Generate all pseudolegal moves

spec/lx_chess/game_spec.cr

@@ -3,66 +3,204 @@ require "../../src/lx_chess/board"
 require "../../src/lx_chess/piece"
 require "../../src/lx_chess/move_set"
 require "../../src/lx_chess/game"
+require "../../src/lx_chess/term_board"
+
+def debug_board(game : LxChess::Game, moves : Array(Int16))
+  puts
+  gb = LxChess::TermBoard.new(game.board)
+  gb.highlight(moves)
+  gb.draw
+  puts
+end
 
 describe LxChess::Game do
   describe "#moves" do
     it "correctly generates white pawn moves from the initial rank" do
       game = LxChess::Game.new
       game.board["e2"] = LxChess::Piece.from_fen('P')
-      moves = game.moves("e2")
-      moves.map { |m| game.board.cord(m) }.should eq(["e3", "e4"])
+      if move_set = game.moves("e2")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[e3 e4])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates black pawn moves from the initial rank" do
       game = LxChess::Game.new
       game.board["e7"] = LxChess::Piece.from_fen('p')
-      moves = game.moves("e7")
-      moves.map { |m| game.board.cord(m) }.should eq(["e6", "e5"])
+      if move_set = game.moves("e7")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[e6 e5])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates single white pawn moves" do
       game = LxChess::Game.new
       game.board["e3"] = LxChess::Piece.from_fen('P')
-      moves = game.moves("e3")
-      moves.map { |m| game.board.cord(m) }.should eq(["e4"])
+      if move_set = game.moves("e3")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[e4])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates black white pawn moves" do
       game = LxChess::Game.new
       game.board["e6"] = LxChess::Piece.from_fen('p')
-      moves = game.moves("e6")
-      moves.map { |m| game.board.cord(m) }.should eq(["e5"])
+      if move_set = game.moves("e6")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[e5])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates knight moves" do
       game = LxChess::Game.new
       game.board["c3"] = LxChess::Piece.from_fen('N')
-      moves = game.moves("c3")
-      moves.map { |m| game.board.cord(m) }.should eq(["a4", "b5", "d5", "e4", "e2", "d1", "b1", "a2"])
+      if move_set = game.moves("c3")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[a4 b5 d5 e4 e2 d1 b1 a2])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "does not generate knight moves that cross the left border edge" do
+      game = LxChess::Game.new
+      game.board["a1"] = LxChess::Piece.from_fen('N')
+      if move_set = game.moves("a1")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[b3 c2])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "does not generate knight moves that cross the right border edge" do
+      game = LxChess::Game.new
+      game.board["h1"] = LxChess::Piece.from_fen('N')
+      if move_set = game.moves("h1")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[f2 g3])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates rook moves" do
       game = LxChess::Game.new
       game.board["e4"] = LxChess::Piece.from_fen('R')
-      moves = game.moves("e4")
-      moves.map { |m| game.board.cord(m) }.should eq([
-        "d4", "c4", "b4", "a4",
-        "e5", "e6", "e7", "e8",
-        "f4", "g4", "h4",
-        "e3", "e2", "e1",
-      ])
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d4 c4 b4 a4
+          e5 e6 e7 e8
+          f4 g4 h4
+          e3 e2 e1
+        ])
+      else
+        raise "no moves"
+      end
     end
 
     it "correctly generates bishop moves" do
       game = LxChess::Game.new
       game.board["e4"] = LxChess::Piece.from_fen('B')
-      moves = game.moves("e4")
-      moves.map { |m| game.board.cord(m) }.should eq([
-        "d5", "c6", "b7", "a8",
-        "f5", "g6", "h7",
-        "f3", "g2", "h1",
-        "d3", "c2", "b1",
-      ])
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d5 c6 b7 a8
+          f5 g6 h7
+          f3 g2 h1
+          d3 c2 b1
+        ])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "correctly generates king moves" do
+      game = LxChess::Game.new
+      game.board["e4"] = LxChess::Piece.from_fen('K')
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d4 d5 e5 f5 f4 f3 e3 d3
+        ])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "does not generate king moves crossing the right border" do
+      game = LxChess::Game.new
+      game.board["h4"] = LxChess::Piece.from_fen('K')
+      if move_set = game.moves("h4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          g4 g5 h5 h3 g3
+        ])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "correctly generates queen moves" do
+      game = LxChess::Game.new
+      game.board["e4"] = LxChess::Piece.from_fen('Q')
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d5 c6 b7 a8
+          f5 g6 h7
+          f3 g2 h1
+          d3 c2 b1
+          d4 c4 b4 a4
+          e5 e6 e7 e8
+          f4 g4 h4
+          e3 e2 e1
+        ])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "blocks moves when a piece is in the way" do
+      game = LxChess::Game.new
+      game.board["e4"] = LxChess::Piece.from_fen('B')
+      game.board["f5"] = LxChess::Piece.from_fen('P')
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d5 c6 b7 a8
+          f3 g2 h1
+          d3 c2 b1
+        ])
+      else
+        raise "no moves"
+      end
+    end
+
+    it "adds captures before blocking further moves" do
+      game = LxChess::Game.new
+      game.board["e4"] = LxChess::Piece.from_fen('B')
+      game.board["f5"] = LxChess::Piece.from_fen('p')
+      if move_set = game.moves("e4")
+        debug_board(game, move_set.moves)
+        move_set.moves.map { |m| game.board.cord(m) }.should eq(%w[
+          d5 c6 b7 a8
+          f5
+          f3 g2 h1
+          d3 c2 b1
+        ])
+      else
+        raise "no moves"
+      end
     end
   end
 end

