it skips hidden courses - this list is typically used for presentational purposes.
        The code performs the filtering on Python level instead of ORM/SQL because filtering on course_runs
        invalidates the prefetch on API level.
        """
        statuses = set()
        return sorted(list(get_course_run_statuses(statuses, self.course_runs.all())))

    @property
    def is_active(self):
        """
        Returns true if any of the course runs of the course is active
        """
        return any(course_run.is_active for course_run in self.course_runs.all())

    def unpublish_inactive_runs(self, published_runs=None):
        """
        Find old course runs that are no longer active but still published, these will be unpublished.

        Designed to work on official runs.

        Arguments:
            published_runs (iterable): optional optimization; pass published CourseRuns to avoid a lookup

        Returns:
            True if any runs were unpublished
        """
        if not self.partner.has_marketing_site:
            return False

        if published_runs is None:
            published_runs = self.course_runs.filter(status=CourseRunStatus.Published).iterator(
                chunk_size=settings.ITERATOR_CHUNK_SIZE)
        published_runs = frozenset(published_runs)

        # Now separate out the active ones from the inactive
        # (done in Python rather than hitting self.active_course_runs to avoid a second db query)
        now = datetime.datetime.now(pytz.UTC)
        inactive_runs = {run for run in published_runs if run.has_enrollment_ended(now)}
        marketable_runs = {run for run in published_runs - inactive_runs if run.could_be_marketable}
        if not marketable_runs or not inactive_runs:
            # if there are no inactive runs, there's no point in continuing - and ensure that we always have at least
            # one marketable run around by not unpublishing if we would get rid of all of them
            return False

        for run in inactive_runs:
            run.status = CourseRunStatus.Unpublished
            run.save()
            if run.draft_version:
                run.draft_version.status = CourseRunStatus.Unpublished
                run.draft_version.save()

        return True

    def _update_or_create_official_version(self, course_run):
        """
        Should only be called from CourseRun.update_or_create_official_version. Because we only need to make draft
        changes official in the context of a course run and because certain actions (like publishing data to ecommerce)
        happen when we make official versions and we want to do those as a bundle with the course run.
        """
        draft_version = Course.everything.get(pk=self.pk)
        # If there isn't an official_version set yet, then this is a create instead of update
        # and we will want to set additional attributes.
        creating = not self.official_version

        official_version = set_official_state(draft_version, Course)

        for entitlement in self.entitlements.all():
            # The draft version could have audit entitlements, but we only
            # want to create official entitlements for the valid entitlement modes.
            if entitlement.mode.slug in Seat.ENTITLEMENT_MODES:
                set_official_state(entitlement, CourseEntitlement, {'course': official_version})

        official_version.set_active_url_slug(self.active_url_slug)

        if creating:
            official_version.canonical_course_run = course_run
            official_version.save()
            self.canonical_course_run = course_run.draft_version
            self.save()

        return official_version

    @transaction.atomic
    def set_active_url_slug(self, slug):
        # logging to help debug error around course url slugs incrementing
        logger.info('The current slug is {}; The slug to be set is {}; Current course is a draft: {}'  # lint-amnesty, pylint: disable=logging-format-interpolation
                    .format(self.url_slug, slug, self.draft))

        # There are too many branches in this method, and it is ok to clear cache than to serve stale data.
        clear_slug_request_cache_for_course(self.uuid)
        if hasattr(self, '_prefetched_active_slug'):
            del self._prefetched_active_slug

        if slug:
            # case 0: if slug is already in use with another, raise an IntegrityError
            excluded_course = self.official_version if self.draft else self.draft_version
            slug_already_in_use = CourseUrlSlug.objects.filter(url_slug__iexact=slug.lower()).exclude(
                course__in=[self, excluded_course]).exists()
            if slug_already_in_use:
                raise IntegrityError(f'This slug {slug} is already in use with another course')

        if self.draft:
            active_draft_url_slug_object = self.url_slug_history.filter(is_active=True).first()

            # case 1: new slug matches an entry in the course's slug history
            if self.official_version:
                found = False
                for url_entry in self.official_version.url_slug_history.filter(Q(is_active_on_draft=True) |
                                                                               Q(url_slug=slug)):
                    match = url_entry.url_slug == slug
                    url_entry.is_active_on_draft = match
                    found = found or match
                    url_entry.save()
                if found:
                    if active_draft_url_slug_object and active_draft_url_slug_object.url_slug != slug:
                        logger.info(f"URL slug for draft course {self.key} found in non-draft course url slug history.")
                        self.set_data_modified_timestamp()
                    # we will get the active slug via the official object, so delete the draft one
                    if active_draft_url_slug_object:
                        active_draft_url_slug_object.delete()
                    return
            # case 2: slug has not been used for this course before
            obj = self.url_slug_history.update_or_create(is_active=True, defaults={
                'course': self,
                'partner': self.partner,
                'is_active': True,
                'url_slug': slug,
            })[0]  # update_or_create returns an (obj, created?) tuple, so just get the object
            # this line necessary to clear the prefetch cache
            self.url_slug_history.add(obj)
            # draft version is using is_active as a criteria  to create/update the CourseUrlSlug.
            # That is why the explicit slug value comparison is required to update data modified timestamp.
            if not active_draft_url_slug_object or active_draft_url_slug_object.url_slug != slug:
                logger.info(f"URL slug for draft course {self.key} has been updated.")
                self.set_data_modified_timestamp()
        else:
            if self.draft_version:
                self.draft_version.url_slug_history.filter(is_active=True).delete()
            obj, created = self.url_slug_history.update_or_create(url_slug=slug, defaults={
                'url_slug': slug,
                'is_active': True,
                'is_active_on_draft': True,
                'partner': self.partner,
            })
            if created:
                # update_or_create is using url_slug to identify if the object is to be
                # created or updated. That means any slug change will create a new slug object and hence
                # why the timestamp is updated.
                logger.info(f"URL slug for non-draft course {self.key} has been updated.")
                self.set_data_modified_timestamp()
            for other_slug in self.url_slug_history.filter(Q(is_active=True) |
                                                           Q(is_active_on_draft=True)).exclude(url_slug=obj.url_slug):
                other_slug.is_active = False
                other_slug.is_active_on_draft = False
                other_slug.save()

    @cached_property
    def advertised_course_run(self):
        now = datetime.datetime.now(pytz.UTC)
        min_date = datetime.datetime.min.replace(tzinfo=pytz.UTC)
        max_date = datetime.datetime.max.replace(tzinfo=pytz.UTC)

        tier_one = []
        tier_two = []
        tier_three = []

        all_runs = self.course_runs.all()
        marketable_course_runs = [course_run for course_run in all_runs if getattr(course_run, "is_marketable", False)]

        for course_run in marketable_course_runs:
            course_run_started = (not course_run.start) or (course_run.start and course_run.start < now)
            if course_run.is_current_and_still_upgradeable():
                tier_one.append(course_run)
            elif not course_run_started and course_run.is_upgradeable():
                tier_two.append(course_run)
            else:
                tier_three.append(course_run)

        advertised_course_run = None

        # start should almost never be null, default added to take care of older incomplete data
        if tier_one:
            advertised_course_run = sorted(tier_one, key=lambda run: run.start or min_date, reverse=True)[0]
        elif tier_two:
            advertised_course_run = sorted(tier_two, key=lambda run: run.start or max_date)[0]
        elif tier_three:
            advertised_course_run = sorted(tier_three, key=lambda run: run.start or min_date, reverse=True)[0]

        if not advertised_course_run:
            advertised_course_run = next(
                (run for run in all_runs if getattr(run, "weeks_to_complete", None) is not None),
                None
            )
        if not advertised_course_run and all_runs.exists():
            advertised_course_run = all_runs.first()

        return advertised_course_run

    def has_marketable_run(self):
        return any(run.is_marketable for run in self.course_runs.all())

    def recommendations(self, excluded_restriction_types=None):
        """
        Recommended set of courses for upsell after finishing a course. Returns de-duped list of Courses that:
        A) belong in the same program as given Course
        B) share the same subject AND same organization (or at least one)
        in priority of A over B
        """
        if excluded_restriction_types is None:
            excluded_restriction_types = []

        program_courses = list(
            Course.objects.filter(
                programs__in=self.programs.all()
            )
            .select_related('partner', 'type')
            .prefetch_related(
                Prefetch('course_runs', queryset=CourseRun.objects.exclude(
                    restricted_run__restriction_type__in=excluded_restriction_types
                ).select_related('type').prefetch_related('seats')),
                'authoring_organizations',
                '_official_version'
            )
            .exclude(key=self.key)
            .distinct()
            .all())

        subject_org_courses = list(
            Course.objects.filter(
                subjects__in=self.subjects.all(),
                authoring_organizations__in=self.authoring_organizations.all()
            )
            .select_related('partner', 'type')
            .prefetch_related(
                Prefetch('course_runs', queryset=CourseRun.objects.exclude(
                    restricted_run__restriction_type__in=excluded_restriction_types
                ).select_related('type').prefetch_related('seats')),
                'authoring_organizations',
                '_official_version'
            )
            .exclude(key=self.key)
            .distinct()
            .all())

        # coercing to set destroys order, looping to remove dupes on union
        seen = set()
        deduped = []
        for course in [*program_courses, *subject_org_courses]:
            if course not in seen and course.has_marketable_run():
                deduped.append(course)
                seen.add(course)
        return deduped

    def set_subdirectory_slug(self):
        """
        Sets the active url slug for draft and non-draft courses if the current
        slug is not validated as per the new format.
        """
        is_slug_in_subdirectory_format = bool(
            re.match(SUBDIRECTORY_SLUG_FORMAT_REGEX, self.active_url_slug)
        ) if self.active_url_slug else False  # Unless assigned, the active slug is None for Studio created courses.
        is_exec_ed_course = self.type.slug == CourseType.EXECUTIVE_EDUCATION_2U
        is_bootcamp_course = self.type.slug == CourseType.BOOTCAMP_2U
        if is_exec_ed_course and not IS_SUBDIRECTORY_SLUG_FORMAT_FOR_EXEC_ED_ENABLED.is_enabled():
            return
        if is_bootcamp_course and not IS_SUBDIRECTORY_SLUG_FORMAT_FOR_BOOTCAMP_ENABLED.is_enabled():
            return
        is_open_course = is_ocm_course(self)
        if not is_slug_in_subdirectory_format and (is_exec_ed_course or is_open_course or is_bootcamp_course):
            slug, error = get_slug_for_course(self)
            if slug:
                self.set_active_url_slug(slug)
                if self.official_version:
                    self.official_version.set_active_url_slug(slug)
            else:
                raise Exception(  # pylint: disable=broad-exception-raised
                    f"Slug generation Failed: unable to set active url slug for course: {self.key} "
                    f"with error {error}"
                )


class CourseEditor(ManageHistoryMixin, TimeStampedModel):
    """
    CourseEditor model, defining who can edit a course and its course runs.

    .. no_pii:
    """
    user = models.ForeignKey(get_user_model(), models.CASCADE, related_name='courses_edited')
    course = models.ForeignKey(Course, models.CASCADE, related_name='editors')

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    class Meta:
        unique_together = ('user', 'course',)

    # The logic for whether a user can edit a course gets a little complicated, so try to use the following class
    # utility methods when possible. Read 0003-publisher-permission.rst for more context on the why.

