/**
 * Telegram → resume PDF relay (Cloudflare Worker).
 *
 * WHY: Hugging Face Spaces block outbound traffic to api.telegram.org, so the HF
 * app can RECEIVE Telegram webhooks but can't SEND replies. This tiny Worker runs
 * on Cloudflare (which can reach Telegram), receives the webhook, calls the HF
 * /api/generate endpoint (which works publicly), and sends the PDF back to Telegram.
 *
 * It acks Telegram instantly and finishes the ~30–60s job via ctx.waitUntil so
 * Telegram never times out and retries.
 *
 * Deploy: paste into a Cloudflare Worker. Set these Variables/Secrets:
 *   TELEGRAM_BOT_TOKEN   — from @BotFather
 *   ALLOWED_USER_IDS     — comma-separated numeric Telegram user IDs (allowlist)
 *   HF_API_URL           — https://<your-space>.hf.space
 *   HF_API_TOKEN         — your API_SECRET_TOKEN (matches the HF secret)
 *   WEBHOOK_SECRET       — optional; must match the setWebhook secret_token
 * Then point the Telegram webhook at the Worker URL (see relay/README.md).
 */

const HELP =
  "👋 Send me a *job link* (or paste the full job description) and I'll send back " +
  "your tailored, ATS-optimized resume PDF.\n\n" +
  "• Company/ATS links (Greenhouse, Lever, Ashby, Naukri) usually work directly.\n" +
  "• If I can't read a LinkedIn/Indeed link, copy the description text and send that.\n\n" +
  "Commands: /start, /help, /v1, /v2, /mode";

export default {
  async fetch(request, env, ctx) {
    if (request.method !== "POST") return new Response("ok"); // health/GET
    if (env.WEBHOOK_SECRET &&
        request.headers.get("x-telegram-bot-api-secret-token") !== env.WEBHOOK_SECRET) {
      return new Response("forbidden", { status: 403 });
    }
    let update;
    try { update = await request.json(); } catch { return new Response("ok"); }
    ctx.waitUntil(handle(update, env));   // finish in background; ack now
    return new Response("ok");
  },
};

function parseAllowed(env) {
  // Robust: tolerate quotes, spaces, newlines around the comma-separated ids.
  return (env.ALLOWED_USER_IDS || "")
    .replace(/["']/g, "")
    .split(/[,\s]+/)
    .map((s) => s.trim())
    .filter(Boolean)
    .map(Number)
    .filter((n) => !Number.isNaN(n));
}

function tgUrl(env, method) {
  return `https://api.telegram.org/bot${env.TELEGRAM_BOT_TOKEN}/${method}`;
}

async function tg(env, method, payload) {
  try {
    await fetch(tgUrl(env, method), {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(payload),
    });
  } catch (_) { /* best-effort */ }
}

async function handle(update, env) {
  const msg = update.message || update.edited_message;
  if (!msg) return;
  const chatId = msg.chat && msg.chat.id;
  const userId = msg.from && msg.from.id;
  const text = (msg.text || "").trim();
  if (chatId == null) return;

  // Diagnostic: /whoami always answers (before the allowlist) so you can compare
  // your real Telegram id against what the Worker actually sees in its env var.
  if (/^\/(whoami|id)\b/i.test(text)) {
    await tg(env, "sendMessage", { chat_id: chatId, text:
      `your id: ${userId}\n` +
      `ALLOWED_USER_IDS (raw): ${JSON.stringify(env.ALLOWED_USER_IDS ?? null)}\n` +
      `parsed: ${JSON.stringify(parseAllowed(env))}` });
    return;
  }

  const allowed = parseAllowed(env);
  if (!allowed.length || !allowed.includes(Number(userId))) {
    await tg(env, "sendMessage", { chat_id: chatId, text:
      `⛔ Not authorized.\nyour id: ${userId}\n` +
      `ALLOWED_USER_IDS seen: ${JSON.stringify(env.ALLOWED_USER_IDS ?? null)}` });
    return;
  }

