Function createPersistQueue

packages/sdk/src/persist-queue.ts:27–83

(
  session: Composition,
  adapter: PersistAdapter,
  opts: PersistQueueOptions = {},
)

}

export function createPersistQueue(
  session: Composition,
  adapter: PersistAdapter,
  opts: PersistQueueOptions = {},
): PersistQueueModule {
  const path = opts.path ?? "composition.html";
  let pendingWrite: ReturnType<typeof setTimeout> | null = null;
  // Promise-chain mutex: each write chains onto the prior, preventing concurrent writes.
  let writeChain: Promise<void> = Promise.resolve();
  let disposed = false;

  function scheduleWrite(): void {
    if (pendingWrite !== null) clearTimeout(pendingWrite);
    pendingWrite = setTimeout(() => {
      pendingWrite = null;
      void doWrite();
    }, 0);
  }

  function doWrite(): Promise<void> {
    if (disposed) return Promise.resolve();
    const content = session.serialize();
    writeChain = writeChain.then(async () => {
      if (disposed) return;
      try {
        await adapter.write(path, content);
      } catch (err) {
        const message = err instanceof Error ? err.message : String(err);
        opts.onError?.({ error: { message, cause: err } });
      }
    });
    return writeChain;
  }

  const unsubscribe = session.on("change", () => {
    scheduleWrite();
  });

  return {
    async flush(): Promise<void> {
      if (pendingWrite !== null) {
        clearTimeout(pendingWrite);
        pendingWrite = null;
      }
      await doWrite();
    },

    dispose(): void {
      disposed = true;
      if (pendingWrite !== null) {
        clearTimeout(pendingWrite);
        pendingWrite = null;
      }
      unsubscribe();
    },
  };
}