# File lib/fog/aws/requests/compute/associate_address.rb, line 43
        def associate_address(instance_id=nil, public_ip=nil, network_interface_id=nil, allocation_id=nil)
          public_ip = allocation_id.nil? ? public_ip : nil
          response = Excon::Response.new
          response.status = 200
          instance = self.data[:instances][instance_id]
          address = public_ip.nil? ? nil : self.data[:addresses][public_ip]
          if ((instance && address) || (instance &&  !allocation_id.nil?) || (!allocation_id.nil? && !network_interface_id.nil?))
            if !allocation_id.nil?
              allocation_ip = describe_addresses( 'allocation-id'  => "#{allocation_id}").body['addressesSet']
              public_ip = allocation_ip['publicIp']
            end
            if current_instance = self.data[:instances][address['instanceId']]
              current_instance['ipAddress'] = current_instance['originalIpAddress']
            end
            address['instanceId'] = instance_id
            # detach other address (if any)
            if self.data[:addresses][instance['ipAddress']]
              self.data[:addresses][instance['ipAddress']]['instanceId'] = nil
            end
            instance['ipAddress'] = public_ip
            instance['dnsName'] = Fog::AWS::Mock.dns_name_for(public_ip)
            response.status = 200
            if !instance_id.nil? && !public_ip.nil?
              response.body = {
                'requestId' => Fog::AWS::Mock.request_id,
                'return'    => true
              }
            elsif !allocation_id.nil?
              response.body = {
                'requestId'     => Fog::AWS::Mock.request_id,
                'return'        => true,
                'associationId' => Fog::AWS::Mock.request_id
              }
            end
            response
          #elsif ! network_interface_id.nil? && allocation_id.nil?
          #  raise Fog::Compute::AWS::NotFound.new("You must specify an AllocationId when specifying a NetworkInterfaceID")
          #elsif instance.nil? && network_interface_id.nil?
          #  raise Fog::Compute::AWS::Error.new("You must specify either an InstanceId or a NetworkInterfaceID")
          #elsif !instance && !network_interface_id
          #  raise Fog::Compute::AWS::Error.new(" 2 You must specify either an InstanceId or a NetworkInterfaceID")
          elsif !instance
            raise Fog::Compute::AWS::NotFound.new("You must specify either an InstanceId or a NetworkInterfaceID")
          elsif !address
            raise Fog::Compute::AWS::Error.new("AuthFailure => The address '#{public_ip}' does not belong to you.")
          end
        end