    @classmethod
    def can_create_course(cls, user, organization_key):
        if user.is_staff:
            return True

        # You must be a member of the organization within which you are creating a course
        return user.groups.filter(organization_extension__organization__key=organization_key).exists()

    @classmethod
    def course_editors(cls, course):
        """
        Returns an iterable of User objects.
        """
        authoring_orgs = course.authoring_organizations.all()

        # No matter what, if an editor or their organization has been removed from the course, they can't be an editor
        # for it. This handles cases of being dropped from an org... But might be too restrictive in case we want
        # to allow outside guest editors on a course? Let's try this for now and see how it goes.
        valid_editors = course.editors.filter(user__groups__organization_extension__organization__in=authoring_orgs)
        valid_editors = valid_editors.select_related('user')

        if valid_editors:
            return {editor.user for editor in valid_editors}

        # No valid editors - this is an edge case where we just grant anyone in an authoring org access
        user_model = get_user_model()
        return user_model.objects.filter(groups__organization_extension__organization__in=authoring_orgs).distinct()

    @classmethod
    def editors_for_user(cls, user):
        if user.is_staff:
            return CourseEditor.objects.all()

        user_orgs = Organization.user_organizations(user)
        return CourseEditor.objects.filter(user__groups__organization_extension__organization__in=user_orgs)

    @classmethod
    def is_course_editable(cls, user, course):
        if user.is_staff:
            return True

        return user in cls.course_editors(course)

    @classmethod
    def editable_courses(cls, user, queryset, check_editors=True):
        if user.is_staff:
            return queryset

        # We must be a valid editor for this course
        if check_editors:
            has_valid_editors = Q(
                authoring_organizations=F('editors__user__groups__organization_extension__organization')
            )
            has_user_editor = Q(editors__user=user)
            queryset = queryset.filter(has_user_editor | ~has_valid_editors)

        # And the course has to be authored by an org we belong to
        user_orgs = Organization.user_organizations(user)
        queryset = queryset.filter(authoring_organizations__in=user_orgs)

        # We use distinct() here because the query is complicated enough, spanning tables and following lists of
        # foreign keys, that django will return duplicate rows if we aren't careful to ask it not to.
        return queryset.distinct()

    @classmethod
    def editable_course_runs(cls, user, queryset):
        if user.is_staff:
            return queryset

        user_orgs = Organization.user_organizations(user)
        has_valid_editors = Q(
            course__authoring_organizations=F('course__editors__user__groups__organization_extension__organization')
        )
        has_user_editor = Q(course__editors__user=user)
        user_can_edit = has_user_editor | ~has_valid_editors

        # We use distinct() here because the query is complicated enough, spanning tables and following lists of
        # foreign keys, that django will return duplicate rows if we aren't careful to ask it not to.
        return queryset.filter(user_can_edit, course__authoring_organizations__in=user_orgs).distinct()


class CourseRun(ManageHistoryMixin, DraftModelMixin, CachedMixin, TimeStampedModel):
    """ CourseRun model. """
    OFAC_RESTRICTION_CHOICES = (
        ('', '--'),
        (True, _('Blocked')),
        (False, _('Unrestricted')),
    )

    PRICE_FIELD_CONFIG = {
        'decimal_places': 2,
        'max_digits': 10,
    }

    IN_REVIEW_STATUS = [CourseRunStatus.InternalReview, CourseRunStatus.LegalReview]
    POST_REVIEW_STATUS = [CourseRunStatus.Reviewed, CourseRunStatus.Published]

    uuid = models.UUIDField(default=uuid4, verbose_name=_('UUID'))
    course = models.ForeignKey(Course, models.CASCADE, related_name='course_runs')
    key = models.CharField(max_length=255)
    # There is a post save function in signals.py that verifies that this is unique within a program
    external_key = models.CharField(max_length=225, blank=True, null=True)
    status = models.CharField(default=CourseRunStatus.Unpublished, max_length=255, null=False, blank=False,
                              db_index=True, choices=CourseRunStatus.choices)
    title_override = models.CharField(
        max_length=255, default=None, null=True, blank=True,
        help_text=_(
            "Title specific for this run of a course. Leave this value blank to default to the parent course's title."))
    start = models.DateTimeField(null=True, blank=True, db_index=True)
    end = models.DateTimeField(null=True, blank=True, db_index=True)
    go_live_date = models.DateTimeField(null=True, blank=True)
    enrollment_start = models.DateTimeField(null=True, blank=True)
    enrollment_end = models.DateTimeField(null=True, blank=True, db_index=True)
    announcement = models.DateTimeField(null=True, blank=True)
    short_description_override = NullHtmlField(
        help_text=_(
            "Short description specific for this run of a course. Leave this value blank to default to "
            "the parent course's short_description attribute."))
    full_description_override = NullHtmlField(
        help_text=_(
            "Full description specific for this run of a course. Leave this value blank to default to "
            "the parent course's full_description attribute."))
    staff = SortedManyToManyField(Person, blank=True, related_name='courses_staffed')
    min_effort = models.PositiveSmallIntegerField(
        null=True, blank=True,
        help_text=_('Estimated minimum number of hours per week needed to complete a course run.'))
    max_effort = models.PositiveSmallIntegerField(
        null=True, blank=True,
        help_text=_('Estimated maximum number of hours per week needed to complete a course run.'))
    weeks_to_complete = models.PositiveSmallIntegerField(
        null=True, blank=True,
        help_text=_('Estimated number of weeks needed to complete this course run.'))
    language = models.ForeignKey(LanguageTag, models.CASCADE, null=True, blank=True)
    transcript_languages = models.ManyToManyField(LanguageTag, blank=True, related_name='transcript_courses')
    ai_languages = models.JSONField(
        null=True,
        blank=True,
        validators=[validate_ai_languages],
        help_text=_('A JSON dict detailing the available translations and transcriptions for this run. '
                    'The dict has two keys: translation_languages and transcription_languages.')
    )
    pacing_type = models.CharField(max_length=255, db_index=True, null=True, blank=True,
                                   choices=CourseRunPacing.choices)
    syllabus = models.ForeignKey(SyllabusItem, models.CASCADE, default=None, null=True, blank=True)
    enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_('Total number of learners who have enrolled in this course run')
    )
    recent_enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_(
            'Total number of learners who have enrolled in this course run in the last 6 months'
        )
    )

    # TODO Ditch this, and fallback to the course
    card_image_url = models.URLField(null=True, blank=True)
    video = models.ForeignKey(Video, models.CASCADE, default=None, null=True, blank=True)
    video_translation_languages = models.ManyToManyField(
        LanguageTag, blank=True, related_name='+')
    slug = AutoSlugField(max_length=255, populate_from=['title', 'key'], slugify_function=uslugify, db_index=True,
                         editable=True)
    hidden = models.BooleanField(
        default=False,
        help_text=_('Whether this run should be hidden from API responses.  Do not edit here - this value will be '
                    'overwritten by the "Course Visibility In Catalog" field in Studio via Refresh Course Metadata.')
    )
    mobile_available = models.BooleanField(default=False)
    course_overridden = models.BooleanField(
        default=False,
        help_text=_('Indicates whether the course relation has been manually overridden.')
    )
    reporting_type = models.CharField(max_length=255, choices=ReportingType.choices, default=ReportingType.mooc)
    eligible_for_financial_aid = models.BooleanField(default=True)
    license = models.CharField(max_length=255, blank=True, db_index=True)
    outcome_override = NullHtmlField(
        help_text=_(
            "'What You Will Learn' description for this particular course run. Leave this value blank to default "
            "to the parent course's Outcome attribute."))
    type = models.ForeignKey(CourseRunType, models.CASCADE, null=True)  # while null IS True, it should always be set

    tags = TaggableManager(
        blank=True,
        help_text=_('Pick a tag from the suggestions. To make a new tag, add a comma after the tag name.'),
    )

    has_ofac_restrictions = models.BooleanField(
        blank=True,
        choices=OFAC_RESTRICTION_CHOICES,
        default=None,
        verbose_name=_('Add OFAC restriction text to the FAQ section of the Marketing site'),
        null=True)
    ofac_comment = models.TextField(blank=True, help_text='Comment related to OFAC restriction')

    # The expected_program_type and expected_program_name are here in support of Publisher and may not reflect the
    # final program information.
    expected_program_type = models.ForeignKey(ProgramType, models.CASCADE, default=None, null=True, blank=True)
    expected_program_name = models.CharField(max_length=255, default='', blank=True)

    everything = CourseRunQuerySet.as_manager()
    objects = DraftManager.from_queryset(CourseRunQuerySet)()

    # Do not record the slug field in the history table because AutoSlugField is not compatible with
    # django-simple-history.  Background: https://github.com/openedx/course-discovery/pull/332
    history = HistoricalRecords(excluded_fields=['slug'])

    salesforce_id = models.CharField(max_length=255, null=True, blank=True)  # Course_Run__c in Salesforce

    enterprise_subscription_inclusion = models.BooleanField(
        default=False,
        help_text=_('This calculated field signifies if this course run is in the enterprise subscription catalog'),
    )

    variant_id = models.UUIDField(
        blank=True, null=True, editable=True,
        help_text=_(
            'The identifier for a product variant. This is used to link a course run to a product variant for external '
            'LOBs (i.e; ExecEd & Bootcamps).'
        )
    )

    fixed_price_usd = models.DecimalField(
        **PRICE_FIELD_CONFIG, null=True, blank=True, editable=True,
        help_text=('The fixed USD price for course runs to minimize the impact of currency fluctuations.')
    )

    STATUS_CHANGE_EXEMPT_FIELDS = [
        'start',
        'end',
        'go_live_date',
        'staff',
        'min_effort',
        'max_effort',
        'weeks_to_complete',
        'language',
        'transcript_languages',
        'pacing_type',
    ]

    INTERNAL_REVIEW_FIELDS = (
        'status',
        'has_ofac_restrictions',
        'ofac_comment',
    )

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        """
        If a course run object has changed, update the data modified timestamp
        of related course object.
        """
        if self.draft and self.has_changed:
            logger.info(
                f"Changes detected in Course Run {self.key}, updating course {self.course.key}."
            )
            # Using filter to update timestamp to avoid triggering save flow  on course
            Course.everything.filter(key=self.course.key).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(key=self.course.key)
            ).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

            self.course.refresh_from_db()

    class Meta:
        unique_together = (
            ('key', 'draft'),
            ('uuid', 'draft'),
        )

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._old_status = self.status

    def _upgrade_deadline_sort(self, seat):
        """
        Stub missing upgrade_deadlines to max datetime so they are ordered last
        """
        if seat and seat.upgrade_deadline:
            return seat.upgrade_deadline
        return datetime.datetime.max.replace(tzinfo=pytz.UTC)

    def _enrollable_paid_seats(self):
        """
        Return a list that may be used to fetch the enrollable paid Seats (Seats with price > 0 and no
        prerequisites) associated with this CourseRun.

        We don't use django's built in filter() here since the API should have prefetched seats and
        filter() would hit the database again
        """
        seats = []
        for seat in self.seats.all():
            if seat.type.slug not in Seat.SEATS_WITH_PREREQUISITES and seat.price > 0.0:
                seats.append(seat)
        return seats

    def clean(self):
        # See https://stackoverflow.com/questions/47819247
        if self.enrollment_count is None:
            self.enrollment_count = 0
        if self.recent_enrollment_count is None:
            self.recent_enrollment_count = 0

    @property
    def first_enrollable_paid_seat_price(self):
        # Sort in python to avoid an additional request to the database for order_by
        seats = sorted(self._enrollable_paid_seats(), key=self._upgrade_deadline_sort)
        if not seats:
            # Enrollable paid seats are not available for this CourseRun.
            return None

        price = int(seats[0].price) if seats[0].price else None
        return price

    def first_enrollable_paid_seat_sku(self):
        # Sort in python to avoid an additional request to the database for order_by
        seats = sorted(self._enrollable_paid_seats(), key=self._upgrade_deadline_sort)
        if not seats:
            # Enrollable paid seats are not available for this CourseRun.
            return None
        first_enrollable_paid_seat_sku = seats[0].sku
        return first_enrollable_paid_seat_sku

    def has_enrollable_paid_seats(self):
        """
        Return a boolean indicating whether or not enrollable paid Seats (Seats with price > 0 and no prerequisites)
        are available for this CourseRun.
        """
        return len(self._enrollable_paid_seats()[:1]) > 0

    def is_current(self):
        # Return true if today is after the run start (or start is none) and two weeks from the run end (or end is none)
        now = datetime.datetime.now(pytz.UTC)
        two_weeks = datetime.timedelta(days=14)
        after_start = (not self.start) or self.start < now
        ends_in_more_than_two_weeks = (not self.end) or (
            now.date() <= self.end.date() - two_weeks  # pylint: disable=no-member
        )
        return after_start and ends_in_more_than_two_weeks

    def is_current_and_still_upgradeable(self):
        """
        Return true if
        1. Today is after the run start (or start is none) and two weeks from the run end (or end is none)
        2. The run has a seat that is still enrollable and upgradeable
        and false otherwise
        """
        return self.is_current() and self.is_upgradeable()

    def is_upcoming(self):
        # Return true if course has start date and start date is in the future

        now = datetime.datetime.now(pytz.UTC)
        return self.start and self.start >= now

    def get_paid_seat_enrollment_end(self):
        """
        Return the final date for which an unenrolled user may enroll and purchase a paid Seat for this CourseRun, or
        None if the date is unknown or enrollable paid Seats are not available.
        """
        # Sort in python to avoid an additional request to the database for order_by
        seats = sorted(
            self._enrollable_paid_seats(),
            key=self._upgrade_deadline_sort,
            reverse=True,
        )
        if not seats:
            # Enrollable paid seats are not available for this CourseRun.
            return None

        # An unenrolled user may not enroll and purchase paid seats after the course or enrollment has ended.
        deadline = self.enrollment_deadline

        seat = seats[0]
        if seat.upgrade_deadline and (deadline is None or seat.upgrade_deadline < deadline):
            deadline = seat.upgrade_deadline

        return deadline

    def is_upgradeable(self):
        upgrade_deadline = self.get_paid_seat_enrollment_end()
        upgradeable = bool(upgrade_deadline) and (datetime.datetime.now(pytz.UTC) < upgrade_deadline)
        return upgradeable

    def enrollable_seats(self, types=None):
        """
        Returns seats, of the given type(s), that can be enrolled in/purchased.

