// Translate — right-click a selection, get a translation in the sidebar.
//
// One sidebar panel; the actual HTTP call runs here on the Node side, not in
// the panel's browser context, so a captive portal, anti-bot page or CORS
// preflight cannot substitute HTML for the JSON the panel expects. The panel
// invokes "translate" with { text, source, target, backend, ltUrl, ltKey }
// and this handler picks the backend, tries the requested URL, then falls
// through a small list of known mirrors if that URL returns HTML or a network
// error (a single mirror going down shouldn't take the whole feature with it).

// Ordered list of LibreTranslate mirrors used as automatic fallbacks when the
// user's chosen URL fails. Kept short on purpose — three tries is plenty to
// route around one mirror being down, and we don't want to spam a chain of
// public instances for one click.
const LT_FALLBACKS = [
  "https://translate.disroot.org",
  "https://translate.plausibility.cloud",
  "https://lingva.ml",
];

function looksLikeHtml(s) {
  const head = String(s || "").trimStart().slice(0, 32).toLowerCase();
  return head.startsWith("<!doctype") || head.startsWith("<html") || head.startsWith("<?xml");
}

async function fetchJson(url, init) {
  const r = await fetch(url, { ...init, redirect: "follow" });
  const text = await r.text();
  if (looksLikeHtml(text)) {
    throw new Error(`server returned an HTML page instead of JSON (probably a captive-portal or anti-bot interstitial in front of ${new URL(url).host})`);
  }
  if (!r.ok) {
    let msg = `HTTP ${r.status}`;
    try { const j = JSON.parse(text); if (j?.error) msg = j.error; } catch {}
    throw new Error(msg);
  }
  try { return JSON.parse(text); }
  catch { throw new Error(`server returned invalid JSON (${text.slice(0, 80)}…)`); }
}

async function translateLibre({ text, source, target }, urlBase, apiKey) {
  const url = urlBase.replace(/\/+$/, "") + "/translate";
  const body = { q: text, source: source === "auto" ? "auto" : source, target, format: "text" };
  if (apiKey) body.api_key = apiKey;
  const j = await fetchJson(url, {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify(body),
  });
  return {
    text: String(j.translatedText || j.translated_text || ""),
    detected: j.detectedLanguage?.language || null,
    via: `libretranslate (${new URL(urlBase).host})`,
  };
}

async function translateGoogle({ text, source, target }) {
  // Unofficial free endpoint used by browser translation extensions. Runs from
  // Node so no browser anti-bot page can slot itself in front of the response.
  const params = new URLSearchParams({
    client: "gtx",
    sl: source === "auto" ? "auto" : source,
    tl: target, dt: "t", q: text,
  });
  const url = `https://translate.googleapis.com/translate_a/single?${params}`;
  const j = await fetchJson(url, {});
  const chunks = Array.isArray(j?.[0]) ? j[0] : [];
  const translated = chunks.map((c) => (Array.isArray(c) ? String(c[0] || "") : "")).join("");
  const detected = typeof j?.[2] === "string" ? j[2] : null;
  return { text: translated, detected, via: "google" };
}

async function doTranslate(payload) {
  const p = payload || {};
  const text = String(p.text || "").trim();
  if (!text) throw new Error("no text");
  const source = String(p.source || "auto");
  const target = String(p.target || "en");
  if (source !== "auto" && source === target) {
    return { text, detected: null, via: "identity" };
  }
  if (p.backend === "google") {
    return translateGoogle({ text, source, target });
  }
  const primary = String(p.ltUrl || LT_FALLBACKS[0]).replace(/\/+$/, "");
  const tried = new Set();
  const order = [primary, ...LT_FALLBACKS.filter((u) => u !== primary)];
  const errs = [];
  for (const url of order) {
    if (tried.has(url)) continue;
    tried.add(url);
    try {
      return await translateLibre({ text, source, target }, url, p.ltKey || "");
    } catch (e) {
      errs.push(`${new URL(url).host}: ${e?.message || e}`);
    }
  }
  throw new Error(`all mirrors failed — ${errs.join(" | ")}`);
}

module.exports = {
  activate(api) {
    api.registerSidebarPanel({
      id: "main",
      title: "Translate",
      icon: "🌐",
      page: "panel.html",
    });

    api.onMessage("context-menu", async (payload) => {
      const text = String(payload && payload.selectionText || "").trim();
      if (!text) { api.log("context-menu fired with no selection"); return; }
      // Cap what we stash to keep storage tiny; the address bar and menu already
      // truncate visually, but the raw selection can be huge.
      const clip = text.length > 12_000 ? text.slice(0, 12_000) : text;
      api.storage.set("__pending", { text: clip, host: payload.host || "", at: Date.now() });
      api.revealSidebar("main");
      api.log(`context-menu → translate ${clip.length} chars from ${payload.host || "?"}`);
      return { ok: true };
    });

    api.onMessage("translate", async (payload) => doTranslate(payload));

    api.log("registered translate panel + context-menu item");
  },
};