-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) ->
                    game_server:apply_move_raw(Game_server_subject, Move),
                    Nodes@1 = Nodes + perft(Game_server_subject, Depth - 1),
                    game_server:undo_move(Game_server_subject),
                    Nodes@1
                end
            ),
            Nodes@2
    end.

-spec main() -> nil.
main() ->
    Server = game_server:new_server(),
    game_server:new_game_from_fen(
        Server,
        <<"r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1"/utf8>>
    ),
    game_server:disable_status(Server),
    Start = os:system_time(second),
    Perft_result = perft(Server, 3),
    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>>).