# Encoding: utf-8
#
# Copyright 2018 Google LLC
#
# 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
#
#     https://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.
#
# Interceptor to log outgoing requests and incoming responses.

require 'google/ads/google_ads/api_versions'
require 'google/ads/google_ads/partial_failure_error_decoder'
require 'grpc/generic/interceptors'
require 'json'

module Google
  module Ads
    module GoogleAds
      class LoggingInterceptor < GRPC::ClientInterceptor

        def initialize(logger)
          # Don't propagate args, parens are necessary
          super()
          @logger = logger
        end

        def request_response(request:, call:, method:, metadata: {})
          begin
            response = yield

            @logger.info { build_summary_message(request, call, method, false) }
            @logger.debug { build_request_message(metadata, request) }
            @logger.debug { build_success_response_message(response) }
            if response.respond_to?(:partial_failure_error) && response.partial_failure_error
              @logger.debug { build_partial_failure_message(response) }
            end
            response
          rescue Exception
            @logger.warn { build_summary_message(request, call, method, true) }
            @logger.info { build_request_message(metadata, request) }
            @logger.info { build_error_response_message }
            raise
          end
        end

        private

        def build_partial_failure_message(response)
          errors = PartialFailureErrorDecoder.decode(
            response.partial_failure_error
          )
          errors.reduce("Partial failure errors: ") do |accum, error|
            accum += error.to_json + "\n"
            accum
          end
        end

        def build_error_response_message
          # this looks like "magic", but the Google::Gax::GaxError grabs
          # the current exception as its cause, and then parses details
          # out of that exception. So this sets it up so that
          # most_recent_error.status_details contains useful information about
          # our failure
          most_recent_error = Google::Gax::GaxError.new('')
          response_message = "Incoming response (errors): \n"

          formatted_details = case most_recent_error.status_details
          when nil
            ""
          when String
            most_recent_error.status_details
          when Array
            most_recent_error.status_details.select { |detail|
              interesting_error_classes.include?(detail.class)
            }.map { |detail|
              response_error_from_detail(detail)
            }.join("\n")
          end

          response_message += formatted_details
          response_message
        end

        def build_success_response_message(response)
          "Incoming response: Payload: #{response.to_json}"
        end

        def build_request_message(metadata, request)
          # calling #to_json on some protos (specifically those with non-UTF8
          # encodable byte values) causes a segfault, however #inspect works
          # so we check if the proto contains a bytevalue, and if it does
          # we #inspect instead of #to_json
          request_inspect = if use_bytes_inspect?(request)
                              request.inspect
                            else
                              request.to_json
                            end
          "Outgoing request: Headers: #{metadata.to_json} Payload: #{request_inspect}"
        end

        def build_summary_message(request, call, method, is_fault)
          customer_id = "N/A"
          customer_id = request.customer_id if request.respond_to?(:customer_id)
          # CustomerService get requests have a different format.
          if request.respond_to?(:resource_name)
            customer_id = request.resource_name.split('/').last
          end

          is_fault_string = if is_fault
            "yes"
          else
            "no"
          end

          [
            "CID: #{customer_id}",
            "Host: #{call.instance_variable_get('@wrapped').peer}",
            "Method: #{method}",
            "IsFault: #{is_fault_string}",
          ].join(", ")
        end

        def response_error_from_detail(detail)
          detail.errors.map.with_index { |error, i|
            "Error #{i + 1}: #{error.to_json}"
          }.join("\n")
        end

        def use_bytes_inspect?(request)
          @cycle_finder = CycleFinder.new
          contains_bytes_field?(request.class.descriptor)
        end

        def contains_bytes_field?(descriptor)
          return false if descriptor.nil?
          return false if @cycle_finder.is_cycle?(descriptor)

          @cycle_finder.add_object(descriptor)

          descriptor.map { |x| x.type == :bytes || (x.type == :message && contains_bytes_field?(x.subtype)) }.any?
        end

        def interesting_error_classes
          @interesting_error_classes ||= Google::Ads::GoogleAds::Errors.namespaces.map do |namespace|
            namespace.const_get(:GoogleAdsFailure)
          end
        end

        class CycleFinder
          def initialize
            @objects_seen = Set.new
          end

          def is_cycle?(object)
            @objects_seen.include?(object.object_id)
          end

          def add_object(object)
            @objects_seen.add(object.object_id)
          end
        end
      end
    end
  end
end