Build a Telegram Downloader Bot

// bot.mjs, Node.js 18+, no packages. Run: BOT_TOKEN=123:abc GIS_KEY=gis_live_... node bot.mjs
const API_URL = "https://developers.getinsaver.com/v1/resolve";
const TELEGRAM = `https://api.telegram.org/bot${process.env.BOT_TOKEN}`;
const HOSTS = { "instagram.com": "instagram", "tiktok.com": "tiktok", "x.com": "x", "twitter.com": "x", "pinterest.com": "pinterest", "pin.it": "pinterest", "t.me": "telegram" };
const HELP = "Send me a public Instagram, TikTok, X, Pinterest or Telegram link.";
const WAIT_MS = 10_000; // one link per chat every 10 seconds, so one person cannot spend all your credits
const lastLink = new Map();
const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

function serviceFor(link) {
  try {
    const url = new URL(link);
    const host = url.hostname.replace(/^(www|m|vm|vt)\./, "");
    if (host === "instagram.com" && url.pathname.startsWith("/stories/highlights/")) return "instagram-highlight";
    if (host === "instagram.com" && url.pathname.startsWith("/stories/")) return "instagram-story";
    return HOSTS[host];
  } catch {
    return undefined;
  }
}

async function telegram(method, body, timeoutMs = 30_000) {
  const response = await fetch(`${TELEGRAM}/${method}`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body),
    signal: AbortSignal.timeout(timeoutMs)
  });
  return response.json();
}

async function resolveLink(service, url, retries = 2) {
  for (let attempt = 0; ; attempt++) {
    const response = await fetch(API_URL, {
      method: "POST",
      headers: { Authorization: `Bearer ${process.env.GIS_KEY}`, "Content-Type": "application/json" },
      body: JSON.stringify({ service, url, max_results: 10 }),
      signal: AbortSignal.timeout(130_000)
    });
    const data = await response.json();
    if (response.ok) return data;
    // 429 = rate or concurrency limit, 502/504 = platform hiccup; none of them is charged
    if ([429, 502, 504].includes(response.status) && attempt < retries) {
      await sleep(Number(response.headers.get("retry-after") || 5) * 1000);
      continue;
    }
    throw new Error(data.message);
  }
}

async function handle(message) {
  const chat_id = message.chat.id;
  const link = message.text?.match(/https?:\/\/\S+/)?.[0];
  const service = link && serviceFor(link);
  if (!service) return telegram("sendMessage", { chat_id, text: HELP });
  if (Date.now() - (lastLink.get(chat_id) || 0) < WAIT_MS) {
    return telegram("sendMessage", { chat_id, text: "One link every 10 seconds, please." });
  }
  lastLink.set(chat_id, Date.now());
  await telegram("sendChatAction", { chat_id, action: "typing" });
  try {
    const { items } = await resolveLink(service, link);
    for (const item of items) {
      const [method, field] = item.type === "image" ? ["sendPhoto", "photo"]
        : item.type === "video" ? ["sendVideo", "video"] : ["sendDocument", "document"];
      const sent = await telegram(method, { chat_id, [field]: item.url });
      // Telegram fetches a URL only up to 5 MB for photos and 20 MB for other files.
      if (!sent.ok) await telegram("sendMessage", { chat_id, text: item.url });
    }
  } catch (error) {
    await telegram("sendMessage", { chat_id, text: error.message });
  }
}

let offset = 0;
for (;;) {
  try {
    const { result = [] } = await telegram("getUpdates", { offset, timeout: 50, allowed_updates: ["message"] }, 60_000);
    for (const update of result) {
      offset = update.update_id + 1;
      if (update.message) handle(update.message).catch(console.error);
    }
  } catch (error) {
    console.error(error.message);
    await sleep(3000);
  }
}