# frozen_string_literal: true

module Users
  # Service for refreshing the authorized projects of a user.
  #
  # This particular service class can not be used to update data for the same
  # user concurrently. Doing so could lead to an incorrect state. To ensure this
  # doesn't happen a caller must synchronize access (e.g. using
  # `Gitlab::ExclusiveLease`).
  #
  # Usage:
  #
  #     user = User.find_by(username: 'alice')
  #     service = Users::RefreshAuthorizedProjectsService.new(some_user)
  #     service.execute
  class RefreshAuthorizedProjectsService
    attr_reader :user, :source

    LEASE_TIMEOUT = 1.minute.to_i

    # user - The User for which to refresh the authorized projects.
    def initialize(user, source: nil, incorrect_auth_found_callback: nil, missing_auth_found_callback: nil)
      @user = user
      @source = source
      @incorrect_auth_found_callback = incorrect_auth_found_callback
      @missing_auth_found_callback = missing_auth_found_callback
    end

    def execute
      lease_key = "refresh_authorized_projects:#{user.id}"
      lease = Gitlab::ExclusiveLease.new(lease_key, timeout: LEASE_TIMEOUT)

      until uuid = lease.try_obtain
        # Keep trying until we obtain the lease. If we don't do so we may end up
        # not updating the list of authorized projects properly. To prevent
        # hammering Redis too much we'll wait for a bit between retries.
        sleep(0.1)
      end

      begin
        # We need an up to date User object that has access to all relations that
        # may have been created earlier. The only way to ensure this is to reload
        # the User object.
        user.reset
        execute_without_lease
      ensure
        Gitlab::ExclusiveLease.cancel(lease_key, uuid)
      end
    end

    # This method returns the updated User object.
    def execute_without_lease
      remove, add = AuthorizedProjectUpdate::FindRecordsDueForRefreshService.new(
        user,
        source: source,
        incorrect_auth_found_callback: incorrect_auth_found_callback,
        missing_auth_found_callback: missing_auth_found_callback
      ).execute

      update_authorizations(remove, add)
    end

    # Updates the list of authorizations for the current user.
    #
    # remove - The IDs of the authorization rows to remove.
    # add - Rows to insert in the form `[user id, project id, access level]`
    def update_authorizations(remove = [], add = [])
      log_refresh_details(remove, add)

      user.remove_project_authorizations(remove) unless remove.empty?
      ProjectAuthorization.insert_authorizations(add) unless add.empty?

      # Since we batch insert authorization rows, Rails' associations may get
      # out of sync. As such we force a reload of the User object.
      user.reset
    end

    private

    attr_reader :incorrect_auth_found_callback, :missing_auth_found_callback

    def log_refresh_details(remove, add)
      Gitlab::AppJsonLogger.info(event: 'authorized_projects_refresh',
                                 user_id: user.id,
                                 'authorized_projects_refresh.source': source,
                                 'authorized_projects_refresh.rows_deleted_count': remove.length,
                                 'authorized_projects_refresh.rows_added_count': add.length,
                                 # most often there's only a few entries in remove and add, but limit it to the first 5
                                 # entries to avoid flooding the logs
                                 'authorized_projects_refresh.rows_deleted_slice': remove.first(5),
                                 'authorized_projects_refresh.rows_added_slice': add.first(5))
    end
  end
end