begin
  # `rescue nil` didn't work for some Ruby versions
  require 'active_job/logging'
rescue LoadError
end

module LogStasher
  module ActiveJob
    class LogSubscriber < ::ActiveJob::Logging::LogSubscriber

      def enqueue(event)
        process_event(event, 'enqueue')
      end

      def enqueue_at(event)
        process_event(event, 'enqueue_at')
      end

      def perform(event)
        process_event(event, 'perform')

        # Revert the request id back, in the event that the inline adapter is being used or a
        # perform_now was used.
        LogStasher.request_context[:request_id] = Thread.current[:old_request_id]
        Thread.current[:old_request_id] = nil
      end

      def perform_start(event)
        # Use the job_id as the request id, so that any custom logging done for a job
        # shares a request id, and has the job id in each log line.
        #
        # It's not being set when the job is enqueued, so enqueuing a job will have it's default
        # request_id. In a lot of cases, it will be because of a web request.
        #
        # Hang onto the old request id, so we can revert after the job is done being performed.
        Thread.current[:old_request_id] = LogStasher.request_context[:request_id]
        LogStasher.request_context[:request_id] = event.payload[:job].job_id

        process_event(event, 'perform_start')
      end

      def logger
        LogStasher.logger
      end

      private

      def process_event(event, type)
        data = extract_metadata(event)
        data.merge! extract_exception(event)
        data.merge! extract_scheduled_at(event) if type == 'enqueue_at'
        data.merge! extract_duration(event) if type == 'perform'
        data.merge! request_context

        tags = ['job', type]
        tags.push('exception') if data[:exception]
        logger << LogStasher.build_logstash_event(data, tags).to_json + "\n"
      end

      def extract_metadata(event)
        {
          :job_id => event.payload[:job].job_id,
          :queue_name => queue_name(event),
          :job_class => event.payload[:job].class.to_s,
          :job_args => args_info(event.payload[:job]),
        }
      end

      def extract_duration(event)
        { :duration => event.duration.to_f.round(2) }
      end

      def extract_exception(event)
        event.payload.slice(:exception)
      end

      def extract_scheduled_at(event)
        { :scheduled_at => scheduled_at(event) }
      end

      def request_context
        LogStasher.request_context
      end

      # The default args_info makes a string. We need objects to turn into JSON.
      def args_info(job)
        job.arguments.map { |arg| arg.try(:to_global_id).try(:to_s) || arg }
      end

    end
  end
end if defined?(::ActiveJob::Logging::LogSubscriber)