Add data_base64 support and simplify CE JSON marshaling

cloudevent.go

@@ -2,8 +2,14 @@
 package cloudevent
 
 import (
+	"encoding/base64"
 	"encoding/json"
+	"fmt"
+	"mime"
+	"strings"
 	"time"
+
+	"github.com/tidwall/sjson"
 )
 
 const (
@@ -95,10 +101,90 @@ type CloudEvent[A any] struct {
 	CloudEventHeader
 	// Data contains domain-specific information about the event.
 	Data A `json:"data"`
+
+	DataBase64 string `json:"data_base64,omitempty"`
 }
 
 // RawEvent is a cloudevent with a json.RawMessage data field.
-type RawEvent = CloudEvent[json.RawMessage]
+// It supports both "data" and "data_base64" (CloudEvents JSON spec).
+type RawEvent struct {
+	CloudEventHeader
+	Data json.RawMessage `json:"data,omitempty"`
+
+	// DataBase64 is the raw "data_base64" string when the event was received with
+	// data_base64 (CloudEvents spec). When set, MarshalJSON emits data_base64 for
+	// round-trip; otherwise wire form is chosen from DataContentType and Data.
+	DataBase64 string `json:"data_base64,omitempty"`
+}
+
+// BytesForSignature returns the bytes that were signed (wire form of data or data_base64).
+// Use for signature verification; not the same as Data when the CE used data_base64.
+func (r RawEvent) BytesForSignature() []byte {
+	if r.DataBase64 != "" {
+		return []byte(r.DataBase64)
+	}
+	return r.Data
+}
+
+// UnmarshalJSON implements json.Unmarshaler so that both "data" and "data_base64"
+// are supported; Data is always set to the resolved payload bytes.
+func (r *RawEvent) UnmarshalJSON(data []byte) error {
+	var dataRaw json.RawMessage
+	var dataBase64 string
+	header, err := unmarshalCloudEventWithPayload(data, func(d json.RawMessage, b64 string) error {
+		dataRaw = d
+		dataBase64 = b64
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	r.CloudEventHeader = header
+	if dataRaw != nil && dataBase64 != "" {
+		return fmt.Errorf("cloudevent: both \"data\" and \"data_base64\" present; only one allowed")
+	}
+	if dataBase64 != "" {
+		decoded, err := base64.StdEncoding.DecodeString(dataBase64)
+		if err != nil {
+			return err
+		}
+		r.Data = decoded
+		r.DataBase64 = dataBase64
+	} else {
+		r.Data = dataRaw
+		r.DataBase64 = ""
+	}
+	return nil
+}
+
+// IsJSONDataContentType returns true if the MIME type indicates a JSON payload.
+// Matches "application/json" and any "+json" suffix type (e.g. "application/cloudevents+json").
+func IsJSONDataContentType(ct string) bool {
+	parsed, _, err := mime.ParseMediaType(strings.TrimSpace(ct))
+	return err == nil && (parsed == "application/json" || strings.HasSuffix(parsed, "+json"))
+}
+
+// MarshalJSON implements json.Marshaler. Uses DataContentType to choose wire form:
+// application/json -> "data"; otherwise -> "data_base64" (CloudEvents spec).
+func (r RawEvent) MarshalJSON() ([]byte, error) {
+	data, err := json.Marshal(r.CloudEventHeader)
+	if err != nil {
+		return nil, err
+	}
+	if len(r.Data) > 0 || r.DataBase64 != "" {
+		if r.DataBase64 != "" {
+			data, err = sjson.SetBytes(data, "data_base64", r.DataBase64)
+		} else if IsJSONDataContentType(r.DataContentType) || (r.DataContentType == "" && json.Valid(r.Data)) {
+			data, err = sjson.SetRawBytes(data, "data", r.Data)
+		} else {
+			data, err = sjson.SetBytes(data, "data_base64", base64.StdEncoding.EncodeToString(r.Data))
+		}
+		if err != nil {
+			return nil, err
+		}
+	}
+	return data, nil
+}
 
 // Equals returns true if the two CloudEventHeaders share the same IndexKey.
 func (c *CloudEventHeader) Equals(other CloudEventHeader) bool {

cloudevent_json.go

@@ -2,31 +2,56 @@ package cloudevent
 
 import (
 	"encoding/json"
+	"fmt"
 	"reflect"
 	"strings"
 
 	"github.com/tidwall/sjson"
 )
 