        Arguments:
            types (list of SeatTypes): Type of seats to limit the returned value to.

        Returns:
            List of Seats
        """
        now = datetime.datetime.now(pytz.UTC)

        enrolls_in_future = self.enrollment_start and self.enrollment_start > now
        if self.has_enrollment_ended(now) or enrolls_in_future:
            return []

        enrollable_seats = []
        types = types or SeatType.objects.all()
        for seat in self.seats.all():
            if seat.type in types and (not seat.upgrade_deadline or now < seat.upgrade_deadline):
                enrollable_seats.append(seat)

        return enrollable_seats

    @property
    def has_enrollable_seats(self):
        """
        Return a boolean indicating whether or not enrollable Seats are available for this CourseRun.
        """
        return len(self.enrollable_seats()) > 0

    @property
    def image_url(self):
        return self.course.image_url

    @property
    def program_types(self):
        """
        Exclude unpublished and deleted programs from list
        so we don't identify that program type if not available
        """
        program_statuses_to_exclude = (ProgramStatus.Unpublished, ProgramStatus.Deleted)
        associated_programs = []
        for program in self.programs.exclude(status__in=program_statuses_to_exclude):
            if self not in program.excluded_course_runs.all():
                associated_programs.append(program)
        return [program.type.name for program in associated_programs]

    @property
    def marketing_url(self):
        # If the type isn't marketable, don't expose a marketing URL at all, to avoid confusion.
        # This is very similar to self.could_be_marketable, but we don't use that because we
        # still want draft runs to expose a marketing URL.
        type_is_marketable = self.type.is_marketable

        if self.slug and type_is_marketable:
            path = f'course/{self.slug}'
            return urljoin(self.course.partner.marketing_site_url_root, path)

        return None

    @property
    def title(self):
        return self.title_override or self.course.title

    @title.setter
    def title(self, value):
        # Treat empty strings as NULL
        value = value or None
        self.title_override = value

    @property
    def short_description(self):
        return self.short_description_override or self.course.short_description

    @short_description.setter
    def short_description(self, value):
        # Treat empty strings as NULL
        value = value or None
        self.short_description_override = value

    @property
    def full_description(self):
        return self.full_description_override or self.course.full_description

    @full_description.setter
    def full_description(self, value):
        # Treat empty strings as NULL
        value = value or None
        self.full_description_override = value

    @property
    def outcome(self):
        return self.outcome_override or self.course.outcome

    @property
    def in_review(self):
        return self.status in CourseRunStatus.REVIEW_STATES()

    @outcome.setter
    def outcome(self, value):
        # Treat empty strings as NULL
        value = value or None
        self.outcome_override = value

    @property
    def subjects(self):
        return self.course.subjects

    @property
    def authoring_organizations(self):
        return self.course.authoring_organizations

    @property
    def sponsoring_organizations(self):
        return self.course.sponsoring_organizations

    @property
    def prerequisites(self):
        return self.course.prerequisites

    @property
    def programs(self):
        return self.course.programs

    @property
    def seat_types(self):
        return [seat.type for seat in self.seats.all()]

    @property
    def type_legacy(self):
        """
        Calculates a single type slug from the seats in this run.

        This is a property that makes less sense these days. It used to be called simply `type`. But now that Tracks
        and Modes and CourseRunType have made our mode / type situation less rigid, this is losing relevance.

        For example, this cannot support modes that don't have corresponding seats (like Masters).

        It's better to just look at all the modes in the run via type -> tracks -> modes and base any logic off that
        rather than trying to read the tea leaves at the entire run level. The mode combinations are just too complex
        these days.
        """
        seat_types = {t.slug for t in self.seat_types}
        mapping = (
            ('credit', {'credit'}),
            ('professional', {'professional', 'no-id-professional'}),
            ('verified', {'verified'}),
            ('honor', {'honor'}),
            ('audit', {'audit'}),
        )

        for course_run_type, matching_seat_types in mapping:
            if matching_seat_types & seat_types:
                return course_run_type

        return None

    @property
    def level_type(self):
        return self.course.level_type

    @property
    def availability(self):
        now = datetime.datetime.now(pytz.UTC)
        upcoming_cutoff = now + datetime.timedelta(days=60)

        if self.has_ended(now):
            return _('Archived')
        elif self.start and (self.start <= now):
            return _('Current')
        elif self.start and (now < self.start < upcoming_cutoff):
            return _('Starting Soon')
        else:
            return _('Upcoming')

    @property
    def external_course_availability(self):
        """
        Property to get course availability for external courses using product status.
        """
        additional_metadata = self.course.additional_metadata
        if additional_metadata.product_status == ExternalProductStatus.Published:
            return _('Current')
        return _('Archived')

    @property
    def get_video(self):
        return self.video or self.course.video

    @classmethod
    def search(cls, query):
        """ Queries the search index.
        Args:
            query (str) -- Elasticsearch querystring (e.g. `title:intro*`)
        Returns:
            Search object
        """
        query = clean_query(query)
        es_document, *_ = registry.get_documents(models=(cls,))
        queryset = es_document.search()
        if query == '(*)':
            # Early-exit optimization. Wildcard searching is very expensive in elasticsearch. And since we just
            # want everything, we don't need to actually query elasticsearch at all
            return queryset.query(ESDSLQ('match_all'))
        dsl_query = ESDSLQ('query_string', query=query, analyze_wildcard=True)
        return queryset.query(dsl_query)

    def __str__(self):
        return f'{self.key}: {self.title}'

    def validate_seat_upgrade(self, seat_types):
        """
        If a course run has an official version, then ecom products have already been created and
        we only support changing mode from audit -> verified
        """
        if self.official_version:
            old_types = set(self.official_version.seats.values_list('type', flat=True))  # returns strings
            new_types = {t.slug for t in seat_types}
            if new_types & set(Seat.REQUIRES_AUDIT_SEAT):
                new_types.add(Seat.AUDIT)
            if old_types - new_types:
                raise ValidationError(_('Switching seat types after being reviewed is not supported. Please reach out '
                                        'to your project coordinator for additional help if necessary.'))

    def get_seat_default_upgrade_deadline(self, seat_type):
        if seat_type.slug != Seat.VERIFIED:
            return None
        return subtract_deadline_delta(self.end, settings.PUBLISHER_UPGRADE_DEADLINE_DAYS)

    def update_or_create_seat_helper(self, seat_type, prices, upgrade_deadline_override):
        default_deadline = self.get_seat_default_upgrade_deadline(seat_type)
        defaults = {'upgrade_deadline': default_deadline}
        if seat_type.slug in prices:
            defaults['price'] = prices[seat_type.slug]
        if seat_type.slug == Seat.VERIFIED:
            defaults['upgrade_deadline_override'] = upgrade_deadline_override
        # Waffle switch to control dummy SKU generation logic for 2U purpose.
        if IS_COURSE_RUN_FOR_DUMMY_SKU_GENERATION.is_enabled():
            generate_sku(None, self)  # Generates a SKU for the provide by Seat
        seat, __ = Seat.everything.update_or_create(
            course_run=self,
            type=seat_type,
            draft=True,
            defaults=defaults,
        )
        return seat

    def update_or_create_seats(self, run_type=None, prices=None, upgrade_deadline_override=None):
        """
        Updates or creates draft seats for a course run.

        Supports being able to switch seat types to any type before an official version of the
        course run exists. After an official version of the course run exists, it only supports
        price changes or upgrades from Audit -> Verified.
        """
        prices = dict(prices or {})
        seat_types = {track.seat_type for track in run_type.tracks.exclude(seat_type=None)}

        self.validate_seat_upgrade(seat_types)

        seats = []
        for seat_type in seat_types:
            seats.append(self.update_or_create_seat_helper(seat_type, prices, upgrade_deadline_override))

        # Deleting seats here since they would be orphaned otherwise.
        # One example of how this situation can happen is if a course team is switching between
        # professional and verified before actually publishing their course run.
        self.seats.exclude(type__in=seat_types).delete()
        self.seats.set(seats)

    def update_or_create_restriction(self, restriction_type):
        """
        Updates or creates a CourseRunRestriction object for a draft course run
        """

        if restriction_type is None:
            return

        if restriction_type and restriction_type not in CourseRunRestrictionType.values:
            raise Exception('Not a valid choice for restriction_type')

        if not restriction_type and hasattr(self, "restricted_run"):
            self.restricted_run.delete()
            official_obj = self.official_version
            if hasattr(official_obj, "restricted_run"):
                official_obj.restricted_run.delete()
        elif restriction_type:
            RestrictedCourseRun.everything.update_or_create(
                course_run=self,
                draft=True,
                defaults={
                    'restriction_type': restriction_type,
                }
            )
        self.refresh_from_db()

    def update_or_create_official_version(self, notify_services=True):
        draft_version = CourseRun.everything.get(pk=self.pk)
        official_version = set_official_state(draft_version, CourseRun)

        for seat in self.seats.all():
            set_official_state(seat, Seat, {'course_run': official_version})

        if hasattr(self, "restricted_run"):
            set_official_state(self.restricted_run, RestrictedCourseRun, {'course_run': official_version})

        official_course = self.course._update_or_create_official_version(official_version)  # pylint: disable=protected-access
        official_version.slug = self.slug
        official_version.course = official_course

        # During this save, the pre_save hook `ensure_external_key_uniqueness__course_run` in signals.py
        # is run. We rely on there being a save of the official version after the call to set_official_state
        # and the setting of the official_course.
        official_version.save()

        if notify_services:
            # Push any track changes to ecommerce and the LMS as well
            push_to_ecommerce_for_course_run(official_version)
            push_tracks_to_lms_for_course_run(official_version)
        return official_version

    def handle_status_change(self, send_emails):
        """
        If a row's status changed, take any cleanup actions necessary.

        Mostly this is sending email notifications to interested parties or converting a draft row to an official
        one.
        """
        if self._old_status == self.status:
            return
        self._old_status = self.status

        # We currently only care about draft course runs
        if not self.draft:
            return

        # OK, now check for various status change triggers

        email_method = None

        if self.status == CourseRunStatus.LegalReview:
            email_method = emails.send_email_for_legal_review

            if IS_SUBDIRECTORY_SLUG_FORMAT_ENABLED.is_enabled():
                self.course.set_subdirectory_slug()

        elif self.status == CourseRunStatus.InternalReview:
            email_method = emails.send_email_for_internal_review

        elif self.status == CourseRunStatus.Reviewed:
            official_version = self.update_or_create_official_version()

            # If we're due to go live already and we just now got reviewed, immediately go live
            if self.go_live_date and self.go_live_date <= datetime.datetime.now(pytz.UTC):
                official_version.publish()  # will edit/save us too
            else:  # The publish status check will send an email for go-live
                email_method = emails.send_email_for_reviewed

        elif self.status == CourseRunStatus.Published:
            email_method = emails.send_email_for_go_live

        if send_emails and email_method:
            email_method(self)
            if self.go_live_date and self.status in [CourseRunStatus.Reviewed, CourseRunStatus.Published]:
                self.refresh_from_db()
                emails.send_email_to_notify_course_watchers_and_marketing(self.course, self.go_live_date, self.status)

    def _check_enterprise_subscription_inclusion(self):
        if not self.course.enterprise_subscription_inclusion:
            return False
        if self.pacing_type == 'instructor_paced':
            return False
        return True

    # there have to be two saves because in order to check for if this is included in the
    # subscription catalog, we need the id that is created on save to access the many-to-many fields
    # and then need to update the boolean in the record based on conditional logic
    def save(self, *args, suppress_publication=False, send_emails=True, **kwargs):
        """
        Arguments:
            suppress_publication (bool): if True, we won't push the run data to the marketing site
            send_emails (bool): whether to send email notifications for status changes from this save
        """
        push_to_marketing = (not suppress_publication and
                             self.course.partner.has_marketing_site and
                             waffle.switch_is_active('publish_course_runs_to_marketing_site') and
                             self.could_be_marketable)

        with transaction.atomic():
            if push_to_marketing:
                previous_obj = CourseRun.objects.get(id=self.id) if self.id else None

            has_end_changed = self.field_tracker.has_changed('end')

            super().save(*args, **kwargs)

            if has_end_changed:
                for seat in self.seats.filter(type=Seat.VERIFIED):
                    seat.upgrade_deadline_override = None
                    seat.save(update_fields=['upgrade_deadline_override'])

            self.enterprise_subscription_inclusion = self._check_enterprise_subscription_inclusion()
            kwargs['force_insert'] = False
            kwargs['force_update'] = True
            super().save(*args, **kwargs)
            self.handle_status_change(send_emails)

            if push_to_marketing:
                self.push_to_marketing_site(previous_obj)

        if self.status == CourseRunStatus.Reviewed and not self.draft:
            retired_programs = self.programs.filter(status=ProgramStatus.Retired)
            for program in retired_programs:
                program.excluded_course_runs.add(self)

    def publish(self, send_emails=True):
        """
        Marks the course run as announced and published if it is time to do so.

