Introduce check if the game has ended (checkmate/stalemate)

api/move.go

@@ -21,6 +21,7 @@ const (
 	MoveMessage        MessageType = "move"
 	InvalidMoveMessage MessageType = "invalidMove"
 	ColorDetermined    MessageType = "colorDetermined"
+	GameEnded          MessageType = "gameEnded"
 )
 
 func (m WebsocketMessage) IsValid() bool {

chess/bishop.go

@@ -9,14 +9,14 @@ type Bishop struct {
 }
 
 func (b Bishop) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return b.GetAllNonBlockedMoves(board, fromSquare)
+	return b.GetAllNonBlockedSquares(board, fromSquare)
 }
 
 func (b Bishop) GetColor() types.ChessColor {
 	return b.Color
 }
 
-func (b Bishop) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (b Bishop) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedDiagonals(fromSquare)
 }
 

chess/board.go

@@ -86,7 +86,7 @@ func (b *Board) CheckAndPlay(move types.Move) (bool, Violation) {
 	}
 
 	if !wasSpecialMove {
-		allMovesExceptBlocked := pieceAtStartSquare.GetAllNonBlockedMoves(tempBoard, move.StartSquare)
+		allMovesExceptBlocked := pieceAtStartSquare.GetAllNonBlockedSquares(tempBoard, move.StartSquare)
 		legal := lo.Contains(allMovesExceptBlocked, move.EndSquare)
 		if !legal {
 			return false, InvalidMove
@@ -204,3 +204,66 @@ func (b *Board) handleSpecialMove(move types.Move) (bool, error) {
 	}
 	return was, err
 }
+
+type GameEndedReason string
+
+const (
+	NoReason          GameEndedReason = "noReason"
+	WhiteIsCheckmated GameEndedReason = "whiteIsCheckmated"
+	BlackIsCheckmated GameEndedReason = "blackIsCheckmated"
+	StalemateReason   GameEndedReason = "stalemate"
+)
+
+func (r GameEndedReason) String() string {
+	return string(r)
+}
+
+func (b *Board) HasGameEnded(lastMove types.Move) (bool, GameEndedReason) {
+	checkForColor := lastMove.ColorMoved.Opposite()
+	if checkmate := b.isColorCheckmated(checkForColor); checkmate {
+		switch checkForColor {
+		case types.White:
+			return true, WhiteIsCheckmated
+		case types.Black:
+			return true, BlackIsCheckmated
+		}
+	}
+	if b.isStalemate() {
+		return true, StalemateReason
+	}
+
+	return false, NoReason
+}
+
+func (b *Board) isColorCheckmated(color types.ChessColor) bool {
+	inCheck, _ := b.isKingOfMovingColorInCheck(color)
+	if !inCheck {
+		return false
+	}
+
+	copyOfBoard := b.getCopyOfBoard()
+
+	var movesToCheck []types.Move
+
+	for startSquare, piece := range b.position {
+		if piece.GetColor() == color {
+			for _, endSquare := range piece.GetAllNonBlockedSquares(*b, startSquare) {
+				move := types.Move{StartSquare: startSquare, EndSquare: endSquare}
+				movesToCheck = append(movesToCheck, move)
+			}
+		}
+	}
+
+	for _, move := range movesToCheck {
+		valid, _ := copyOfBoard.CheckAndPlay(move)
+		if valid {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (b *Board) isStalemate() bool {
+	return false
+}

