argh.h

#pragma once

#include <algorithm>
#include <sstream>
#include <limits>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <cassert>

namespace argh
{
    // Terminology:
    // A command line is composed of 2 types of args:
    // 1. Positional args, i.e. free standing values
    // 2. Options: args beginning with '-'. We identify two kinds:
    //    2.1: Flags: boolean options =>  (exist ? true : false)
    //    2.2: Parameters: a name followed by a non-option value

#if !defined(__GNUC__) || (__GNUC__ >= 5)
    using string_stream = std::istringstream;
#else
    // Until GCC 5, istringstream did not have a move constructor.
    // stringstream_proxy is used instead, as a workaround.
    class stringstream_proxy
    {
    public:
        stringstream_proxy() = default;

        // Construct with a value.
        stringstream_proxy(std::string const& value) :
            stream_(value)
        {}

        // Copy constructor.
        stringstream_proxy(const stringstream_proxy& other) :
            stream_(other.stream_.str())
        {
            stream_.setstate(other.stream_.rdstate());
        }

        void setstate(std::ios_base::iostate state) { stream_.setstate(state); }

        // Stream out the value of the parameter.
        // If the conversion was not possible, the stream will enter the fail state,
        // and operator bool will return false.
        template<typename T>
        stringstream_proxy& operator >> (T& thing)
        {
            stream_ >> thing;
            return *this;
        }


        // Get the string value.
        std::string str() const { return stream_.str(); }

        std::stringbuf* rdbuf() const { return stream_.rdbuf(); }

        // Check the state of the stream.
        // False when the most recent stream operation failed
        explicit operator bool() const { return !!stream_; }

        ~stringstream_proxy() = default;
    private:
        std::istringstream stream_;
    };
    using string_stream = stringstream_proxy;
#endif

    class multimap_iteration_wrapper
    {
    public:
        using container_t = std::multimap<std::string, std::string>;
        using iterator_t = container_t::const_iterator;
        using difference_t = container_t::difference_type;
        explicit multimap_iteration_wrapper(const iterator_t& lb, const iterator_t& ub)
            : lb_(lb)
            , ub_(ub)
        {}

        iterator_t begin() const { return lb_; }
        iterator_t end() const { return ub_; }
        difference_t size() const { return std::distance(lb_, ub_); }

    private:
        iterator_t lb_;
        iterator_t ub_;
    };

    class parser
    {
    public:
        enum Mode {
            PREFER_FLAG_FOR_UNREG_OPTION = 1 << 0,
            PREFER_PARAM_FOR_UNREG_OPTION = 1 << 1,
            NO_SPLIT_ON_EQUALSIGN = 1 << 2,
            SINGLE_DASH_IS_MULTIFLAG = 1 << 3,
        };

        parser() = default;

        parser(std::initializer_list<char const* const> pre_reg_names)
        {
            add_params(pre_reg_names);
        }

        void add_param(std::string const& name);
        void add_params(std::initializer_list<char const* const> init_list);

        void parse(std::vector<std::string> args, int mode = PREFER_FLAG_FOR_UNREG_OPTION);

        std::multiset<std::string>               const& flags()    const { return flags_; }
        std::multimap<std::string, std::string>  const& params()   const { return params_; }
        multimap_iteration_wrapper                      params(std::string const& name) const;
        std::vector<std::string>                 const& pos_args() const { return pos_args_; }

        // begin() and end() for using range-for over positional args.
        std::vector<std::string>::const_iterator begin() const { return pos_args_.cbegin(); }
        std::vector<std::string>::const_iterator end()   const { return pos_args_.cend(); }
        size_t size()                                    const { return pos_args_.size(); }

        //////////////////////////////////////////////////////////////////////////
        // Accessors

        // flag (boolean) accessors: return true if the flag appeared, otherwise false.
        bool operator[](std::string const& name) const;

        // multiple flag (boolean) accessors: return true if at least one of the flag appeared, otherwise false.
        bool operator[](std::initializer_list<char const* const> init_list) const;

        // returns positional arg string by order. Like argv[] but without the options
        std::string const& operator[](size_t ind) const;

        // returns a std::istream that can be used to convert a positional arg to a typed value.
        string_stream operator()(size_t ind) const;

        // same as above, but with a default value in case the arg is missing (index out of range).
        template<typename T>
        string_stream operator()(size_t ind, T&& def_val) const;