        Course run must be an official version - both it and any draft version will be published.
        Marketing site redirects will also be updated.

        Args:
            send_emails (bool): whether to send email notifications for this publish action

        Returns:
            True if the run was published, False if it was not eligible
        """
        if self.draft:
            return False

        now = datetime.datetime.now(pytz.UTC)
        with transaction.atomic():
            for run in filter(None, [self, self.draft_version]):
                run.announcement = now
                run.status = CourseRunStatus.Published
                run.save(send_emails=send_emails)

        # It is likely that we are sunsetting an old run in favor of this new run, so unpublish old runs just in case
        self.course.unpublish_inactive_runs()

        # Add a redirect from the course run URL to the canonical course URL if one doesn't already exist
        existing_slug = CourseUrlSlug.objects.filter(url_slug=self.slug,
                                                     partner=self.course.partner).first()
        if existing_slug and existing_slug.course.uuid == self.course.uuid:
            return True
        self.course.url_slug_history.create(url_slug=self.slug, partner=self.course.partner, course=self.course)

        return True

    def push_to_marketing_site(self, previous_obj):
        publisher = CourseRunMarketingSitePublisher(self.course.partner)
        publisher.publish_obj(self, previous_obj=previous_obj)

    def has_ended(self, when=None):
        """
        Returns:
            True if course run has a defined end and it has passed
        """
        when = when or datetime.datetime.now(pytz.UTC)
        return bool(self.end and self.end < when)

    def has_enrollment_ended(self, when=None):
        """
        Returns:
            True if the enrollment deadline is defined and has passed
        """
        when = when or datetime.datetime.now(pytz.UTC)
        deadline = self.enrollment_deadline
        return bool(deadline and deadline < when)

    @property
    def enrollment_deadline(self):
        """
        Returns:
            The datetime past which this run cannot be enrolled in (or ideally, marketed) or None if no restriction
        """
        dates = set(filter(None, [self.end, self.enrollment_end]))
        return min(dates) if dates else None

    @property
    def is_enrollable(self):
        """
        Checks if the course run is currently enrollable

        Note that missing enrollment_end or enrollment_start are considered to
        mean that the course run does not have a restriction on the respective
        fields.
        Additionally, we don't consider the end date because archived course
        runs may have ended, but they are always enrollable since they have
        null enrollment_start and enrollment_end.
        """
        now = datetime.datetime.now(pytz.UTC)
        return ((not self.enrollment_end or self.enrollment_end >= now) and
                (not self.enrollment_start or self.enrollment_start <= now))

    @property
    def could_be_marketable(self):
        """
        Checks if the course_run is possibly marketable.

        A course run is considered possibly marketable if it would ever be put on
        a marketing site (so things that would *never* be marketable are not).
        """
        if not self.type.is_marketable:
            return False
        if CourseKey.from_string(self.key).deprecated:  # Old Mongo courses are not marketed
            return False
        return not self.draft

    @property
    def is_marketable(self):
        """
        Checks if the course_run is currently marketable

        A course run is considered marketable if it's published, has seats, and
        a non-empty marketing url.

        If you change this, also change the marketable() queries in query.py.
        """
        if not self.could_be_marketable:
            return False

        is_published = self.status == CourseRunStatus.Published
        return is_published and self.seats.exists() and bool(self.marketing_url)

    @property
    def is_marketable_external(self):
        """
        Determines if the course_run is suitable for external marketing.

        If already marketable, simply return self.is_marketable.

        Else, a course run is deemed suitable for external marketing if it is an
        executive education (EE) course, the discovery service status is
        'Reviewed', and the course go_live_date & start_date is in the future.
        """
        if self.is_marketable:
            return self.is_marketable
        is_exec_ed_course = self.course.type.slug == CourseType.EXECUTIVE_EDUCATION_2U
        if is_exec_ed_course:
            current_time = datetime.datetime.now(pytz.UTC)
            is_reviewed = self.status == CourseRunStatus.Reviewed
            has_future_go_live_date = self.go_live_date and self.go_live_date > current_time
            return is_reviewed and self.is_upcoming() and has_future_go_live_date
        return False

    @property
    def is_active(self):
        """
        Returns True if the course run is active, meaning it is both enrollable, marketable and has not ended.
        - `has_ended()`: method of the CourseRun Model to check if the course end date has passed.
        """
        return self.is_enrollable and self.is_marketable and not self.has_ended()

    def complete_review_phase(self, has_ofac_restrictions, ofac_comment):
        """
        Complete the review phase of the course run by marking status as reviewed and adding
        ofac fields' values.
        """
        self.has_ofac_restrictions = has_ofac_restrictions
        self.ofac_comment = ofac_comment
        self.status = CourseRunStatus.Reviewed
        self.save()


class CourseReview(TimeStampedModel):
    """ CourseReview model to save Outcome Survey analytics coming from Snowflake. """

    CHANGE_CAREERS = 'changecareers'
    JOB_ADVANCEMENT = 'jobadvancement'
    LEARN_VALUABLE_SKILLS = 'valuableskills'
    LEARN_FOR_FUN = 'learnforfun'

    COMMON_GOAL_CHOICES = (
        (CHANGE_CAREERS, _('Change careers')),
        (JOB_ADVANCEMENT, _('Job advancement')),
        (LEARN_VALUABLE_SKILLS, _('Learn valuable skills')),
        (LEARN_FOR_FUN, _('Learn for fun')),
    )

    course_key = models.CharField(max_length=255, primary_key=True)
    reviews_count = models.IntegerField(
        help_text='Total number of survey responses associated with a course'
    )
    avg_course_rating = models.DecimalField(
        decimal_places=6,
        max_digits=7,
        help_text='Average rating of the course on a 5 star scale'
    )
    confident_learners_percentage = models.DecimalField(
        decimal_places=6,
        max_digits=9,
        help_text='Percentage of learners who are confident this course will help them reach their goals ("Extremely'
                  ' confident" or "Very confident" on survey)'
    )
    most_common_goal = models.CharField(
        max_length=255,
        help_text='Most common goal is determined by goal most selected by learners for that course',
        choices=COMMON_GOAL_CHOICES
    )
    most_common_goal_learners_percentage = models.DecimalField(
        decimal_places=6,
        max_digits=9,
        help_text='Percentage of learners who selected the most common goal'
    )
    total_enrollments = models.IntegerField(
        help_text='Total no. of enrollments in the course in past 12 months'
    )


class Seat(ManageHistoryMixin, DraftModelMixin, TimeStampedModel):
    """ Seat model. """

    # This set of class variables is historic. Before CourseType and Mode and all that jazz, Seat used to just hold
    # a CharField 'type' and the logic around what that meant often used these variables. We can slowly remove
    # these hardcoded variables as code stops referencing them and using dynamic Modes.
    HONOR = 'honor'
    AUDIT = 'audit'
    VERIFIED = 'verified'
    PROFESSIONAL = 'professional'
    CREDIT = 'credit'
    MASTERS = 'masters'
    EXECUTIVE_EDUCATION = 'executive-education'
    PAID_EXECUTIVE_EDUCATION = 'paid-executive-education'
    UNPAID_EXECUTIVE_EDUCATION = 'unpaid-executive-education'
    PAID_BOOTCAMP = 'paid-bootcamp'
    UNPAID_BOOTCAMP = 'unpaid-bootcamp'
    ENTITLEMENT_MODES = [
        VERIFIED, PROFESSIONAL, EXECUTIVE_EDUCATION, PAID_EXECUTIVE_EDUCATION,
        PAID_BOOTCAMP
    ]
    REQUIRES_AUDIT_SEAT = [VERIFIED]
    # Seat types that may not be purchased without first purchasing another Seat type.
    # EX: 'credit' seats may not be purchased without first purchasing a 'verified' Seat.
    SEATS_WITH_PREREQUISITES = [CREDIT]

    PRICE_FIELD_CONFIG = {
        'decimal_places': 2,
        'max_digits': 10,
        'null': False,
        'default': 0.00,
    }
    course_run = models.ForeignKey(CourseRun, models.CASCADE, related_name='seats')
    # The 'type' field used to be a CharField but when we converted to a ForeignKey, we kept the db column the same,
    # by specifying a bunch of these extra kwargs.
    type = models.ForeignKey(SeatType, models.CASCADE,
                             to_field='slug',  # this keeps the columns as a string, not an int
                             db_column='type')  # this avoids renaming the column to type_id
    price = models.DecimalField(**PRICE_FIELD_CONFIG)
    currency = models.ForeignKey(Currency, models.CASCADE, default='USD')
    _upgrade_deadline = models.DateTimeField(null=True, blank=True, db_column='upgrade_deadline')
    upgrade_deadline_override = models.DateTimeField(null=True, blank=True)
    credit_provider = models.CharField(max_length=255, null=True, blank=True)
    credit_hours = models.IntegerField(null=True, blank=True)
    sku = models.CharField(max_length=128, null=True, blank=True)
    bulk_sku = models.CharField(max_length=128, null=True, blank=True)

    field_tracker = FieldTracker()
    history = HistoricalRecords()

    class Meta:
        unique_together = (
            ('course_run', 'type', 'currency', 'credit_provider', 'draft')
        )
        ordering = ['created']

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        """
        If the draft seat object has changed, update the data modified timestamp
        of related course object on the course run.
        """
        if self.draft and self.has_changed:
            logger.info(
                f"Seat update_product_data_modified_timestamp triggered for {self.pk}."
                f"Updating timestamp for related products."
            )
            Course.everything.filter(key=self.course_run.course.key).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(key=self.course_run.course.key)
            ).update(data_modified_timestamp=datetime.datetime.now(pytz.UTC))
            self.course_run.course.refresh_from_db()

    @property
    def upgrade_deadline(self):
        return self.upgrade_deadline_override or self._upgrade_deadline

    @upgrade_deadline.setter
    def upgrade_deadline(self, value):
        self._upgrade_deadline = value


class CourseEntitlement(ManageHistoryMixin, DraftModelMixin, TimeStampedModel):
    """ Model storing product metadata for a Course. """
    PRICE_FIELD_CONFIG = {
        'decimal_places': 2,
        'max_digits': 10,
        'null': False,
        'default': 0.00,
    }
    course = models.ForeignKey(Course, models.CASCADE, related_name='entitlements')
    mode = models.ForeignKey(SeatType, models.CASCADE)
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    price = models.DecimalField(**PRICE_FIELD_CONFIG)
    currency = models.ForeignKey(Currency, models.CASCADE, default='USD')
    sku = models.CharField(max_length=128, null=True, blank=True)

    history = HistoricalRecords()
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        """
        If a draft course entitlement has changed, update the data modified timestamp
        of related products.
        """
        if self.draft and self.has_changed:
            logger.info(
                f"Changes detected in Course Entitlement {self.pk}, updating course {self.course.key}"
            )
            Course.everything.filter(key=self.course.key).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )
            Program.objects.filter(
                courses__in=Course.everything.filter(key=self.course.key)
            ).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

            self.course.refresh_from_db()

    class Meta:
        unique_together = (
            ('course', 'draft')
        )
        ordering = ['created']


class Endorsement(TimeStampedModel):
    endorser = models.ForeignKey(Person, models.CASCADE, blank=False, null=False)
    quote = models.TextField(blank=False, null=False)

    def __str__(self):
        return self.endorser.full_name


class CorporateEndorsement(TimeStampedModel):
    corporation_name = models.CharField(max_length=128, blank=False, null=False)
    statement = models.TextField(null=True, blank=True)
    image = models.ForeignKey(Image, models.CASCADE, blank=True, null=True)
    individual_endorsements = SortedManyToManyField(Endorsement)

    def __str__(self):
        return self.corporation_name


class FAQ(TimeStampedModel):
    question = models.TextField(blank=False, null=False)
    answer = models.TextField(blank=False, null=False)

    class Meta:
        verbose_name = _('FAQ')
        verbose_name_plural = _('FAQs')
        ordering = ['created']

    def __str__(self):
        return f'{self.pk}: {self.question}'


