/*
 * 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 https://mozilla.org/MPL/2.0/.
 */
module;

#include <variant>
#include <string>
#include <stdexcept>
#include <algorithm>
#include <cstring>

#include <boost/program_options.hpp>

export module katja.command_line;

namespace katja
{
    export enum class command
    {
        updates,
        search,
        help
    };

    export struct command_line
    {
        const command type;
        const std::vector<std::string> arguments;
    };

    export struct search_command
    {
        const std::string needle;
    };

    export struct updates_command
    {
    };

    export struct help_command
    {
    };

    export using subcommand = std::variant<
        search_command,
        updates_command,
        help_command
    >;

    export class invalid_command_error : public std::runtime_error
    {
        const std::string command;

    public:
        invalid_command_error()
            : std::runtime_error("Expecting the command line to begin with a command.")
        {
        }

        explicit invalid_command_error(const std::string& invalid_command)
            : command{ invalid_command },
            std::runtime_error("Unknown command given on the command line.")
        {
        }
    };

    export class command_line_error : public std::runtime_error
    {
        boost::program_options::options_description description;

    public:
        command_line_error(const std::string& message,
                boost::program_options::options_description&& description)
            : description(std::move(description)),
            std::runtime_error(message)
        {
        }
    };

    export command_line parse_command_line(int argc, const char **argv)
    {
        if (argc == 1)
        {
            throw invalid_command_error();
        }
        std::vector<std::string> arguments;
        std::copy(argv + 2, argv + argc, std::back_inserter(arguments));

        if (strcmp("updates", argv[1]) == 0)
        {
            return command_line{ command::updates, std::move(arguments) };
        }
        if (strcmp("search", argv[1]) == 0)
        {
            return command_line{ command::search, std::move(arguments) };
        }
        if (strcmp("help", argv[1]) == 0)
        {
            return command_line{ command::help, std::move(arguments) };
        }
        throw invalid_command_error(argv[1]);
    }

    search_command parse_search_command(const std::vector<std::string>& arguments)
    {
        boost::program_options::options_description search_description("Search packages");
        search_description
            .add_options()("name", "Find packages by name");

        boost::program_options::positional_options_description positional_arguments;
        positional_arguments.add("name", 1);

        boost::program_options::variables_map option_map;
        auto command_parser = boost::program_options::command_line_parser(arguments)
            .options(search_description).positional(positional_arguments);
        boost::program_options::store(command_parser.run(), option_map);
        boost::program_options::notify(option_map);

        if (!option_map.count("name"))
        {
            throw command_line_error("Search string wasn't specified.",
                    std::move(search_description));
        }
        return search_command{ option_map["name"].as<std::string>() };
    }

    export subcommand parse_subcommand(const command_line& subcommand_line)
    {
        switch (subcommand_line.type)
        {
        case command::updates:
            return updates_command();
        case command::search:
            return parse_search_command(subcommand_line.arguments);
        case command::help:
            return help_command();
        default:
            std::unreachable();
        }
    }
}