implement userTouch method

src/backend/Board.java

@@ -7,6 +7,14 @@ public class Board {
 	private int width;
 	private int height;
 	private ArrayList<Piece> pieces; 
+	
+	// new fields for userTouch
+	private int turnNumber = 0;
+	private boolean turnWhite = true;
+	private boolean hasSelection = false;
+	private int selectedX;
+	private int selectedY;
+	
 
 	public Board(int width, int height) {
 		this.width = width;
@@ -24,12 +32,11 @@ public class Board {
 
 	public int getTurnNumber() {
 		//TODO
-		return 0;
+		return turnNumber;
 	}
 
 	public boolean isTurnWhite() {
-		//TODO
-		return false;
+		return turnWhite;
 	}
 
 	public void setPiece(boolean isWhite, PieceType type, int x, int y) {
@@ -114,8 +121,53 @@ public class Board {
 	}
 
 	public void userTouch(int x, int y) {
-		//TODO
-		
+		// 1. find if u clicked on a piece at (x,y)
+		Piece clicked = null;
+		for (int i = 0; i < pieces.size(); i++) {
+			Piece p = pieces.get(i);
+			if (p.getX() == x && p.getY() == y) {
+				clicked = p;
+				break;
+			}
+		}
+		// 2. if nothing is selected 
+		if (!hasSelection) {
+			if(clicked != null) {
+				hasSelection = true;
+				selectedX = x;
+				selectedY = y;
+			}
+			return;
+		}
+		// 3. if u click on the same cell twice, cancel selection 
+		if (selectedX == x && selectedY == y) {
+			hasSelection = false;
+			return;
+		}
+		// 4. otherwise, move the previously selected to (x,y)
+		// a, remove any piece that was already on the cell
+		pieces.removeIf(p -> p.getX() == x && p.getY() == y);
+        // remove p if p.getX() == x && p.getY() == y
+//	    b) locate the selected piece object
+        Piece toMove = null;
+        for (int i = 0; i < pieces.size(); i++) {
+            Piece p = pieces.get(i);
+            if (p.getX() == selectedX && p.getY() == selectedY) {
+                toMove = p;
+                break;
+            }
+        }
+//      c) re-place it at the new coordinates
+        if (toMove != null) {
+            pieces.remove(toMove);
+            // we need to remove it from its old place 
+            pieces.add(new Piece(x, y, toMove.getType(),toMove.isWhite()));
+        }   // change the x y but still the same color and type 
+     // 5) Advance half-move counter and switch player
+        turnNumber++;
+        turnWhite = !turnWhite;
+     // 6) Clear the selection so you can pick again next turn
+        hasSelection = false;
 	}
 
 	public boolean isSelected(int x, int y) {