class Program(ManageHistoryMixin, PkSearchableMixin, TimeStampedModel):
    OFAC_RESTRICTION_CHOICES = (
        ('', '--'),
        (True, _('Blocked')),
        (False, _('Unrestricted')),
    )
    uuid = models.UUIDField(blank=True, default=uuid4, editable=False, unique=True, verbose_name=_('UUID'))
    title = models.CharField(
        help_text=_('The user-facing display title for this Program.'), max_length=255)
    subtitle = models.CharField(
        help_text=_('A brief, descriptive subtitle for the Program.'), max_length=255, blank=True)
    marketing_hook = models.CharField(
        help_text=_('A brief hook for the marketing website'), max_length=255, blank=True)
    type = models.ForeignKey(ProgramType, models.CASCADE, null=True, blank=True)
    status = models.CharField(
        help_text=_('The lifecycle status of this Program.'), max_length=24, null=False, blank=False, db_index=True,
        choices=ProgramStatus.choices, default=ProgramStatus.Unpublished
    )
    marketing_slug = models.CharField(
        unique=True, max_length=255, db_index=True,
        help_text=_('Leave this field blank to have the value generated automatically.')
    )
    # Normally you don't need this limit_choices_to line, because Course.objects will return official rows by default.
    # But our Django admin form for this field does more low level querying than that and needs to be limited.
    courses = SortedManyToManyField(Course, related_name='programs', limit_choices_to={'draft': False})
    order_courses_by_start_date = models.BooleanField(
        default=True, verbose_name='Order Courses By Start Date',
        help_text=_('If this box is not checked, courses will be ordered as in the courses select box above.')
    )
    # NOTE (CCB): Editors of this field should validate the values to ensure only CourseRuns associated
    # with related Courses are stored.
    excluded_course_runs = models.ManyToManyField(CourseRun, blank=True)
    product_source = models.ForeignKey(Source, models.SET_NULL, null=True, blank=True, related_name='programs')
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    overview = models.TextField(null=True, blank=True)
    total_hours_of_effort = models.PositiveSmallIntegerField(
        null=True, blank=True,
        help_text='Total estimated time needed to complete all courses belonging to this program. This field is '
                  'intended for display on program certificates.')
    # The weeks_to_complete field is now deprecated
    weeks_to_complete = models.PositiveSmallIntegerField(
        null=True, blank=True,
        help_text=_('This field is now deprecated (ECOM-6021).'
                    'Estimated number of weeks needed to complete a course run belonging to this program.'))
    min_hours_effort_per_week = models.PositiveSmallIntegerField(null=True, blank=True)
    max_hours_effort_per_week = models.PositiveSmallIntegerField(null=True, blank=True)
    authoring_organizations = SortedManyToManyField(Organization, blank=True, related_name='authored_programs')
    banner_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/programs/banner_images'),
        blank=True,
        null=True,
        variations={
            'large': (1440, 480),
            'medium': (726, 242),
            'small': (435, 145),
            'x-small': (348, 116),
        },
        render_variations=custom_render_variations
    )
    banner_image_url = models.URLField(null=True, blank=True, help_text='DEPRECATED: Use the banner image field.')
    card_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/programs/card_images'),
        blank=True,
        null=True,
        variations={
            'card': (378, 225),
        }
    )
    card_image_url = models.URLField(null=True, blank=True, help_text=_('DEPRECATED: Use the card image field'))
    video = models.ForeignKey(Video, models.CASCADE, default=None, null=True, blank=True)
    expected_learning_items = SortedManyToManyField(ExpectedLearningItem, blank=True)
    faq = SortedManyToManyField(FAQ, blank=True)
    instructor_ordering = SortedManyToManyField(
        Person,
        blank=True,
        help_text=_('This field can be used by API clients to determine the order in which instructors will be '
                    'displayed on program pages. Instructors in this list should appear before all others associated '
                    'with this programs courses runs.')
    )
    credit_backing_organizations = SortedManyToManyField(
        Organization, blank=True, related_name='credit_backed_programs'
    )
    corporate_endorsements = SortedManyToManyField(CorporateEndorsement, blank=True)
    job_outlook_items = SortedManyToManyField(JobOutlookItem, blank=True)
    individual_endorsements = SortedManyToManyField(Endorsement, blank=True)
    credit_redemption_overview = models.TextField(
        help_text=_('The description of credit redemption for courses in program'),
        blank=True, null=True
    )
    one_click_purchase_enabled = models.BooleanField(
        default=True,
        help_text=_('Allow courses in this program to be purchased in a single transaction')
    )
    hidden = models.BooleanField(
        default=False, db_index=True,
        help_text=_('Hide program on marketing site landing and search pages. This program MAY have a detail page.'))
    enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_(
            'Total number of learners who have enrolled in courses this program'
        )
    )
    recent_enrollment_count = models.IntegerField(
        null=True, blank=True, default=0, help_text=_(
            'Total number of learners who have enrolled in courses in this program in the last 6 months'
        )
    )
    credit_value = models.PositiveSmallIntegerField(
        blank=True, default=0, help_text=_(
            'Number of credits a learner will earn upon successful completion of the program')
    )
    enterprise_subscription_inclusion = models.BooleanField(
        default=False,
        help_text=_('This calculated field signifies if all the courses in '
                    'this program are included in the enterprise subscription catalog '),
    )
    organization_short_code_override = models.CharField(max_length=255, blank=True, help_text=_(
        'A field to override Organization short code alias specific for this program.')
    )
    organization_logo_override = models.ImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='organization/logo_override'),
        blank=True,
        null=True,
        validators=[FileExtensionValidator(['png'])],
        help_text=_('A field to override Organization logo specific for this program.')
    )
    primary_subject_override = models.ForeignKey(
        Subject, models.SET_NULL, default=None, null=True, blank=True, help_text=_(
            'Primary subject field specific for this program. '
            'Useful field in case there are no courses associated with this program.')
    )
    level_type_override = models.ForeignKey(
        LevelType, models.SET_NULL, default=None, null=True, blank=True, help_text=_(
            'Level type specific for this program. '
            'Useful field in case there are no courses associated with this program.')
    )
    language_override = models.ForeignKey(
        LanguageTag, models.SET_NULL, default=None, null=True, blank=True, help_text=_(
            'Language code specific for this program. '
            'Useful field in case there are no courses associated with this program.')
    )
    geolocation = models.ForeignKey(
        GeoLocation, models.SET_NULL, related_name='programs', default=None, null=True, blank=True
    )
    in_year_value = models.ForeignKey(
        ProductValue, models.SET_NULL, related_name='programs', default=None, null=True, blank=True
    )
    excluded_from_search = models.BooleanField(
        null=True,
        blank=True,
        default=False,
        verbose_name='Excluded From Search (Algolia Indexing)',
        help_text=_('If checked, this item will not be indexed in Algolia and will not show up in search results.')
    )

    excluded_from_seo = models.BooleanField(
        null=True,
        blank=True,
        default=False,
        verbose_name='Excluded From SEO (noindex tag)',
        help_text=_('If checked, the About Page will have a meta tag with noindex value')
    )
    taxi_form = models.OneToOneField(
        TaxiForm,
        on_delete=models.DO_NOTHING,
        blank=True,
        null=True,
        default=None,
        related_name='program',
    )
    program_duration_override = models.CharField(
        help_text=_(
            'Useful field to overwrite the duration of a program. It can be a text describing a period of time, '
            'Ex: 6-9 months.'),
        max_length=20,
        blank=True,
        null=True)
    # nosemgrep
    labels = TaggableManager(
        blank=True,
        related_name='program_tags',
        help_text=_('Pick a tag/label from the suggestions. To make a new tag, add a comma after the tag name.'),
    )

    has_ofac_restrictions = models.BooleanField(
        blank=True,
        choices=OFAC_RESTRICTION_CHOICES,
        default=None,
        verbose_name=_('Add OFAC restriction text to the FAQ section of the Marketing site'),
        null=True)
    ofac_comment = models.TextField(blank=True, help_text='Comment related to OFAC restriction')
    data_modified_timestamp = models.DateTimeField(
        default=None, blank=True, null=True, help_text=_('The last time this program was modified.')
    )

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        if not self.pk:
            return False
        excluded_fields = [
            'data_modified_timestamp',
        ]
        return self.has_model_changed(excluded_fields=excluded_fields)

    objects = ProgramQuerySet.as_manager()

    history = HistoricalRecords()

    class Meta:
        ordering = ['created']
        get_latest_by = 'created'

    def __str__(self):
        return f"{self.title} - {self.marketing_slug}"

    def clean(self):
        # See https://stackoverflow.com/questions/47819247
        if self.enrollment_count is None:
            self.enrollment_count = 0
        if self.recent_enrollment_count is None:
            self.recent_enrollment_count = 0

    @property
    def is_program_eligible_for_one_click_purchase(self):
        """
        Checks if the program is eligible for one click purchase.

        To pass the check the program must have one_click_purchase field enabled
        and all its courses must contain only one course run and the remaining
        not excluded course run must contain a purchasable seat.
        """
        if not self.one_click_purchase_enabled:
            return False

        excluded_course_runs = set(self.excluded_course_runs.all())
        applicable_seat_types = self.type.applicable_seat_types.all()

        for course in self.courses.all():
            # Filter the entitlements in python, to avoid duplicate queries for entitlements after prefetching
            all_entitlements = course.entitlements.all()
            entitlement_products = {entitlement for entitlement in all_entitlements
                                    if entitlement.mode in applicable_seat_types}
            if len(entitlement_products) == 1:
                continue

            # Filter the course_runs in python, to avoid duplicate queries for course_runs after prefetching
            all_course_runs = course.course_runs.all()
            course_runs = {course_run for course_run in all_course_runs
                           if course_run.status == CourseRunStatus.Published} - excluded_course_runs

            if len(course_runs) != 1:
                return False

            if not course_runs.pop().enrollable_seats(applicable_seat_types):
                return False

        return True

    @cached_property
    def _course_run_weeks_to_complete(self):
        return [course_run.weeks_to_complete for course_run in self.canonical_course_runs
                if course_run.weeks_to_complete is not None]

    @property
    def weeks_to_complete_min(self):
        return min(self._course_run_weeks_to_complete) if self._course_run_weeks_to_complete else None

    @property
    def weeks_to_complete_max(self):
        return max(self._course_run_weeks_to_complete) if self._course_run_weeks_to_complete else None

    @property
    def marketing_url(self):
        if self.marketing_slug:
            if self.marketing_slug.find('/') != -1:
                return urljoin(self.partner.marketing_site_url_root, self.marketing_slug)
            path = f'{self.type.slug.lower()}/{self.marketing_slug}'
            return urljoin(self.partner.marketing_site_url_root, path)

        return None

    @property
    def course_runs(self):
        """
        Warning! Only call this method after retrieving programs from `ProgramSerializer.prefetch_queryset()`.
        Otherwise, this method will incur many, many queries when fetching related courses and course runs.
        """
        excluded_course_run_ids = [course_run.id for course_run in self.excluded_course_runs.all()]

        for course in self.courses.all():
            for run in course.course_runs.all():
                if run.id not in excluded_course_run_ids:
                    yield run

    @property
    def canonical_course_runs(self):
        excluded_course_run_ids = [course_run.id for course_run in self.excluded_course_runs.all()]

        for course in self.courses.all():
            canonical_course_run = course.canonical_course_run
            if canonical_course_run and canonical_course_run.id not in excluded_course_run_ids:
                yield canonical_course_run

    @property
    def course_run_statuses(self):
        """
        Returns all unique course run status values inside the courses in this program.

        Note that it skips hidden courses - this list is typically used for presentational purposes.
        The code performs the filtering on Python level instead of ORM/SQL because filtering on course_runs
        invalidates the prefetch on API level.
        """
        statuses = set()
        for course in self.courses.all():
            get_course_run_statuses(statuses, course.course_runs.all())
        return sorted(list(statuses))

    @property
    def languages(self):
        return {course_run.language for course_run in self.course_runs if course_run.language is not None}

    @property
    def active_languages(self):
        """
        :return: The list of languages; It gives preference to the language_override over the languages
        extracted from the course runs.
        """
        if self.language_override:
            return {self.language_override}
        return self.languages

    @property
    def transcript_languages(self):
        languages = [course_run.transcript_languages.all() for course_run in self.course_runs]
        languages = itertools.chain.from_iterable(languages)
        return set(languages)

    @property
    def subjects(self):
        """
        :return: The list of subjects; the first subject should be the most common primary subjects of its courses,
        other subjects should be collected and ranked by frequency among the courses.
        """
        primary_subjects = []
        course_subjects = []
        for course in self.courses.all():
            subjects = course.subjects.all()
            primary_subjects.extend(subjects[:1])  # "Primary" subject is the first one
            course_subjects.extend(subjects)
        common_primary = [s for s, _ in Counter(primary_subjects).most_common()][:1]
        common_others = [s for s, _ in Counter(course_subjects).most_common() if s not in common_primary]
        return common_primary + common_others

    @property
    def active_subjects(self):
        """
        :return: The list of subjects; the first subject should be the most common primary subjects of its courses,
        other subjects should be collected and ranked by frequency among the courses.

