# Copyright (C) 2009-2014 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.

require 'mongo/operation/parallel_scan/result'

module Mongo
  module Operation

    # A MongoDB parallel scan operation.
    #
    # @example Create the parallel scan operation.
    #   ParallelScan.new({
    #     :db_name  => 'test_db',
    #     :coll_name = > 'test_collection',
    #     :cursor_count => 5
    #   })
    #
    # Initialization:
    #   param [ Hash ] spec The specifications for the operation.
    #
    #   option spec :db_name [ String ] The name of the database on which
    #     the operation should be executed.
    #   option spec :coll_name [ String ] The collection to scan.
    #   option spec :cursor_count [ Integer ] The number of cursors to use.
    #   option spec :options [ Hash ] Options for the command.
    #
    # @since 2.0.0
    class ParallelScan
      include Executable
      include Specifiable
      include Limited
      include ReadPreferrable

      # Execute the parallel scan operation.
      #
      # @example Execute the operation.
      #   operation.execute(context)
      #
      # @param [ Mongo::Server::Context ] context The context for this operation.
      #
      # @return [ Result ] The operation response, if there is one.
      #
      # @since 2.0.0
      def execute(context)
        execute_message(context)
      end

      private

      def execute_message(context)
        context.with_connection do |connection|
          Result.new(connection.dispatch([ message(context) ])).validate!
        end
      end

      def selector
        { :parallelCollectionScan => coll_name, :numCursors => cursor_count }
      end

      def query_coll
        Database::COMMAND
      end
    end
  end
end