读取与保存

import type { AutosaveOptions, AutosaveSession, SaveSnapshot } from "./types";
/** @param options - Host persistence policy and one current document. @returns Serial save ownership for that document only. */
export function attachAutosave(options: AutosaveOptions): AutosaveSession {
  const { editor } = options;
  const scope = editor.documentScope.fork();
  let dirty = false;
  let timer: ReturnType<typeof setTimeout> | undefined;
  let running: Promise<void> | undefined;
  /** Writes successive immutable snapshots; slow responses never replace the open source. */
  async function drain(): Promise<void> {
    while (dirty && !scope.disposed) {
      dirty = false;
      const snapshot: SaveSnapshot = { documentId: editor.documentId, revision: editor.revision, markdown: editor.getMarkdown() };
      options.status("saving");
      try {
        await options.save(snapshot, scope.signal);
        if (scope.disposed) return;
        if (!dirty && editor.revision === snapshot.revision) options.status("saved");
      } catch (error) {
        if (!scope.disposed) { dirty = true; options.status("error"); options.error(error); }
        return; // An explicit flush or the next source edit retries; no busy retry loop.
      }
    }
  }
  /** @returns Completion of prior work and any source dirty when this flush can acquire the writer. */
  async function flush(): Promise<void> {
    clearTimeout(timer);
    // Recheck after awaiting: another flush may have acquired the single writer.
    while (running) await running;
    if (scope.disposed || !dirty) return;
    running = drain().finally(() => { running = undefined; });
    await running;
  }
  scope.own(editor.onChange(() => {
    dirty = true;
    options.status("dirty");
    clearTimeout(timer);
    timer = setTimeout(() => { void flush(); }, options.delay ?? 600);
  }));
  scope.own(() => clearTimeout(timer));
  return { flush, dispose: () => scope.dispose() };
}