  // ── Per-user version mode (Workers KV optional) ──────────────────────────
  const verKey = `ver:${userId}`;
  let userVer = 'v2';
  if (env.USER_STATE) {
    try { userVer = (await env.USER_STATE.get(verKey)) || 'v2'; } catch (_) {}
  }

  if (/^\/v1\b/i.test(text)) {
    if (env.USER_STATE) { try { await env.USER_STATE.put(verKey, 'v1'); } catch (_) {} }
    await tg(env, "sendMessage", { chat_id: chatId, text: "✅ Mode set to V1 (Structured keyword placement)." });
    return;
  }
  if (/^\/v2\b/i.test(text)) {
    if (env.USER_STATE) { try { await env.USER_STATE.put(verKey, 'v2'); } catch (_) {} }
    await tg(env, "sendMessage", { chat_id: chatId, text: "✅ Mode set to V2 (Natural AI sentence integration)." });
    return;
  }
  if (/^\/mode\b/i.test(text)) {
    await tg(env, "sendMessage", { chat_id: chatId, text: `Current mode: ${userVer.toUpperCase()}` });
    return;
  }

  if (!text || /^\/(start|help)\b/i.test(text)) {
    await tg(env, "sendMessage", { chat_id: chatId, text: HELP, parse_mode: "Markdown" });
    return;
  }

  const urlMatch = text.match(/https?:\/\/\S+/);
  const form = new FormData();
  if (urlMatch) {
    await tg(env, "sendMessage", { chat_id: chatId, text: "🔍 Reading the job & generating your resume… V2 runs several AI models, this can take 1–2 min." });
    form.append("jd_url", urlMatch[0].replace(/[).,]+$/, ""));
  } else if (text.length >= 200) {
    await tg(env, "sendMessage", { chat_id: chatId, text: "⚙️ Generating your ATS resume… V2 runs several AI models, this can take 1–2 min." });
    form.append("jd_text", text);
  } else {
    await tg(env, "sendMessage", { chat_id: chatId, text: "Send a job link, or paste the full job description (a paragraph or more)." });
    return;
  }
  form.append("maximum_ats_mode", "1");
  form.append("version", userVer);

  let res;
  try {
    const r = await fetch(`${env.HF_API_URL.replace(/\/$/, "")}/api/generate`, {
      method: "POST",
      headers: { "X-Api-Token": env.HF_API_TOKEN || "" },
      body: form,
    });
    res = await r.json();
  } catch (e) {
    await tg(env, "sendMessage", { chat_id: chatId, text: "❌ Generation service is waking up or busy. Try again in a minute." });
    return;
  }

  if (res.error === "jd_unreadable") {
    await tg(env, "sendMessage", { chat_id: chatId, text: "⚠️ I couldn't read that link (LinkedIn/Indeed block server access). Please copy the *job description text* and send it to me." , parse_mode: "Markdown" });
    return;
  }
  if (res.error) {
    await tg(env, "sendMessage", { chat_id: chatId, text: `❌ ${res.detail || res.error}` });
    return;
  }

  const cov = res.external_coverage_pct != null ? res.external_coverage_pct
            : (res.scores && res.scores.jd_match);
  if (res.pdf_b64) {
    await sendDoc(env, chatId, res.pdf_b64, "Saiteja_Tirunagari_Resume.pdf", "application/pdf",
                  `✅ Tailored resume — ~${cov ?? "?"}% JD keyword coverage.`);
  } else if (res.tex_b64) {
    await sendDoc(env, chatId, res.tex_b64, "Saiteja_Tirunagari_Resume.tex", "application/x-tex",
                  "⚠️ PDF compile failed — here's the .tex (compile at overleaf.com).");
  } else {
    await tg(env, "sendMessage", { chat_id: chatId, text: "❌ Generation produced no file. Try again." });
  }
}

function b64ToBytes(b64) {
  const bin = atob(b64);
  const bytes = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) bytes[i] = bin.charCodeAt(i);
  return bytes;
}

async function sendDoc(env, chatId, b64, filename, mime, caption) {
  try {
    const fd = new FormData();
    fd.append("chat_id", String(chatId));
    fd.append("caption", caption.slice(0, 1024));
    fd.append("document", new Blob([b64ToBytes(b64)], { type: mime }), filename);
    await fetch(tgUrl(env, "sendDocument"), { method: "POST", body: fd });
  } catch (_) {
    await tg(env, "sendMessage", { chat_id: chatId, text: "❌ Couldn't upload the file to Telegram. Try again." });
  }
}