basic model

app/src/main/java/chess/model/visitor/PermissiveRuleChecker.java

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+package chess.model.visitor;
+
+import chess.model.Coordinate;
+import chess.model.Direction;
+import chess.model.Move;
+import chess.model.Piece;
+import chess.model.PieceVisitor;
+import chess.model.pieces.Bishop;
+import chess.model.pieces.King;
+import chess.model.pieces.Knight;
+import chess.model.pieces.Pawn;
+import chess.model.pieces.Queen;
+import chess.model.pieces.Rook;
+
+public class PermissiveRuleChecker implements PieceVisitor<Boolean> {
+
+	private final Move move;
+
+	public PermissiveRuleChecker(Move move) {
+		this.move = move;
+		assert move.isValid() : "Move is invalid!";
+	}
+
+	public boolean isValidFor(Piece piece) {
+		return visit(piece);
+	}
+
+	@Override
+	public Boolean visitPiece(Bishop bishop) {
+		Direction moveDirection = Direction.findDirection(this.move);
+
+		switch (moveDirection) {
+			case FrontLeft:
+			case BackLeft:
+			case FrontRight:
+			case BackRight:
+				return true;
+
+			default:
+				return false;
+		}
+	}
+
+	@Override
+	public Boolean visitPiece(King king) {
+		return this.move.traversedCells() == 1;
+	}
+
+	@Override
+	public Boolean visitPiece(Knight knight) {
+		Coordinate piecePos = move.getStart();
+		final Coordinate[] positions = {
+				new Coordinate(piecePos.getX() - 1, piecePos.getY() - 2),
+				new Coordinate(piecePos.getX() - 1, piecePos.getY() + 2),
+				new Coordinate(piecePos.getX() + 1, piecePos.getY() - 2),
+				new Coordinate(piecePos.getX() + 1, piecePos.getY() + 2),
+				new Coordinate(piecePos.getX() + 2, piecePos.getY() - 1),
+				new Coordinate(piecePos.getX() + 2, piecePos.getY() + 1),
+				new Coordinate(piecePos.getX() - 2, piecePos.getY() - 1),
+				new Coordinate(piecePos.getX() - 2, piecePos.getY() + 1),
+		};
+
+		for (int i = 0; i < positions.length; i++) {
+			if (this.move.getFinish().equals(positions[i]))
+				return true;
+		}
+
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(Pawn pawn) {
+		Direction moveDirection = Direction.findDirection(this.move);
+		int directionIndexOffset = moveDirection.getIndexOffset();
+		int distance = this.move.traversedCells();
+
+		// Revoke moving backwards
+		if (directionIndexOffset * pawn.multiplier() < 0)
+			return false;
+
+		// Allowing straight moves
+		if (Math.abs(directionIndexOffset) == Direction.Front.getIndexOffset()) {
+			if (pawn.hasMoved())
+				return distance == 1;
+			return distance == 1 || distance == 2;
+		}
+
+		// Allowing small diagonal moves
+		if (Math.abs(directionIndexOffset) == Direction.FrontLeft.getIndexOffset()
+				|| Math.abs(directionIndexOffset) == Direction.FrontRight.getIndexOffset()) {
+			return distance == 1;
+		}
+
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(Queen queen) {
+		Direction moveDirection = Direction.findDirection(this.move);
+		return moveDirection != Direction.Unset;
+	}
+
+	@Override
+	public Boolean visitPiece(Rook rook) {
+		Direction moveDirection = Direction.findDirection(this.move);
+
+		switch (moveDirection) {
+			case Front:
+			case Back:
+			case Left:
+			case Right:
+				return true;
+
+			default:
+				return false;
+		}
+	}
+
+}