# frozen_string_literal: true

# Copyright (C) 2015-2020 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

module Mongo
  class Cluster
    module Topology
      # Defines behavior for when a cluster is in an unknown state.
      #
      # @since 2.0.0
      class Unknown < Base
        include NoReplicaSetOptions

        # The display name for the topology.
        #
        # @since 2.0.0
        NAME = 'Unknown'

        # Get the display name.
        #
        # @example Get the display name.
        #   Unknown.display_name
        #
        # @return [ String ] The display name.
        #
        # @since 2.0.0
        def display_name
          self.class.name.gsub(/.*::/, '')
        end

        # @note This method is experimental and subject to change.
        #
        # @api experimental
        # @since 2.7.0
        def summary
          details = server_descriptions.keys.join(',')
          "#{display_name}[#{details}]"
        end

        # Determine if the topology would select a readable server for the
        # provided candidates and read preference.
        #
        # @example Is a readable server present?
        #   topology.has_readable_server?(cluster, server_selector)
        #
        # @param [ Cluster ] cluster The cluster.
        # @param [ ServerSelector ] server_selector The server
        #   selector.
        #
        # @return [ false ] An Unknown topology will never have a readable server.
        #
        # @since 2.4.0
        def has_readable_server?(_cluster, _server_selector = nil)
          false
        end

        # Determine if the topology would select a writable server for the
        # provided candidates.
        #
        # @example Is a writable server present?
        #   topology.has_writable_server?(servers)
        #
        # @param [ Cluster ] cluster The cluster.
        #
        # @return [ false ] An Unknown topology will never have a writable server.
        #
        # @since 2.4.0
        def has_writable_server?(_cluster)
          false
        end

        # An unknown topology is not a replica set.
        #
        # @example Is the topology a replica set?
        #   Unknown.replica_set?
        #
        # @return [ false ] Always false.
        #
        # @since 2.0.0
        def replica_set?
          false
        end

        # Select appropriate servers for this topology.
        #
        # @example Select the servers.
        #   Unknown.servers(servers)
        #
        # @param [ Array<Server> ] servers The known servers.
        #
        # @raise [ Unknown ] Cannot select servers when the topology is
        #   unknown.
        #
        # @since 2.0.0
        def servers(_servers)
          []
        end

        # An unknown topology is not sharded.
        #
        # @example Is the topology sharded?
        #   Unknown.sharded?
        #
        # @return [ false ] Always false.
        #
        # @since 2.0.0
        def sharded?
          false
        end

        # An unknown topology is not single.
        #
        # @example Is the topology single?
        #   Unknown.single?
        #
        # @return [ true ] Always false.
        #
        # @since 2.0.0
        def single?
          false
        end

        # An unknown topology is unknown.
        #
        # @example Is the topology unknown?
        #   Unknown.unknown?
        #
        # @return [ true ] Always true.
        #
        # @since 2.0.0
        def unknown?
          true
        end
      end
    end
  end
end
