# encoding: utf-8

module OneApm
  class Transaction

    class << self

      def start_new_transaction(state, category, options)
        txn = Transaction.new(category, options)
        state.reset(txn)
        txn.start(state)
        txn
      end

      def start(state, category, options)
        category ||= :controller
        txn = state.current_transaction

        if txn
          txn.create_nested_frame(state, category, options)
        else
          txn = start_new_transaction(state, category, options)
        end

        txn
      rescue => e
        OneApm::Manager.logger.error("Exception during Transaction.start", e)
        nil
      end

      def stop(state, end_time=Time.now)
        txn = state.current_transaction

        if txn.nil?
          OneApm::Manager.logger.error(Transaction::FAILED_TO_STOP_MESSAGE)
          return
        end

        nested_frame = txn.frame_stack.pop

        if txn.frame_stack.empty?
          txn.stop(state, end_time, nested_frame)
          state.reset
        else
          nested_name = nested_transaction_name(nested_frame.name)

          if nested_name.start_with?(Transaction::MIDDLEWARE_PREFIX)
            summary_metrics = Transaction::MIDDLEWARE_SUMMARY_METRICS
          else
            summary_metrics = Transaction::EMPTY_SUMMARY_METRICS
          end

          OneApm::Support::MethodTracer::Helpers.trace_execution_scoped_footer(
            state,
            nested_frame.start_time.to_f,
            nested_name,
            summary_metrics,
            nested_frame,
            Transaction::NESTED_TRACE_STOP_OPTIONS,
            end_time.to_f)
        end

        :transaction_stopped
      rescue => e
        state.reset
        OneApm::Manager.logger.error("Exception during Transaction.stop", e)
        nil
      end

      def wrap(state, name, category, options = {})
        Transaction.start(state, category, options.merge(:transaction_name => name))
        begin
          yield
        rescue => e
          Transaction.notice_error(e)
          raise e
        ensure
          Transaction.stop(state)
        end
      end

      def nested_transaction_name(name)
        if name.start_with?(Transaction::CONTROLLER_PREFIX) || name.start_with?(Transaction::OTHER_TRANSACTION_PREFIX)
          "#{Transaction::SUBTRANSACTION_PREFIX}#{name}"
        else
          name
        end
      end

      #
      # * duration: response time
      # * failed: the request is failed or not
      # * apdex_s: satisfy
      # * apdex_t: tolerate
      # * apdex_f: frustrate
      #
      def apdex_bucket(duration, failed, apdex_t)
        case
        when failed
          :apdex_f  # frustrate if request failed
        when duration <= apdex_t
          :apdex_s  # satisfy if duration < tolerate
        when duration <= 4 * apdex_t
          :apdex_t  # tolerate if duration < 4 * tolerate
        else
          :apdex_f  # otherwise frustrate
        end
      end

      # Make a safe attempt to get the URI, without the host and query string.
      def uri_from_request(req)
        approximate_uri = case
                          when req.respond_to?(:fullpath   ) then req.fullpath
                          when req.respond_to?(:path       ) then req.path
                          when req.respond_to?(:request_uri) then req.request_uri
                          when req.respond_to?(:uri        ) then req.uri
                          when req.respond_to?(:url        ) then req.url
                          end
        return approximate_uri[%r{^(https?://.*?)?(/[^?]*)}, 2] || '/' if approximate_uri
      end

      # Make a safe attempt to get the referer from a request object, generally successful when
      # it's a Rack request.
      def referer_from_request(req)
        if req && req.respond_to?(:referer)
          req.referer.to_s.split('?').first
        end
      end

    end
  end
end