Implement king moves

chess/board.go

@@ -711,8 +711,100 @@ func (b *Board) moveQueen(position string) error {
 }
 
 func (b *Board) moveKing(position string) error {
-	// TODO: implement king moves
-	return nil
+	var (
+		x     int
+		y     int
+		xPrev int
+		yPrev int
+		piece *Piece
+		err   error
+	)
+
+	if x, y, err = getXY(position); err != nil {
+		return err
+	}
+
+	// ^
+	xPrev = x + 0
+	yPrev = y - 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// ^>
+	xPrev = x + 1
+	yPrev = y - 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// >
+	xPrev = x + 1
+	yPrev = y + 0
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// v>
+	xPrev = x + 1
+	yPrev = y + 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// v
+	xPrev = x + 0
+	yPrev = y + 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// <v
+	xPrev = x - 1
+	yPrev = y + 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// <
+	xPrev = x - 1
+	yPrev = y + 0
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	// <^
+	xPrev = x - 1
+	yPrev = y - 1
+	piece = b.getPiece(xPrev, yPrev)
+	if piece != nil && piece.Name == King && piece.Color == b.turn {
+		b.tiles[xPrev][yPrev] = nil
+		b.tiles[x][y] = piece
+		return nil
+	}
+
+	return fmt.Errorf("no king found that can move to %s", position)
 }
 
 func (b *Board) mustSetPiece(name PieceName, color Color, position string) {

chess/board_test.go

@@ -265,6 +265,29 @@ func TestBoardMoveQueenInvalid(t *testing.T) {
 	assertMoveError(t, b, "Qd3", "no queen found that can move to d3")
 }
 
+func TestBoardMoveKing(t *testing.T) {
+	b := chess.NewBoard()
+
+	b.Parse("e4 e5 Ke2 Ke7 Kf3 Kd6 Kg3 Kc6")
+	assertNoPiece(t, b, "e1")
+	assertNoPiece(t, b, "e8")
+	assertNoPiece(t, b, "e2")
+	assertNoPiece(t, b, "e7")
+	assertNoPiece(t, b, "f3")
+	assertNoPiece(t, b, "d6")
+
+	assertPiece(t, b, "g3", chess.King, chess.Light)
+	assertPiece(t, b, "c6", chess.King, chess.Dark)
+}
+
+func TestBoardMoveKingInvalid(t *testing.T) {
+	b := chess.NewBoard()
+
+	assertMoveError(t, b, "Ke1", "e1 blocked by white king")
+	assertMoveError(t, b, "Ke2", "e2 blocked by white pawn")
+	assertMoveError(t, b, "Ke3", "no king found that can move to e3")
+}
+
 func assertPiece(t *testing.T, b *chess.Board, position string, name chess.PieceName, color chess.Color) {
 	p := b.At(position)