// Player is X, CPU is O. Squares are numbered left-to-right, top-to-bottom.
// Graphical tic-tac-toe; the same strategy as TicTacToe.smp.
// Click an empty square or press 1-9. R/Space replays; Q/Escape quits.
// Pass any argument for a five-poll window smoke test.
val main = { u8[~][] args ->
    val screen = new sys.draw.Canvas(600,780);
    val board = new u8[9];
    _reset(board);
    if( sys.gfx.open("Simple tic-tac-toe",screen.width,screen.height) != sys.gfx.OK ) return 1;
    sys.audio.open(); // Audio is optional; failure leaves the game silent.
    _draw(screen,board,-1);
    int result = sys.gfx.present(screen.pixels);
    bool mouseHeld = false, keyHeld = false, replayHeld = false;
    int hover = -1, frames = 0;

    while( result == sys.gfx.OK ) {
        result = sys.gfx.wait(17);
        if( result != sys.gfx.OK ) break;
        if( sys.gfx.key('Q') ) break;
        bool down = sys.gfx.button(sys.gfx.LEFT);
        bool replay = sys.gfx.key('R') || sys.gfx.key(' ');
        int square = _square(sys.gfx.mouseX(),sys.gfx.mouseY());
        bool dirty = square != hover;
        hover = square;
        if( replay && !replayHeld ) { sys.audio.stop(); _reset(board); dirty = true; }
        bool digit = false;
        int choice = down && !mouseHeld ? square : -1;
        for( int i = 0; i < 9; i++ ) {
            int key = '1'+i;
            if( sys.gfx.key(key) ) {
                digit = true;
                if( !keyHeld ) choice = i;
            }
        }
        if( !(replay && !replayHeld) && _move(board,choice) ) {
            sys.audio.play(_sound(board));
            dirty = true;
        }
        mouseHeld = down;
        keyHeld = digit;
        replayHeld = replay;
        if( dirty ) {
            _draw(screen,board,hover);
            result = sys.gfx.present(screen.pixels);
        }
        if( args# > 1 && ++frames == 5 ) break;
    }
    sys.audio.close();
    sys.gfx.close();
    return result == sys.gfx.ERROR ? 1 : 0;
};

// Called only for an accepted move; invalid input never requests a sound.
val _sound = { u8[~] board ->
    int winner = _winner(board);
    return winner == 'X' ? sys.audio.WIN : winner == 'O' ? sys.audio.LOSE : sys.audio.BOOP;
};

val _reset = { u8[] board ->
    for( int i = 0; i < 9; i++ ) board[i] = ' ';
};
val _square = { int x, int y ->
    if( x < 48 || x >= 552 || y < 168 || y >= 672 ) return -1;
    return (y-168)/168*3+(x-48)/168;
};

// One player turn followed by one CPU turn. Invalid/finished moves do nothing.
val _move = { u8[] board, int square ->
    if( square < 0 || square >= 9 || board[square] != ' ' || _finished(board) ) return false;
    board[square] = 'X';
    if( !_finished(board) ) {
        int reply = _cpu(board);
        if( reply >= 0 ) board[reply] = 'O';
    }
    return true;
};

val _finished = { u8[~] board ->
    if( _winner(board) ) return true;
    for( int i = 0; i < 9; i++ ) if( board[i] == ' ' ) return false;
    return true;
};

val _winningLine = { u8[~] board ->
    for( int i = 0; i < 3; i++ ) {
        int row = i*3;
        if( board[row] != ' ' && board[row] == board[row+1] && board[row] == board[row+2] ) return i;
        if( board[i] != ' ' && board[i] == board[i+3] && board[i] == board[i+6] ) return 3+i;
    }
    if( board[4] != ' ' ) {
        if( board[0] == board[4] && board[4] == board[8] ) return 6;
        if( board[2] == board[4] && board[4] == board[6] ) return 7;
    }
    return -1;
};
// Return the winning mark, or zero.
val _winner = { u8[~] board ->
    int line = _winningLine(board);
    return line < 0 ? 0 : line < 3 ? board[line*3] : line < 6 ? board[line-3] : board[4];
};