        Note: This method gives preference to the primary_subject_override over the primary subject of the courses.
        """
        subjects = self.subjects

        if self.primary_subject_override:
            if self.primary_subject_override not in subjects:
                subjects = [self.primary_subject_override] + subjects
            else:
                subjects = [self.primary_subject_override] + \
                    [subject for subject in subjects if subject != self.primary_subject_override]

        return subjects

    @property
    def topics(self):
        """
        :return: The set of topic tags associated with this program's courses
        """
        topic_set = set()
        for course in self.courses.all():
            topic_set.update(course.topics.all())
        return topic_set

    @property
    def seats(self):
        applicable_seat_types = set(self.type.applicable_seat_types.all())

        for run in self.course_runs:
            for seat in run.seats.all():
                if seat.type in applicable_seat_types:
                    yield seat

    @property
    def canonical_seats(self):
        applicable_seat_types = set(self.type.applicable_seat_types.all())

        for run in self.canonical_course_runs:
            for seat in run.seats.all():
                if seat.type in applicable_seat_types:
                    yield seat

    @property
    def entitlements(self):
        """
        Property to retrieve all of the entitlements in a Program.
        """
        # Warning: The choice to not use a filter method on the queryset here was deliberate. The filter
        # method resulted in a new queryset being made which results in the prefetch_related cache being
        # ignored.
        return [
            entitlement
            for course in self.courses.all()
            for entitlement in course.entitlements.all()
            if entitlement.mode in set(self.type.applicable_seat_types.all())
        ]

    @property
    def seat_types(self):
        return {seat.type for seat in self.seats}

    @property
    def organization_logo_override_url(self):
        """
        Property to get url for organization_logo_override.
        """
        if self.organization_logo_override:
            return self.organization_logo_override.url
        return None

    def _select_for_total_price(self, selected_seat, candidate_seat):
        """
        A helper function to determine which course_run seat is best suitable to be used to calculate
        the program total price. A seat is most suitable if the related course_run is now enrollable,
        has not ended, and the enrollment_start date is most recent
        """
        end_valid = not candidate_seat.course_run.has_ended()

        selected_enrollment_start = selected_seat.course_run.enrollment_start or \
            pytz.utc.localize(datetime.datetime.min)

        # Only select the candidate seat if the candidate seat has no enrollment start,
        # or make sure the candidate course_run is enrollable and
        # the candidate seat enrollment start is most recent
        enrollment_start_valid = candidate_seat.course_run.enrollment_start is None or (
            candidate_seat.course_run.enrollment_start > selected_enrollment_start and
            candidate_seat.course_run.enrollment_start < datetime.datetime.now(pytz.UTC)
        )

        return end_valid and enrollment_start_valid

    def _get_total_price_by_currency(self):
        """
        This helper function returns the total program price indexed by the currency
        """
        currencies_with_total = defaultdict()
        course_map = defaultdict(list)
        for seat in self.canonical_seats:
            course_uuid = seat.course_run.course.uuid
            # Identify the most relevant course_run seat for a course.
            # And use the price of the seat to represent the price of the course
            selected_seats = course_map.get(course_uuid)
            if not selected_seats:
                # If we do not have this course yet, create the seats array
                course_map[course_uuid] = [seat]
            else:
                add_seat = False
                seats_to_remove = []
                for selected_seat in selected_seats:
                    if seat.currency != selected_seat.currency:
                        # If the candidate seat has a different currency than the one in the array,
                        # always add to the array
                        add_seat = True
                    elif self._select_for_total_price(selected_seat, seat):
                        # If the seat has same currency, the course has not ended,
                        # and the course is enrollable, then choose the new seat associated with the course instead,
                        # and mark the original seat in the array to be removed
                        logger.info(
                            "Use course_run {} instead of course_run {} for total program price calculation".format(  # lint-amnesty, pylint: disable=logging-format-interpolation
                                seat.course_run.key,
                                selected_seat.course_run.key
                            )
                        )
                        add_seat = True
                        seats_to_remove.append(selected_seat)

                if add_seat:
                    course_map[course_uuid].append(seat)
                for removable_seat in seats_to_remove:
                    # Now remove the seats that should not be counted for calculation for program total
                    course_map[course_uuid].remove(removable_seat)

        for entitlement in self.entitlements:
            course_uuid = entitlement.course.uuid
            selected_seats = course_map.get(course_uuid)
            if not selected_seats:
                course_map[course_uuid] = [entitlement]
            else:
                for selected_seat in selected_seats:
                    if entitlement.currency == selected_seat.currency:
                        # If the seat in the array has the same currency as the entitlement,
                        # dont consider it for pricing by remove it from the course_map
                        course_map[course_uuid].remove(selected_seat)
                # Entitlement should be considered for pricing instead of removed seat.
                course_map[course_uuid].append(entitlement)

        # Now calculate the total price of the program indexed by currency
        for course_products in course_map.values():
            for product in course_products:
                current_total = currencies_with_total.get(product.currency, 0)
                current_total += product.price
                currencies_with_total[product.currency] = current_total

        return currencies_with_total

    @property
    def price_ranges(self):
        currencies = defaultdict(list)
        for seat in self.canonical_seats:
            currencies[seat.currency].append(seat.price)
        for entitlement in self.entitlements:
            currencies[entitlement.currency].append(entitlement.price)

        total_by_currency = self._get_total_price_by_currency()

        price_ranges = []
        for currency, prices in currencies.items():
            price_ranges.append({
                'currency': currency.code,
                'min': min(prices),
                'max': max(prices),
                'total': total_by_currency.get(currency, 0)
            })

        return price_ranges

    @property
    def start(self):
        """ Start datetime, calculated by determining the earliest start datetime of all related course runs. """
        if self.course_runs:  # pylint: disable=using-constant-test
            start_dates = [course_run.start for course_run in self.course_runs if course_run.start]

            if start_dates:
                return min(start_dates)

        return None

    @property
    def staff(self):
        advertised_course_runs = [course.advertised_course_run for
                                  course in self.courses.all() if
                                  course.advertised_course_run]
        staff = [advertised_course_run.staff.all() for advertised_course_run in advertised_course_runs]
        staff = itertools.chain.from_iterable(staff)
        return set(staff)

    @property
    def is_active(self):
        return self.status == ProgramStatus.Active

    def _check_enterprise_subscription_inclusion(self):
        # We exclude Bachelors, Masters, and Doctorate programs as the cost per user would be too high
        if not ProgramType.is_enterprise_catalog_program_type(self.type):
            return False

        for course in self.courses.all():
            if not course.enterprise_subscription_inclusion:
                return False
        return True

    def update_data_modified_timestamp(self):
        """
        Update the data_modified_timestamp field to the current time if the program has changed.
        """
        if not self.data_modified_timestamp:
            self.data_modified_timestamp = datetime.datetime.now(pytz.UTC)
        elif self.has_changed:
            self.data_modified_timestamp = datetime.datetime.now(pytz.UTC)

    def save(self, *args, **kwargs):
        suppress_publication = kwargs.pop('suppress_publication', False)
        is_publishable = (
            self.partner.has_marketing_site and
            waffle.switch_is_active('publish_program_to_marketing_site') and
            # Pop to clean the kwargs for the base class save call below
            not suppress_publication
        )

        self.update_data_modified_timestamp()

        if self.is_active:
            # only call the trigger flow for published programs to avoid
            # unnecessary fetch calls in the method every time a program is saved.
            # Calling this here before save is needed to compare unsaved data
            # with persisted data
            self.trigger_program_skills_update_flow()

        if is_publishable:
            publisher = ProgramMarketingSitePublisher(self.partner)
            previous_obj = Program.objects.get(id=self.id) if self.id else None

            # there have to be two saves because in order to check for if this is included in the
            # subscription catalog, we need the id that is created on save to access the many-to-many fields
            # and then need to update the boolean in the record based on conditional logic
            with transaction.atomic():
                super().save(*args, **kwargs)
                self.enterprise_subscription_inclusion = self._check_enterprise_subscription_inclusion()
                kwargs['force_insert'] = False
                kwargs['force_update'] = True
                super().save(*args, **kwargs)
                publisher.publish_obj(self, previous_obj=previous_obj)
        else:
            super().save(*args, **kwargs)
            self.enterprise_subscription_inclusion = self._check_enterprise_subscription_inclusion()
            kwargs['force_insert'] = False
            kwargs['force_update'] = True
            super().save(*args, **kwargs)

    @property
    def is_2u_degree_program(self):
        # this is a temporary field used by prospectus to easily and semantically
        # determine if a program is a 2u degree
        return hasattr(self, 'degree') and hasattr(self.degree, 'additional_metadata')

    def trigger_program_skills_update_flow(self):
        """
        Utility to trigger the program skills update flow if applicable.
        """
        previous_obj = Program.objects.get(id=self.id) if self.id else None
        if settings.FIRE_UPDATE_PROGRAM_SKILLS_SIGNAL and previous_obj and \
                ((not previous_obj.is_active and self.is_active) or (self.overview != previous_obj.overview)):
            # If a Program is published or overview field is changed then fire signal
            # so that a background task in taxonomy update the program skills.
            logger.info('Signal fired to update program skills. Program: [%s]', self.uuid)
            UPDATE_PROGRAM_SKILLS.send(self.__class__, program_uuid=self.uuid)

    def mark_ofac_restricted(self):
        self.has_ofac_restrictions = True
        self.ofac_comment = f"Program type {self.type.slug} is OFAC restricted for {self.product_source.name}"
        self.save()


class ProgramSubscription(PkSearchableMixin, TimeStampedModel):
    """Model for storing program subscription eligibility"""
    uuid = models.UUIDField(primary_key=True, default=uuid4, editable=False, unique=True, verbose_name=_('ID'))
    program = models.OneToOneField(Program, on_delete=models.CASCADE, related_name='subscription', db_index=True)
    subscription_eligible = models.BooleanField(default=False)

    def __str__(self):
        return f"{self.program} subscription ({'eligible' if self.subscription_eligible else 'not eligible'})"


class ProgramSubscriptionPrice(TimeStampedModel):
    """Model for storing program subscription prices"""
    PRICE_FIELD_CONFIG = {
        'decimal_places': 2,
        'max_digits': 10,
        'null': False,
        'default': 0.00,
    }

    uuid = models.UUIDField(primary_key=True, default=uuid4, editable=False, unique=True, verbose_name=_('ID'))
    program_subscription = models.ForeignKey(ProgramSubscription, related_name='prices',
                                             on_delete=models.CASCADE, db_index=True)
    price = models.DecimalField(**PRICE_FIELD_CONFIG)
    currency = models.ForeignKey(Currency, on_delete=models.CASCADE, default="USD")

    class Meta:
        constraints = [
            UniqueConstraint(fields=['program_subscription', 'currency'], name='unique_subscription_currency')
        ]

    def __str__(self):
        return f"{self.program_subscription.program} has subscription Price {self.price} {self.currency}"


class Ranking(ManageHistoryMixin, TimeStampedModel):
    """
    Represents the rankings of a program
    """
    rank = models.CharField(max_length=10, verbose_name=_('The actual rank number'))
    description = models.CharField(max_length=255, verbose_name=_('What does the rank number mean'))
    source = models.CharField(max_length=100, verbose_name=_('From where the rank is obtained'))

