const Settings = require('@overleaf/settings')
const { User } = require('../../models/User')
const { db, ObjectId } = require('../../infrastructure/mongodb')
const bcrypt = require('bcrypt')
const EmailHelper = require('../Helpers/EmailHelper')
const {
  InvalidEmailError,
  InvalidPasswordError,
  ParallelLoginError,
} = require('./AuthenticationErrors')
const util = require('util')
const { Client } = require('ldapts');
const ldapEscape = require('ldap-escape');
const HaveIBeenPwned = require('./HaveIBeenPwned')

const BCRYPT_ROUNDS = Settings.security.bcryptRounds || 12
const BCRYPT_MINOR_VERSION = Settings.security.bcryptMinorVersion || 'a'

const _checkWriteResult = function (result, callback) {
  // for MongoDB
  if (result && result.modifiedCount === 1) {
    callback(null, true)
  } else {
    callback(null, false)
  }
}

const AuthenticationManager = {
  authenticate(query, password, callback) {
    // Using Mongoose for legacy reasons here. The returned User instance
    // gets serialized into the session and there may be subtle differences
    // between the user returned by Mongoose vs mongodb (such as default values)
    User.findOne(query, (error, user) => {
      if (error) {
        return callback(error)
      }
      if (!user || !user.hashedPassword) {
        return callback(null, null)
      }
      bcrypt.compare(password, user.hashedPassword, function (error, match) {
        if (error) {
          return callback(error)
        }
        const update = { $inc: { loginEpoch: 1 } }
        if (!match) {
          update.$set = { lastFailedLogin: new Date() }
        }
        User.updateOne(
          { _id: user._id, loginEpoch: user.loginEpoch },
          update,
          {},
          (err, result) => {
            if (err) {
              return callback(err)
            }
            if (result.nModified !== 1) {
              return callback(new ParallelLoginError())
            }
            if (!match) {
              return callback(null, null)
            }
            AuthenticationManager.checkRounds(
              user,
              user.hashedPassword,
              password,
              function (err) {
                if (err) {
                  return callback(err)
                }
                callback(null, user)
                HaveIBeenPwned.checkPasswordForReuseInBackground(password)
              }
            )
          }
        )
      })
    })
  },

  //oauth2
  createUserIfNotExist(oauth_user, callback) {
    const query = {
      //name: ZHANG San
      email: oauth_user.email,
      first_name: oauth_user.given_name, //San
      last_name: oauth_user.family_name //Zhang
    };
    User.findOne(query, (error, user) => {
      if ((!user || !user.hashedPassword)) {
        //create random pass for local userdb, does not get checked for ldap users during login
        let pass = require("crypto").randomBytes(32).toString("hex")
        const userRegHand = require('../User/UserRegistrationHandler.js')
        userRegHand.registerNewUser({
              email: query.email,
              first_name: query.first_name,
              last_name: query.last_name,
              password: pass
            },
            function (error, user) {
              if (error) {
                return callback(error, null);
              }
              user.admin = false
              user.emails[0].confirmedAt = Date.now()
              user.save()
              console.log("user %s added to local library", query.email)
              User.findOne(query, (error, user) => {
                    if (error) {
                      return callback(error, null);
                    }
                    if (user && user.hashedPassword) {
                      return callback(null, user);
                    } else {
                      return callback("Unknown error", null);
                    }
                  }
              )
            })
      } else {
        return callback(null, user);
      }
    });
  },

  //LDAP
  createIfNotExistAndLogin(query, user, callback, uid, firstname, lastname, mail, isAdmin) {
    if (!user) {
      //console.log("Creating User:" + JSON.stringify(query))
      //create random pass for local userdb, does not get checked for ldap users during login
      let pass = require("crypto").randomBytes(32).toString("hex")
      //console.log("Creating User:" + JSON.stringify(query) + "Random Pass" + pass)

      const userRegHand = require('../User/UserRegistrationHandler.js')
      userRegHand.registerNewUser({
            email: mail,
            first_name: firstname,
            last_name: lastname,
            password: pass
          },
          function (error, user) {
            if (error) {
              console.log(error)
            }
            user.email = mail
            user.isAdmin = isAdmin
            user.emails[0].confirmedAt = Date.now()
            user.save()
            //console.log("user %s added to local library: ", mail)
            User.findOne(query, (error, user) => {
              if (error) {
                console.log(error)
              }
              if (user && user.hashedPassword) {
                AuthenticationManager.login(user, "randomPass", callback)
              }
            })
          }) // end register user
    } else {
      AuthenticationManager.login(user, "randomPass", callback)
    }
  },

  authUserObj(error, user, query, password, callback) {
    if ( process.env.ALLOW_EMAIL_LOGIN && user && user.hashedPassword) {
      console.log("email login for existing user " + query.email)
      // check passwd against local db
      bcrypt.compare(password, user.hashedPassword, function (error, match) {
        if (match) {
          console.log("Local user password match")
          AuthenticationManager.login(user, password, callback)
        } else {
          console.log("Local user password mismatch, trying LDAP")
          // check passwd against ldap
          AuthenticationManager.ldapAuth(query, password, AuthenticationManager.createIfNotExistAndLogin, callback, user)
        }
      })
    } else {
      // No local passwd check user has to be in ldap and use ldap credentials
      AuthenticationManager.ldapAuth(query, password, AuthenticationManager.createIfNotExistAndLogin, callback, user)
    }
    return null
  },

  validateEmail(email) {
    // we use the emailadress from the ldap
    // therefore we do not enforce checks here
    const parsed = EmailHelper.parseEmail(email)
    //if (!parsed) {
    //    return new InvalidEmailError({ message: 'email not valid' })
    //}
    return null
  },

