# encoding: utf-8

module OneApm
  module Agent
    module CrossAppTracingMessage

      class Error < RuntimeError; end

      OA_ID_MESSAGE_HEADER = 'BlueWareID'

      OA_TXN_MESSAGE_HEADER = 'BlueWareTransaction'

      OA_SYNTHETICS_MESSAGE_HEADER = 'BlueWareSynthetics'

      ###############
      module_function
      ###############

      def request_data(state)
        rpc_request = {}
        inject_rpc_request_headers(state, rpc_request) if cross_app_enabled?
        json_rpc_request = OneApm::JSONWrapper.dump(rpc_request)
        # OneApm::Manager.logger.debug "Thrift Header Message: #{json_rpc_request}"
        obfuscator.obfuscate(json_rpc_request)
      rescue OneApm::Agent::CrossAppTracingMessage::Error => err
        OneApm::Manager.logger.debug "Not injecting x-process header", err
      end

      # TODO: just stub
      def process_request message
        OneApm::Manager.logger.debug "Thrift Process Message: #{message}"
      end

      def inject_rpc_request_headers state, rpc_request
        txn_guid = state.request_guid
        txn = state.current_transaction
        if txn
          trip_id   = txn.cat_trip_id(state)
          path_hash = txn.cat_path_hash(state)
          if txn.raw_synthetics_header
            rpc_request[OA_SYNTHETICS_MESSAGE_HEADER] = txn.raw_synthetics_header
          end
        end
        rpc_request[OA_ID_MESSAGE_HEADER]  = cross_app_id
        rpc_request[OA_TXN_MESSAGE_HEADER] = [txn_guid, true, trip_id, path_hash, '']
      rescue OneApm::Agent::CrossAppTracingMessage::Error => err #TODO
        OneApm::Manager.logger.debug "Not injecting x-process header", err
      end

      def cross_app_id
        OneApm::Manager.config[:cross_process_id] or
          raise OneApm::Agent::CrossAppTracingMessage::Error, "no cross app ID configured"
      end

      def start_trace(state, t0, rpc_request)
        state.is_cross_app_caller = true
        stack = state.traced_method_stack
        segment = stack.push_frame(state, :rpc_request, t0)
        return segment
      rescue => err
        OneApm::Manager.logger.error "Uncaught exception while tracing RPC request", err
        return nil
      rescue Exception => e
        OneApm::Manager.logger.debug "Unexpected exception raised while tracing RPC request", e
        raise e
      end

      def finish_trace(state, t0, segment, request, metrics)
        unless t0
          OneApm::Manager.logger.error("RPC request trace finished without start time. This is probably an agent bug.")
          return
        end

        t1 = Time.now
        duration = t1.to_f - t0.to_f
        begin
          if request
            scoped_metric, *other_metrics = metrics
            OneApm::Manager.agent.stats_engine.record_scoped_and_unscoped_metrics(state, scoped_metric, nil, duration)
            if segment
              segment.name = scoped_metric
            end
          end
        ensure
          # If we have a segment, always pop the traced method stack to avoid
          # an inconsistent state, which prevents tracing of whole transaction.
          if segment
            stack = state.traced_method_stack
            stack.pop_frame(state, segment, scoped_metric, t1)
          end
        end
      rescue OneApm::Agent::CrossAppTracingMessage::Error => err
        OneApm::Manager.logger.debug "while cross app tracing", err
      rescue => err
        OneApm::Manager.logger.error "Uncaught exception while finishing an RPC request trace", err
      end

      # Return +true+ if cross app tracing is enabled in the config.
      def cross_app_enabled?
        valid_cross_process_id? &&
          valid_encoding_key? &&
          cross_application_tracer_enabled?
      end

      def valid_cross_process_id?
        OneApm::Manager.config[:cross_process_id] && OneApm::Manager.config[:cross_process_id].length > 0
      end

      def valid_encoding_key?
        OneApm::Manager.config[:encoding_key] && OneApm::Manager.config[:encoding_key].length > 0
      end

      def cross_application_tracer_enabled?
        OneApm::Manager.config[:"cross_application_tracer.enabled"]
      end

      # Fetcher for the cross app encoding key. Raises a
      # OneApm::Agent::CrossAppTracingMessage::Error if the key isn't configured.
      def cross_app_encoding_key
        OneApm::Manager.config[:encoding_key] or
          raise OneApm::Agent::CrossAppTracingMessage::Error, "No encoding_key set."
      end

      def obfuscator
        @obfuscator ||= OneApm::Agent::Obfuscator.new(cross_app_encoding_key)
      end

    end
  end
end