refactor: ask move to tell the board what operation to perform

the idea is, that castling and en passant can return the
special operation they need, like capturing a piece on
another position and castling actually moving two
pieces. maybe should actually be two classes
that perform operation on the board.

lib/board.rb

@@ -34,17 +34,16 @@ def legal_target_positions_for(position)
   end
 
   def move(origin, target)
-    origin = Position.parse(origin)
-    target = Position.parse(target)
-
-    origin_square = get(origin)
-    target_square = get(target)
-
-    piece = origin_square.piece
-    piece.moved = true
-    capture(target_square)
-    get(target).piece = piece
-    origin_square.piece = nil
+    move_type = find_move_type(origin, target)
+    current_move = move_type.new(self, origin, target)
+    current_move.operations_on_board.each do |operation|
+      case operation[:type]
+      when :capture
+        capture(get(operation[:target]))
+      when :move
+        move_operation(operation[:origin], operation[:target])
+      end
+    end
   end
 
   def squares_occupied_by(color)
@@ -81,6 +80,16 @@ def capture(target_square)
     target_square.piece = nil
   end
 
+  def move_operation(origin, target)
+    origin_square = get(origin)
+    target_square = get(target)
+
+    piece = origin_square.piece
+    piece.moved = true
+    target_square.piece = piece
+    origin_square.piece = nil
+  end
+
   def create_squares
     @squares = (1..8).map.with_index do |row, row_index|
       ("A".."H").map.with_index do |col, col_index|
@@ -93,4 +102,12 @@ def create_squares
   def find_king(color)
     @squares.find { |square| square.piece == King.new(color) }
   end
+
+  def find_move_type(origin, _target)
+    origin = Position.parse(origin)
+    types = get(origin).piece.move_types
+    types.find do |type|
+      type.new(self, origin).send(:position_candidates).include?(Position.parse(origin))
+    end || Move::Base
+  end
 end

lib/move/base.rb

@@ -3,14 +3,22 @@
 module Move
   # unlimited horizontal movement for a piece
   class Base
-    attr_reader :board, :position, :piece
+    attr_reader :board, :position, :piece, :target
 
-    def initialize(board, position)
+    def initialize(board, position, target = nil)
       @board = board
       @position = Position.parse(position)
+      @target = Position.parse(target)
       @piece = board.get(position).piece
     end
 
+    def operations_on_board
+      [
+        { type: :capture, target: target },
+        { type: :move, origin: position, target: target }
+      ]
+    end
+
     def legal_target_positions
       positions = position_candidates
       positions -= target_positions_that_are_occupied_by_friend

lib/position.rb

@@ -18,7 +18,8 @@ def self.new(letter, number)
   end
 
   def self.parse(input)
-    return input.map { |pos| Position.parse(pos) } if input.is_a? Array
+    return nil if input.nil?
+    return parse_array(input) if input.is_a? Array
     return input if input.is_a? Position
 
     letter = input.strip.chars[0].upcase
@@ -30,6 +31,10 @@ def self.parse(input)
     new(letter, number)
   end
 
+  def self.parse_array(array)
+    array.map { |pos| Position.parse(pos) }
+  end
+
   def initialize(letter, number)
     @letter = letter
     @number = number.to_i

test/board_test.rb

@@ -77,4 +77,9 @@ def test_returns_checkmate
     board = Board.from_fen("8/8/6r1/4K1r1/6q1/2b5/3R4/8 w - - 0 1")
     assert board.in_checkmate?(:white)
   end
+
+  def test_get_move_type
+    board = Board.with_setup
+    assert Move::Vertical, board.send(:find_move_type, "C7", "C5")
+  end
 end