src/lx_chess.cr

@@ -44,7 +44,9 @@ loop do
   if input
     notation = LxChess::Notation.new(input)
     input = input.to_i16 if input =~ /^\d+$/
-    puts game.moves(input).map { |m| game.board.cord(m) }
+    if move_set = game.moves(input)
+      puts move_set.moves.map { |m| game.board.cord(m) }
+    end
     # from, to = game.parse_san(notation)
     # if from && to
     #   puts "#{notation.to_s}: #{game.board.cord(from)} => #{game.board.cord(to)}"

src/lx_chess/game.cr

@@ -76,9 +76,7 @@ module LxChess
             {x: -1, y: -1}, # down left
           ])
         end
-        set.moves
-      else
-        [] of Int16
+        set
       end
     end
   end

src/lx_chess/move_set.cr

@@ -11,13 +11,17 @@ module LxChess
       @moves = [] of Int16
     end
 
-    def add_vector(x : Int16, y : Int16, limit : Int16)
-      add_vector(y * @board.width + x, limit)
+    def origin
+      @piece.index.as(Int16)
     end
 
-    def add_vector(offset : Int16, limit : Int16)
+    def add_vector(x : Int16, y : Int16, limit : Int16)
+      dist_edge = @board.dist_left(origin) if x.negative?
+      dist_edge = @board.dist_right(origin) if x.positive?
+      limit = dist_edge if dist_edge && dist_edge < limit
+
+      offset = y * @board.width + x
       step = offset
-      location = @piece.index.as(Int16)
       limit.times do
         info = add_offset(offset)
         offset += step
@@ -27,25 +31,22 @@ module LxChess
 
     def add_offsets(offsets : Array(NamedTuple(x: Int32, y: Int32)))
       offsets.each do |cord|
+        # Check if the offset crosses the border
+        next if cord[:x].negative? && origin + cord[:x] < @board.border_left(origin)
+        next if cord[:x].positive? && origin + cord[:x] > @board.border_right(origin)
         offset = cord[:y] * @board.width + cord[:x]
         add_offset(offset.to_i16)
       end
     end
 
-    def add_offsets(offsets : Array(Int16))
-      offsets.each do |offset|
-        add_offset(offset)
-      end
-    end
-
     def add_offset(x : Int16, y : Int16)
       add_offset(y * @board.width + x)
     end
 
-    # TODO: Stop at the board edges
+    # Does not check for crossing border edges
     def add_offset(offset : Int16)
       added = false; stop = false
-      location = @piece.index.as(Int16) + offset
+      location = origin + offset
       if location < 0 || location >= @board.squares.size
         # Beyond top or bottom
         stop = true

src/lx_chess/term_board.cr

@@ -8,6 +8,7 @@ module LxChess
 
     def initialize(@board : Board)
       @flipped = false
+      @highlights = {} of Int16 => Tuple(Symbol, Symbol)
 
       @bg_dark = :green
       @bg_light = :light_green
@@ -42,6 +43,16 @@ module LxChess
       @flipped ? (width - 1).downto(0) : 0.upto(width - 1)
     end
 
+    def highlight(indicies : Array(Int16), color = {:light_yellow, :yellow})
+      indicies.each do |index|
+        @highlights[index] = color
+      end
+    end
+
+    def clear
+      @highlights = {} of Int16 => Tuple(Symbol, Symbol)
+    end
+
     def draw(io = STDOUT)
       ranks.each do |y|
         io << (y + 1) << ": "
@@ -50,7 +61,14 @@ module LxChess
           index = @board.index(x, y)
           piece = @board[index]
 
-          background = (index + y) % 2 == 0 ? @bg_dark : @bg_light
+          tint = (index + y) % 2 == 0 ? :light : :dark
+
+          background =
+            if @highlights[index]?
+              @highlights[index][tint == :light ? 0 : 1]
+            else
+              tint == :light ? @bg_light : @bg_dark
+            end
 
           if piece
             foreground = piece.white? ? @fg_light : @fg_dark