# Copyright 2011-2012 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
#     http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file 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 AWS
  module Core
    class Client

      # When a client class extends this module, its API configuration
      # is parsed.  For each operation in the API configuration, one
      # client method is added.
      #
      # Clients extending QueryXML all have in common their method
      # of serializing request (input) paramters and parsing response
      # (output) XML.
      #
      module QueryXML
        
        # @private
        def self.extended base
          base.send(:include, ErrorParser)
          base.send(:define_parsers)
        end
  
        # @return [Hash<Symbol,OptionGrammar>] Returns a hash option
        #   parsers.  Hash keys are client method names and hash
        #   values are {OptionGrammar} objects.
        # @private
        def option_parsers
          @option_parsers ||= {}
        end
  
        # @return [Hash<Symbol,XML::Parser>] Returns a hash of xml
        #   parsers.  Hash keys are client method names and hash
        #   values are {XML::Parser} objects.
        # @private
        def xml_parsers
          @xml_parsers ||= {}
        end
  
        protected
  
        # Enumerates through the operations specified in the API 
        # configuration (yaml configuration file found in lib/api_config/)
        # and defines one request method per operation.
        def define_parsers
          api_config[:operations].each do |op|
  
            method_name = op[:method]
  
            option_parsers[method_name] = OptionGrammar.customize(op[:inputs])
            xml_parsers[method_name] = XML::Parser.new(op[:outputs])
  
          end
        end
  
        def define_client_method method_name, operation_name
          add_client_request_method(method_name) do
  
            configure_request do |request, options|
  
              now = Time.now.utc.strftime('%Y-%m-%dT%H:%M:%SZ')
  
              request.headers['Content-Type'] = 
                'application/x-www-form-urlencoded; charset=utf-8'
  
              request.http_method = 'POST'
              request.add_param 'Timestamp', now
              request.add_param 'Version', self.class::API_VERSION
              request.add_param 'Action', operation_name
  
              parser = self.class.option_parsers[method_name]
              parser.request_params(options).each do |param|
                request.add_param(param)
              end
  
            end
  
            process_response do |response|
              parser = self.class.xml_parsers[method_name]
              response.data = parser.parse(response.http_response.body)
            end
  
            simulate_response do |response|
              parser = self.class.xml_parsers[method_name]
              response.data = parser.simulate
            end
  
          end
        end
  
        module ErrorParser
  
          protected
  
          def extract_error_details response
            if 
              response.http_response.status >= 300 and
              body = response.http_response.body and
              error = errors_module::GRAMMAR.parse(body) and
              error[:code]
            then
              [error[:code], error[:message]]
            end
          end
          
        end

      end
    end
  end
end