// The part of an R2 bucket snapshots.ts uses (put, get and list with prefix, startAfter and// limit), in memory. Keys list in byte order, as they do in R2.type Stored = { text: string; uploaded: Date };export class MemoryBucket {  objects = new Map<string, Stored>();  failNext = false;  #clock: () => Date;  constructor(clock: () => Date = () => new Date()) {    this.#clock = clock;  }  async put(key: string, value: string): Promise<void> {    if (this.failNext) {      this.failNext = false;      throw new Error("R2 put failed: 503 Service Unavailable");    }    this.objects.set(key, { text: value, uploaded: this.#clock() });  }  async get(key: string) {    const o = this.objects.get(key);    return o ? { text: async () => o.text } : null;  }  async list({ prefix = "", startAfter = "", limit = 1000 }: { prefix?: string; startAfter?: string; limit?: number }) {    const keys = [...this.objects.keys()].filter((k) => k.startsWith(prefix) && k > startAfter).sort();    const objects = keys.slice(0, limit).map((key) => ({ key, size: new TextEncoder().encode(this.objects.get(key)!.text).length, uploaded: this.objects.get(key)!.uploaded }));    return { objects, truncated: keys.length > limit };  }}export function memoryBucket(clock?: () => Date): MemoryBucket & R2Bucket {  return new MemoryBucket(clock) as MemoryBucket & R2Bucket;}