// api/order.js — Vercel serverless function (optional backend)
// Receives an exchange request from the website and forwards it to your
// own Telegram chat via a bot, so you get the order even if the user
// never presses "send" in their own Telegram.
//
// Setup (see DEPLOY.md):
//   1. Create a bot with @BotFather -> get the bot token.
//   2. Create a Telegram group "Orders", add your bot to it.
//   3. Find the group's chat id (DEPLOY.md explains how).
//   4. In Vercel project -> Settings -> Environment Variables add:
//        TELEGRAM_BOT_TOKEN = <token from BotFather>
//        TELEGRAM_CHAT_ID   = <your chat/group id, e.g. -1001234567890>
//   5. In index.html set:  var BACKEND_ENABLED = true;

export default async function handler(req, res) {
  if (req.method !== "POST") {
    return res.status(405).json({ ok: false, error: "Method not allowed" });
  }

  const token = process.env.TELEGRAM_BOT_TOKEN;
  const chatId = process.env.TELEGRAM_CHAT_ID;
  if (!token || !chatId) {
    return res.status(500).json({ ok: false, error: "Server not configured" });
  }

  const b = req.body || {};
  // Basic sanity checks (we only expect 2–4 requests, keep it simple)
  const id = String(b.id || "").slice(0, 20);
  const send = String(b.send || "").slice(0, 80);
  const get = String(b.get || "").slice(0, 80);
  const address = String(b.address || "").slice(0, 120);
  const telegram = String(b.telegram || "").slice(0, 60);
  const email = String(b.email || "").slice(0, 80);

  if (!id || !address || !telegram) {
    return res.status(400).json({ ok: false, error: "Missing fields" });
  }

  const text =
    `🟢 New exchange request ${id}\n` +
    `Send: ${send}\n` +
    `Get: ${get}\n` +
    `Receive address: ${address}\n` +
    `Telegram: ${telegram}` +
    (email ? `\nEmail: ${email}` : "");

  try {
    const r = await fetch(`https://api.telegram.org/bot${token}/sendMessage`, {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ chat_id: chatId, text, disable_web_page_preview: true }),
    });
    const j = await r.json();
    return res.status(200).json({ ok: !!j.ok });
  } catch (e) {
    return res.status(500).json({ ok: false, error: "Telegram send failed" });
  }
}