Tinasha-Bot/dashboard/routes/discord.js

const express = require("express"),
  router = express.Router();

const fetch = require("node-fetch"),
  btoa = require("btoa");

// Gets login page
router.get("/login", async function (req, res) {
  if (!req.user || !req.user.id || !req.user.guilds) {
    return res.redirect(
      `https://discordapp.com/api/oauth2/authorize?client_id=${
        req.client.user.id
      }&scope=identify%20guilds&response_type=code&redirect_uri=${encodeURIComponent(
        req.client.config.DASHBOARD.baseURL + "/api/callback"
      )}&state=${req.query.state || "no"}`
    );
  }
  res.redirect("/selector");
});

router.get("/callback", async (req, res) => {
  if (!req.query.code) return res.redirect(req.client.config.DASHBOARD.failureURL);
  if (req.query.state && req.query.state.startsWith("invite")) {
    if (req.query.code) {
      const guildID = req.query.state.substr("invite".length, req.query.state.length);
      req.client.knownGuilds.push({ id: guildID, user: req.user.id });
      return res.redirect("/manage/" + guildID);
    }
  }
  const redirectURL = req.client.states[req.query.state] || "/selector";
  const params = new URLSearchParams();
  params.set("grant_type", "authorization_code");
  params.set("code", req.query.code);
  params.set("redirect_uri", `${req.client.config.DASHBOARD.baseURL}/api/callback`);
  let response = await fetch("https://discord.com/api/oauth2/token", {
    method: "POST",
    body: params.toString(),
    headers: {
      Authorization: `Basic ${btoa(`${req.client.user.id}:${process.env.BOT_SECRET}`)}`,
      "Content-Type": "application/x-www-form-urlencoded",
    },
  });
  // Fetch tokens (used to fetch user information's)
  const tokens = await response.json();
  // If the code isn't valid
  if (tokens.error || !tokens.access_token) return res.redirect(`/api/login&state=${req.query.state}`);
  const userData = {
    infos: null,
    guilds: null,
  };
  while (!userData.infos || !userData.guilds) {
    /* User infos */
    if (!userData.infos) {
      response = await fetch("http://discordapp.com/api/users/@me", {
        method: "GET",
        headers: { Authorization: `Bearer ${tokens.access_token}` },
      });
      const json = await response.json();
      if (json.retry_after) await req.client.wait(json.retry_after);
      else userData.infos = json;
    }
    /* User guilds */
    if (!userData.guilds) {
      response = await fetch("https://discordapp.com/api/users/@me/guilds", {
        method: "GET",
        headers: { Authorization: `Bearer ${tokens.access_token}` },
      });
      const json = await response.json();
      if (json.retry_after) await req.client.wait(json.retry_after);
      else userData.guilds = json;
    }
  }
  /* Change format (from "0": { data }, "1": { data }, etc... to [ { data }, { data } ]) */
  const guilds = [];
  for (const guildPos in userData.guilds) guilds.push(userData.guilds[guildPos]);

  // Update session
  req.session.user = { ...userData.infos, ...{ guilds } }; // {user-info, guilds: [{}]}
  res.redirect(redirectURL);
});

module.exports = router;