# Copyright (C) 2014 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 Server
    class Description

      # Defines behaviour around what features a specific server supports.
      #
      # @since 2.0.0
      class Features

        # List of features and the wire protocol version they appear in.
        #
        # @since 2.0.0
        MAPPINGS = {
          :list_collections => 3,
          :list_indexes => 3,
          :scram_sha_1 => 3,
          :write_command => 2
        }.freeze

        # The wire protocol versions that this version of the driver supports.
        #
        # @since 2.0.0
        DRIVER_WIRE_VERSIONS = (0..3).freeze

        # Create the methods for each mapping to tell if they are supported.
        #
        # @since 2.0.0
        MAPPINGS.each do |name, version|

          # Determine whether or not the feature is enabled.
          #
          # @example Is a feature enabled?
          #   features.list_collections_enabled?
          #
          # @return [ true, false ] If the feature is enabled.
          #
          # @since 2.0.0
          define_method("#{name}_enabled?") do
            server_wire_versions.include?(MAPPINGS[name])
          end
        end

        # @return [ Range ] server_wire_versions The server's supported wire
        #   versions.
        attr_reader :server_wire_versions

        # Initialize the features.
        #
        # @example Initialize the features.
        #   Features.new(0..3)
        #
        # @param [ Range ] server_wire_versions The server supported wire
        #   versions.
        #
        # @since 2.0.0
        def initialize(server_wire_versions)
          @server_wire_versions = server_wire_versions
          check_driver_support!
        end

        private

        def check_driver_support!
          if DRIVER_WIRE_VERSIONS.max < server_wire_versions.max
            raise Error::UnsupportedFeatures.new(server_wire_versions)
          end
        end
      end
    end
  end
end