feat: 文件清单与图片预览的 P2P 部分挪到浏览器端(WebRTC)，服务端仅缓存兜底

2026-10-16 19:39:16 +08:00
parent bab0218b57
commit cc6cb76d67
5 changed files with 189 additions and 28 deletions
@@ -0,0 +1,115 @@
+// 浏览器端 WebTorrent（WebRTC）：把 P2P 流量放到用户自己的设备，
+// 绕开 Vercel / Cloudflare 等 Serverless 不支持 UDP/DHT 的限制。
+// 服务端仍保留非 P2P 的缓存服务兜底；这里是真正的 P2P 取数据路径。
+
+// 浏览器只支持 WebRTC 节点，需要走 wss:// 的 tracker 才能发现对端
+const WS_TRACKERS = [
+  'wss://tracker.openwebtorrent.com',
+  'wss://tracker.btorrent.xyz',
+  'wss://tracker.webtorrent.dev'
+]
+
+function normPath(p: string): string {
+  return p.replace(/\\/g, '/').replace(/^\.\//, '')
+}
+
+function withWsTrackers(magnet: string): string {
+  const existing = new Set<string>()
+  for (const m of magnet.matchAll(/[?&]tr=([^&]+)/g)) {
+    try {
+      existing.add(decodeURIComponent(m[1]))
+    } catch {
+      /* ignore */
+    }
+  }
+  const add = WS_TRACKERS.filter((t) => !existing.has(t))
+  if (!add.length) return magnet
+  const sep = magnet.includes('?') ? '&' : '?'
+  return magnet + sep + add.map((t) => `tr=${encodeURIComponent(t)}`).join('&')
+}
+
+let wtPromise: Promise<any> | null = null
+function loadWebTorrent(): Promise<any> {
+  if (!wtPromise) {
+    // 仅在浏览器运行时按需加载，Vite 会将其单独拆包；服务端不会执行到此处
+    wtPromise = import('webtorrent').then((m) => (m as any).default || m)
+  }
+  return wtPromise
+}
+
+function waitForMetadata(torrent: any, timeoutMs: number): Promise<void> {
+  return new Promise((resolve, reject) => {
+    if (torrent.metadata || torrent.ready) return resolve()
+    const timer = setTimeout(
+      () => reject(new Error('浏览器 P2P 获取元数据超时，可能该种子没有 WebRTC 节点')),
+      timeoutMs
+    )
+    const done = () => {
+      clearTimeout(timer)
+      resolve()
+    }
+    torrent.on('metadata', done)
+    torrent.on('ready', done)
+    torrent.on('error', (e: Error) => {
+      clearTimeout(timer)
+      reject(e)
+    })
+  })
+}
+
+export async function resolveMetadataClient(
+  magnet: string,
+  timeoutMs = 30000
+): Promise<{ name: string; files: { path: string; length: number }[]; size: number }> {
+  const WebTorrent = await loadWebTorrent()
+  const client = new WebTorrent()
+  try {
+    const torrent = client.add(withWsTrackers(magnet))
+    await waitForMetadata(torrent, timeoutMs)
+    const files = (torrent.files || []).map((f: any) => ({
+      path: normPath(String(f.path || f.name || '')),
+      length: Number(f.length) || 0
+    }))
+    if (!files.length) throw new Error('已连上节点，但对方没有返回任何文件信息')
+    return { name: String(torrent.name || ''), files, size: files.reduce((s, f) => s + f.length, 0) }
+  } finally {
+    try {
+      client.destroy()
+    } catch {
+      /* ignore */
+    }
+  }
+}
+
+export async function readFileBytesClient(
+  magnet: string,
+  filePath: string,
+  timeoutMs = 25000
+): Promise<ArrayBuffer> {
+  const WebTorrent = await loadWebTorrent()
+  const client = new WebTorrent()
+  try {
+    const torrent = client.add(withWsTrackers(magnet))
+    await waitForMetadata(torrent, timeoutMs)
+    const target = (torrent.files || []).find(
+      (f: any) => normPath(String(f.path || f.name || '')) === normPath(filePath)
+    )
+    if (!target) throw new Error('这个种子里没有该文件，文件清单可能已过期')
+    return await target.arrayBuffer()
+  } finally {
+    try {
+      client.destroy()
+    } catch {
+      /* ignore */
+    }
+  }
+}
+
+export async function isClientWebTorrentAvailable(): Promise<boolean> {
+  try {
+    await loadWebTorrent()
+    return true
+  } catch {
+    return false
+  }
+}