Add button to download list of game moves

takhta.html

@@ -177,6 +177,7 @@
 				<form id="actions">
 					<input type="button" value="Undo" onclick="undoMove()">
 					<input type="button" value="Flip board" onclick="flipBoard()">
+					<input type="button" value="Download moves" onclick="download()">
 				</form>
 			</p>
 		</section>
@@ -437,6 +438,56 @@
 				// Replace the old board with the new one
 				document.getElementById('board').replaceChild(newBoard, oldBoard);
 			}
+
+			function download() {
+				let actions = document.getElementById("actions");
+				let moves = document.getElementById("movelist");
+				let link = document.createElement("a");
+
+				link.setAttribute("download", "moves.text");
+				link.style.display = "none";
+				actions.appendChild(link);
+
+				var pos = 0;
+				var game = [];
+				var longest = 0;
+
+				for(let move = 0; move < moves.children.length; move += 1) {
+					let record = moves.children[move];
+
+					if(move % 2 === 0) {
+						if(record.innerHTML.length > longest) {
+							longest = record.innerHTML.length;
+						}
+
+						game[pos] = [record.innerHTML];
+					} else {
+						game[pos].push(record.innerHTML);
+						pos += 1;
+					}
+				}
+
+				let file = [];
+				let padding = Math.floor(Math.log10(game.length));
+
+				for(let entry = 0; entry < game.length; entry += 1) {
+					var line = `${entry + 1}`.padStart(padding + 1, " ") + ": ";
+
+					if(game[entry][1] !== undefined) {
+						line += `${game[entry][0].padEnd(longest, " ")} ${game[entry][1]}`;
+					} else {
+						line += game[entry][0];
+					}
+
+					file.push(line);
+				}
+
+				let contents = encodeURIComponent(file.join("\n"));
+
+				link.setAttribute("href", "data:text/plain;charset=utf-8," + contents);
+				link.click();
+				actions.removeChild(link);
+			}
 		</script>
 	</body>
 </html>