module OpenProject::LdapGroups
  class Synchronization
    attr_reader :ldap, :synced_groups

    def initialize(ldap)
      @ldap = ldap

      # Get current synced groups in OP
      @synced_groups = ::LdapGroups::SynchronizedGroup.where(auth_source: ldap)

      synchronize!
    rescue StandardError => e
      error = "[LDAP groups] Failed to perform LDAP group synchronization: #{e.class}: #{e.message}"
      Rails.logger.error(error)
    end

    def synchronize!
      ldap_con = ldap.instance_eval { initialize_ldap_con(account, account_password) }

      ::LdapGroups::Membership.transaction do
        @synced_groups.find_each do |group|
          members = get_members(ldap_con, group)
          users = User.where(login: members)
          update_memberships!(group, users)
        end
      end
    end

    ##
    # Apply memberships from the ldap group and remove outdated
    def update_memberships!(sync, users)
      # Get the user ids of the current members in ldap
      ldap_member_ids = users.pluck(:id)
      set_by_us = ::LdapGroups::Membership.where(group_id: sync.id, user_id: ldap_member_ids).pluck(:user_id)

      # Remove group users no longer in ids
      no_longer_present = ::LdapGroups::Membership.where(group_id: sync.id).where.not(user_id: ldap_member_ids)
      remove_memberships!(no_longer_present, sync)

      # Add new memberships
      group_members = sync.group.users.pluck(:id)
      new_members = ldap_member_ids - set_by_us - group_members
      new_users = User.where(id: new_members)
      add_memberships!(new_users, sync)
    end

    ##
    # Get the current members from the ldap group
    def get_members(ldap_con, group)

      # Get user login attribute and base dn which are private
      attr_login = ldap.send :attr_login
      base_dn = ldap.send :base_dn

      # memberOf filter to identifiy member entries of the group
      memberof_filter = Net::LDAP::Filter.eq('memberOf', group.dn)

      logins = []
      ldap_con.search(base: base_dn,
                      filter: memberof_filter,
                      attributes: [attr_login]) do |entry|
        logins << ::LdapAuthSource.get_attr(entry, attr_login)
      end

      logins
    end

    ##
    # Add new users to the synced group
    def add_memberships!(new_users, sync)
      if new_users.empty?
        Rails.logger.info "[LDAP groups] No new users to add for #{sync.entry}"
        return
      end

      Rails.logger.info { "[LDAP groups] Adding users #{new_users.pluck(:login)} to #{sync.entry}" }
      sync.users << new_users.map {|user| ::LdapGroups::Membership.new(group: sync, user: user)}
      sync.group.users << new_users
    end

    ##
    # Remove a set of memberships
    def remove_memberships!(memberships, sync)
      if memberships.empty?
        Rails.logger.info "[LDAP groups] No users to remove for #{sync.entry}"
        return
      end

      Rails.logger.info "[LDAP groups] Removing users #{memberships.pluck(:user_id)} from #{sync.entry}"
      sync.remove_members!(memberships)
    end
  end
end
