package mqtt

import (
	"context"
	"fmt"

	"cloud.google.com/go/pubsub"
)

// ResponseTopicWrapper is a Publisher that is used to send chariot pubsub responses back to the appropriate clients.
type GCPPubSubTopicWrapper struct {
	Topic *pubsub.Topic
}

// NewGooglePubSubResponseTopicPublisher creates and wraps a pubsub.Topic for the given topicID.
func NewGooglePubSubTopicWrapper(ctx context.Context, client *pubsub.Client, projectID, topicID string) (*GCPPubSubTopicWrapper, error) {
	topic := client.TopicInProject(topicID, projectID)
	if exists, err := topic.Exists(ctx); err != nil {
		return nil, fmt.Errorf("error checking if topic %q exists: %w", topicID, err)
	} else if !exists {
		return nil, fmt.Errorf("topic %q does not exist", topicID)
	}
	return &GCPPubSubTopicWrapper{Topic: topic}, nil
}

// Publish satisfies the Publisher interface.
func (w *GCPPubSubTopicWrapper) Publish(ctx context.Context, m Payload) error {
	_, err := w.Topic.Publish(ctx, &pubsub.Message{
		Data:       m.Data(),
		Attributes: m.Attributes(),
	}).Get(ctx)
	return err
}

// Stop ensures that the topic's resources are cleaned up
func (w *GCPPubSubTopicWrapper) Stop() {
	if w.Topic != nil {
		w.Topic.Stop()
	}
}