-var definedCloudeEventHdrFields = getJSONFieldNames(reflect.TypeOf(CloudEventHeader{}))
+var definedCloudeEventHdrFields = getJSONFieldNames(reflect.TypeFor[CloudEventHeader]())
 
 type cloudEventHeader CloudEventHeader
 
 // UnmarshalJSON implements custom JSON unmarshaling for CloudEvent.
+// It transparently handles both "data" and "data_base64" wire formats.
 func (c *CloudEvent[A]) UnmarshalJSON(data []byte) error {
-	var err error
-	c.CloudEventHeader, err = unmarshalCloudEvent(data, c.setDataField)
-	return err
+	var dataRaw json.RawMessage
+	var dataBase64 string
+	header, err := unmarshalCloudEventWithPayload(data, func(d json.RawMessage, b64 string) error {
+		dataRaw = d
+		dataBase64 = b64
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	c.CloudEventHeader = header
+	if dataRaw != nil && dataBase64 != "" {
+		return fmt.Errorf("cloudevent: both \"data\" and \"data_base64\" present; only one allowed")
+	}
+	if dataBase64 != "" {
+		c.DataBase64 = dataBase64
+	} else if dataRaw != nil {
+		if err := json.Unmarshal(dataRaw, &c.Data); err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
-// MarshalJSON implements custom JSON marshaling for CloudEventHeader.
+// MarshalJSON implements custom JSON marshaling for CloudEvent[A].
+// When DataBase64 is set, emits "data_base64"; otherwise emits "data".
 func (c CloudEvent[A]) MarshalJSON() ([]byte, error) {
-	// Marshal the base struct
 	data, err := json.Marshal(c.CloudEventHeader)
 	if err != nil {
 		return nil, err
 	}
-	data, err = sjson.SetBytes(data, "data", c.Data)
+	if c.DataBase64 != "" {
+		data, err = sjson.SetBytes(data, "data_base64", c.DataBase64)
+	} else {
+		data, err = sjson.SetBytes(data, "data", c.Data)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -42,21 +67,18 @@ func (c *CloudEventHeader) UnmarshalJSON(data []byte) error {
 
 // MarshalJSON implements custom JSON marshaling for CloudEventHeader.
 func (c CloudEventHeader) MarshalJSON() ([]byte, error) {
-	// Marshal the base struct
 	aux := (cloudEventHeader)(c)
 	aux.SpecVersion = SpecVersion
 	data, err := json.Marshal(aux)
 	if err != nil {
 		return nil, err
 	}
-	// Add all extras using sjson]
 	for k, v := range c.Extras {
 		data, err = sjson.SetBytes(data, k, v)
 		if err != nil {
 			return nil, err
 		}
 	}
-
 	return data, nil
 }
 
@@ -90,30 +112,48 @@ func getJSONFieldNames(t reflect.Type) map[string]struct{} {
 
 // unmarshalCloudEvent unmarshals the CloudEventHeader and data field.
 func unmarshalCloudEvent(data []byte, dataFunc func(json.RawMessage) error) (CloudEventHeader, error) {
-	c := CloudEventHeader{}
-	aux := cloudEventHeader{}
-	// Unmarshal known fields directly into the struct
-	if err := json.Unmarshal(data, &aux); err != nil {
+	return unmarshalCloudEventWithPayload(data, func(dataRaw json.RawMessage, _ string) error {
+		return dataFunc(dataRaw)
+	})
+}
+
+// unmarshalCloudEventWithPayload unmarshals the CloudEventHeader and returns both
+// "data" and "data_base64" for RawEvent.
+func unmarshalCloudEventWithPayload(data []byte, payloadFunc func(dataRaw json.RawMessage, dataBase64 string) error) (CloudEventHeader, error) {
+	// Unmarshal known header fields via the type alias (no custom UnmarshalJSON).
+	var c CloudEventHeader
+	if err := json.Unmarshal(data, (*cloudEventHeader)(&c)); err != nil {
 		return c, err
 	}
-	aux.SpecVersion = SpecVersion
-	c = (CloudEventHeader)(aux)
-	// Create a map to hold all JSON fields
+	c.SpecVersion = SpecVersion
+
+	// Second pass into raw map to extract data, data_base64, and extras.
 	rawFields := make(map[string]json.RawMessage)
 	if err := json.Unmarshal(data, &rawFields); err != nil {
 		return c, err
 	}
 
-	// Separate known and unknown fields
+	var dataRaw json.RawMessage
+	var dataBase64 string
+	if raw, ok := rawFields["data_base64"]; ok && len(raw) > 0 {
+		if err := json.Unmarshal(raw, &dataBase64); err != nil {
+			return c, err
+		}
+	}
+	if raw, ok := rawFields["data"]; ok {
+		dataRaw = raw
+	}
+	if dataRaw != nil || dataBase64 != "" {
+		if err := payloadFunc(dataRaw, dataBase64); err != nil {
+			return c, err
+		}
+	}
+
 	for key, rawValue := range rawFields {
 		if _, ok := definedCloudeEventHdrFields[key]; ok {
-			// Skip defined fields
 			continue
 		}
-		if key == "data" {
-			if err := dataFunc(rawValue); err != nil {
-				return c, err
-			}
+		if key == "data" || key == "data_base64" {
 			continue
 		}
 		if c.Extras == nil {
@@ -131,9 +171,3 @@ func unmarshalCloudEvent(data []byte, dataFunc func(json.RawMessage) error) (Clo
 // ignoreDataField is a function that ignores the data field.
 // It is used when unmarshalling the CloudEventHeader so that the data field is not added to the Extras map.
 func ignoreDataField(json.RawMessage) error { return nil }
-
-// setDataField is a function that sets the data field.
-// It is used to unmarshal the data field into the CloudEvent[A].Data field.
-func (c *CloudEvent[A]) setDataField(data json.RawMessage) error {
-	return json.Unmarshal(data, &c.Data)
-}