From 1e06e07a1005deb54ffe1f6dd0c496bfdf9427fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juhani=20Krekel=C3=A4?= <juhani@krekelä.fi>
Date: Thu, 7 Jan 2021 23:23:36 +0200
Subject: [PATCH] Add piece promotion

---
 shatrizualizer.html | 69 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 52 insertions(+), 17 deletions(-)

diff --git a/shatrizualizer.html b/shatrizualizer.html
index d1b0d2d..09c461c 100644
--- a/shatrizualizer.html
+++ b/shatrizualizer.html
@@ -194,6 +194,7 @@
 					return;
 				}
 
+				// Piece
 				let piece = move.slice(0, 1);
 				let index = 0;
 				switch(piece) {
@@ -220,6 +221,7 @@
 						return;
 				}
 
+				// Start square
 				let startLetter = move.slice(index, index + 1);
 				let startNumber = move.slice(index + 1, index + 2);
 				index += 2;
@@ -231,12 +233,14 @@
 					return;
 				}
 
+				// Capturing
 				let captures = false;
 				if (move.slice(index, index + 1) === 'x') {
 					captures = true;
 					index++;
 				}
 
+				// End square
 				let endLetter = move.slice(index, index + 1);
 				let endNumber = move.slice(index + 1, index + 2);
 				index += 2;
@@ -248,6 +252,33 @@
 					return;
 				}
 
+				// Promotion
+				let promotion = null;
+				if (move.slice(index, index + 1) === '=') {
+					index++;
+					switch (move.slice(index, index + 1)) {
+						case 'Q':
+						case 'B':
+						case 'N':
+						case 'R':
+							promotion = move.slice(index, index + 1);
+							break;
+						case 'K':
+							alert('Cannot promote a piece to king');
+							return;
+							break;
+						case 'P':
+							alert('Cannot promote a piece to pawn');
+							return;
+							break;
+						default:
+							alert('Unrecognized piece: ' + move.slice(index, index + 1));
+							return;
+					}
+					index++;
+				}
+
+				// Check(mate)
 				switch(move.slice(index)) {
 					case '':
 						// nothing
@@ -263,16 +294,16 @@
 						return;
 				}
 
+				// End of parsing, start of move construction
 				let whitePieces = {'K': '♔', 'Q': '♕', 'R': '♖', 'B': '♗', 'N': '♘', 'P': '♙'};
 				let blackPieces = {'K': '♚', 'Q': '♛', 'R': '♜', 'B': '♝', 'N': '♞', 'P': '♟'};
 
 				let whiteMove = document.getElementById('tomove').childNodes[0].data == 'White';
 
-				let renderedPiece = null;
-				if (whiteMove) {
-					renderedPiece = whitePieces[piece];
-				} else {
-					renderedPiece = blackPieces[piece];
+				let renderedPiece = whiteMove ? whitePieces[piece] : blackPieces[piece];
+				let renderedPromotion = null;
+				if (promotion) {
+					renderedPromotion = whiteMove ? whitePieces[promotion] : blackPieces[promotion];
 				}
 
 				// Are we moving the piece from where it is located?
@@ -282,7 +313,7 @@
 					return;
 				}
 				if (startSquare.childNodes[0].data !== renderedPiece) {
-					let pieceNames = {'K': 'King', 'Q': 'Vizier', 'R': 'Rook', 'B': 'Elephant', 'N': 'Horse', 'P': 'Pawn'};
+					let pieceNames = {'K': 'king', 'Q': 'vizier', 'R': 'rook', 'B': 'elephant', 'N': 'horse', 'P': 'pawn'};
 					alert((whiteMove ? 'White' : 'Black') + ' ' + pieceNames[piece] + ' not on square ' + startLetter + startNumber);
 					return;
 				}
@@ -301,17 +332,21 @@
 				}
 
 				// Record our alterations to the table
-				let movedPiece = {start: startLetter + startNumber, end: endLetter + endNumber, piece: renderedPiece};
-				let capturedPiece = captures ? endSquare.childNodes[0].data : null;
-				moveHistory.push({move: movedPiece, capture: capturedPiece});
-				console.log(moveHistory);
+				let moveRecord = {
+					start: startLetter + startNumber,
+					end: endLetter + endNumber,
+					startPiece: renderedPiece,
+					endPiece: promotion ? renderedPromotion : renderedPiece,
+					capturedPiece: captures ? endSquare.childNodes[0].data : null
+				};
+				moveHistory.push(moveRecord);
 
 				// Apply move
 				if (captures) {
 					endSquare.removeChild(endSquare.childNodes[0]);
 				}
 				startSquare.removeChild(startSquare.childNodes[0]);
-				endSquare.appendChild(document.createTextNode(renderedPiece))
+				endSquare.appendChild(document.createTextNode(promotion ? renderedPromotion : renderedPiece))
 
 				// Flip whose turn it is
 				document.getElementById('tomove').childNodes[0].data = whiteMove ? 'Black' : 'White';
@@ -332,13 +367,13 @@
 				}
 
 				// Undo move on the board
-				let {move, capture} = moveHistory.pop();
-				let startSquare = document.getElementById(move.start);
-				let endSquare = document.getElementById(move.end);
+				let {start, end, startPiece, endPiece, capturedPiece} = moveHistory.pop();
+				let startSquare = document.getElementById(start);
+				let endSquare = document.getElementById(end);
 				endSquare.removeChild(endSquare.childNodes[0]);
-				startSquare.appendChild(document.createTextNode(move.piece));
-				if (capture) {
-					endSquare.appendChild(document.createTextNode(capture));
+				startSquare.appendChild(document.createTextNode(startPiece));
+				if (capturedPiece) {
+					endSquare.appendChild(document.createTextNode(capturedPiece));
 				}
 
 				// Flip whose turn it is