// Try each empty square, restoring it before returning.
val _threat = { u8[] board, u8 mark ->
    for( int i = 0; i < 9; i++ )
        if( board[i] == ' ' ) {
            board[i] = mark;
            bool wins = _winner(board) == mark;
            board[i] = ' ';       // Restore board
            if( wins ) return i;
        }
    return -1;
};
// Win if possible, otherwise block, then prefer center, corners, and edges.
// Called only after _finished has ruled out a full board.
val _cpu = { u8[] board ->
    // If O can win, do so
    int win = _threat(board,'O');
    if( win >= 0 ) return win;
    // If X will win next move, block
    int block = _threat(board,'X');
    if( block >= 0 ) return block;
    // If center is open, take it
    if( board[4] == ' ' ) return 4;
    // If a corner is open, take it
    for( int i = 0; i < 9; i += 2 ) if( board[i] == ' ' ) return i;
    // Take whatever is available
    for( int i = 0; i < 9; i++ ) if( board[i] == ' ' ) return i;
    return -1;
};

val _draw = { !sys.draw.Canvas screen, u8[~] board, int hover ->
    u32 background = 0x142e36, paper = 0xf2eddf, ink = 0x35535a;
    u32 cross = 0xe47b57, ring = 0x248b89, accent = 0xf0c778;
    int winner = _winner(board);
    bool finished = _finished(board);
    screen.clear(background);
    screen.text(48,34,"TIC TAC TOE",6,paper);
    screen.fillRect(48,90,504,3,ink);
    screen.text(48,116,finished ? (winner == 'X' ? "YOU WIN!" : winner == 'O' ? "CPU WINS" : "DRAW") : "YOUR TURN",4,accent);
    screen.line(428,112,450,134,5,cross).line(450,112,428,134,5,cross);
    screen.circle(496,123,13,5,0x70c9bf);
    screen.text(428,145,"YOU",2,0xa2b9b7);
    screen.text(484,145,"CPU",2,0xa2b9b7);
    screen.fillRect(48,168,504,504,paper);
    if( !finished && hover >= 0 && hover < 9 && board[hover] == ' ' )
        screen.fillRect(48+(hover-hover/3*3)*168,168+hover/3*168,168,168,0xd9e8de);
    for( int i = 1; i < 3; i++ ) {
        screen.fillRect(48+i*168-3,168,6,504,ink);
        screen.fillRect(48,168+i*168-3,504,6,ink);
    }
    for( int i = 0; i < 9; i++ ) {
        int cx = 132+(i-i/3*3)*168, cy = 252+i/3*168;
        if( board[i] == 'X' )
            screen.line(cx-38,cy-38,cx+38,cy+38,12,cross).line(cx+38,cy-38,cx-38,cy+38,12,cross);
        else if( board[i] == 'O' ) screen.circle(cx,cy,48,11,ring);
        else screen.text(cx-6,cy-10,i == 0 ? "1" : i == 1 ? "2" : i == 2 ? "3" :
            i == 3 ? "4" : i == 4 ? "5" : i == 5 ? "6" : i == 6 ? "7" : i == 7 ? "8" : "9",4,0x95a59e);
    }
    int line = _winningLine(board);
    if( line >= 0 ) {
        int first = line < 3 ? line*3 : line < 6 ? line-3 : line == 6 ? 0 : 2;
        int last = line < 3 ? first+2 : line < 6 ? first+6 : line == 6 ? 8 : 6;
        screen.line(132+(first-first/3*3)*168,252+first/3*168,132+(last-last/3*3)*168,252+last/3*168,5,0xeab64e);
    }
    screen.text(48,704,"CLICK A SQUARE OR PRESS 1-9",3,paper);
    screen.text(48,738,"R OR SPACE REPLAY   Q OR ESC QUIT",3,0xa2b9b7);
    screen.rect(48,168,504,504,3,ink);
};