        // parameter accessors, give a name get an std::istream that can be used to convert to a typed value.
        // call .str() on result to get as string
        string_stream operator()(std::string const& name) const;

        // accessor for a parameter with multiple names, give a list of names, get an std::istream that can be used to convert to a typed value.
        // call .str() on result to get as string
        // returns the first value in the list to be found.
        string_stream operator()(std::initializer_list<char const* const> init_list) const;

        // same as above, but with a default value in case the param was missing.
        // Non-string def_val types must have an operator<<() (output stream operator)
        // If T only has an input stream operator, pass the string version of the type as in "3" instead of 3.
        template<typename T>
        string_stream operator()(std::string const& name, T&& def_val) const;

        // same as above but for a list of names. returns the first value to be found.
        template<typename T>
        string_stream operator()(std::initializer_list<char const* const> init_list, T&& def_val) const;

    private:
        string_stream bad_stream() const;
        std::string trim_leading_dashes(std::string const& name) const;
        bool is_number(std::string const& arg) const;
        bool is_option(std::string const& arg) const;
        bool got_flag(std::string const& name) const;
        bool is_param(std::string const& name) const;

    private:
        std::vector<std::string> args_;
        std::multimap<std::string, std::string> params_;
        std::vector<std::string> pos_args_;
        std::multiset<std::string> flags_;
        std::set<std::string> registeredParams_;
        std::string empty_;
    };


    //////////////////////////////////////////////////////////////////////////

    inline void parser::parse(std::vector<std::string> args, int mode /*= PREFER_FLAG_FOR_UNREG_OPTION*/)
    {
        // clear out possible previous parsing remnants
        flags_.clear();
        params_.clear();
        pos_args_.clear();
        args_ = args;

        // parse line
        for (auto i = 0u; i < args_.size(); ++i)
        {
            if (!is_option(args_[i]))
            {
                pos_args_.emplace_back(args_[i]);
                continue;
            }

            auto name = trim_leading_dashes(args_[i]);

            if (!(mode & NO_SPLIT_ON_EQUALSIGN))
            {
                auto equalPos = name.find('=');
                if (equalPos != std::string::npos)
                {
                    params_.insert({ name.substr(0, equalPos), name.substr(equalPos + 1) });
                    continue;
                }
            }

            // if the option is unregistered and should be a multi-flag
            if (1 == (args_[i].size() - name.size()) &&         // single dash
                argh::parser::SINGLE_DASH_IS_MULTIFLAG & mode && // multi-flag mode
                !is_param(name))                                  // unregistered
            {
                std::string keep_param;

                if (!name.empty() && is_param(std::string(1ul, name.back()))) // last char is param
                {
                    keep_param += name.back();
                    name.resize(name.size() - 1);
                }

                for (auto const& c : name)
                {
                    flags_.emplace(std::string{ c });
                }

                if (!keep_param.empty())
                {
                    name = keep_param;
                }
                else
                {
                    continue; // do not consider other options for this arg
                }
            }

            // any potential option will get as its value the next arg, unless that arg is an option too
            // in that case it will be determined a flag.
            if (i == args_.size() - 1 || is_option(args_[i + 1]))
            {
                flags_.emplace(name);
                continue;
            }

            // if 'name' is a pre-registered option, then the next arg cannot be a free parameter to it is skipped
            // otherwise we have 2 modes:
            // PREFER_FLAG_FOR_UNREG_OPTION: a non-registered 'name' is determined a flag.
            //                               The following value (the next arg) will be a free parameter.
            //
            // PREFER_PARAM_FOR_UNREG_OPTION: a non-registered 'name' is determined a parameter, the next arg
            //                                will be the value of that option.

            assert(!(mode & argh::parser::PREFER_FLAG_FOR_UNREG_OPTION)
                || !(mode & argh::parser::PREFER_PARAM_FOR_UNREG_OPTION));

            bool preferParam = mode & argh::parser::PREFER_PARAM_FOR_UNREG_OPTION;

            if (is_param(name) || preferParam)
            {
                params_.insert({ name, args_[i + 1] });
                ++i; // skip next value, it is not a free parameter
                continue;
            }
            else
            {
                flags_.emplace(name);
            }
        }
    }