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.pk and self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in Ranking {self.pk}, updating data modified "
                f"timestamps for related programs."
            )
            Degree.objects.filter(rankings=self).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return self.description


class Specialization(ManageHistoryMixin, AbstractValueModel):
    """Specialization model for degree"""
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.pk and self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in Specialization {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            Degree.objects.filter(specializations=self).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )


class Degree(Program):
    """
    This model captures information about a Degree (e.g. a Master's Degree).
    It mostly stores information relevant to the marketing site's product page for this degree.
    """
    apply_url = models.CharField(
        help_text=_('Callback URL to partner application flow'), max_length=255, blank=True
    )
    overall_ranking = models.CharField(
        help_text=_('Overall program ranking (e.g. "#1 in the U.S.")'),
        max_length=255,
        blank=True
    )
    banner_border_color = models.CharField(
        help_text=_("""The 6 character hex value of the color to make the banner borders
            (e.g. "#ff0000" which equals red) No need to provide the `#`"""),
        max_length=6,
        blank=True
    )
    campus_image = models.ImageField(
        upload_to='media/degree_marketing/campus_images/',
        blank=True,
        null=True,
        help_text=_('Provide a campus image for the header of the degree'),
    )
    title_background_image = models.ImageField(
        upload_to='media/degree_marketing/campus_images/',
        blank=True,
        null=True,
        help_text=_('Provide a background image for the title section of the degree'),
    )
    prerequisite_coursework = models.TextField(default='TBD')
    application_requirements = models.TextField(default='TBD')
    costs_fine_print = models.TextField(
        help_text=_('The fine print that displays at the Tuition section\'s bottom'),
        null=True,
        blank=True,
    )
    deadlines_fine_print = models.TextField(
        help_text=_('The fine print that displays at the Deadline section\'s bottom'),
        null=True,
        blank=True,
    )
    rankings = SortedManyToManyField(Ranking, blank=True)

    lead_capture_list_name = models.CharField(
        help_text=_('The sailthru email list name to capture leads'),
        max_length=255,
        default='Master_default',
    )
    lead_capture_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/degree_marketing/lead_capture_images/'),
        blank=True,
        null=True,
        variations={
            'large': (1440, 480),
            'medium': (726, 242),
            'small': (435, 145),
            'x-small': (348, 116),
        },
        help_text=_('Please provide an image file for the lead capture banner.'),
    )
    hubspot_lead_capture_form_id = models.CharField(
        help_text=_('The Hubspot form ID for the lead capture form'),
        null=True,
        blank=True,
        max_length=128,
    )
    micromasters_url = models.URLField(
        help_text=_('URL to micromasters landing page'),
        max_length=255,
        blank=True,
        null=True
    )
    micromasters_long_title = models.CharField(
        help_text=_('Micromasters verbose title'),
        max_length=255,
        blank=True,
        null=True
    )
    micromasters_long_description = models.TextField(
        help_text=_('Micromasters descriptive paragraph'),
        blank=True,
        null=True
    )
    micromasters_background_image = StdImageField(
        upload_to=UploadToFieldNamePath(populate_from='uuid', path='media/degree_marketing/mm_images/'),
        blank=True,
        null=True,
        variations={
            'large': (1440, 480),
            'medium': (726, 242),
            'small': (435, 145),
        },
        help_text=_('Customized background image for the MicroMasters section.'),
    )
    micromasters_org_name_override = models.CharField(
        help_text=_(
            'Override org name if micromasters program comes from different organization than Masters program'
        ),
        max_length=50,
        blank=True,
        null=True,
    )
    search_card_ranking = models.CharField(
        help_text=_('Ranking display for search card (e.g. "#1 in the U.S."'),
        max_length=50,
        blank=True,
        null=True,
    )
    search_card_cost = models.CharField(
        help_text=_('Cost display for search card (e.g. "$9,999"'),
        max_length=50,
        blank=True,
        null=True,
    )
    search_card_courses = models.CharField(
        help_text=_('Number of courses for search card (e.g. "11 Courses"'),
        max_length=50,
        blank=True,
        null=True,
    )
    specializations = SortedManyToManyField(Specialization, blank=True, null=True)
    display_on_org_page = models.BooleanField(
        null=False, default=False,
        help_text=_('Designates whether the degree should be displayed on the owning organization\'s page')
    )

    field_tracker = FieldTracker()

    class Meta:
        verbose_name_plural = "Degrees"

    def __str__(self):
        return str(f'Degree: {self.title}')


class DegreeAdditionalMetadata(ManageHistoryMixin, TimeStampedModel):
    """
    This model holds 2U degree related additional fields
    """

    external_url = models.URLField(
        blank=True, null=False, max_length=511,
        help_text=_('The redirect URL of the degree on external site')
    )
    external_identifier = models.CharField(max_length=255, blank=True, null=False)
    organic_url = models.URLField(
        blank=True, null=False, max_length=511,
        help_text=_('The URL of the landing page on external site')
    )

    degree = models.OneToOneField(
        Degree,
        on_delete=models.CASCADE,
        blank=True,
        null=True,
        default=None,
        related_name='additional_metadata',
    )

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in DegreeAdditionalMetadata {self.pk}, updating data modified "
                f"timestamps for related degree {self.degree_id}."
            )
            Degree.objects.filter(id__in=[self.degree_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return f"{self.external_url} - {self.external_identifier}"


class IconTextPairing(ManageHistoryMixin, TimeStampedModel):
    """
    Represents an icon:text model
    """
    BELL = 'fa-bell'
    CERTIFICATE = 'fa-certificate'
    CHECK = 'fa-check-circle'
    CLOCK = 'fa-clock-o'
    DESKTOP = 'fa-desktop'
    INFO = 'fa-info-circle'
    SITEMAP = 'fa-sitemap'
    USER = 'fa-user'
    DOLLAR = 'fa-dollar'
    BOOK = 'fa-book'
    MORTARBOARD = 'fa-mortar-board'
    STAR = 'fa-star'
    TROPHY = 'fa-trophy'

    ICON_CHOICES = (
        (BELL, _('Bell')),
        (CERTIFICATE, _('Certificate')),
        (CHECK, _('Checkmark')),
        (CLOCK, _('Clock')),
        (DESKTOP, _('Desktop')),
        (INFO, _('Info')),
        (SITEMAP, _('Sitemap')),
        (USER, _('User')),
        (DOLLAR, _('Dollar')),
        (BOOK, _('Book')),
        (MORTARBOARD, _('Mortar Board')),
        (STAR, _('Star')),
        (TROPHY, _('Trophy')),
    )

    degree = models.ForeignKey(Degree, models.CASCADE, related_name='quick_facts')
    icon = models.CharField(max_length=100, verbose_name=_('Icon FA class'), choices=ICON_CHOICES)
    text = models.CharField(max_length=255, verbose_name=_('Paired text'))

    field_tracker = FieldTracker()

    class Meta:
        verbose_name_plural = "IconTextPairings"

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in IconTextPairing {self.pk}, updating data modified "
                f"timestamps for related degree {self.degree_id}."
            )
            Degree.objects.filter(id__in=[self.degree_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return str(f'IconTextPairing: {self.text}')


class DegreeDeadline(ManageHistoryMixin, TimeStampedModel):
    """
    DegreeDeadline stores a Degree's important dates. Each DegreeDeadline
    displays in the Degree product page's "Details" section.
    """
    class Meta:
        ordering = ['created']

    degree = models.ForeignKey(Degree, models.CASCADE, related_name='deadlines', null=True)
    semester = models.CharField(
        help_text=_('Deadline applies for this semester (e.g. Spring 2019'),
        max_length=255,
    )
    name = models.CharField(
        help_text=_('Describes the deadline (e.g. Early Admission Deadline)'),
        max_length=255,
    )
    date = models.CharField(
        help_text=_('The date after which the deadline expires (e.g. January 1, 2019)'),
        max_length=255,
    )
    time = models.CharField(
        help_text=_('The time after which the deadline expires (e.g. 11:59 PM EST).'),
        max_length=255,
        blank=True,
    )

    history = HistoricalRecords()
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in DegreeDeadline {self.pk}, updating data modified "
                f"timestamps for related degree {self.degree_id}."
            )
            Degree.objects.filter(id__in=[self.degree_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return f"{self.name} {self.date}"


class DegreeCost(ManageHistoryMixin, TimeStampedModel):
    """
    Degree cost stores a Degree's associated costs. Each DegreeCost displays in
    a Degree product page's "Details" section.
    """
    class Meta:
        ordering = ['created']

    degree = models.ForeignKey(Degree, models.CASCADE, related_name='costs', null=True)
    description = models.CharField(
        help_text=_('Describes what the cost is for (e.g. Tuition)'),
        max_length=255,
    )
    amount = models.CharField(
        help_text=_('String-based field stating how much the cost is (e.g. $1000).'),
        max_length=255,
    )

    history = HistoricalRecords()
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self):
        if self.has_changed:
            logger.info(
                f"Changes detected in DegreeCost {self.pk}, updating data modified "
                f"timestamps for related degree {self.degree_id}."
            )
            Degree.objects.filter(id__in=[self.degree_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    def __str__(self):
        return str(f'{self.description}, {self.amount}')


class Curriculum(ManageHistoryMixin, TimeStampedModel):
    """
    This model links a program to the curriculum associated with that program, that is, the
    courses and programs that compose the program.
    """
    uuid = models.UUIDField(blank=True, default=uuid4, editable=False, unique=True, verbose_name=_('UUID'))
    program = models.ForeignKey(
        Program,
        models.CASCADE,
        related_name='curricula',
        null=True,
        default=None,
    )
    name = models.CharField(blank=True, max_length=255)
    is_active = models.BooleanField(default=True)
    marketing_text_brief = NullHtmlField(
        max_length=750,
        help_text=_(
            """A high-level overview of the degree\'s courseware. The "brief"
            text is the first 750 characters of "marketing_text" and must be
            valid HTML."""
        ),
    )
    marketing_text = HtmlField(
        null=True,
        blank=False,
        help_text=_('A high-level overview of the degree\'s courseware.'),
    )
    program_curriculum = models.ManyToManyField(
        Program, through='course_metadata.CurriculumProgramMembership', related_name='degree_program_curricula'
    )
    course_curriculum = models.ManyToManyField(
        Course, through='course_metadata.CurriculumCourseMembership', related_name='degree_course_curricula'
    )

    history = HistoricalRecords()

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            if self.program:
                logger.info(
                    f"Changes detected in Curriculum {self.pk}, updating data modified "
                    f"timestamps for related program {self.program_id}."
                )
                Program.objects.filter(id=self.program_id).update(
                    data_modified_timestamp=datetime.datetime.now(pytz.UTC)
                )

    def __str__(self):
        return str(self.name) if self.name else str(self.uuid)


class CurriculumProgramMembership(ManageHistoryMixin, TimeStampedModel):
    """
    Represents the Programs that compose the curriculum of a degree.
    """
    program = models.ForeignKey(Program, models.CASCADE)
    curriculum = models.ForeignKey(Curriculum, models.CASCADE)
    is_active = models.BooleanField(default=True)

    history = HistoricalRecords()

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"Changes detected in CurriculumProgramMembership {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            Program.objects.filter(id__in=[self.curriculum.program_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    class Meta(TimeStampedModel.Meta):
        unique_together = (
            ('curriculum', 'program')
        )


class CurriculumCourseMembership(ManageHistoryMixin, TimeStampedModel):
    """
    Represents the Courses that compose the curriculum of a degree.
    """
    curriculum = models.ForeignKey(Curriculum, models.CASCADE)
    course = models.ForeignKey(Course, models.CASCADE, related_name='curriculum_course_membership')
    course_run_exclusions = models.ManyToManyField(
        CourseRun, through='course_metadata.CurriculumCourseRunExclusion', related_name='curriculum_course_membership'
    )
    is_active = models.BooleanField(default=True)

    history = HistoricalRecords()

    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"Changes detected in CurriculumCourseMembership {self.pk}, updating data modified "
                f"timestamps for related products."
            )
            Program.objects.filter(id__in=[self.curriculum.program_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )

    class Meta(TimeStampedModel.Meta):
        unique_together = (
            ('curriculum', 'course')
        )

    @property
    def course_runs(self):
        return set(self.course.course_runs.all()) - set(self.course_run_exclusions.all())

    def __str__(self):
        return str(self.curriculum) + " : " + str(self.course)


class CurriculumCourseRunExclusion(TimeStampedModel):
    """
    Represents the CourseRuns that are excluded from a course curriculum.
    """
    course_membership = models.ForeignKey(CurriculumCourseMembership, models.CASCADE)
    course_run = models.ForeignKey(CourseRun, models.CASCADE)

    history = HistoricalRecords()


class Pathway(TimeStampedModel):
    """
    Pathway model
    """
    uuid = models.UUIDField(default=uuid4, editable=False, unique=True, verbose_name=_('UUID'))
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    name = models.CharField(max_length=255)
    # this field doesn't necessarily map to our normal org models, it's just a convenience field for pathways
    # while we figure them out
    org_name = models.CharField(max_length=255, verbose_name=_("Organization name"))
    email = models.EmailField(blank=True)
    programs = SortedManyToManyField(Program)
    description = models.TextField(null=True, blank=True)
    destination_url = models.URLField(null=True, blank=True)
    pathway_type = models.CharField(
        max_length=32,
        choices=[(tag.value, tag.value) for tag in PathwayType],
        default=PathwayType.CREDIT.value,
    )
    status = models.CharField(
        default=PathwayStatus.Unpublished,
        max_length=255, null=False, blank=False,
        choices=PathwayStatus.choices
    )

    def __str__(self):
        return self.name

    # Define a validation method to be used elsewhere - we can't use it in normal model validation flow because
    # ManyToMany fields are hard to validate (doesn't support validators field kwarg, can't be referenced before
    # first save(), etc). Instead, this method is used in form validation and we rely on that.
    @classmethod
    def validate_partner_programs(cls, partner, programs):
        """ Throws a ValidationError if any program has a different partner than 'partner' """
        bad_programs = [str(x) for x in programs if x.partner != partner]
        if bad_programs:
            msg = _('These programs are for a different partner than the pathway itself: {}')
            raise ValidationError(msg.format(', '.join(bad_programs)))

    @property
    def course_run_statuses(self):
        """
        Returns all unique course run status values inside the programs in this pathway.

