Class: TTT::ComputerPlayer

Inherits:
Object
  • Object
show all
Defined in:
lib/ttt/computer_player.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(game) ⇒ ComputerPlayer

Returns a new instance of ComputerPlayer.



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# File 'lib/ttt/computer_player.rb', line 8

def initialize(game)
  self.game = game
end

Instance Attribute Details

#game ⇒ Object

Returns the value of attribute game.



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# File 'lib/ttt/computer_player.rb', line 6

def game
  @game
end

Instance Method Details

#best_move ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 20

def best_move
  return imperative_move if imperative_move?  # allow to customize certain situations
  move, rating, game = moves_by_rating.first  # otherwise go by rating
  move
end

#board ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 66

def board
  game.board
end

#imperative_move ⇒ Object

allows us to override ratings in cases where they make the robot look stupid



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# File 'lib/ttt/computer_player.rb', line 42

def imperative_move
  # if we can win *this turn*, then take it because
  # it rates winning next turn the same as winning in 3 turns
  game.available_moves.each do |move|
    new_game = game.pristine_mark move
    return move if new_game.over? && new_game.winner == player_number
  end
  
  # if we can block the opponent from winning *this turn*, then take it, because
  # it rates losing this turn the same as losing in 3 turns
  if moves_by_rating.all? { |move, rating, game| rating == -1 }
    Game.winning_states do |position1, position2, position3|
      a, b, c = board[position1-1, 1].to_i, board[position2-1, 1].to_i, board[position3-1, 1].to_i
      if a + b + c == opponent_number * 2
        return a.zero? ? position1 : b.zero? ? position2 : position3
      end
    end
  end
end

#imperative_move? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ttt/computer_player.rb', line 62

def imperative_move?
  !!imperative_move
end

#moves_by_rating ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 26

def moves_by_rating
  return to_enum(:moves_by_rating) unless block_given?
  moves = []
  game.available_moves.each do |move|
    new_game = game.pristine_mark move
    moves << [ move, rate(new_game), new_game ]
  end
  moves = moves.sort_by { |move, rating, new_game| -rating } # highest rating first
  moves.each     { |move, rating, new_game| yield move, rating, new_game }
end

#opponent_number ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 70

def opponent_number
  player_number == 1 ? 2 : 1
end

#player_number ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 12

def player_number
  game.turn
end

#rate(game) ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 37

def rate(game)
  RATINGS[game.board][player_number]
end

#take_turn ⇒ Object 



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# File 'lib/ttt/computer_player.rb', line 16

def take_turn
  game.mark best_move
end