Class: Upwords::Player

Inherits:
Object
  • Object
show all
Defined in:
lib/upwords/player.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, rack_capacity = 7, cpu = false) ⇒ Player

Returns a new instance of Player.



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# File 'lib/upwords/player.rb', line 10

def initialize(name, rack_capacity=7, cpu=false)
  @name = name
  @rack = LetterRack.new(rack_capacity)
  @score = 0
  @last_turn = nil
  @cpu = cpu
end

Instance Attribute Details

#last_turn ⇒ Object

Returns the value of attribute last_turn.



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# File 'lib/upwords/player.rb', line 8

def last_turn
  @last_turn
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/upwords/player.rb', line 7

def name
  @name
end

#score ⇒ Object

Returns the value of attribute score.



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# File 'lib/upwords/player.rb', line 8

def score
  @score
end

Instance Method Details

#cpu? ⇒ Boolean

AI move methods

Returns:

  • (Boolean) 


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# File 'lib/upwords/player.rb', line 84

def cpu?
  @cpu
end

#cpu_move(board, dict, batch_size = 1000, min_score = 0) ⇒ Object

Execute a legal move based on a predefined strategy

Basic strategy:

  • Find all legal move shapes and all possible letter permutations across those shapes (this computation is relatively quick)

  • Retun the highest score from permutation that do not produce in any illegal new words (this computation is slow…)

  • To speed up the above computation: + Only check a batch of permutations at a time (specified in ‘batch_size’ argument) + After each batch, terminate the subroutine if it finds a score that is at least as high as the given ‘min_score’ + Decrement the ‘min_score’ after each batch that does not terminate the subroutine to prevent endless searches

TODO: refactor the the ‘strategy’ component out of this method, so different strategies can be swapped in and out



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# File 'lib/upwords/player.rb', line 135

def cpu_move(board, dict, batch_size = 1000, min_score = 0)
  possible_moves = self.legal_move_shapes_letter_permutations(board)      
  possible_moves.shuffle!
  
  top_score = 0
  top_score_move = nil
  
  while top_score_move.nil? || (top_score < min_score) do
    
    # Check if next batch contains any legal moves and save the top score
    ([batch_size, possible_moves.size].min).times do
      move_arr = possible_moves.pop
      move = Move.new(move_arr)

      if move.legal_words?(board, dict)
        move_score = move.score(board, self)
        if move_score >= top_score
          top_score = move_score
          top_score_move = move_arr
        end
      end
    end
    
    # Decrement minimum required score after each cycle to help prevent long searches
    min_score = [(min_score - 1), 0].max
  end
  
  top_score_move
end

#legal_move_shapes(board) ⇒ Object

Return a list of legal move shapes that player could make on board



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# File 'lib/upwords/player.rb', line 89

def legal_move_shapes(board)
  one_space_moves = board.coordinates.map {|posn| [posn]}
  
  # Collect board positions grouped by rows
  (0...board.num_rows).map do |row| 
    (0...board.num_columns).map {|col| [row, col]} 
    
    # Collect all positions of all possible horizontal multi-position moves that player could make
  end.flat_map do |posns|
    (2..(letters.size)).flat_map {|sz| posns.combination(sz).to_a}
    
    # Collect all positions of all possible vertical and horizontal moves that player could make
  end.reduce(one_space_moves) do |all_moves, move|
    all_moves << move                           # Horizontal moves
    all_moves << move.map {|posn| posn.rotate}  # Vertical moves
    
    # Filter out illegal move shapes  
  end.select do |move_posns|
    Shape.new(move_posns).legal?(board)
  end
end

#legal_move_shapes_letter_permutations(board) ⇒ Object

Return list of all possible letter permutations on legal move shapes that player could make on board Elements in the list will be in form of [(row, col), letter]



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# File 'lib/upwords/player.rb', line 113

def legal_move_shapes_letter_permutations(board)
  # Cache result of letter permutation computation for each move size
  letter_perms = Hash.new {|perms, sz| perms[sz] = letters.permutation(sz).to_a}
  
  legal_move_shapes(board).reduce([]) do |all_moves, move|
    letter_perms[move.size].reduce(all_moves) do |move_perms, perm|
      move_perms << move.zip(perm)
    end
  end
end

#letters ⇒ Object 



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# File 'lib/upwords/player.rb', line 18

def letters
  @rack.letters.dup
end

#play_letter(board, letter, row, col) ⇒ Object 



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# File 'lib/upwords/player.rb', line 54

def play_letter(board, letter, row, col)
  rack_letter = @rack.remove(letter)
  begin
    board.play_letter(rack_letter, row, col)
  rescue IllegalMove => exn
    take_letter(rack_letter)
    raise IllegalMove, exn
  end
end

#rack_capacity ⇒ Object 



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# File 'lib/upwords/player.rb', line 34

def rack_capacity
  @rack.capacity
end

#rack_empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/upwords/player.rb', line 30

def rack_empty?
  @rack.empty?
end

#rack_full? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/upwords/player.rb', line 26

def rack_full?
  @rack.full?
end

#refill_rack(letter_bank) ⇒ Object 



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# File 'lib/upwords/player.rb', line 74

def refill_rack(letter_bank)
  until rack_full? || letter_bank.empty? do
    take_letter(letter_bank.draw)
  end
end

#show_rack(masked = false) ⇒ Object 



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# File 'lib/upwords/player.rb', line 22

def show_rack(masked = false)
  masked ? @rack.show_masked : @rack.show
end

#swap_letter(letter, letter_bank) ⇒ Object 



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# File 'lib/upwords/player.rb', line 64

def swap_letter(letter, letter_bank)
  if letter_bank.empty?
    raise IllegalMove, "Letter bank is empty!"
  else
    trade_letter = @rack.remove(letter)
    take_letter(letter_bank.draw)
    letter_bank.deposit(trade_letter)
  end
end

#take_from(board, row, col) ⇒ Object

Game object interaction methods



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# File 'lib/upwords/player.rb', line 46

def take_from(board, row, col)
  if board.stack_height(row, col) == 0
    raise IllegalMove, "No letters in #{row}, #{col}!"
  else
    take_letter(board.remove_top_letter(row, col))
  end
end

#take_letter(letter) ⇒ Object 



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# File 'lib/upwords/player.rb', line 38

def take_letter(letter)
  @rack.add(letter)
end