noctbot/web/src/routes/login/discord/callback.ts

import { Request, Response, NextFunction } from "express";
import request from "request-promise-native";
import { Response as Res } from "request";
import { botService } from "src/util/rpc_client";

const API_ENDPOINT = "https://discordapp.com/api";

export async function get(req : Request, res : Response, next: NextFunction) {
    if(!req.query.code)
        throw new Error("NoCodeProvided");

    let code = req.query.code;
    let response = await request("/oauth2/token", {
        method: "POST",
        baseUrl: API_ENDPOINT,
        qs: {
            grant_type: "authorization_code",
            code: code,
            redirect_uri: `${process.env.ADMIN_URL}/login/discord/callback`
        },
        auth: {
            user: process.env.BOT_CLIENT_ID,
            pass: process.env.BOT_CLIENT_SECRET
        },
        resolveWithFullResponse: true
    }) as Res;

    let authResponse: AuthResponse = JSON.parse(response.body);

    let userInfoResponse = await request("/users/@me", {
        method: "GET",
        baseUrl: API_ENDPOINT,
        auth: {
            bearer: authResponse.access_token
        },
        resolveWithFullResponse: true
    });

    let discordUser : DiscordUser = JSON.parse(userInfoResponse.body);

    try {
        let userInfo = await botService.getModeratorUserInfo({id: discordUser.id});
        req.session.user = userInfo;
        res.redirect(`${process.env.ADMIN_URL}/`);
    } catch(e) {
        console.log(`Failed to authorise user because: ${e}`);
        res.redirect(`${process.env.ADMIN_URL}/login/?error=invalid_user`);
        return;
    }
};

interface AuthResponse {
    access_token: string;
    token_type: string;
    expires_in: number;
    refresh_token?: string;
    scope: string;
}

interface DiscordUser {
    id: string;
    username: string;
    discriminator: string;
    avatar?: string;
    bot?: boolean;
    mfa_enabled?: boolean;
    locale?: string;
    verified?: boolean;
    email?: string;
    flags?: number;
    premium_type?: number;
}