let UserSessionsManager
const Settings = require('settings-sharelatex')
const logger = require('logger-sharelatex')
const Async = require('async')
const _ = require('underscore')
const UserSessionsRedis = require('./UserSessionsRedis')
const rclient = UserSessionsRedis.client()

module.exports = UserSessionsManager = {
  // mimic the key used by the express sessions
  _sessionKey(sessionId) {
    return `sess:${sessionId}`
  },

  trackSession(user, sessionId, callback) {
    if (!user) {
      logger.log({ sessionId }, 'no user to track, returning')
      return callback(null)
    }
    if (!sessionId) {
      logger.log({ user_id: user._id }, 'no sessionId to track, returning')
      return callback(null)
    }
    logger.log({ user_id: user._id, sessionId }, 'onLogin handler')
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    const value = UserSessionsManager._sessionKey(sessionId)
    rclient
      .multi()
      .sadd(sessionSetKey, value)
      .pexpire(sessionSetKey, `${Settings.cookieSessionLength}`) // in milliseconds
      .exec(function(err, response) {
        if (err) {
          logger.warn(
            { err, user_id: user._id, sessionSetKey },
            'error while adding session key to UserSessions set'
          )
          return callback(err)
        }
        UserSessionsManager._checkSessions(user, function() {})
        callback()
      })
  },

  untrackSession(user, sessionId, callback) {
    if (!callback) {
      callback = function() {}
    }
    if (!user) {
      logger.log({ sessionId }, 'no user to untrack, returning')
      return callback(null)
    }
    if (!sessionId) {
      logger.log({ user_id: user._id }, 'no sessionId to untrack, returning')
      return callback(null)
    }
    logger.log({ user_id: user._id, sessionId }, 'onLogout handler')
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    const value = UserSessionsManager._sessionKey(sessionId)
    rclient
      .multi()
      .srem(sessionSetKey, value)
      .pexpire(sessionSetKey, `${Settings.cookieSessionLength}`) // in milliseconds
      .exec(function(err, response) {
        if (err) {
          logger.warn(
            { err, user_id: user._id, sessionSetKey },
            'error while removing session key from UserSessions set'
          )
          return callback(err)
        }
        UserSessionsManager._checkSessions(user, function() {})
        callback()
      })
  },

  getAllUserSessions(user, exclude, callback) {
    exclude = _.map(exclude, UserSessionsManager._sessionKey)
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    rclient.smembers(sessionSetKey, function(err, sessionKeys) {
      if (err) {
        logger.warn(
          { user_id: user._id },
          'error getting all session keys for user from redis'
        )
        return callback(err)
      }
      sessionKeys = _.filter(sessionKeys, k => !_.contains(exclude, k))
      if (sessionKeys.length === 0) {
        logger.log({ user_id: user._id }, 'no other sessions found, returning')
        return callback(null, [])
      }

      Async.mapSeries(sessionKeys, (k, cb) => rclient.get(k, cb), function(
        err,
        sessions
      ) {
        if (err) {
          logger.warn(
            { user_id: user._id },
            'error getting all sessions for user from redis'
          )
          return callback(err)
        }

        const result = []
        for (let session of Array.from(sessions)) {
          if (!session) {
            continue
          }
          session = JSON.parse(session)
          let sessionUser = session.passport && session.passport.user
          if (!sessionUser) {
            sessionUser = session.user
          }

          result.push({
            ip_address: sessionUser.ip_address,
            session_created: sessionUser.session_created
          })
        }

        callback(null, result)
      })
    })
  },

  revokeAllUserSessions(user, retain, callback) {
    if (!retain) {
      retain = []
    }
    retain = retain.map(i => UserSessionsManager._sessionKey(i))
    if (!user) {
      logger.log({}, 'no user to revoke sessions for, returning')
      return callback(null)
    }
    logger.log({ user_id: user._id }, 'revoking all existing sessions for user')
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    rclient.smembers(sessionSetKey, function(err, sessionKeys) {
      if (err) {
        logger.warn(
          { err, user_id: user._id, sessionSetKey },
          'error getting contents of UserSessions set'
        )
        return callback(err)
      }
      const keysToDelete = _.filter(
        sessionKeys,
        k => !Array.from(retain).includes(k)
      )
      if (keysToDelete.length === 0) {
        logger.log(
          { user_id: user._id },
          'no sessions in UserSessions set to delete, returning'
        )
        return callback(null)
      }
      logger.log(
        { user_id: user._id, count: keysToDelete.length },
        'deleting sessions for user'
      )

      const deletions = keysToDelete.map(k => cb => rclient.del(k, cb))

      Async.series(deletions, function(err, _result) {
        if (err) {
          logger.warn(
            { err, user_id: user._id, sessionSetKey },
            'errror revoking all sessions for user'
          )
          return callback(err)
        }
        rclient.srem(sessionSetKey, keysToDelete, function(err) {
          if (err) {
            logger.warn(
              { err, user_id: user._id, sessionSetKey },
              'error removing session set for user'
            )
            return callback(err)
          }
          callback(null)
        })
      })
    })
  },

  touch(user, callback) {
    if (!user) {
      logger.log({}, 'no user to touch sessions for, returning')
      return callback(null)
    }
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    rclient.pexpire(
      sessionSetKey,
      `${Settings.cookieSessionLength}`, // in milliseconds
      function(err, response) {
        if (err) {
          logger.warn(
            { err, user_id: user._id },
            'error while updating ttl on UserSessions set'
          )
          return callback(err)
        }
        callback(null)
      }
    )
  },

  _checkSessions(user, callback) {
    if (!user) {
      logger.log({}, 'no user, returning')
      return callback(null)
    }
    logger.log({ user_id: user._id }, 'checking sessions for user')
    const sessionSetKey = UserSessionsRedis.sessionSetKey(user)
    rclient.smembers(sessionSetKey, function(err, sessionKeys) {
      if (err) {
        logger.warn(
          { err, user_id: user._id, sessionSetKey },
          'error getting contents of UserSessions set'
        )
        return callback(err)
      }
      logger.log(
        { user_id: user._id, count: sessionKeys.length },
        'checking sessions for user'
      )
      Async.series(
        sessionKeys.map(key => next =>
          rclient.get(key, function(err, val) {
            if (err) {
              return next(err)
            }
            if (!val) {
              logger.log(
                { user_id: user._id, key },
                '>> removing key from UserSessions set'
              )
              rclient.srem(sessionSetKey, key, function(err, result) {
                return next(err)
              })
            } else {
              next()
            }
          })
        ),
        function(err, results) {
          logger.log({ user_id: user._id }, 'done checking sessions for user')
          callback(err)
        }
      )
    })
  }
}