        Note that it skips hidden courses - this list is typically used for presentational purposes.
        The code performs the filtering on Python level instead of ORM/SQL because filtering on course_runs
        invalidates the prefetch on API level.
        """
        statuses = set()
        for program in self.programs.all():
            for course in program.courses.all():
                get_course_run_statuses(statuses, course.course_runs.all())
        return sorted(list(statuses))


class PersonSocialNetwork(TimeStampedModel):
    """ Person Social Network model. """
    FACEBOOK = 'facebook'
    TWITTER = 'twitter'
    BLOG = 'blog'
    OTHERS = 'others'

    SOCIAL_NETWORK_CHOICES = {
        FACEBOOK: _('Facebook'),
        TWITTER: _('Twitter'),
        BLOG: _('Blog'),
        OTHERS: _('Others'),
    }

    type = models.CharField(max_length=15, choices=sorted(list(SOCIAL_NETWORK_CHOICES.items())), db_index=True)
    url = models.CharField(max_length=500)
    title = models.CharField(max_length=255, blank=True)
    person = models.ForeignKey(Person, models.CASCADE, related_name='person_networks')

    class Meta:
        verbose_name_plural = 'Person SocialNetwork'

        unique_together = (
            ('person', 'type', 'title'),
        )
        ordering = ['created']

    def __str__(self):
        return f'{self.display_title}: {self.url}'

    @property
    def display_title(self):
        if self.title:
            return self.title
        elif self.type == self.OTHERS:
            return self.url
        else:
            return self.SOCIAL_NETWORK_CHOICES[self.type]


class PersonAreaOfExpertise(AbstractValueModel):
    """ Person Area of Expertise model. """
    person = models.ForeignKey(Person, models.CASCADE, related_name='areas_of_expertise')

    class Meta:
        verbose_name_plural = 'Person Areas of Expertise'


def slugify_with_slashes(text):
    """
    Given a text and it will convert disallowed characters to `-` in the text
    """
    disallowed_chars = re.compile(r'[^-a-zA-Z0-9/]+')
    return uslugify(text, regex_pattern=disallowed_chars)


class CourseUrlSlug(TimeStampedModel):
    course = models.ForeignKey(Course, models.CASCADE, related_name='url_slug_history')
    # need to have these on the model separately for unique_together to work, but it should always match course.partner
    partner = models.ForeignKey(Partner, models.CASCADE)
    url_slug = AutoSlugWithSlashesField(populate_from='course__title', editable=True,
                                        slugify_function=slugify_with_slashes, overwrite_on_add=False, max_length=255)
    is_active = models.BooleanField(default=False)

    # useful if a course editor decides to edit a draft and provide a url_slug that has already been associated
    # with the course
    is_active_on_draft = models.BooleanField(default=False)

    # ensure partner matches course
    def save(self, **kwargs):
        if self.partner != self.course.partner:
            msg = _('Partner {partner_key} and course partner {course_partner_key} do not match when attempting'
                    ' to save url slug {url_slug}')
            raise ValidationError({'partner': [msg.format(partner_key=self.partner.name,
                                                          course_partner_key=self.course.partner.name,
                                                          url_slug=self.url_slug), ]})
        super().save(**kwargs)

    class Meta:
        unique_together = (
            ('partner', 'url_slug')
        )


class CourseUrlRedirect(AbstractValueModel):
    course = models.ForeignKey(Course, models.CASCADE, related_name='url_redirects')
    # need to have these on the model separately for unique_together to work, but it should always match course.partner
    partner = models.ForeignKey(Partner, models.CASCADE)

    def save(self, **kwargs):
        if self.partner != self.course.partner:
            msg = _('Partner {partner_key} and course partner {course_partner_key} do not match when attempting'
                    ' to save url redirect {url_path}')
            raise ValidationError({'partner': [msg.format(partner_key=self.partner.name,
                                                          course_partner_key=self.course.partner.name,
                                                          url_slug=self.value), ]})
        super().save(**kwargs)

    class Meta:
        unique_together = (
            ('partner', 'value')
        )


class BulkUploadTagsConfig(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in bulk_upload_tags.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format ")
    )


class ArchiveCoursesConfig(ConfigurationModel):
    """
    Configuration to store a csv file for the archive_courses command
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("A csv file containing uuid of the courses to be archived")
    )
    mangle_end_date = models.BooleanField(default=False)
    mangle_title = models.BooleanField(default=False)


class GeotargetingDataLoaderConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in import_geotargeting_data.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class GeolocationDataLoaderConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in import_geolocation_data.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class ProductValueDataLoaderConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in import_product_value_data.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class ProgramLocationRestriction(ManageHistoryMixin, AbstractLocationRestrictionModel):
    """ Program location restriction """
    program = models.OneToOneField(
        Program, on_delete=models.CASCADE, null=True, blank=True, related_name='location_restriction'
    )
    field_tracker = FieldTracker()

    @property
    def has_changed(self):
        return self.has_model_changed()

    def update_product_data_modified_timestamp(self, bypass_has_changed=False):
        if self.has_changed or bypass_has_changed:
            logger.info(
                f"Changes detected in ProgramLocationRestriction {self.pk}, updating data modified "
                f"timestamps for related program {self.program_id}."
            )
            Program.objects.filter(id__in=[self.program_id]).update(
                data_modified_timestamp=datetime.datetime.now(pytz.UTC)
            )


class CSVDataLoaderConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in import_course_metadata.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class DegreeDataLoaderConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in import_degree_data.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class MigrateCourseSlugConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in migrate_course_slugs and update_course_active_url_slugs.
    """
    OPEN_COURSE = 'open-course'
    COURSE_TYPE_CHOICES = (
        (OPEN_COURSE, _('Open Courses')),
        (CourseType.EXECUTIVE_EDUCATION_2U, _('2U Executive Education Courses')),
        (CourseType.BOOTCAMP_2U, _('Bootcamps'))
    )
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers."),
        null=True,
        blank=True
    )
    course_uuids = models.TextField(default=None, null=True, blank=True, verbose_name=_('Course UUIDs'))
    dry_run = models.BooleanField(default=True)
    count = models.IntegerField(null=True, blank=True)
    course_type = models.CharField(choices=COURSE_TYPE_CHOICES, default=OPEN_COURSE, max_length=255)
    product_source = models.ForeignKey(Source, models.CASCADE, null=True, blank=False)


class MigrateProgramSlugConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in update_program_url_slugs.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers."),
        null=True,
        blank=True
    )


class ProgramSubscriptionConfiguration(ConfigurationModel):
    """
    Configuration to store a csv file that will be used in manage_program_subscription.
    """
    # Timeout set to 0 so that the model does not read from cached config in case the config entry is deleted.
    cache_timeout = 0
    csv_file = models.FileField(
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers.")
    )


class BackpopulateCourseTypeConfig(SingletonModel):
    """
    Configuration for the backpopulate_course_type management command.
    """
    class Meta:
        verbose_name = 'backpopulate_course_type argument'

    arguments = models.TextField(
        blank=True,
        help_text='Useful for manually running a Jenkins job. Specify like "--org=key1 --org=key2".',
        default='',
    )

    def __str__(self):
        return self.arguments


class DataLoaderConfig(SingletonModel):
    """
    Configuration for data loaders used in the refresh_course_metadata command.
    """
    max_workers = models.PositiveSmallIntegerField(default=7)


class DeletePersonDupsConfig(SingletonModel):
    """
    Configuration for the delete_person_dups management command.
    """
    class Meta:
        verbose_name = 'delete_person_dups argument'

    arguments = models.TextField(
        blank=True,
        help_text='Useful for manually running a Jenkins job. Specify like "--partner-code=edx A:B C:D".',
        default='',
    )

    def __str__(self):
        return self.arguments


class DrupalPublishUuidConfig(SingletonModel):
    """
    Configuration for data loaders used in the publish_uuids_to_drupal command.
    """
    course_run_ids = models.TextField(default=None, null=False, blank=True, verbose_name=_('Course Run IDs'))
    push_people = models.BooleanField(default=False)


class MigratePublisherToCourseMetadataConfig(SingletonModel):
    """
    Configuration for the migrate_publisher_to_course_metadata command.
    """
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    orgs = SortedManyToManyField(Organization, blank=True)


class ProfileImageDownloadConfig(SingletonModel):
    """
    Configuration for management command to Download Profile Images from Drupal.
    """
    person_uuids = models.TextField(default=None, null=False, blank=False, verbose_name=_('Profile Image UUIDs'))


class TagCourseUuidsConfig(SingletonModel):
    """
    Configuration for management command add_tag_to_courses.
    """
    tag = models.TextField(default=None, null=True, blank=False, verbose_name=_('Tag'))
    course_uuids = models.TextField(default=None, null=True, blank=False, verbose_name=_('Course UUIDs'))


class MigrateCommentsToSalesforce(SingletonModel):
    """
    Configuration for the migrate_comments_to_salesforce command.
    """
    partner = models.ForeignKey(Partner, models.CASCADE, null=True, blank=False)
    orgs = SortedManyToManyField(Organization, blank=True)


class RemoveRedirectsConfig(SingletonModel):
    """
    Configuration for management command remove_redirects_from_courses.
    """
    remove_all = models.BooleanField(default=False, verbose_name=_('Remove All Redirects'))
    url_paths = models.TextField(default='', null=False, blank=True, verbose_name=_('Url Paths'))


class BulkModifyProgramHookConfig(SingletonModel):
    program_hooks = models.TextField(blank=True, null=True)


class BackfillCourseRunSlugsConfig(SingletonModel):
    all = models.BooleanField(default=False, verbose_name=_('Add redirects from all published course url slugs'))
    uuids = models.TextField(default='', null=False, blank=True, verbose_name=_('Course uuids'))


class BulkUpdateImagesConfig(SingletonModel):
    image_urls = models.TextField(blank=True)


class DeduplicateHistoryConfig(SingletonModel):
    """
    Configuration for the deduplicate_course_metadata_history management command.
    """
    class Meta:
        verbose_name = 'deduplicate_course_metadata_history argument'

    cache_timeout = 0

    arguments = models.TextField(
        blank=True,
        help_text='Useful for manually running a Jenkins job. Specify like "course_metadata.CourseRun '
                  '-v=3 --dry  --excluded_fields url_slug --m 26280"',
        default='',
    )

    def __str__(self):
        return self.arguments


class RestrictedCourseRun(DraftModelMixin, TimeStampedModel):
    """
    Model to hold information for restricted Course Runs. Restricted course
    runs will only be exposed in the APIs if explicitly asked for through
    a query param. Consult ADR-27 for more details
    """
    course_run = models.OneToOneField(
        CourseRun, models.CASCADE, related_name='restricted_run',
        help_text='Course Run that will be restricted'
    )
    restriction_type = models.CharField(
        max_length=255, null=True, blank=True,
        choices=CourseRunRestrictionType.choices,
        help_text='The type of restriction for the course run'
    )

    def __str__(self):
        return f"{self.course_run.key}: <{self.restriction_type}>"


class BulkOperationTask(TimeStampedModel):
    """
    Model to store information related to bulk operations.
    """
    csv_file = models.FileField(
        upload_to=bulk_operation_upload_to_path,
        validators=[FileExtensionValidator(allowed_extensions=['csv'])],
        help_text=_("It expects the data will be provided in a csv file format "
                    "with first row containing all the headers."),
        blank=False,
        null=False
    )
    uploaded_by = models.ForeignKey(
        User,
        models.CASCADE,
        related_name='bulk_operation_tasks',
        null=True,
        blank=True,
        help_text=_('User who uploaded the file')
    )
    task_summary = models.JSONField(
        null=True,
        blank=True,
        help_text=_('Summary of the task')
    )
    task_type = models.CharField(
        verbose_name=_('Task Type'),
        max_length=255,
        choices=BulkOperationType.choices,
        help_text=_('Type of Bulk Task to be performed'),
    )
    status = models.CharField(
        verbose_name=_('Status'),
        max_length=50,
        choices=BulkOperationStatus.choices,
        help_text=_('Status of the Bulk Task'),
        default=BulkOperationStatus.Pending,
    )
    task_id = models.CharField(
        max_length=255,
        unique=True,
        null=True,
        blank=True,
        help_text=_('Identifier of the celery task associated with this bulk task')
    )

    def save(self, *args, **kwargs):
        user = kwargs.pop('user', None)
        if not self.uploaded_by:
            if user is None:
                raise ValueError("User is required to save the BulkOperationTask")
            self.uploaded_by = user
        super().save(*args, **kwargs)

    def __str__(self):
        username = self.uploaded_by.username if self.uploaded_by else ""
        return f"{self.csv_file.name} - {self.task_type} - {self.status} - {username}"

    @property
    def task_result(self):
        """
        Returns the TaskResult object associated with the task_id of this bulk task.
        """
        if not self.task_id:
            return None
        try:
            return TaskResult.objects.get(task_id=self.task_id)
        except TaskResult.DoesNotExist:
            return None