  // validates a password based on a similar set of rules to `complexPassword.js` on the frontend
  // note that `passfield.js` enforces more rules than this, but these are the most commonly set.
  // returns null on success, or an error object.
  validatePassword(password, email) {
    if (password == null) {
      return new InvalidPasswordError({
        message: 'password not set',
        info: { code: 'not_set' },
      })
    }

    let allowAnyChars, min, max
    if (Settings.passwordStrengthOptions) {
      allowAnyChars = Settings.passwordStrengthOptions.allowAnyChars === true
      if (Settings.passwordStrengthOptions.length) {
        min = Settings.passwordStrengthOptions.length.min
        max = Settings.passwordStrengthOptions.length.max
      }
    }
    allowAnyChars = !!allowAnyChars
    min = min || 6
    max = max || 72

    // we don't support passwords > 72 characters in length, because bcrypt truncates them
    if (max > 72) {
      max = 72
    }

    if (password.length < min) {
      return new InvalidPasswordError({
        message: 'password is too short',
        info: { code: 'too_short' },
      })
    }
    if (password.length > max) {
      return new InvalidPasswordError({
        message: 'password is too long',
        info: { code: 'too_long' },
      })
    }
    if (
      !allowAnyChars &&
      !AuthenticationManager._passwordCharactersAreValid(password)
    ) {
      return new InvalidPasswordError({
        message: 'password contains an invalid character',
        info: { code: 'invalid_character' },
      })
    }
    if (typeof email === 'string' && email !== '') {
      const startOfEmail = email.split('@')[0]
      if (
        password.indexOf(email) !== -1 ||
        password.indexOf(startOfEmail) !== -1
      ) {
        return new InvalidPasswordError({
          message: 'password contains part of email address',
          info: { code: 'contains_email' },
        })
      }
    }
    return null
  },

  setUserPassword(user, password, callback) {
    AuthenticationManager.setUserPasswordInV2(user, password, callback)
  },

  checkRounds(user, hashedPassword, password, callback) {
    // Temporarily disable this function, TODO: re-enable this
    if (Settings.security.disableBcryptRoundsUpgrades) {
      return callback()
    }
    // check current number of rounds and rehash if necessary
    const currentRounds = bcrypt.getRounds(hashedPassword)
    if (currentRounds < BCRYPT_ROUNDS) {
      AuthenticationManager.setUserPassword(user, password, callback)
    } else {
      callback()
    }
  },

  hashPassword(password, callback) {
    bcrypt.genSalt(BCRYPT_ROUNDS, BCRYPT_MINOR_VERSION, function (error, salt) {
      if (error) {
        return callback(error)
      }
      bcrypt.hash(password, salt, callback)
    })
  },

  setUserPasswordInV2(user, password, callback) {
    if (!user || !user.email || !user._id) {
      return callback(new Error('invalid user object'))
    }
    const validationError = this.validatePassword(password, user.email)
    if (validationError) {
      return callback(validationError)
    }
    this.hashPassword(password, function (error, hash) {
      if (error) {
        return callback(error)
      }
      db.users.updateOne(
        {
          _id: ObjectId(user._id.toString()),
        },
        {
          $set: {
            hashedPassword: hash,
          },
          $unset: {
            password: true,
          },
        },
        function (updateError, result) {
          if (updateError) {
            return callback(updateError)
          }
          _checkWriteResult(result, callback)
          HaveIBeenPwned.checkPasswordForReuseInBackground(password)
        }
      )
    })
  },

  _passwordCharactersAreValid(password) {
    let digits, letters, lettersUp, symbols
    if (
      Settings.passwordStrengthOptions &&
      Settings.passwordStrengthOptions.chars
    ) {
      digits = Settings.passwordStrengthOptions.chars.digits
      letters = Settings.passwordStrengthOptions.chars.letters
      lettersUp = Settings.passwordStrengthOptions.chars.letters_up
      symbols = Settings.passwordStrengthOptions.chars.symbols
    }
    digits = digits || '1234567890'
    letters = letters || 'abcdefghijklmnopqrstuvwxyz'
    lettersUp = lettersUp || 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
    symbols = symbols || '@#$%^&*()-_=+[]{};:<>/?!£€.,'

