Test and fix promotion by capture

chess/src/main/scala/Actor.scala

@@ -24,10 +24,12 @@ case class Actor(piece: Piece, pos: Pos, board: Board) {
 
     case Pawn ⇒ pawnDir(pos) map { next ⇒
       val fwd = Some(next) filterNot board.occupations
-      def capture(horizontal: Direction): Option[Move] = for {
-        p ← horizontal(next); if enemies(p);
-        b ← board.taking(pos, p)
-      } yield move(p, b, Some(p))
+      def capture(horizontal: Direction): Option[Move] = {
+        for {
+          p ← horizontal(next); if enemies(p);
+          b ← board.taking(pos, p)
+        } yield move(p, b, Some(p))
+      } flatMap maybePromote
       def enpassant(horizontal: Direction): Option[Move] = for {
         victimPos ← horizontal(pos); if pos.y == color.passablePawnY
         victim ← board(victimPos); if victim == !color - Pawn
@@ -37,10 +39,14 @@ case class Actor(piece: Piece, pos: Pos, board: Board) {
         b ← board.taking(pos, targetPos, Some(victimPos))
       } yield move(targetPos, b, Some(victimPos), enpassant = true)
       def forward(p: Pos): Option[Move] =
-        if (pos.y == color.promotablePawnY)
-          board.promote(pos, p) map { b ⇒ move(p, b, promotion = Some(Queen)) }
-        else
-          board.move(pos, p) map { b ⇒ move(p, b) }
+        board.move(pos, p) map { move(p, _) } flatMap maybePromote
+      def maybePromote(m: Move): Option[Move] =
+        if (m.dest.y == m.color.promotablePawnY)
+          (m.after promote m.dest) map { b2 ⇒
+            m.copy(after = b2, promotion = Some(Queen))
+          }
+        else Some(m)
+
       List(
         for {
           p ← fwd

chess/src/main/scala/Board.scala

@@ -81,11 +81,11 @@ case class Board(pieces: Map[Pos, Piece], history: History) {
 
   lazy val occupations = pieces.keySet
 
-  def promote(orig: Pos, dest: Pos): Option[Board] = for {
-    pawn ← apply(orig)
-    b1 ← move(orig, dest)
-    b2 ← b1.take(dest)
-    b3 ← b2.place(pawn.color.queen, dest)
+  def promote(pos: Pos): Option[Board] = for {
+    pawn ← apply(pos)
+    if (pawn is Pawn)
+    b2 ← take(pos)
+    b3 ← b2.place(pawn.color.queen, pos)
   } yield b3
 
   def withHistory(h: History): Board = copy(history = h)

chess/src/main/scala/Color.scala

@@ -29,7 +29,7 @@ case object White extends Color {
 
   val unmovedPawnY = 2
   val passablePawnY = 5
-  val promotablePawnY = 7
+  val promotablePawnY = 8
 
   val letter = 'w'
   val name = "white"
@@ -41,7 +41,7 @@ case object Black extends Color {
 
   val unmovedPawnY = 7
   val passablePawnY = 4
-  val promotablePawnY = 2
+  val promotablePawnY = 1
 
   val letter = 'b'
   val name = "black"

chess/src/test/scala/BoardTest.scala

@@ -43,7 +43,7 @@ class BoardTest extends ChessTest {
     }
 
     "allow a pawn to be promoted to a queen" in {
-      Board.empty.place(Black.pawn, A7) flatMap (_.promote(A7, A8)) must beSome.like {
+      Board.empty.place(Black.pawn, A8) flatMap (_ promote A8) must beSome.like {
         case b ⇒ b(A8) must beSome(Black.queen)
       }
     }

chess/src/test/scala/PromotionTest.scala

@@ -8,20 +8,53 @@ class PromotionTest extends ChessTest {
   p
 K      """
     val game = Game(board, Black)
-     "promote to a queen" in {
-       game.playMove(C2, C1, Queen) must beGame("""
+    "promote to a queen" in {
+      game.playMove(C2, C1, Queen) must beGame("""
 
 K q    """)
-     }
-     "promote to a queen by default" in {
-       game.playMove(C2, C1) must beGame("""
+    }
+    "promote to a queen by default" in {
+      game.playMove(C2, C1) must beGame("""
 
 K q    """)
-     }
-     "promote to a knight" in {
-       game.playMove(C2, C1, Knight) must beGame("""
+    }
+    "promote to a knight" in {
+      game.playMove(C2, C1, Knight) must beGame("""
 
 K n    """)
-     }
+    }
+    "promote to a queen by killing" in {
+      Game("""
+  p
+K  R""", Black).playMove(C2, D1) must beGame("""
+
+K  q""")
+    }
+    "promote to a knight by killing" in {
+      Game("""
+  p
+K  R""", Black).playMove(C2, D1, Knight) must beGame("""
+
+K  n""")
+    }
+    "promote to a whiteknight" in {
+      Game("""
+
+P
+
+
+
+
+
+K n    """).playMove(A7, A8, Knight) must beGame("""
+N
+
+
+
+
+
+
+K n    """)
+    }
   }
 }