github.com/wfusion/gofusion@v1.1.14/common/infra/watermill/components/forwarder/envelope.go (about)

     1  package forwarder
     2  
     3  import (
     4  	"github.com/pkg/errors"
     5  
     6  	"github.com/wfusion/gofusion/common/infra/watermill/message"
     7  	"github.com/wfusion/gofusion/common/utils"
     8  	"github.com/wfusion/gofusion/common/utils/serialize/json"
     9  )
    10  
    11  // messageEnvelope wraps Watermill message and contains destination topic.
    12  type messageEnvelope struct {
    13  	DestinationTopic string `json:"destination_topic"`
    14  
    15  	UUID     string            `json:"uuid"`
    16  	Payload  []byte            `json:"payload"`
    17  	Metadata map[string]string `json:"metadata"`
    18  }
    19  
    20  func newMessageEnvelope(destTopic string, msg *message.Message) (*messageEnvelope, error) {
    21  	e := &messageEnvelope{
    22  		DestinationTopic: destTopic,
    23  		UUID:             msg.UUID,
    24  		Payload:          msg.Payload,
    25  		Metadata:         msg.Metadata,
    26  	}
    27  
    28  	if err := e.validate(); err != nil {
    29  		return nil, errors.Wrap(err, "cannot create a message envelope")
    30  	}
    31  
    32  	return e, nil
    33  }
    34  
    35  func (e *messageEnvelope) validate() error {
    36  	if e.DestinationTopic == "" {
    37  		return errors.New("unknown destination topic")
    38  	}
    39  
    40  	return nil
    41  }
    42  
    43  func wrapMessageInEnvelope(destinationTopic string, msg *message.Message) (*message.Message, error) {
    44  	envelope, err := newMessageEnvelope(destinationTopic, msg)
    45  	if err != nil {
    46  		return nil, errors.Wrap(err, "cannot envelope a message")
    47  	}
    48  
    49  	envelopedMessage, err := json.Marshal(envelope)
    50  	if err != nil {
    51  		return nil, errors.Wrap(err, "cannot marshal a message")
    52  	}
    53  
    54  	wrappedMsg := message.NewMessage(utils.UUID(), envelopedMessage)
    55  	wrappedMsg.SetContext(msg.Context())
    56  
    57  	return wrappedMsg, nil
    58  }
    59  
    60  func unwrapMessageFromEnvelope(msg *message.Message) (
    61  	destinationTopic string, unwrappedMsg *message.Message, err error) {
    62  	envelopedMsg := messageEnvelope{}
    63  	if err := json.Unmarshal(msg.Payload, &envelopedMsg); err != nil {
    64  		return "", nil, errors.Wrap(err, "cannot unmarshal message wrapped in an envelope")
    65  	}
    66  
    67  	if err := envelopedMsg.validate(); err != nil {
    68  		return "", nil, errors.Wrap(err, "an unmarshalled message envelope is invalid")
    69  	}
    70  
    71  	watermillMessage := message.NewMessage(envelopedMsg.UUID, envelopedMsg.Payload)
    72  	watermillMessage.Metadata = envelopedMsg.Metadata
    73  	watermillMessage.SetContext(msg.Context())
    74  
    75  	return envelopedMsg.DestinationTopic, watermillMessage, nil
    76  }