    for (let charIndex = 0; charIndex <= password.length - 1; charIndex++) {
      if (
        digits.indexOf(password[charIndex]) === -1 &&
        letters.indexOf(password[charIndex]) === -1 &&
        lettersUp.indexOf(password[charIndex]) === -1 &&
        symbols.indexOf(password[charIndex]) === -1
      ) {
        return false
      }
    }
    return true
  },


  async ldapAuth(query, password, onSuccessCreateUserIfNotExistent, callback, user) {
    const client = new Client({
      url: process.env.LDAP_SERVER,
    });

    const ldap_reader = process.env.LDAP_BIND_USER
    const ldap_reader_pass = process.env.LDAP_BIND_PW
    const ldap_base = process.env.LDAP_BASE

    var mail = query.email
    var uid = query.email.split('@')[0]
    var firstname = ""
    var lastname = ""
    var isAdmin = false
    var userDn = ""

    //replace all appearences of %u with uid and all %m with mail:
    const replacerUid = new RegExp("%u", "g")
    const replacerMail = new RegExp("%m","g")
    const filterstr = process.env.LDAP_USER_FILTER.replace(replacerUid, ldapEscape.filter`${uid}`).replace(replacerMail, ldapEscape.filter`${mail}`) //replace all appearances
    // check bind
    try {
      if(process.env.LDAP_BINDDN){ //try to bind directly with the user trying to log in
        userDn = process.env.LDAP_BINDDN.replace(replacerUid,ldapEscape.filter`${uid}`).replace(replacerMail, ldapEscape.filter`${mail}`);
        await client.bind(userDn,password);
      }else{// use fixed bind user
        await client.bind(ldap_reader, ldap_reader_pass);
      }
    } catch (ex) {
      if(process.env.LDAP_BINDDN){
        console.log("Could not bind user: " + userDn);
      }else{
        console.log("Could not bind LDAP reader: " + ldap_reader + " err: " + String(ex))
      }
      return callback(null, null)
    }

    // get user data
    try {
      const {searchEntries, searchRef,} = await client.search(ldap_base, {
        scope: 'sub',
        filter: filterstr ,
      });
      await searchEntries
      console.log(JSON.stringify(searchEntries))
      if (searchEntries[0]) {
        mail = searchEntries[0].mail
        uid = searchEntries[0].uid
        firstname = searchEntries[0].givenName
        lastname = searchEntries[0].sn
        if(!process.env.LDAP_BINDDN){ //dn is already correctly assembled
          userDn = searchEntries[0].dn
        }
        console.log("Found user: " + mail + " Name: " + firstname + " " + lastname + " DN: " + userDn)
      }
    } catch (ex) {
      console.log("An Error occured while getting user data during ldapsearch: " + String(ex))
      await client.unbind();
      return callback(null, null)
    }

    try {
      // if admin filter is set - only set admin for user in ldap group
      // does not matter - admin is deactivated: managed through ldap
      if (process.env.LDAP_ADMIN_GROUP_FILTER) {
        const adminfilter = process.env.LDAP_ADMIN_GROUP_FILTER.replace(replacerUid, ldapEscape.filter`${uid}`).replace(replacerMail, ldapEscape.filter`${mail}`)
        adminEntry = await client.search(ldap_base, {
          scope: 'sub',
          filter: adminfilter,
        });
        await adminEntry;
        //console.log("Admin Search response:" + JSON.stringify(adminEntry.searchEntries))
        if (adminEntry.searchEntries[0]) {
          console.log("is Admin")
          isAdmin=true;
        }
      }
    } catch (ex) {
      console.log("An Error occured while checking for admin rights - setting admin rights to false: " + String(ex))
      isAdmin = false;
    } finally {
      await client.unbind();
    }
    if (mail == "" || userDn == "") {
      console.log("Mail / userDn not set - exit. This should not happen - please set mail-entry in ldap.")
      return callback(null, null)
    }

    if(!process.env.BINDDN){//since we used a fixed bind user to obtain the correct userDn we need to bind again to authenticate
      try {
        await client.bind(userDn, password);
      } catch (ex) {
        console.log("Could not bind User: " + userDn + " err: " + String(ex))
        return callback(null, null)
      } finally{
        await client.unbind()
      }
    }
    //console.log("Logging in user: " + mail + " Name: " + firstname + " " + lastname + " isAdmin: " + String(isAdmin))
    // we are authenticated now let's set the query to the correct mail from ldap
    query.email = mail
    User.findOne(query, (error, user) => {
      if (error) {
        console.log(error)
      }
      if (user && user.hashedPassword) {
        //console.log("******************** LOGIN ******************")
        AuthenticationManager.login(user, "randomPass", callback)
      } else {
        onSuccessCreateUserIfNotExistent(query, user, callback, uid, firstname, lastname, mail, isAdmin)
      }
    })
  }



}

AuthenticationManager.promises = {
  authenticate: util.promisify(AuthenticationManager.authenticate),
  hashPassword: util.promisify(AuthenticationManager.hashPassword),
  setUserPassword: util.promisify(AuthenticationManager.setUserPassword),
}

module.exports = AuthenticationManager