Add disambiguation to SAN generation

shard.yml

@@ -1,5 +1,5 @@
 name: lx_chess
-version: 0.1.0
+version: 0.1.3
 
 authors:
   - Alex Clink <alexclink@gmail.com>

spec/lx_chess/game/move_to_san_spec.cr

@@ -0,0 +1,100 @@
+require "../../spec_helper"
+
+include LxChess
+
+describe Game do
+  describe "#move_to_san" do
+    it "converts pawn captures" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {
+        "e4" => 'P',
+        "d5" => 'p',
+      })
+      debug_board(game, ["e4", "d5"])
+      san = game.move_to_san(from: "e4", to: "d5", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("exd5")
+    end
+
+    it "converts pawn moves" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {"e2" => 'P'})
+      debug_board(game, ["e2", "e4"])
+      san = game.move_to_san(from: "e2", to: "e4", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("e4")
+    end
+
+    it "disambiguates pawn captures" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {
+        "c4" => 'P',
+        "e4" => 'P',
+        "d5" => 'p',
+      })
+      debug_board(game, ["e4", "d5"])
+      san = game.move_to_san(from: "e4", to: "d5", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("exd5")
+      debug_board(game, ["c4", "d5"])
+      san = game.move_to_san(from: "c4", to: "d5", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("cxd5")
+    end
+
+    it "disambiguates rook moves" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {
+        "e4" => 'R',
+        "d5" => 'R',
+      })
+      debug_board(game, ["e4", "e5"])
+      san = game.move_to_san(from: "e4", to: "e5", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("Ree5")
+    end
+
+    it "disambiguates knight moves" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {
+        "f3" => 'N',
+        "e2" => 'N',
+      })
+      debug_board(game, ["e2", "d4"])
+      san = game.move_to_san(from: "e2", to: "d4", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("Ned4")
+    end
+
+    it "disambiguates knight moves on the same file" do
+      game = Game.new players: [Player.new, Player.new]
+      place(game.board, {
+        "e4" => 'N',
+        "e2" => 'N',
+      })
+      debug_board(game, ["e2", "c3"])
+      san = game.move_to_san(from: "e2", to: "c3", turn: 0)
+      puts san.to_s
+      san.to_s.should eq("Ne2c3")
+    end
+
+    it "detects check" do
+      game = Game.new players: [Player.new, Player.new]
+      game.board["e1"] = Piece.from_fen('K')
+      game.board["c8"] = Piece.from_fen('r')
+      debug_board(game, ["c8", "e8"])
+      san = game.move_to_san(from: "c8", to: "e8", turn: 1)
+      puts san.to_s
+      san.to_s.should eq("Re8+")
+    end
+
+    it "detects checkmate" do
+      fen = Fen.parse("r1bqkb1r/pppp1ppp/2n2n2/4p2Q/2B1P3/8/PPPP1PPP/RNB1K1NR w KQkq - 4 4")
+      game = Game.new(board: fen.board, players: [Player.new, Player.new])
+      san = game.move_to_san(from: "h5", to: "f7", turn: 0)
+      debug_board(game, ["h5", "f7"])
+      puts san.to_s
+      san.to_s.should eq("Qxf7#")
+    end
+  end
+end

spec/lx_chess/game_spec.cr

@@ -74,25 +74,6 @@ describe Game do
     end
   end
 
-  describe "#move_to_san" do
-    it "detects check" do
-      game = Game.new players: [Player.new, Player.new]
-      game.board["e1"] = Piece.from_fen('K')
-      game.board["c8"] = Piece.from_fen('r')
-      debug_board(game, ["c8", "e8"])
-      san = game.move_to_san(from: "c8", to: "e8", turn: 1)
-      san.to_s.should eq("Re8+")
-    end
-
-    it "detects checkmate" do
-      fen = Fen.parse("r1bqkb1r/pppp1ppp/2n2n2/4p2Q/2B1P3/8/PPPP1PPP/RNB1K1NR w KQkq - 4 4")
-      game = Game.new(board: fen.board, players: [Player.new, Player.new])
-      san = game.move_to_san(from: "h5", to: "f7", turn: 0)
-      debug_board(game, ["h5", "f7"])
-      san.to_s.should eq("Qxf7#")
-    end
-  end
-
   describe "#in_check?" do
     it "detects if the player is in check" do
       game = Game.new players: [Player.new, Player.new]

src/lx_chess/game.cr

@@ -175,18 +175,46 @@ module LxChess
         end
       end
 
+      candidate_move_sets = @board.select do |candidate|
+        next unless candidate
+        next if candidate == piece
+        candidate.fen_symbol == piece.fen_symbol
+      end.compact.map do |candidate|
+        moves(candidate.index)
+      end.compact.select do |move_set|
+        move_set.moves.includes?(to)
+      end
+
+      origin = nil
+      takes = en_passant || !@board[to].nil?
+
+      if candidate_move_sets.any?
+        origin ||= ""
+        origin += @board.cord(from)[0]
+      end
+
+      if candidate_move_sets.any? { |set| @board.cord(set.piece.index)[0] == @board.cord(from)[0] }
+        origin ||= ""
+        origin += @board.cord(from)[1]
+      end
+
+      if origin.nil? && piece.pawn? && takes
+        origin = @board.cord(from)[0].to_s
+      end
+
       Notation.new(
         square: @board.cord(to),
         promotion: promotion,
         piece_abbr: piece.fen_symbol,
         from: @board.cord(from),
         to: @board.cord(to),
-        takes: en_passant || !@board[to].nil?,
+        takes: takes,
         en_passant: en_passant,
         check: check && !checkmate,
         checkmate: checkmate,
         castles_k: castles_k,
-        castles_q: castles_q
+        castles_q: castles_q,
+        origin: origin
       )
     end
 

src/lx_chess/notation.cr

@@ -156,7 +156,7 @@ module LxChess
       when castles_q?
         "O-O-O"
       else
-        piece_abbr != 'P' || @takes ? piece_abbr : nil
+        piece_abbr unless piece_abbr == 'P'
       end
 
       if @en_passant

src/lx_chess/version.cr

@@ -1,3 +1,3 @@
 module LxChess
-  VERSION = "0.1.2"
+  VERSION = "0.1.3"
 end