/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2013-2016 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "introspection/name.hpp"
#include "introspection/enum_manual.hpp"
#include "iterator/infix.hpp"

#include <exception>
#include <functional>
#include <memory>
#include <string>
#include <vector>
#include <map>
#include <sstream>


///////////////////////////////////////////////////////////////////////////////
namespace cruft::cmdopt {
    ///////////////////////////////////////////////////////////////////////////
    class error : public std::exception { };

    //-------------------------------------------------------------------------
    class invalid_key : public error {
    public:
        explicit invalid_key (std::string _key);
        const char* what (void) const noexcept override;

    private:
        const std::string m_key;
    };

    //-------------------------------------------------------------------------
    class invalid_value : public error {
    public:
        explicit invalid_value (std::string _value);
        const char* what (void) const noexcept override;

    private:
        const std::string m_value;
    };

    //-------------------------------------------------------------------------
    class invalid_null : public error {
    public:
        const char* what (void) const noexcept override;
    };

    //-------------------------------------------------------------------------
    class invalid_required : public error {
    public:
        const char* what (void) const noexcept override;
    };

    //-------------------------------------------------------------------------
    class unhandled_argument : public error {
    public:
        explicit unhandled_argument (int index);
        const char* what (void) const noexcept override;

        int index (void) const noexcept;

    private:
        const int m_index;
    };

    namespace option { class base; }


    ///////////////////////////////////////////////////////////////////////////
    namespace option {
        class base {
        public:
            base ();

            // we deal almost exclusively with vtables, so disable copying
            // just in case we do something stupid.
            base (const base&) = delete;
            base& operator= (const base&) = delete;

            virtual ~base ();

            virtual void execute (void);
            virtual void execute (const char *restrict);
            virtual void start   (void);
            virtual void finish  (void);

            virtual const std::string& example (void) const = 0;

            /// Sets a callback query to determine if the option is required.
            ///
            /// The default is `return false;`
            void required (std::function<bool(void)>);
            /// Sets a constant value function for the required query.
            /// The value provided will be unconditionally returned.
            void required (bool);
            /// Tests if the option is required by invoking the stored query.
            bool required (void) const;

            /// Tests if the option has been seen.
            ///
            /// Not to be confused with `fulfilled` which describes whether
            /// the `seen` and `required` constraints are both satisfied.
            bool seen (void) const;
            /// Sets the seen flag of the option to the value provided.
            bool seen (bool);

            /// Tests if all `required` and `seen` constraints have been
            /// satisfied.
            ///
            /// If there are no `required` constraints it return true.
            bool fulfilled (void) const;

        private:
            std::function<bool(void)> m_required;
            bool m_seen = false;
        };


        class null : public base {
        public:
            virtual void execute (void) override;
            virtual void execute (const char *restrict) override;

            virtual const std::string& example (void) const override;
        };


        class present : public base {
        public:
            explicit present (bool&);
            explicit present (bool&&) = delete;

            using base::execute;
            virtual void execute (void) override;

            virtual const std::string& example (void) const override;

            virtual void finish (void) override;

        private:
            bool &m_data;
        };


        namespace detail {
            template <typename T>
            std::enable_if_t<!std::is_enum<T>::value, const std::string&>
            value_example (void)
            {
                static const std::string EXAMPLE =
                    std::string {"<"} +
                    std::string {cruft::introspection::name::bare<T> ()} +
                    std::string {">"};

                return EXAMPLE;
            }

            template <typename T>
            std::enable_if_t<std::is_enum<T>::value, const std::string&>
            value_example (void)
            {
                static const std::string EXAMPLE = [] (void) {
                    std::ostringstream os;
                    std::copy (std::cbegin (introspection::enum_traits<T>::names),
                               std::cend   (introspection::enum_traits<T>::names),
                               iterator::infix_iterator<const char*> (os, "|"));
                    return os.str ();
                } ();
                return EXAMPLE;
            }
        }


        template <typename T>
        class value : public base {
        public:
            explicit value (T &_data): m_data (_data) { }
            explicit value (T&&) = delete;

            using base::execute;

            void execute (const char *restrict str) override
            {
                try {
                    std::istringstream is (str);
                    is.exceptions (
                        std::istringstream::failbit
                        | std::istringstream::badbit
                    );

                    is >> m_data;
                } catch (...) {
                    throw invalid_value (__func__);
                }

                seen (true);
            }


            /// Returns a callback that tests if this option has been set to
            /// a specified value.
            ///
            /// If the option has not been seen it is treated as
            /// unconditionally not equal.
            ///
            /// The returned function is handy to use in the `required`
            /// clauses of dependent options.
            template <typename TargetT>
            std::function<bool(void)>
            is (TargetT &&_target)&
            {
                return [&, target = std::forward<TargetT>(_target)] (void) {
                    return seen () && m_data == target;
                };
            }

            const std::string& example (void) const override
            {
                return detail::value_example<T> ();
            }

            const T& data (void) const&
            {
                return m_data;
            }


            T& data (void) &
            {
                return m_data;
            }


            T& data (T _data) &
            {
                return m_data = _data;
            }

        private:
            T& m_data;
        };

        template <>
        inline void
        value<bool>::execute (const char *restrict str)
        {
            static const std::string TRUE_STRING[] = {
                "true",
                "yes",
                "y",
                "1"
            };

            if (std::any_of (std::begin (TRUE_STRING),
                             std::end (TRUE_STRING),
                             [str] (auto i) { return i == str; }))
            {
                m_data = true;
                return;
            }

            static const std::string FALSE_STRING[] = {
                "false",
                "no",
                "n",
                "0"
            };

            if (std::any_of (std::begin (FALSE_STRING),
                             std::end (FALSE_STRING),
                             [str] (auto i) { return i == str; }))
            {
                m_data = false;
                return;
            }

            base::execute (str);
            seen (true);
        }



        template <typename T = unsigned>
        class count : public value<T> {
        public:
            explicit count (T&);
            explicit count (T&&) = delete;

            using value<T>::execute;
            void execute (void) override;
        };


        class bytes : public value<size_t> {
        public:
            explicit bytes (size_t &_value): value (_value) { }

            using value<size_t>::execute;
            void execute (const char *restrict) override;
        };
    }


    //-------------------------------------------------------------------------
    class parser {
    public:
        template <typename T, typename ...Args>
        T& add (char shortname,
                std::string const &longname,
                std::string const &description,
                Args&&... args)
        {
            auto handler = std::make_unique<T> (std::forward<Args> (args)...);
            T& ref = *handler;

            m_short.insert({ shortname, ref });
            m_long.insert({ longname,  ref });

            m_options.push_back ({ description, std::move (handler) });

            return ref;
        }

        template <typename T, typename ...Args>
        T&
        append (std::string const &description, Args&&...args)
        {
            auto handler = std::make_unique<T> (std::forward<Args> (args)...);
            auto &ref = *handler;
            m_positional.push_back (ref);
            m_options.push_back ({ description, std::move (handler) });
            return ref;
        }

        int scan (int argc, const char *const *argv);

    private:
        int parse_long  (int pos, int argc, const char *const *argv);
        int parse_short (int pos, int argc, const char *const *argv);

        void print_help [[noreturn]] (int argc, const char *const *argv) const;

        std::map<char,std::reference_wrapper<option::base>> m_short;
        std::map<std::string,std::reference_wrapper<option::base>> m_long;

        std::vector<std::reference_wrapper<option::base>> m_positional;

        struct entry {
            std::string description;
            std::unique_ptr<option::base> handler;
        };

        std::vector<entry> m_options;
    };
}