chess/board_test.go

@@ -374,3 +374,78 @@ func Test_Promotion_BlackKing(t *testing.T) {
 		assert.False(t, good)
 	})
 }
+
+func Test_Board_HasGameEnded(t *testing.T) {
+	board := newBoard()
+
+	t.Run("no checkmate yet", func(t *testing.T) {
+		board.position[types.Coordinate{Col: 1, Row: 1}] = King{Color: types.White}
+		board.position[types.Coordinate{Col: 7, Row: 6}] = Queen{Color: types.White}
+		board.position[types.Coordinate{Col: 7, Row: 7}] = Queen{Color: types.White}
+
+		board.position[types.Coordinate{Col: 2, Row: 8}] = King{Color: types.Black}
+
+		whiteMove := types.Move{
+			StartSquare: types.Coordinate{Col: 7, Row: 6},
+			EndSquare:   types.Coordinate{Col: 8, Row: 6},
+			ColorMoved:  types.White,
+		}
+		valid, violation := board.CheckAndPlay(whiteMove)
+		assert.True(t, valid)
+		assert.Empty(t, violation)
+
+		gameEnded, reason := board.HasGameEnded(whiteMove)
+
+		assert.False(t, gameEnded)
+		assert.Equal(t, NoReason, reason)
+	})
+
+	t.Run("checkmate move is made", func(t *testing.T) {
+		blackMove := types.Move{
+			StartSquare: types.Coordinate{Col: 2, Row: 8},
+			EndSquare:   types.Coordinate{Col: 1, Row: 8},
+			ColorMoved:  types.Black,
+		}
+		valid, violation := board.CheckAndPlay(blackMove)
+		assert.True(t, valid)
+		assert.Empty(t, violation)
+
+		checkmateMove := types.Move{
+			StartSquare: types.Coordinate{Col: 8, Row: 6},
+			EndSquare:   types.Coordinate{Col: 8, Row: 8},
+			ColorMoved:  types.White,
+		}
+
+		valid, violation = board.CheckAndPlay(checkmateMove)
+		assert.True(t, valid)
+		assert.Empty(t, violation)
+
+		gameEnded, reason := board.HasGameEnded(checkmateMove)
+		assert.True(t, gameEnded)
+		assert.Equal(t, BlackIsCheckmated, reason)
+	})
+}
+
+func Test_Board_HasGameEnded_RookBlocks(t *testing.T) {
+	board := newBoard()
+
+	board.position[types.Coordinate{Col: 1, Row: 1}] = King{Color: types.White}
+	board.position[types.Coordinate{Col: 8, Row: 7}] = Queen{Color: types.White}
+	board.position[types.Coordinate{Col: 7, Row: 7}] = Queen{Color: types.White}
+
+	board.position[types.Coordinate{Col: 1, Row: 8}] = King{Color: types.Black}
+	board.position[types.Coordinate{Col: 2, Row: 2}] = Rook{Color: types.Black}
+
+	whiteMove := types.Move{
+		StartSquare: types.Coordinate{Col: 8, Row: 7},
+		EndSquare:   types.Coordinate{Col: 8, Row: 8},
+		ColorMoved:  types.White,
+	}
+	valid, violation := board.CheckAndPlay(whiteMove)
+	assert.True(t, valid)
+	assert.Empty(t, violation)
+
+	gameEnded, reason := board.HasGameEnded(whiteMove)
+	assert.False(t, gameEnded)
+	assert.Equal(t, NoReason, reason)
+}

chess/game.go

@@ -27,6 +27,7 @@ const (
 	PlayerToMove
 	CheckMove
 	CheckPlayerChange
+	GameEnded
 )
 
 func NewGame() *Game {
@@ -85,6 +86,7 @@ func (game *Game) Handle() {
 	defer game.killGame()
 
 	var receivedMove types.Move
+	var gameEndReason GameEndedReason
 	var err error
 
 	for {
@@ -110,9 +112,7 @@ func (game *Game) Handle() {
 		case CheckMove:
 			valid, ruleViolation := game.board.CheckAndPlay(receivedMove)
 
-			if valid {
-				game.gameState = CheckPlayerChange
-			} else {
+			if !valid {
 				invalidMoveMessage, err := api.GetInvalidMoveMessage(receivedMove, ruleViolation.String())
 				if err != nil {
 					log.Println("Error marshalling 'colorDetermined' message for player 1", err)
@@ -120,7 +120,17 @@ func (game *Game) Handle() {
 				}
 				game.currentTurnPlayer.writeMessage(invalidMoveMessage)
 				game.gameState = PlayerToMove
+				continue
 			}
+
+			gameEnded, reason := game.board.HasGameEnded(receivedMove)
+			if gameEnded {
+				gameEndReason = reason
+				continue
+			}
+
+			game.gameState = CheckPlayerChange
+
 		case CheckPlayerChange:
 			if game.currentTurnPlayer.Uuid == game.players[0].Uuid {
 				game.currentTurnPlayer = game.players[1]
@@ -135,6 +145,10 @@ func (game *Game) Handle() {
 			}
 
 			game.gameState = PlayerToMove
+
+		case GameEnded:
+			game.broadcastGameEnd(gameEndReason)
+			return
 		}
 		log.Println("GameState = ", game.gameState)
 	}
@@ -181,6 +195,20 @@ func (game Game) broadcastMove(move types.Move) error {
 	return nil
 }
 
+func (game Game) broadcastGameEnd(reason GameEndedReason) error {
+	err := game.GetPlayer1().SendGameEnded(reason)
+	if err != nil {
+		return err
+	}
+
+	err = game.GetPlayer2().SendGameEnded(reason)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (game *Game) playerDisconnected(p *Player) {
 	log.Println(string(p.color), " disconnected")
 	playerStillInGame := lo.Filter(game.players, func(player *Player, _ int) bool {

chess/king.go

@@ -9,14 +9,14 @@ type King struct {
 }
 
 func (k King) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return k.GetAllNonBlockedMoves(board, fromSquare)
+	return k.GetAllNonBlockedSquares(board, fromSquare)
 }
 
 func (k King) GetColor() types.ChessColor {
 	return k.Color
 }
 
-func (k King) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (k King) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedKingMoves(fromSquare)
 }
 

chess/knight.go

@@ -9,14 +9,14 @@ type Knight struct {
 }
 
 func (n Knight) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return n.GetAllNonBlockedMoves(board, fromSquare)
+	return n.GetAllNonBlockedSquares(board, fromSquare)
 }
 
 func (n Knight) GetColor() types.ChessColor {
 	return n.Color
 }
 
-func (n Knight) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (n Knight) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedKnightMoves(fromSquare)
 }
 

chess/pawn.go

@@ -12,7 +12,7 @@ type Pawn struct {
 
 func (p Pawn) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	attackingMoves := make([]types.Coordinate, 0, 2)
-	allMoves := p.GetAllNonBlockedMoves(board, fromSquare)
+	allMoves := p.GetAllNonBlockedSquares(board, fromSquare)
 	for _, move := range allMoves {
 		if move.Col != fromSquare.Col {
 			attackingMoves = append(attackingMoves, move)
@@ -21,7 +21,7 @@ func (p Pawn) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []
 	return attackingMoves
 }
 
