Class: ChessEngine::Board

Inherits:
Object
  • Object
show all
Defined in:
lib/chess_engine/board.rb

Overview

This class provides a data structure for the chess board. It is responsible for storing information about pieces positions and moving them. It doesn’t implement move validations and chess rules, so it is possible to make any moves at this level of abstraction.

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Board

Creates an empty 8x8 board as a 2-dimensional array



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# File 'lib/chess_engine/board.rb', line 15

def initialize
  @board = Array.new(8) { Array.new(8) { nil } }
end

Instance Method Details

#at(coordinates) ⇒ Object 



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# File 'lib/chess_engine/board.rb', line 41

def at(coordinates)
  return nil unless self.exists_at?(coordinates)
  @board[coordinates[0]][coordinates[1]]
end

#exists_at?(coordinates) ⇒ Boolean

Checks if the values of coordinates are between 0 and 7

Example

exists_at?([0, 0]) #=> true
exists_at?([8, -1]) #=> false

Returns:

  • (Boolean) 


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# File 'lib/chess_engine/board.rb', line 59

def exists_at?(coordinates)
  coordinates.all? { |c| c.between?(0, 7) }
end

#king_coords(color) ⇒ Object

Returns the coordinates of the king of given color



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# File 'lib/chess_engine/board.rb', line 100

def king_coords(color)
  Board.coordinates_list.find do |coord|
    at(coord) && at(coord).king? && at(coord).color == color
  end
end

#move_piece(from, to) ⇒ Object

Moves the value of from coords to to coords. Sets the value of to to nil



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# File 'lib/chess_engine/board.rb', line 91

def move_piece(from, to)
  piece = self.at(from)
  self.set_at(from, nil)
  self.set_at(to, piece)
end

#piece_coordinates(color) ⇒ Object

Returns the array of coordinates where pieces of given color a located



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# File 'lib/chess_engine/board.rb', line 109

def piece_coordinates(color)
  Board.coordinates_list.select do |coord|
    piece = at(coord)
    !piece.nil? && piece.color == color
  end
end

#set_at(coordinates, piece) ⇒ Object

Sets the board on given coordinates to piece



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# File 'lib/chess_engine/board.rb', line 49

def set_at(coordinates, piece)
  @board[coordinates[0]][coordinates[1]] = piece
end

#set_default ⇒ Object

Sets the initial board position according to the classic chess rules



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# File 'lib/chess_engine/board.rb', line 22

def set_default
  [[:white, 0, 1], [:black, 7, 6]].each do |color, row1, row2|
    ["Rook", "Knight", "Elephant", "Queen", "King", "Elephant", "Knight", "Rook"].each.with_index do |class_name, column|
      self[column, row1] = Module.const_get("ChessEngine::#{class_name}").new(color)
    end

    0.upto(7) do |column|
      self[column, row2] = Pawn.new(color)
    end
  end
end

#to_s ⇒ Object

Returns a string containing the board in printable format (uses colorize gem to paint the squares)



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# File 'lib/chess_engine/board.rb', line 67

def to_s
  string = ""
  colors = [[:default, :light_white].cycle, [:light_white, :default].cycle].cycle

  7.downto(0) do |row|
    string += "#{row + 1} "
    colors_cycle = colors.next

    0.upto(7) do |column|
      piece = self[column, row]
      string += piece.nil? ? " " : piece.symbol
      string += " "
      string[-2..-1] = string[-2..-1].colorize(background: colors_cycle.next)
    end
    string += "\n"
  end

  string += "  a b c d e f g h"
  string
end