snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

components/cqrs/marshaler.go

@@ -0,0 +1,55 @@
+package cqrs
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/ThreeDotsLabs/watermill/message"
+)
+
+// CommandEventMarshaler marshals Commands and Events to Watermill's messages and vice versa.
+// Payload of the command needs to be marshaled to []bytes.
+type CommandEventMarshaler interface {
+	// Marshal marshals Command or Event to Watermill's message.
+	Marshal(v interface{}) (*message.Message, error)
+
+	// Unmarshal unmarshals watermill's message to v Command or Event.
+	Unmarshal(msg *message.Message, v interface{}) (err error)
+
+	// Name returns the name of Command or Event.
+	// Name is used to determine, that received command or event is event which we want to handle.
+	Name(v interface{}) string
+
+	// NameFromMessage returns the name of Command or Event from Watermill's message (generated by Marshal).
+	//
+	// When we have Command or Event marshaled to Watermill's message,
+	// we should use NameFromMessage instead of Name to avoid unnecessary unmarshaling.
+	NameFromMessage(msg *message.Message) string
+}
+
+// CommandEventMarshalerDecorator decorates CommandEventMarshaler with additional functionality.
+// It can be used to add additional metadata to the message.
+type CommandEventMarshalerDecorator struct {
+	CommandEventMarshaler
+
+	// DecorateFunc is called after marshaling the message.
+	DecorateFunc func(v any, msg *message.Message) error
+}
+
+// Marshal marshals Command or Event to Watermill's message and decorates it.
+func (c CommandEventMarshalerDecorator) Marshal(v any) (*message.Message, error) {
+	msg, err := c.CommandEventMarshaler.Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+
+	if c.DecorateFunc == nil {
+		return nil, errors.New("DecorateFunc is nil")
+	}
+
+	if err := c.DecorateFunc(v, msg); err != nil {
+		return nil, fmt.Errorf("cannot decorate message: %w", err)
+	}
+
+	return msg, nil
+}