func getBackgroundEvent()

in funcframework/events.go [108:156]
32 lines of code
10 McCabe index (conditional complexity)

func getBackgroundEvent(body []byte, path string) (*metadata.Metadata, interface{}, error) {
	// Known background event types that the incoming request could represent.
	// Event types are mutually exclusive. During unmarshalling, only the field
	// for the matching type is populated.
	type possibleEvents struct {
		*pubsub.LegacyPushSubscriptionEvent
		*fftypes.BackgroundEvent
	}

	// Attempt to unmarshal into one of the known background event types.
	possible := possibleEvents{}
	if err := json.Unmarshal(body, &possible); err != nil {
		return nil, nil, err
	}

	event := possible.BackgroundEvent
	// If the background event payload is missing, check if it's a legacy
	// Pub/Sub event.
	if possible.BackgroundEvent == nil && possible.LegacyPushSubscriptionEvent != nil {
		topic, err := pubsub.ExtractTopicFromRequestPath(path)
		if err != nil {
			fmt.Printf("WARNING: %s", err)
		}
		event = possible.LegacyPushSubscriptionEvent.ToBackgroundEvent(topic)
	}

	// If there is no "data" payload, this isn't a background event, but that's okay.
	if event == nil || event.Data == nil {
		return nil, nil, nil
	}

	// If the "context" field was present, we have a complete event and so return.
	if event.Metadata != nil {
		return event.Metadata, event.Data, nil
	}

	// Otherwise, try to directly populate a metadata object.
	m := &metadata.Metadata{}
	if err := json.Unmarshal(body, m); err != nil {
		return nil, nil, err
	}

	// Check for event ID to see if this is a background event, but if not that's okay.
	if m.EventID == "" {
		return nil, nil, nil
	}

	return m, event.Data, nil
}