%% Copyright (c) 2019-2022, Sergei Semichev <chessvegas@chessvegas.com>. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%    http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.

-module(binbo_uci_protocol).

-export([command_spec_uci/0, command_spec_bestmove/2]).
-export([simple_prefix_handler/3]).
-export([bestmove_prefix_handler/3]).
-export([default_handler/1]).
-export([bestmove_search_time/1]).

%%%------------------------------------------------------------------------------
%%%   Macros
%%%------------------------------------------------------------------------------

-define(DEFAULT_UCI_MOVETIME, 1000).

%%%------------------------------------------------------------------------------
%%%   Types
%%%------------------------------------------------------------------------------

-type bestmove_opt_key() :: depth | wtime | btime | winc | binc | movestogo | nodes | movetime.
-type bestmove_opts() :: #{
    depth       => pos_integer(),       % depth <x> (search x plies only)
    wtime       => non_neg_integer(),   % wtime <x> (white has x msec left on the clock)
    btime       => non_neg_integer(),   % btime <x> (black has x msec left on the clock)
    winc        => pos_integer(),       % winc <x> (white increment per move in mseconds if x > 0)
    binc        => pos_integer(),       % binc <x> (black increment per move in mseconds if x > 0)
    movestogo   => pos_integer(),       % movestogo <x> (there are x moves to the next time control, this will only be sent if x > 0, if you don't get this and get the wtime and btime it's sudden death)
    nodes       => pos_integer(),       % nodes <x> (search x nodes only)
    movetime    => pos_integer()        % movetime <x> (search exactly x mseconds)
}.
-type command_spec() :: {binary(), binary(), fun()}.

-export_type([command_spec/0]).
-export_type([bestmove_opts/0]).

%%%------------------------------------------------------------------------------
%%%   API
%%%------------------------------------------------------------------------------

%% command_spec_uci/0
-spec command_spec_uci() -> command_spec().
command_spec_uci() ->
    {<<"uci">>, <<"uciok">>, fun ?MODULE:simple_prefix_handler/3}.

%% command_spec_bestmove/1
-spec command_spec_bestmove(bestmove_opts(), pos_integer() | undefined) -> command_spec().
command_spec_bestmove(Opts, Movetime0) ->
    % The behaviour of searching best move changed since Stockfish 12.
    % We have to set 'movetime' option explicitly to avoid infinite search.
    Movetime = case is_integer(Movetime0) of
        true  -> Movetime0;
        false -> ?DEFAULT_UCI_MOVETIME
    end,
    Command = get_bestmove_cmd(Opts#{movetime => Movetime}),
    {Command, <<"bestmove ">>, fun ?MODULE:bestmove_prefix_handler/3}.

%% simple_prefix_handler/3
-spec simple_prefix_handler(binary(), binary(), pos_integer()) -> reply_ok | skip.
simple_prefix_handler(Data, Prefix, PrefixSize) ->
    Binaries = split_data(Data),
    case prefix_match_any(Binaries, Prefix, PrefixSize) of
        {match, _}   -> reply_ok;
        nomatch -> skip
    end.

%% simple_prefix_handler/3
-spec bestmove_prefix_handler(binary(), binary(), pos_integer()) -> {reply, binary()} | skip.
bestmove_prefix_handler(Data, Prefix, PrefixSize) ->
    Binaries = split_data(Data),
    case prefix_match_any(Binaries, Prefix, PrefixSize) of
        {match, B} -> {reply, parse_bestmove(B)};
        nomatch    -> skip
    end.

%% default_handler/1
-spec default_handler(binary()) -> ok.
default_handler(Data) ->
    _ = io:format("~n--- UCI LOG BEGIN ---~n~s--- UCI LOG END ---~n", [Data]),
    ok.

%% bestmove_search_time/2
-spec bestmove_search_time(bestmove_opts()) -> pos_integer() | undefined.
bestmove_search_time(Opts) ->
    case Opts of
        #{movetime := Movetime} when is_integer(Movetime) andalso (Movetime > 0) ->
            Movetime;
        _ ->
            undefined
    end.

%%%------------------------------------------------------------------------------
%%%   Internal functions
%%%------------------------------------------------------------------------------

%% prefix_match_any/3
-spec prefix_match_any([binary()], binary(), pos_integer()) -> {match, binary()} | nomatch.
prefix_match_any([], _, _) ->
    nomatch;
prefix_match_any([B|Tail], Prefix, PrefixSize) ->
    case B of
        <<Prefix:PrefixSize/binary, _/bits>> ->
            {match, B};
        <<_/bits>> ->
            prefix_match_any(Tail, Prefix, PrefixSize)
    end.

%% split_data/1
-spec split_data(binary()) -> [binary()].
split_data(Data) ->
    uef_bin:split(Data, <<"\n">>).

%% get_bestmove_cmd/1
-spec get_bestmove_cmd(bestmove_opts()) -> iodata().
get_bestmove_cmd(Opts) ->
    Keys = [depth, wtime, btime, winc, binc, movestogo, nodes, movetime],
    get_bestmove_cmd(<<"go">>, Opts, Keys).

%% get_bestmove_cmd/3
-spec get_bestmove_cmd(iodata(), bestmove_opts(), [bestmove_opt_key()]) -> iodata().
get_bestmove_cmd(Cmd, _, []) ->
    Cmd;
get_bestmove_cmd(Cmd, Opts, [Key|Tail]) ->
    Cmd2 = case Opts of
        #{Key := Val} -> [Cmd, $\s, to_iodata(Key), $\s, to_iodata(Val)];
        _ -> Cmd
    end,
    get_bestmove_cmd(Cmd2, Opts, Tail).

%% parse_bestmove/1
-spec parse_bestmove(binary()) -> binary().
parse_bestmove(B) ->
    [_, Move|_] = uef_bin:split(B, <<$\s>>),
    Move.

%% to_iodata/1
-spec to_iodata(list() | binary() | pos_integer() | atom()) -> list() | binary().
to_iodata(Arg) when is_list(Arg) -> Arg;
to_iodata(Arg) when is_binary(Arg) -> Arg;
to_iodata(Arg) when is_integer(Arg) -> erlang:integer_to_binary(Arg);
to_iodata(Arg) when is_atom(Arg) -> erlang:atom_to_binary(Arg, latin1).