package p2p

import (
	"bytes"
	"context"
	"reflect"

	"github.com/gogo/protobuf/proto"
	"github.com/pkg/errors"
	"github.com/prysmaticlabs/prysm/shared/hashutil"
	"github.com/prysmaticlabs/prysm/shared/traceutil"
	"go.opencensus.io/trace"
)

// ErrMessageNotMapped occurs on a Broadcast attempt when a message has not been defined in the
// GossipTypeMapping.
var ErrMessageNotMapped = errors.New("message type is not mapped to a PubSub topic")

// Broadcast a message to the p2p network.
func (s *Service) Broadcast(ctx context.Context, msg proto.Message) error {
	ctx, span := trace.StartSpan(ctx, "p2p.Broadcast")
	defer span.End()
	topic, ok := GossipTypeMapping[reflect.TypeOf(msg)]
	if !ok {
		traceutil.AnnotateError(span, ErrMessageNotMapped)
		return ErrMessageNotMapped
	}
	span.AddAttributes(trace.StringAttribute("topic", topic))

	buf := new(bytes.Buffer)
	if _, err := s.Encoding().Encode(buf, msg); err != nil {
		err := errors.Wrap(err, "could not encode message")
		traceutil.AnnotateError(span, err)
		return err
	}

	if span.IsRecordingEvents() {
		id := hashutil.FastSum64(buf.Bytes())
		messageLen := int64(buf.Len())
		span.AddMessageSendEvent(int64(id), messageLen /*uncompressed*/, messageLen /*compressed*/)
	}

	if err := s.pubsub.Publish(topic+s.Encoding().ProtocolSuffix(), buf.Bytes()); err != nil {
		err := errors.Wrap(err, "could not publish message")
		traceutil.AnnotateError(span, err)
		return err
	}
	return nil
}