Class: Pawn

Inherits:
Piece show all
Defined in:
lib/pieces/pawn.rb

Class Method Summary collapse

Methods inherited from Piece

capturable?, destination_occupied?, obstructed?

Class Method Details

.dest_occupied?(dest, board) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pieces/pawn.rb', line 54

def self.dest_occupied?(dest, board)
  dest_y = dest[0]
  dest_x = dest[1]
  !board[dest_y][dest_x].nil?
end

.en_passant(orig, dest, board, en_passant) ⇒ Object 



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# File 'lib/pieces/pawn.rb', line 36

def self.en_passant(orig, dest, board, en_passant)
  orig_y, orig_x = orig
  dest_y, dest_x = dest
  piece_type = board[orig_y][orig_x]
  opposite_color = piece_type[0].downcase == 'w' ? :black : :white
  direction = opposite_color == :white ? -1 : 1

  return false if en_passant[opposite_color].nil?

  if en_passant[opposite_color] == [dest[0] + direction, dest[1]]
    if (orig_x - dest_x).abs == 1 &&
       (orig_y - dest_y) * direction == 1
      return true
    end
  end
  false
end

.move_is_valid?(orig, dest, board, en_passant) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pieces/pawn.rb', line 6

def self.move_is_valid?(orig, dest, board, en_passant)
  return true if en_passant(orig, dest, board, en_passant)

  orig_y, orig_x = orig
  dest_y, dest_x = dest
  piece_type = board[orig_y][orig_x]
  piece_color = piece_type[0].downcase

  if piece_color == 'w'
    direction = 1
  elsif piece_color == 'b'
    direction = -1
  else
    return false
  end

  if capturable?(orig, dest, board) &&
     (orig_x - dest_x).abs == 1 &&
     (orig_y - dest_y) * direction == 1
    return true
  end

  not_obstructed = !obstructed?(orig, dest, board) && !dest_occupied?(dest, board)

  basic_move = ((orig_y - dest_y) * direction == 1 && orig_x == dest_x)
  move_double_on_first_turn = (orig_y - dest_y == (2 * direction)) && (orig_x == dest_x)

  not_obstructed && (move_double_on_first_turn || basic_move)
end