Allow piece to move onto its own square and capture itself

takhta.html

@@ -390,11 +390,6 @@
 					renderedPromotion = whiteMove ? whitePieces[promotion] : blackPieces[promotion];
 				}
 
-				// Are we moving the piece onto itself?
-				if (startLetter === endLetter && startNumber === endNumber) {
-					return {error: 'Start and end squares of the move cannot be identical'};
-				}
-
 				// Are we moving the piece from where it is located?
 				let startSquare = document.getElementById(startLetter + startNumber);
 				if (startSquare.childNodes.length === 0) {
@@ -409,34 +404,38 @@
 
 				// Can the piece move to this location?
 				let endSquare = document.getElementById(endLetter + endNumber);
-				if (endSquare.childNodes.length !== 0 && !captures) {
+				if (endSquare.childNodes.length !== 0 && !captures && startSquare !== endSquare) {
 					return {error: 'Square ' + endLetter + endNumber + ' is occupied, did you mean to capture?'};
 				}
 				if (endSquare.childNodes.length === 0 && captures) {
 					return {error: 'Square ' + endLetter + endNumber + ' empty even though capture was specified'};
 				}
 
-				// Record our alterations to the table
-				let moveRecord = {
-					start: startLetter + startNumber,
-					end: endLetter + endNumber,
-					startPiece: renderedPiece,
-					endPiece: promotion ? renderedPromotion : renderedPiece,
-					capturedPiece: captures ? endSquare.childNodes[0].data : null,
-					moveText: move
-				};
-				moveHistory.push(moveRecord);
-
 				// Apply move
+				let removedPieces = {}
+				let placedPieces = {}
 				if (captures) {
+					removedPieces[endLetter + endNumber] = endSquare.childNodes[0].data;
 					endSquare.removeChild(endSquare.childNodes[0]);
 				}
-				startSquare.removeChild(startSquare.childNodes[0]);
-				endSquare.appendChild(document.createTextNode(promotion ? renderedPromotion : renderedPiece))
+				if (startSquare !== endSquare || !captures) {
+					removedPieces[startLetter + startNumber] = renderedPiece;
+					startSquare.removeChild(startSquare.childNodes[0]);
+					placedPieces[endLetter + endNumber] = promotion ? renderedPromotion : renderedPiece;
+					endSquare.appendChild(document.createTextNode(promotion ? renderedPromotion : renderedPiece))
+				}
 
 				// Flip whose turn it is
 				document.getElementById('tomove').childNodes[0].data = whiteMove ? 'Black' : 'White';
 
+				// Record our alterations to the table
+				let moveRecord = {
+					removedPieces: removedPieces,
+					placedPieces: placedPieces,
+					moveText: move
+				};
+				moveHistory.push(moveRecord);
+
 				return {}
 			}
 
@@ -447,13 +446,14 @@
 				}
 
 				// Undo move on the board
-				let {start, end, startPiece, capturedPiece, moveText} = moveHistory.pop();
-				let startSquare = document.getElementById(start);
-				let endSquare = document.getElementById(end);
-				endSquare.removeChild(endSquare.childNodes[0]);
-				startSquare.appendChild(document.createTextNode(startPiece));
-				if (capturedPiece) {
-					endSquare.appendChild(document.createTextNode(capturedPiece));
+				let {removedPieces, placedPieces, moveText} = moveHistory.pop();
+				for (let coords in placedPieces) {
+					let square = document.getElementById(coords);
+					square.removeChild(square.childNodes[0]);
+				}
+				for (let coords in removedPieces) {
+					let square = document.getElementById(coords);
+					square.appendChild(document.createTextNode(removedPieces[coords]));
 				}
 
 				// Flip whose turn it is