Method executeBackup

shift/shift.ts:930–1124

(
    taskId: string,
    options: BackupCallbacks,
    signal?: AbortSignal
  )

    try {
      throwIfAborted(signal);
      // 获取消息总数
      const messages = await safeGetMessages(client, task.sourceId, { limit: 1 });
      const totalCount = (messages as any).total || 0;
      task.totalMessages = totalCount;

      if (task.reverse) {
        // ===== 正序模式：两阶段 =====
        // Phase 1: 收集所有消息 ID（API 返回顺序：新→旧）
        const allIds: number[] = [];
        let collectOffset = 0;
        let collecting = true;

        while (collecting) {
          throwIfAborted(signal);
          const batch = await safeGetMessages(client, task.sourceId, {
            limit: batchSize,
            offsetId: collectOffset,
          });

          if (batch.length === 0) {
            collecting = false;
            break;
          }

          for (const msg of batch) {
            allIds.push(msg.id);
          }
          collectOffset = batch[batch.length - 1].id;

          // 收集阶段进度（每 200 条报告一次）
          if (options.onProgress && allIds.length % 200 === 0) {
            await options.onProgress(0, totalCount);
          }
        }

        // 反转：旧→新（正序）
        allIds.reverse();
        task.totalMessages = allIds.length;

        // Phase 2: 按正序逐条转发
        const startIndex = task.lastMessageId
          ? allIds.indexOf(task.lastMessageId) + 1
          : 0;

        for (let i = startIndex; i < allIds.length; i++) {
          if (task.status !== "running") break;

          try {
            throwIfAborted(signal);
            await this.rateLimiter.throttle(signal);
            throwIfAborted(signal);

            await client.forwardMessages(task.targetId, {
              messages: [allIds[i]],
              fromPeer: task.sourceId,
            });