    //////////////////////////////////////////////////////////////////////////

    inline string_stream parser::bad_stream() const
    {
        string_stream bad;
        bad.setstate(std::ios_base::failbit);
        return bad;
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool parser::is_number(std::string const& arg) const
    {
        // inefficient but simple way to determine if a string is a number (which can start with a '-')
        std::istringstream istr(arg);
        double number;
        istr >> number;
        return !(istr.fail() || istr.bad());
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool parser::is_option(std::string const& arg) const
    {
        assert(0 != arg.size());
        if (is_number(arg))
            return false;
        return '-' == arg[0];
    }

    //////////////////////////////////////////////////////////////////////////

    inline std::string parser::trim_leading_dashes(std::string const& name) const
    {
        auto pos = name.find_first_not_of('-');
        return std::string::npos != pos ? name.substr(pos) : name;
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool argh::parser::got_flag(std::string const& name) const
    {
        return flags_.end() != flags_.find(trim_leading_dashes(name));
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool argh::parser::is_param(std::string const& name) const
    {
        return registeredParams_.count(name);
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool parser::operator[](std::string const& name) const
    {
        return got_flag(name);
    }

    //////////////////////////////////////////////////////////////////////////

    inline bool parser::operator[](std::initializer_list<char const* const> init_list) const
    {
        return std::any_of(init_list.begin(), init_list.end(), [&](char const* const name) { return got_flag(name); });
    }

    //////////////////////////////////////////////////////////////////////////

    inline std::string const& parser::operator[](size_t ind) const
    {
        if (ind < pos_args_.size())
            return pos_args_[ind];
        return empty_;
    }

    //////////////////////////////////////////////////////////////////////////

    inline string_stream parser::operator()(std::string const& name) const
    {
        auto optIt = params_.find(trim_leading_dashes(name));
        if (params_.end() != optIt)
            return string_stream(optIt->second);
        return bad_stream();
    }

    //////////////////////////////////////////////////////////////////////////

    inline string_stream parser::operator()(std::initializer_list<char const* const> init_list) const
    {
        for (auto& name : init_list)
        {
            auto optIt = params_.find(trim_leading_dashes(name));
            if (params_.end() != optIt)
                return string_stream(optIt->second);
        }
        return bad_stream();
    }

    //////////////////////////////////////////////////////////////////////////

    template<typename T>
    string_stream parser::operator()(std::string const& name, T&& def_val) const
    {
        auto optIt = params_.find(trim_leading_dashes(name));
        if (params_.end() != optIt)
            return string_stream(optIt->second);

        std::ostringstream ostr;
        ostr.precision(std::numeric_limits<long double>::max_digits10);
        ostr << def_val;
        return string_stream(ostr.str()); // use default
    }

    //////////////////////////////////////////////////////////////////////////

    // same as above but for a list of names. returns the first value to be found.
    template<typename T>
    string_stream parser::operator()(std::initializer_list<char const* const> init_list, T&& def_val) const
    {
        for (auto& name : init_list)
        {
            auto optIt = params_.find(trim_leading_dashes(name));
            if (params_.end() != optIt)
                return string_stream(optIt->second);
        }
        std::ostringstream ostr;
        ostr.precision(std::numeric_limits<long double>::max_digits10);
        ostr << def_val;
        return string_stream(ostr.str()); // use default
    }

    //////////////////////////////////////////////////////////////////////////

    inline string_stream parser::operator()(size_t ind) const
    {
        if (pos_args_.size() <= ind)
            return bad_stream();

        return string_stream(pos_args_[ind]);
    }

    //////////////////////////////////////////////////////////////////////////

    template<typename T>
    string_stream parser::operator()(size_t ind, T&& def_val) const
    {
        if (pos_args_.size() <= ind)
        {
            std::ostringstream ostr;
            ostr.precision(std::numeric_limits<long double>::max_digits10);
            ostr << def_val;
            return string_stream(ostr.str());
        }

        return string_stream(pos_args_[ind]);
    }

    //////////////////////////////////////////////////////////////////////////

    inline void parser::add_param(std::string const& name)
    {
        registeredParams_.insert(trim_leading_dashes(name));
    }

    //////////////////////////////////////////////////////////////////////////

    inline void parser::add_params(std::initializer_list<char const* const> init_list)
    {
        for (auto& name : init_list)
            registeredParams_.insert(trim_leading_dashes(name));
    }

    //////////////////////////////////////////////////////////////////////////

    inline multimap_iteration_wrapper parser::params(std::string const& name) const
    {
        auto trimmed_name = trim_leading_dashes(name);
        return multimap_iteration_wrapper(params_.lower_bound(trimmed_name), params_.upper_bound(trimmed_name));
    }
}