tictactoe.rb

class TicTacToe
  attr_reader :action_size

  def initialize(size = 3)
    @rows = size
    @cols = size
    @action_size = @rows * @cols
  end

  def get_initial_state
    Array.new(@rows) { Array.new(@cols) { 0 } }
  end

  def get_next_state(state, action, player)
    row, col = get_row_col(action)
    state[row][col] = player
    state
  end

  def get_legal_moves(state)
    state.flatten.map { |s| s === 0 }
  end

  def get_diagonals(state, indices)
    state.flatten.reject.with_index { !indices.include? _2 }
  end

  def is_diag_connected(state, player)
    left_diag = []
    right_diag = []
    i = 0
    j = @cols - 1
    @cols.times do
      left_diag.push(i)
      right_diag.push(j)
      i += @cols + 1
      j += @cols - 1
    end
    is_rdiag_connected = get_diagonals(state, right_diag).sum === player * @cols
    is_ldiag_connected = get_diagonals(state, left_diag).sum === player * @cols
    is_ldiag_connected || is_rdiag_connected
  end

  def get_row_col(action)
    [action / @cols, action % @cols]
  end

  def check_win(state, action)
    return false if action.nil?

    row, col = get_row_col(action)
    player = state[row][col]
    is_row_connected = state[row].sum === player * @rows
    is_col_connected = state.transpose[col].sum === player * @cols
    is_row_connected || is_col_connected || is_diag_connected(state, player)
  end

  def get_winner(state, action)
    row, col = get_row_col(action)
    state[row][col]
  end

  def check_gameover(state, action)
    return 1, true if check_win(state, action)
    # Draw if no legal move
    return 0, true unless get_legal_moves(state).any?

    [0, false]
  end

  def get_opponent(player)
    -player
  end

  def clone_state(state)
    state.map { |r| r.map(&:clone) }
  end

  def change_perspective(state, player)
    state_ = state.map { |r| r.map(&:clone) }
    state_.each_with_index do |row, r|
      state_[r] = row.map { |i| i * player }
    end
  end

  def print_board(state, p1, p2, p1_score, p2_score, match_no)
    board_width = 9 * @cols
    title = "#{p1} : #{p1_score} | [#{match_no}] |  #{p2_score} : #{p2} "
    puts
    state.each_with_index do |row, r|
      if r === 0
        puts title.upcase.center(board_width)
        puts '=' * board_width
      end
      row.each_with_index do |val, c|
        print ' | '
        if val === 1
          print p1.center(4)
        elsif val === -1
          print p2.center(4)
        else
          print (c + (@cols * r) + 1).to_s.center(5)
        end
        print ' |' if c === @cols - 1
      end
      puts
      print r === @rows - 1 ? '=' * board_width : '-' * board_width
      puts
    end
  end
end