#pragma once

#include <algorithm>
#include <sstream>
#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
    operator bool() const { return !!stream_; }

    ~stringstream_proxy() = default;

private:
    std::istringstream stream_;
};
using string_stream = stringstream_proxy;
#endif

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); }

    parser(const char* const argv[], int mode = PREFER_FLAG_FOR_UNREG_OPTION) { parse(argv, mode); }

    parser(int argc, const char* const argv[], int mode = PREFER_FLAG_FOR_UNREG_OPTION) { parse(argc, argv, mode); }

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

    void parse(const char* const argv[], int mode = PREFER_FLAG_FOR_UNREG_OPTION);
    void parse(int argc, const char* const argv[], int mode = PREFER_FLAG_FOR_UNREG_OPTION);

    std::multiset<std::string> const& flags() const { return flags_; }
    std::map<std::string, std::string> const& params() const { return params_; }
    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::map<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(const char* const argv[], int mode)
{
    int argc = 0;
    for(auto argvp = argv; *argvp; ++argc, ++argvp)
        ;
    parse(argc, argv, mode);
}

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

inline void parser::parse(int argc, const char* const argv[], int mode /*= PREFER_FLAG_FOR_UNREG_OPTION*/)
{
    // convert to strings
    args_.resize(argc);
    std::transform(argv, argv + argc, args_.begin(), [](const char* const arg) { return arg; });

    // 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 << 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 << 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 << 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));
}
}
