Add extendMainline to PGN/game

src/pgn.test.ts

@@ -10,7 +10,9 @@ import {
   parsePgn,
   transform,
   startingPosition,
+  defaultGame,
   emptyHeaders,
+  extendMainline,
   parseComment,
   makeComment,
   isChildNode,
@@ -79,6 +81,17 @@ test('make pgn', () => {
   );
 });
 
+test('extend mainline', () => {
+  let game: Game<PgnNodeData> = defaultGame(emptyHeaders);
+  const mainline = 'e4 d5 a3 h6 Bg5'.split(' ').map(san => {
+    return {
+      san: san,
+    };
+  });
+  extendMainline(game, mainline);
+  expect(makePgn(game)).toEqual('1. e4 d5 2. a3 h6 3. Bg5 *\n');
+});
+
 test('parse headers', () => {
   const games = parsePgn(
     [

src/pgn.ts

@@ -131,6 +131,19 @@ export class Node<T> {
   }
 }
 
+export const extendMainline = <T>(game: Game<T>, data: T[]) => {
+  let node = game.moves;
+  while (node.children.length) {
+    const child = node.children[0];
+    node = child;
+  }
+  data.forEach(d => {
+    const newNode = new ChildNode(d);
+    node.children = [newNode];
+    node = newNode;
+  });
+};
+
 export class ChildNode<T> extends Node<T> {
   constructor(public data: T) {
     super();