/*
 * This file is part of smolbote. It's copyrighted by the contributors recorded
 * in the version control history of the file, available from its original
 * location: https://neueland.iserlohn-fortress.net/gitea/aqua/smolbote
 *
 * SPDX-License-Identifier: GPL-3.0
 */

#ifndef SMOLBOTE_CONFIGURATION_H
#define SMOLBOTE_CONFIGURATION_H

#include <initializer_list>
#include <memory>
#include <optional>
#include <source_location>
#include <spdlog/spdlog.h>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <variant>

using conf_value_t = std::variant<std::string, int, bool>;

template <typename T>
concept concept_value_t = std::is_arithmetic_v<T> || std::is_same_v<T, bool> || std::is_constructible_v<T, std::string>;

class Configuration : private std::unordered_map<std::string, conf_value_t>
{
    friend std::ostream &operator<<(std::ostream &out, const Configuration &obj);

public:
    using kv_pair = std::pair<std::string, conf_value_t>;

    Configuration();
    Configuration(std::initializer_list<std::pair<std::string, conf_value_t>> p_list) noexcept;

    Configuration(const Configuration &) = delete;
    Configuration &operator=(const Configuration &) = delete;

    Configuration(Configuration &&other) = default;
    Configuration &operator=(Configuration &&) = delete;

    ~Configuration() = default;

    bool read_file(const std::string &location);
    void read(std::basic_istream<char> &input);

    template <typename T>
    [[nodiscard]] std::optional<T> value(const char *path, const std::source_location location = std::source_location::current()) const
    {
        if(use_global) {
            return instance()->value<T>(path, location);
        }

        if(count(path) == 0) {
            return std::nullopt;
        }

        return std::get<T>(at(path));
    }

    template <concept_value_t T>
    [[nodiscard]] std::optional<T> value(const char *p_path, const std::source_location location = std::source_location::current()) const
    {
        if(use_global) {
            return instance()->value<T>(p_path, location);
        }

        if(this->count(p_path) == 0) {
            spdlog::warn("requested non-existent configuration value {} at {}:{}", p_path, location.file_name(), location.line());
            return std::nullopt;
        }

        // path is guaranteed to exist
        const auto value = at(p_path);

        if(std::holds_alternative<int>(value)) {
            if constexpr(std::is_arithmetic<T>::value) {
                return static_cast<T>(std::get<int>(value));
            } else if constexpr(std::is_constructible<T, std::string>::value) {
                return T{ std::to_string(std::get<int>(value)) };
            }

        } else if(std::holds_alternative<bool>(value)) {
            if constexpr(std::is_constructible_v<T, bool> || std::is_same_v<T, bool>) {
                return std::get<bool>(value);
            } else if constexpr(std::is_arithmetic_v<T>) {
                return static_cast<T>(std::get<bool>(value));
            } else if constexpr(std::is_constructible_v<T, const char *>) {
                return std::get<bool>(value) ? T{ "true" } : T{ "false" };
            }

        } else if(std::holds_alternative<std::string>(value)) {
            auto str = std::get<std::string>(value);

            try {
                if constexpr(std::is_same_v<T, bool>) {
                    return (str == "true");
                } else if constexpr(std::is_floating_point<T>::value) {
                    return static_cast<T>(std::stod(str));
                } else if constexpr(std::is_arithmetic<T>::value) {
                    return static_cast<T>(std::stol(str));
                }
            } catch(std::invalid_argument &) {
                return std::nullopt;
            }

            if(str.front() == '~') {
                str.replace(0, 1, m_homePath);
            }

            if constexpr(std::is_constructible<T, std::string>::value) {
                return T{ str };
            }
        }

        return std::nullopt;
    }

    template <typename T>
    T &shortcut(T & /* unused */, const char * /* unused */, const std::source_location location = std::source_location::current()) const
    {
        return T{};
    }

    static std::string init_global(const std::string &p_path);
    static void move_global(std::unique_ptr<Configuration> && conf);

protected:
    void insert_or_assign(const kv_pair &pair);

private:
    static Configuration *instance();

    const std::string m_homePath;
    const bool use_global = false;
};

#ifndef NO_QT_SPEC
#include "qt_specialization.h"
#endif

std::ostream &operator<<(std::ostream &out, const Configuration &obj);

#endif // SMOLBOTE_CONFIGURATION_H