Function ensureViewerIsPolling

examples/pdf-server/server.ts:264–276

* Wait for the viewer's first poll_pdf_commands call. * * Called before waitForPageData() / waitForSaveData() so a viewer that never * mounted fails in ~8s with a specific message instead of a generic 45s * "Timeout waiting for ..." that gives no hint why. * * Intentionally does NOT touch poll

(uuid: string)

 * can wait independently and all observe the same add() when it happens.
 */
async function ensureViewerIsPolling(uuid: string): Promise<void> {
  const deadline = Date.now() + VIEWER_FIRST_POLL_GRACE_MS;
  while (!viewsPolled.has(uuid)) {
    if (Date.now() >= deadline) {
      throw new Error(
        `Viewer never connected for viewUUID ${uuid} (no poll within ${VIEWER_FIRST_POLL_GRACE_MS / 1000}s). ` +
          `The iframe likely failed to mount — this happens when the conversation ` +
          `goes idle before the viewer finishes loading. Call display_pdf again to get a fresh viewUUID.`,
      );
    }
    await new Promise((r) => setTimeout(r, 100));
  }
}

// =============================================================================
// Pending save_as Requests (request-response bridge via client)