import { postToWorker } from './workerClient';

/**
 * 页面这一侧的「边下边播」:把条目登记成一个 /__wd_stream/<id> 地址交给 <video>/<audio>,
 * 播放器的每个 Range 请求由 Service Worker(public/stream-sw.js)转给这里,
 * 这里把 SW 给的 MessagePort 直接交给加密线程,解密后的数据不再经过页面。
 */
interface Entry { resourceId: string; itemId: string; size: number; mime: string }
interface SwMessage { type: 'wd-stream'; id: string; range: { start?: number; end?: number; suffix?: number }; port: MessagePort }

const entries = new Map<string, Entry>();
let ready: Promise<boolean> | undefined;

function setup(): Promise<boolean> {
  if (!('serviceWorker' in navigator)) return Promise.resolve(false);
  return (async () => {
    navigator.serviceWorker.addEventListener('message', (event: MessageEvent<SwMessage>) => {
      const message = event.data;
      if (message?.type !== 'wd-stream') return;
      const entry = entries.get(message.id);
      if (!entry) { message.port.postMessage({ error: 'gone', status: 404 }); message.port.close(); return; }
      postToWorker({ operation: 'streamRange', payload: { ...entry, ...message.range } }, [message.port]);
    });
    await navigator.serviceWorker.register(`${import.meta.env.BASE_URL}stream-sw.js`);
    await navigator.serviceWorker.ready;
    if (!navigator.serviceWorker.controller) {
      // 第一次安装:等 SW 接管当前页面(clients.claim)
      await new Promise<void>((resolve) => {
        const timer = setTimeout(resolve, 2000);
        navigator.serviceWorker.addEventListener('controllerchange', () => { clearTimeout(timer); resolve(); }, { once: true });
      });
    }
    return navigator.serviceWorker.controller !== null;
  })().catch(() => false);
}

/** 登记一个可以边下边播的条目,返回播放地址;浏览器或环境不支持时返回 undefined(调用方退回整个下载) */
export async function playbackUrl(resourceId: string, itemId: string, size: number, mime: string): Promise<string | undefined> {
  ready ??= setup();
  if (!(await ready)) return undefined;
  const id = `${crypto.randomUUID()}`;
  entries.set(id, { resourceId, itemId, size, mime });
  return `${import.meta.env.BASE_URL}__wd_stream/${id}`;
}

export function releasePlayback(url: string): void {
  entries.delete(url.slice(url.lastIndexOf('/') + 1));
}