-func (p Pawn) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (p Pawn) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	theoreticalSquares := p.getAllMoves(fromSquare)
 	legalSquares := p.filterBlockedSquares(board, fromSquare, theoreticalSquares)
 

chess/piece_interface.go

@@ -6,7 +6,7 @@ import (
 )
 
 type Piece interface {
-	GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate
+	GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate
 	GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate
 	GetColor() types.ChessColor
 	AfterMoveAction(board *Board, fromSquare types.Coordinate)

chess/player.go

@@ -107,6 +107,24 @@ func (p *Player) SendMoveAndPosition(move types.Move, boardPosition string) erro
 	return nil
 }
 
+func (p *Player) SendGameEnded(reason GameEndedReason) error {
+	reasonToSend := reason.String()
+	messageToSend, err := json.Marshal(api.WebsocketMessage{
+		Type:   api.GameEnded,
+		Reason: &reasonToSend,
+	})
+	if err != nil {
+		log.Println("Error while marshalling: ", err)
+		return err
+	}
+	err = p.writeMessage(messageToSend)
+	if err != nil {
+		log.Println("Error during message writing:", err)
+		return err
+	}
+	return nil
+}
+
 func (p *Player) writeMessage(msg []byte) error {
 	return p.Conn.Write(msg)
 }

chess/queen.go

@@ -9,14 +9,14 @@ type Queen struct {
 }
 
 func (q Queen) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return q.GetAllNonBlockedMoves(board, fromSquare)
+	return q.GetAllNonBlockedSquares(board, fromSquare)
 }
 
 func (q Queen) GetColor() types.ChessColor {
 	return q.Color
 }
 
-func (q Queen) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (q Queen) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	squares := board.GetNonBlockedRowAndColumn(fromSquare)
 	squares = append(squares, board.GetNonBlockedDiagonals(fromSquare)...)
 	return squares

chess/rook.go

@@ -9,14 +9,14 @@ type Rook struct {
 }
 
 func (r Rook) GetAllAttackedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
-	return r.GetAllNonBlockedMoves(board, fromSquare)
+	return r.GetAllNonBlockedSquares(board, fromSquare)
 }
 
 func (r Rook) GetColor() types.ChessColor {
 	return r.Color
 }
 
-func (r Rook) GetAllNonBlockedMoves(board Board, fromSquare types.Coordinate) []types.Coordinate {
+func (r Rook) GetAllNonBlockedSquares(board Board, fromSquare types.Coordinate) []types.Coordinate {
 	return board.GetNonBlockedRowAndColumn(fromSquare)
 }
 

chess/rook_test.go

@@ -14,7 +14,7 @@ func Test_Rook_GetNonBlockedSquares(t *testing.T) {
 		rook := Rook{Color: types.Black}
 
 		board.position[types.Coordinate{Col: 5, Row: 5}] = rook
-		squares := rook.GetAllNonBlockedMoves(board, types.Coordinate{Col: 5, Row: 5})
+		squares := rook.GetAllNonBlockedSquares(board, types.Coordinate{Col: 5, Row: 5})
 		assert.Len(t, squares, 14)
 	})
 
@@ -28,7 +28,7 @@ func Test_Rook_GetNonBlockedSquares(t *testing.T) {
 		board.position[types.Coordinate{Col: 5, Row: 6}] = Pawn{Color: types.White}
 		board.position[types.Coordinate{Col: 6, Row: 5}] = Pawn{Color: types.Black}
 
-		squares := rook.GetAllNonBlockedMoves(board, rookCoordinate)
+		squares := rook.GetAllNonBlockedSquares(board, rookCoordinate)
 
 		squaresOnLeft := lo.Filter(squares, func(square types.Coordinate, _ int) bool {
 			return square.Row == rookCoordinate.Row && square.Col < rookCoordinate.Col

connection/type.go

@@ -96,7 +96,7 @@ func (conn *Connection) Read() ([]byte, error) {
 	msg, err := conn.buffer.Get()
 	if err != nil {
 		conn.ws = nil
-		return nil, err // Tell game-handler that connection was lost
+		return nil, err // TODO: Tell game-handler that connection was lost
 	}
 
 	return []byte(msg), err

types/common.go

@@ -3,6 +3,7 @@ package types
 type ChessColor string
 
 const (
+	NoColor ChessColor = "no_color"
 	White   ChessColor = "white"
 	Black   ChessColor = "black"
 )