class Board {
  // Array of 0 by default
  // X=1
  // O=2
  field Array gameState;
  field int turn;

  constructor Board new() {
    var int i;
    let i=0;
    let turn = 0;
    let gameState = Array.new(9);
    while(i<9) {
      let gameState[i] = 0;
      let i=i+1;
    }

    return this;
  }

  method boolean isRowTaken(int row, int value) {
    if (gameState[row*3] = value &
      gameState[(row*3)+1] = value &
      gameState[(row*3)+2] = value) {
      return true;
    }
    return false;
  }

  method boolean isColumnTaken(int column, int value) {
    if (gameState[column] = value &
      gameState[column+3] = value &
      gameState[column+6] = value) {
      return true;
    }

    return false;
  }

  method boolean isWon(int value) {
    if (isRowTaken(0,value) | isRowTaken(1, value) | isRowTaken(1, value)) {
      return true;
    }
    if (isColumnTaken(0, value) | isColumnTaken(1, value) | isColumnTaken(2, value)) {
      return true;
    }

    if (isDiagonalTaken(value)) {
      return true;
    }
    return false;
  }

  method boolean isDiagonalTaken(int value) {
    // ensure center is correct first
    if (~(gameState[4] = value )) {
      return false;
    }
    // NORTH WEST TO SOUTH EAST
    if (gameState[0] = value & gameState[8] = value) {
      return true;
    }

    if (gameState[2] = value & gameState[6] = value) {
      return true;
    }

    return false;
  }

  // returns 1 if player X won
  // returns 2 if player O won
  // 0 otherwise
  method int winner() {

    if(isWon(1)) {
      return 1;
    }

    if(isWon(2)) {
      return 2;
    }

    return 0;
  }

  method boolean play(int row, int column) {
    var int move, remainder;
    let move = 0;

    if (~ (gameState[(row*3) + column] = 0)) {
      return false;
    }

    let remainder = turn - (2 * (turn/2));
    if (remainder = 0) {
      let move = 1;
    } else {
      let move = 2;
    }

    let gameState[row*3 + column] = move;
    if (move = 1) {
      do Draw.DrawX(row, column);
    } else {
      if (move = 2) {
        do Draw.DrawO(row, column);
      }
    }

    if(isWon(1)) {
      return true;
    }

    if(isWon(2)) {
      return true;
    }

    if (turn = 8) {
      return true;
    }

    let turn = turn + 1;
    return false;
  }
}