Add board scoring and basic suggestion

spec/lx_chess/game_spec.cr

@@ -9,6 +9,15 @@ require "../../src/lx_chess/player"
 include LxChess
 
 describe Game do
+  describe "#score" do
+    it "scores the board" do
+      game = Game.new
+      game.board["e4"] = Piece.from_fen('P')
+      debug_board(game)
+      game.score.should eq(100)
+    end
+  end
+
   describe "#remove_illegal_moves" do
     it "removes illegal moves" do
       game = Game.new players: [Player.new, Player.new]

src/lx_chess/game.cr

@@ -481,6 +481,46 @@ module LxChess
       @move_clock -= 1
     end
 
+    # evaluate a position
+    def score(board = @board)
+      @board.reduce(0) do |score, piece|
+        next score unless piece
+        val =
+          case piece.id
+          when Piece::PAWN   then 100
+          when Piece::KING   then 10000
+          when Piece::QUEEN  then 900
+          when Piece::ROOK   then 500
+          when Piece::BISHOP then 310
+          when Piece::KNIGHT then 300
+          else
+            0
+          end
+        piece.black? ? score - val : score + val
+      end
+    end
+
+    def suggest
+      best_score = 0
+      selected_piece = nil
+      best_move = nil
+      pieces_for.each do |piece|
+        next unless move_set = moves(piece.index)
+        move_set.moves.reduce(best_score) do |best, move_index|
+          move_score = tmp_move(from: piece.index, to: move_index) { score }
+          if move_score > best_score
+            selected_piece = piece
+            best_move = move_index
+            move_score
+          else
+            best
+          end
+        end
+      end
+      return nil unless selected_piece && best_move
+      [selected_piece.index, best_move]
+    end
+
     # Return the pieces for a specified player
     def pieces_for(turn = @turn)
       color = turn == 0 ? :black : :white

src/lx_chess/piece.cr

@@ -22,6 +22,10 @@ module LxChess
     def initialize(@id : Int8 = 0)
     end
 
+    def id
+      @id & 0b0111
+    end
+
     def white?
       @id & 0b1000 == 0
     end

src/lx_chess/term_game.cr

@@ -49,6 +49,12 @@ module LxChess
         msg.lines.reverse.each { |l| @log.unshift(l) }
       when /flip/i
         @gb.flip!
+      when /score/i
+        @log.unshift "score: #{@game.score}"
+      when /suggest/i
+        if suggestion = @game.suggest
+          @log.unshift "suggestion: #{suggestion.map { |s| @game.board.cord(s) }.join(" => ")}"
+        end
       when /(undo|back)/i
         if last_change = @changes.pop?
           @game.undo(last_change)