91 lines
2.9 KiB
TypeScript
91 lines
2.9 KiB
TypeScript
import { mkdir, rm } from 'node:fs/promises'
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import { tmpdir } from 'node:os'
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import { join } from 'node:path'
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import { loadWebTorrent, withDefaultTrackers } from './torrent'
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/** 会话空闲多久后释放（毫秒） */
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const IDLE_MS = 120_000
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interface SwarmSession {
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client: any
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torrent: any
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dir: string
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ready: Promise<any>
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timer: NodeJS.Timeout | null
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}
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const sessions = new Map<string, SwarmSession>()
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/**
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* 复用一个常驻的 webtorrent 会话来取文件内容。
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* 每张图片都重建一次客户端就得重新找一遍节点（快则 1 秒，慢则十几秒），
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* 所以同一个 infoHash 的连续预览共用一条会话，空闲 2 分钟自动释放。
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*/
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export async function withSwarm<T>(
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infoHash: string,
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magnet: string,
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timeoutMs: number,
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fn: (torrent: any) => Promise<T>
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): Promise<T> {
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const key = infoHash.toLowerCase()
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let session = sessions.get(key)
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if (!session) {
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session = await createSession(key, magnet, timeoutMs)
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sessions.set(key, session)
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}
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touchSession(key, session)
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const torrent = await session.ready
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return fn(torrent)
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}
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function touchSession(key: string, session: SwarmSession) {
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if (session.timer) clearTimeout(session.timer)
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session.timer = setTimeout(() => releaseSession(key), IDLE_MS)
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session.timer.unref?.()
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}
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async function createSession(infoHash: string, magnet: string, timeoutMs: number): Promise<SwarmSession> {
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const WebTorrent = await loadWebTorrent()
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const dir = join(tmpdir(), `dsl-swarm-${infoHash.slice(0, 8)}-${Date.now().toString(36)}`)
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await mkdir(dir, { recursive: true })
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const client = new WebTorrent({ dht: true, lsd: false, utp: false })
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client.on('error', () => {})
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const torrent = client.add(withDefaultTrackers(magnet), { path: dir })
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torrent.on('warning', () => {})
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const ready = new Promise<any>((resolve, reject) => {
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const timer = setTimeout(() => {
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reject(new Error(`获取种子元数据超时（${Math.round(timeoutMs / 1000)}s），可能没有可用节点或 tracker 被墙`))
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}, timeoutMs)
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const done = (fn: () => void) => {
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clearTimeout(timer)
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fn()
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}
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if (torrent.metadata) return done(() => resolve(torrent))
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torrent.on('metadata', () => done(() => resolve(torrent)))
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torrent.on('error', (err: Error) => done(() => reject(err)))
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client.on('error', (err: Error) => done(() => reject(err)))
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})
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const session: SwarmSession = { client, torrent, dir, ready, timer: null }
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touchSession(infoHash, session)
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// 元数据都拿不到就别留着占资源
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ready.catch(() => releaseSession(infoHash))
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return session
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}
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function releaseSession(infoHash: string) {
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const session = sessions.get(infoHash)
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if (!session) return
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sessions.delete(infoHash)
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if (session.timer) clearTimeout(session.timer)
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try {
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session.client.destroy(() => {})
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} catch {
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/* ignore */
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}
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rm(session.dir, { recursive: true, force: true }).catch(() => {})
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}
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