const passport = require('passport')
const bcrypt = require('./libs/bcryptjs')
const jwt = require('./libs/jsonwebtoken')
const LocalStrategy = require('passport-local')
const JwtStrategy = require('passport-jwt').Strategy;
const ExtractJwt = require('passport-jwt').ExtractJwt;
const GoogleStrategy = require('passport-google-oauth20').Strategy;
const User = require('./objects/user/User.js')

/**
 * @class Class for handling all the authentication related functionality.
 */
class Auth {

  constructor(db) {
    this.db = db
  }

  /**
   * Inializes all passportjs stragegies and other passportjs ralated initialization.
   */
  initPassportJs() {
    // Check if we should load the local strategy
    if (global.ServerSettings.authActiveAuthMethods.includes("local")) {
      passport.use(new LocalStrategy(this.localAuthCheckUserPw.bind(this)))
    }
    // Check if we should load the google-oauth20 strategy
    if (global.ServerSettings.authActiveAuthMethods.includes("google-oauth20")) {
      passport.use(new GoogleStrategy({
        clientID: global.ServerSettings.authGoogleOauth20ClientID,
        clientSecret: global.ServerSettings.authGoogleOauth20ClientSecret,
        callbackURL: global.ServerSettings.authGoogleOauth20CallbackURL
      }, function (accessToken, refreshToken, profile, done) {
        // TODO: what to use as username
        // TODO: do we want to create the users which does not exist?
        return done(null, { username: profile.emails[0].value })
      }))
    }

    // Load the JwtStrategy (always) -> for bearer token auth 
    passport.use(new JwtStrategy({
      jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
      secretOrKey: global.ServerSettings.tokenSecret
    }, this.jwtAuthCheck.bind(this)))

    // define how to seralize a user (to be put into the session)
    passport.serializeUser(function (user, cb) {
      process.nextTick(function () {
        // only store username and id to session
        // TODO: do we want to store more info in the session?
        return cb(null, JSON.stringify({
          "username": user.username,
          "id": user.id,
        }));
      });
    });

    // define how to deseralize a user (use the username to get it from the database)
    passport.deserializeUser((function (user, cb) {
      process.nextTick((function () {
        const parsedUserInfo = JSON.parse(user)
        // TODO: do the matching on username or better on id?
        var dbUser = this.db.users.find(u => u.username.toLowerCase() === parsedUserInfo.username.toLowerCase())
        return cb(null, new User(dbUser));
      }).bind(this));
    }).bind(this));
  }

  /**
   * Creates all (express) routes required for authentication.
   * @param {express.Router} router 
   */
  initAuthRoutes(router) {
    // just a route saying "you need to login" where we redirect e.g. after logout
    // TODO: replace with a 401?
    router.get('/login', function (req, res) {
      res.send('please login')
    })

    // Local strategy login route (takes username and password)
    router.post('/login', passport.authenticate('local', {
      failureRedirect: '/login'
    }),
      (function (req, res) {
        // return the user login response json if the login was successfull
        res.json(this.getUserLoginResponsePayload(req.user.username))
      }).bind(this)
    )

    // google-oauth20 strategy login route (this redirects to the google login)
    router.get('/auth/google', passport.authenticate('google', { scope: ['email'] }))

    // google-oauth20 strategy callback route (this receives the token from google)
    router.get('/auth/google/callback',
      passport.authenticate('google', { failureRedirect: '/login' }),
      (function (req, res) {
        // return the user login response json if the login was successfull
        res.json(this.getUserLoginResponsePayload(req.user.username))
      }).bind(this)
    )

    // Logout route
    router.get('/logout', function (req, res) {
      // TODO: invalidate possible JWTs
      req.logout()
      res.redirect('/login')
    })
  }

  /**
   * middleware to use in express to only allow authenticated users.
   * @param {express.Request} req 
   * @param {express.Response} res 
   * @param {express.NextFunction} next  
   */
  isAuthenticated(req, res, next) {
    // check if session cookie says that we are authenticated
    if (req.isAuthenticated()) {
      next()
    } else {
      // try JWT to authenticate
      passport.authenticate("jwt")(req, res, next)
    }
  }

  /**
   * Function to generate a jwt token for a given user.
   * @param {Object} user 
   * @returns the token.
   */
  generateAccessToken(user) {
    return jwt.sign({ userId: user.id, username: user.username }, global.ServerSettings.tokenSecret);
  }

  /**
   * Generate a token for each user.
   */
  async initTokenSecret() {
    if (process.env.TOKEN_SECRET) { // User can supply their own token secret
      this.db.serverSettings.tokenSecret = process.env.TOKEN_SECRET
    } else {
      this.db.serverSettings.tokenSecret = require('crypto').randomBytes(256).toString('base64')
    }
    await this.db.updateServerSettings()

    // New token secret creation added in v2.1.0 so generate new API tokens for each user
    if (this.db.users.length) {
      for (const user of this.db.users) {
        user.token = await this.generateAccessToken({ userId: user.id, username: user.username })
      }
      await this.db.updateEntities('user', this.db.users)
    }
  }

  /**
   * Checks if the user in the validated jwt_payload really exists and is active.
   * @param {Object} jwt_payload 
   * @param {function} done 
   */
  jwtAuthCheck(jwt_payload, done) {
    var user = this.db.users.find(u => u.username.toLowerCase() === jwt_payload.username.toLowerCase())

    if (!user || !user.isActive) {
      done(null, null)
      return
    }
    done(null, user)
    return
  }

  /**
   * Checks if a username and passpword touple is valid and the user active.
   * @param {string} username 
   * @param {string} password 
   * @param {function} done 
   */
  localAuthCheckUserPw(username, password, done) {
    var user = this.db.users.find(u => u.username.toLowerCase() === username.toLowerCase())

    if (!user || !user.isActive) {
      done(null, null)
      return
    }

    // Check passwordless root user
    if (user.id === 'root' && (!user.pash || user.pash === '')) {
      if (password) {
        done(null, null)
        return
      }
      done(null, user)
      return
    }

    // Check password match
    var compare = bcrypt.compareSync(password, user.pash)
    if (compare) {
      done(null, user)
      return
    }
    done(null, null)
    return
  }

  /**
   * Hashes a password with bcrypt.
   * @param {string} password 
   * @returns {string} hash 
   */
  hashPass(password) {
    return new Promise((resolve) => {
      bcrypt.hash(password, 8, (err, hash) => {
        if (err) {
          resolve(null)
        } else {
          resolve(hash)
        }
      })
    })
  }

  /**
   * Return the login info payload for a user.
   * @param {string} username 
   * @returns {string} jsonPayload
   */
  getUserLoginResponsePayload(username) {
    var user = this.db.users.find(u => u.username.toLowerCase() === username.toLowerCase())
    user = new User(user)
    return {
      user: user.toJSONForBrowser(),
      userDefaultLibraryId: user.getDefaultLibraryId(this.db.libraries),
      serverSettings: this.db.serverSettings.toJSONForBrowser(),
      Source: global.Source
    }
  }
}

module.exports = Auth