| import http from "node:http"; |
| import { URL } from "node:url"; |
| import { fetchTranscript, listLanguages } from "youtube-transcript-plus"; |
|
|
| const PORT = Number(process.env.TRANSCRIPT_PORT || 8765); |
| const HOST = process.env.TRANSCRIPT_HOST || "127.0.0.1"; |
| const ALLOW_ORIGIN = process.env.ALLOW_ORIGIN || "*"; |
| const USER_AGENT = process.env.YT_USER_AGENT || "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36"; |
|
|
| function json(res, status, payload) { |
| res.writeHead(status, { |
| "Content-Type": "application/json; charset=utf-8", |
| "Access-Control-Allow-Origin": ALLOW_ORIGIN, |
| "Access-Control-Allow-Methods": "GET, OPTIONS", |
| "Access-Control-Allow-Headers": "Content-Type", |
| "Cache-Control": "no-store", |
| }); |
| res.end(JSON.stringify(payload)); |
| } |
|
|
| function extractVideoId(value) { |
| const s = String(value || "").trim(); |
| if (/^[A-Za-z0-9_-]{11}$/.test(s)) return s; |
| try { |
| const u = new URL(s); |
| if (u.hostname === "youtu.be") { |
| const id = u.pathname.split("/").filter(Boolean)[0]; |
| return /^[A-Za-z0-9_-]{11}$/.test(id || "") ? id : null; |
| } |
| const v = u.searchParams.get("v"); |
| if (v && /^[A-Za-z0-9_-]{11}$/.test(v)) return v; |
| const parts = u.pathname.split("/").filter(Boolean); |
| if (parts.length >= 2 && ["embed", "shorts", "live"].includes(parts[0])) { |
| return /^[A-Za-z0-9_-]{11}$/.test(parts[1]) ? parts[1] : null; |
| } |
| } catch {} |
| return null; |
| } |
|
|
| function normalize(items) { |
| return (Array.isArray(items) ? items : []).map((x, i) => ({ |
| index: i + 1, |
| start: Number(x.offset ?? x.start ?? x.startTime ?? 0), |
| duration: Number(x.duration ?? 0), |
| text: String(x.text ?? x.content ?? "").replace(/\s+/g, " ").trim(), |
| })).filter(x => x.text); |
| } |
|
|
| async function fetchWithFallback(video, lang) { |
| const base = { |
| ...(lang ? { lang } : {}), |
| userAgent: USER_AGENT, |
| retries: 2, |
| retryDelay: 700, |
| }; |
| let firstError = null; |
| try { |
| return await fetchTranscript(video, base); |
| } catch (error) { |
| firstError = error; |
| } |
| |
| |
| try { |
| return await fetchTranscript(video, { ...base, disableHttps: true }); |
| } catch (secondError) { |
| const e = new Error(secondError?.message || String(secondError)); |
| e.firstError = firstError; |
| throw e; |
| } |
| } |
|
|
| const server = http.createServer(async (req, res) => { |
| if (req.method === "OPTIONS") return json(res, 204, {}); |
| const u = new URL(req.url, `http://${req.headers.host || "localhost"}`); |
|
|
| if (u.pathname === "/health") return json(res, 200, { ok: true, service: "english-lab-transcript-backend" }); |
| if (u.pathname === "/languages") { |
| const video = extractVideoId(u.searchParams.get("video") || u.searchParams.get("url")); |
| if (!video) return json(res, 400, { ok: false, error: "invalid_youtube_video_id" }); |
| try { |
| const languages = await listLanguages(video, { userAgent: USER_AGENT, retries: 2, retryDelay: 700 }); |
| return json(res, 200, { ok: true, videoId: video, languages }); |
| } catch (error) { |
| return json(res, 502, { ok: false, videoId: video, error: "languages_fetch_failed", message: String(error?.message || error) }); |
| } |
| } |
| if (u.pathname !== "/transcript") return json(res, 404, { ok: false, error: "not_found" }); |
|
|
| const video = extractVideoId(u.searchParams.get("video") || u.searchParams.get("url")); |
| const requestedLang = u.searchParams.get("lang") || "en"; |
| if (!video) return json(res, 400, { ok: false, error: "invalid_youtube_video_id" }); |
|
|
| try { |
| let raw; |
| let usedLang = requestedLang; |
| try { |
| raw = await fetchWithFallback(video, requestedLang === "auto" ? undefined : requestedLang); |
| } catch (primaryError) { |
| if (requestedLang !== "auto") { |
| |
| raw = await fetchWithFallback(video, undefined); |
| usedLang = "auto"; |
| } else { |
| throw primaryError; |
| } |
| } |
| const segments = normalize(raw); |
| return json(res, 200, { |
| ok: true, |
| videoId: video, |
| language: usedLang, |
| count: segments.length, |
| segments, |
| }); |
| } catch (error) { |
| return json(res, 502, { |
| ok: false, |
| videoId: video, |
| error: "transcript_fetch_failed", |
| message: String(error?.message || error), |
| firstError: error?.firstError ? String(error.firstError?.message || error.firstError) : undefined, |
| hint: "YouTube may be blocking the Space outbound request, the video may have no captions, or the requested language may be unavailable. Try /languages or import SRT/VTT manually.", |
| }); |
| } |
| }); |
|
|
| server.listen(PORT, HOST, () => { |
| console.log(`English Lab transcript backend listening on http://${HOST}:${PORT}`); |
| }); |
|
|
