Merge branch 'worktree-agent-ab151ac84f067999f' into revise/edge-cases-and-sources

course/08-push-chains/reference/ts/src/engine/puzzle/level.ts

@@ -74,6 +74,10 @@ export class Level {
    * move one at a time, the one furthest ahead in `dir` first (oldest first on a
    * tie); each one's move is planned in full, then committed, before the next is
    * planned. Every move uses the rules in force before the first.
+   *
+   * An object steps at most once in a movement phase. A `YOU` object that an
+   * earlier move already carried along (pushed, or moved by any other response)
+   * doesn't start a move of its own, and no later move can make it step again.
    */
   moveYou(dir: Dir): void {
     const [dx, dy] = delta(dir);
@@ -83,10 +87,15 @@ export class Level {
       .filter((o) => this.hasProperty(o.id, YOU))
       .sort((a, b) => ahead(b) - ahead(a) || a.id - b.id)
       .map((o) => o.id);
+    const stepped = new Set<ObjectId>();
     for (const id of you) {
       if (this.board.find(id) === undefined) continue; // destroyed by an earlier move
-      const planner = new Planner(this, dir);
-      if (planner.tryMove(id)) this.commit(planner.result(), dir);
+      if (stepped.has(id)) continue; // already moved, by an earlier move
+      const planner = new Planner(this, dir, stepped);
+      if (!planner.tryMove(id)) continue;
+      const plan = planner.result();
+      this.commit(plan, dir);
+      for (const moved of plan.moving) if (!plan.destroyed.has(moved)) stepped.add(moved);
     }
     this.reparse();
   }

course/08-push-chains/reference/ts/src/engine/puzzle/movement.ts

@@ -63,13 +63,18 @@ export interface MoveContext {
   responses(): readonly Response[];
 }
 
-/** Plans one move on a board it only reads. */
+/**
+ * Plans one move on a board it only reads. `stepped` holds the objects that have
+ * already stepped in this movement phase, in an earlier committed plan: an object
+ * steps at most once per phase, so none of them can step again.
+ */
 export class Planner {
   private plan: Plan = { moving: new Set(), destroyed: new Set() };
 
   constructor(
     private readonly level: MoveContext,
     private readonly dir: Dir,
+    private readonly stepped: ReadonlySet<ObjectId>,
   ) {}
 
   /** Does object `id` have `property`, under the rules in force before the move? */
@@ -98,10 +103,13 @@ export class Planner {
    * Plan object `id` stepping one tile in the move's direction, with whatever
    * the responses add. Returns whether it can. If it can't, the plan is left as
    * it was before the call. An object already planned to move, or to be
-   * destroyed, is out of the way: the answer is yes, and nothing is added.
+   * destroyed, is out of the way: the answer is yes, and nothing is added. An
+   * object that has already stepped in this movement phase can't step again: the
+   * answer is no.
    */
   tryMove(id: ObjectId): boolean {
     if (this.plan.moving.has(id) || this.plan.destroyed.has(id)) return true;
+    if (this.stepped.has(id)) return false;
     const o = this.level.board.get(id);
     const [dx, dy] = delta(this.dir);
     const to: Pos = [o.x + dx, o.y + dy];