index.cjs

const { Strategy: PassportStrategy } = require('passport');
const crypto = require('crypto');
const fetch = require('node-fetch');

const generateRandomString = (symbols) => {
  const keys = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~';
  let text = '';
  do {
    text += keys[Math.floor(Math.random() * keys.length)];
    symbols -= 1;
  } while (symbols);
  return text;
};

class Strategy extends PassportStrategy {
  constructor(options, verify) {
    super();
    this.name = 'twitter';
    this.scope = options.scope || [
      "tweet.read",
      "offline.access",
      "users.read",
    ];
    this._callbackURL = options.callbackURL;
    this._clientID = options.clientID;
    this._clientSecret = options.clientSecret;
    this._verify = verify;
  }
  async authenticate(req) {
    if (req.query?.code && req.query?.state) {
      try {
        const {
          code,
          state,
        } = req.query;
        const {
          code_verifier,
          state: session_state
        } = req.session;
        if (!code || !code_verifier || !session_state || !state) {
          return this.fail('You denied the app or your session expired!');
        }
        if (state !== session_state) {
          return this.fail('Stored tokens didn\'t match!');
        }
        let body = new URLSearchParams({
          client_id: this._clientID,
          client_secret: this._clientSecret,
          code,
          code_verifier,
          grant_type: 'authorization_code',
          redirect_uri: this._callbackURL,
        });
        let data = await fetch('https://api.twitter.com/2/oauth2/token', {
          method: 'POST',
          headers: {
            Authorization: `Basic ${Buffer.from(`${encodeURIComponent(this._clientID)}:${encodeURIComponent(this._clientSecret)}`).toString('base64')}`,
          },
          body,
        }).then(res => res.json());
        const {
          access_token,
          refresh_token,
        } = data;
        if (!access_token) {
          return this.fail('No access token!');
        }
        let {
          data: profile
        } = await fetch('https://api.twitter.com/2/users/me', {
          headers: {
            Authorization: `Bearer ${access_token}`,
          }
        }).then(res => res.json());
        if (!profile) {
          return this.fail('No profile!');
        }
        return this._verify(req, access_token, refresh_token, profile, (error, user, info) => {
          if (error) return this.error(error);
          if (!user) return this.fail(info);
          return this.success(user, info);
        });
      } catch (error) {
        return this.error(error);
      }
    }
    if (req.query?.error) {
      return this.fail(
        req.query.error === "access_denied"
         ? "You denied the app!"
         : String(req.query.error)
      );
    }
    let state = generateRandomString(32);
    let code_verifier = generateRandomString(128);
    let code_challenge = crypto
      .createHash('sha256')
      .update(code_verifier)
      .digest('base64')
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/\=/g, '');
    req.session.code_challenge = code_challenge;
    req.session.code_verifier = code_verifier;
    req.session.state = state;
    const params = new URLSearchParams({
      client_id: this._clientID,
      code_challenge,
      code_challenge_method: 'S256',
      redirect_uri: this._callbackURL,
      response_type: 'code',
      scope: this.scope.join(' '),
      state,
    }).toString();
    return this.redirect(`https://twitter.com/i/oauth2/authorize?${params}`);
  }
}

module.exports = {
  default: Strategy,
  Strategy
};