const functions = require("firebase-functions");
const admin = require("firebase-admin");
const fs = require("fs");
const xss = require("xss");
admin.initializeApp(functions.config().firebase);

const isBot = userAgent => {
  return userAgent.includes("googlebot") ||
    userAgent.includes("yahoou") ||
    userAgent.includes("bingbot") ||
    userAgent.includes("baiduspider") ||
    userAgent.includes("yandex") ||
    userAgent.includes("yeti") ||
    userAgent.includes("yodaobot") ||
    userAgent.includes("gigabot") ||
    userAgent.includes("ia_archiver") ||
    userAgent.includes("facebookexternalhit") ||
    userAgent.includes("twitterbot") ||
    userAgent.includes("developers.google.com")
    ? true
    : false;
};

const getReplaceHtml = (HTML, title, description, uri) => {
  const html = HTML.replace(
    /<title>.*<\/title>/g,
    "<title>" + title + "</title>"
  )
    .replace(
      /<\s*meta name="description" content="[^>]*>/g,
      '<meta name="description" content="' + description + '" />'
    )
    .replace(
      /<\s*meta property="og:title" content="[^>]*>/g,
      '<meta property="og:title" content="' + title + '" />'
    )
    .replace(
      /<\s*meta property="og:url" content="[^>]*>/g,
      '<meta property="og:url" content="' + uri + '" />'
    )
    .replace(
      /<\s*meta property="og:description" content="[^>]*>/g,
      '<meta property="og:description" content="' + description + '" />'
    )
    .replace(
      /<\s*meta property="og:image" content="[^>]*>/g,
      '<meta property="og:image" content="~~.png" />'
    );

  return html;
};

exports.returnHtmlWithOGP = functions.https.onRequest((req, res) => {
  // Access URL '/answer/{quizId}'
  const domain = "https://min-study.com/";
  const userAgent = req.headers["user-agent"].toLowerCase();
  const path = req.path.split("/");
  const id = path ? path[path.length - 1] : null;
  const indexHTML = fs.readFileSync("./index.html").toString();

  if (isBot(userAgent) && id !== null) {
    const firestore = admin.firestore();
    const docRef = firestore.collection("quiz").doc(id);
    docRef
      .get()
      .then(snapshot => {
        const user = snapshot.data();
        const title = xss(user.title);
        const description = xss(user.description);
        const uri = xss(domain + "answer/" + id);
        const replacedHTML = getReplaceHtml(indexHTML, title, description, uri);
        res.status(200).send(replacedHTML);
        return true;
      })
      .catch(err => {
        console.log(err);
        res.status(404).send(indexHTML);
        throw new Error(err);
      });
  } else {
    res.status(200).send(indexHTML);
    return true;
  }
});