template.yaml

AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31
Description: >
  Transformation of LoRaWAN binary payloads 

Parameters:
  ParamBinaryDecoderName:
    Type: String
    Default: sample_device
    Description: Name of binary decoder as configured in src-iotrule-transformation/app.py

  TopicOutgoingErrors:
    Type: String
    Default: lorawanerror
    Description: Topic for errors

  TopicOutgoingTransformedMessages:
    Type: String
    Default: lorawantransformed
    Description: Prefix for outgoing transformed messages

Resources:
  
  ############################################################################################
  # Payload transformation Lambda function to be called from AWS IoT Core. This function will refer to 
  # layer "DecoderLayer" to include the necessary decoding libraries 
  ############################################################################################

  TransformLoRaWANBinaryPayloadFunction:
    Type: AWS::Serverless::Function
    Name: !Sub '${AWS::StackName}-TransformLoRaWANBinaryPayloadFunction'
    Properties:
      CodeUri: src-iotrule-transformation
      Handler: app.lambda_handler
      Runtime: python3.7
      Layers:  
        - Ref:  LoRaWANPayloadDecoderLayer
      Environment:
        Variables:
          RETURN_RAW_DATA: True


  ############################################################################################
  # LAYERS
  ############################################################################################
  LoRaWANPayloadDecoderLayer:
    Type: AWS::Serverless::LayerVersion
    Properties:
      LayerName: !Sub '${AWS::StackName}-LoRaWANPayloadDecoderLayer'
      Description: Payload decoders for LoRaWAN devices
      ContentUri: src-payload-decoders
      CompatibleRuntimes:
        - python3.8
      RetentionPolicy: Retain
  
  ############################################################################################
  # This IoT Rule converts a binary message to a JSON message using a payload decoder, and then 
  # republishes the JSON message.
  # After transformation, the rule will republish the JSON payload to:
  # dt/lorawantransformed
  ############################################################################################
  
  TransformLoRaWANBinaryPayloadRule:
    Type: "AWS::IoT::TopicRule"
    Properties:
      RuleName: !Sub '${AWS::StackName}_TransformLoRaWANBinaryPayloadFor_${ParamBinaryDecoderName}'
      TopicRulePayload:
        AwsIotSqlVersion: "2016-03-23"
        RuleDisabled: false

        Sql:
            !Sub 
              - |
                SELECT aws_lambda("${LambdaARN}",
                                  {"PayloadDecoderName": "${ParamBinaryDecoderName}", 
                                  "PayloadData":PayloadData, 
                                  "WirelessDeviceId": DeviceId, 
                                   "WirelessMetadata": WirelessMetadata}) as transformed_payload, 
                        WirelessDeviceId as transformed_payload.WirelessDeviceId,                                   
                        WirelessMetadata.LoRaWAN.DevEui as transformed_payload.DevEui,
                        WirelessDeviceId as lns_payload.WirelessDeviceId, 
                        WirelessMetadata as lns_payload.WirelessMetadata,
                        PayloadData as lns_payload.PayloadData,
                        timestamp() as timestamp
              - { LambdaARN: !GetAtt TransformLoRaWANBinaryPayloadFunction.Arn}            
        Actions:
            - Republish:
                RoleArn: !GetAtt TransformLoRaWANBinaryPayloadRuleActionRole.Arn
                Topic:
                  !Join [
                    "",
                    [
                      !Ref TopicOutgoingTransformedMessages
                    ],
                  ]
                Qos: 0
        ErrorAction:
            Republish:
              RoleArn: !GetAtt TransformLoRaWANBinaryPayloadRuleActionRole.Arn
              Topic: !Ref TopicOutgoingErrors
              Qos: 0

  TransformLoRaWANBinaryPayloadFunctionPermission:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !GetAtt TransformLoRaWANBinaryPayloadFunction.Arn
      Action: lambda:InvokeFunction
      Principal: iot.amazonaws.com

  TransformLoRaWANBinaryPayloadRuleActionRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - iot.amazonaws.com
            Action:
              - "sts:AssumeRole"
      Policies:
        - PolicyName: root
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action: iot:Publish
                Resource:
                  !Join [
                    "",
                    [
                      "arn:aws:iot:",
                      !Ref "AWS::Region",
                      ":",
                      !Ref "AWS::AccountId",
                      ":topic/*",
                    ],
                  ]

Outputs:
  IoTRuleName:
    Description: "Please add this AWS IoT Rule name as a Destination to AWS IoT LoRaWAN Core"
    Value: !Ref TransformLoRaWANBinaryPayloadRule

  TransformPayloadFunctionFunction:
    Description: "Lambda Function ARN"
    Value: !GetAtt TransformLoRaWANBinaryPayloadFunction.Arn
  TransformPayloadFunctionIamRole:
    Description: "Implicit IAM Role created for Lambda function"
    Value: !GetAtt TransformLoRaWANBinaryPayloadRuleActionRole.Arn
  DecoderLayerARN:
    Value: !Ref LoRaWANPayloadDecoderLayer
    Description: "ARN of payload decoder layer "