-module(gchess).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([perft/2, main/0]).

-spec perft(gleam@erlang@process:subject(game_server:message()), integer()) -> integer().
perft(Game_server_subject, Depth) ->
    case Depth of
        0 ->
            1;

        _ ->
            Moves = game_server:all_legal_moves(Game_server_subject),
            Nodes@2 = gleam@list:fold(
                Moves,
                0,
                fun(Nodes, Move) ->
                    _assert_subject = game_server:apply_move_raw(
                        Game_server_subject,
                        Move
                    ),
                    {ok, _} = case _assert_subject of
                        {ok, _} -> _assert_subject;
                        _assert_fail ->
                            erlang:error(#{gleam_error => let_assert,
                                        message => <<"Assertion pattern match failed"/utf8>>,
                                        value => _assert_fail,
                                        module => <<"gchess"/utf8>>,
                                        function => <<"perft"/utf8>>,
                                        line => 34})
                    end,
                    Nodes@1 = Nodes + perft(Game_server_subject, Depth - 1),
                    _assert_subject@1 = game_server:undo_move(
                        Game_server_subject
                    ),
                    {ok, _} = case _assert_subject@1 of
                        {ok, _} -> _assert_subject@1;
                        _assert_fail@1 ->
                            erlang:error(#{gleam_error => let_assert,
                                        message => <<"Assertion pattern match failed"/utf8>>,
                                        value => _assert_fail@1,
                                        module => <<"gchess"/utf8>>,
                                        function => <<"perft"/utf8>>,
                                        line => 38})
                    end,
                    Nodes@1
                end
            ),
            Nodes@2
    end.

-spec main() -> {ok, nil} | {error, gleam@otp@actor:start_error()}.
main() ->
    gleam@result:'try'(
        game_server:new_server(),
        fun(Server) ->
            _assert_subject = game_server:new_game_from_fen(
                Server,
                <<"8/3k4/8/2BKB3/2PRP3/8/8/8 w - - 0 1"/utf8>>
            ),
            {ok, _} = case _assert_subject of
                {ok, _} -> _assert_subject;
                _assert_fail ->
                    erlang:error(#{gleam_error => let_assert,
                                message => <<"Assertion pattern match failed"/utf8>>,
                                value => _assert_fail,
                                module => <<"gchess"/utf8>>,
                                function => <<"main"/utf8>>,
                                line => 10})
            end,
            _assert_subject@1 = game_server:disable_status(Server),
            {ok, _} = case _assert_subject@1 of
                {ok, _} -> _assert_subject@1;
                _assert_fail@1 ->
                    erlang:error(#{gleam_error => let_assert,
                                message => <<"Assertion pattern match failed"/utf8>>,
                                value => _assert_fail@1,
                                module => <<"gchess"/utf8>>,
                                function => <<"main"/utf8>>,
                                line => 12})
            end,
            Start = os:system_time(second),
            Perft_result = perft(Server, 2),
            End = os:system_time(second),
            gleam@io:print(<<"Perft result: "/utf8>>),
            gleam@io:print(gleam@int:to_string(Perft_result)),
            gleam@io:print(<<"\n"/utf8>>),
            gleam@io:print(<<"Time: "/utf8>>),
            gleam@io:print(gleam@int:to_string(End - Start)),
            gleam@io:print(<<" seconds"/utf8>>),
            gleam@io:print(<<"\n"/utf8>>),
            {ok, nil}
        end
    ).