[feature] Enable federation in/out of profile PropertyValue fields (#1722)

Co-authored-by: kim <grufwub@gmail.com>
Co-authored-by: kim <89579420+NyaaaWhatsUpDoc@users.noreply.github.com>

internal/ap/serialize.go

@@ -18,13 +18,41 @@
 package ap
 
 import (
-	"errors"
+	"fmt"
 
 	"github.com/superseriousbusiness/activity/streams"
 	"github.com/superseriousbusiness/activity/streams/vocab"
 )
 
-// SerializeOrderedCollection is a custom serializer for an ActivityStreamsOrderedCollection.
+// Serialize is a custom serializer for ActivityStreams types.
+//
+// In most cases, it will simply call the go-fed streams.Serialize function under the hood.
+// However, if custom serialization is required on a specific type (eg for inter-implementation
+// compatibility), it can be inserted into the switch as necessary.
+//
+// Callers should always call this function instead of streams.Serialize, unless there's a
+// very good reason to do otherwise.
+//
+// Currently, the following things will be custom serialized:
+//
+//   - OrderedCollection: 'orderedItems' property will always be made into an array.
+//   - Any Accountable type: 'attachment' property will always be made into an array.
+//   - Update: any Accountable 'object's set on an update will be custom serialized as above.
+func Serialize(t vocab.Type) (m map[string]interface{}, e error) {
+	switch t.GetTypeName() {
+	case ObjectOrderedCollection:
+		return serializeOrderedCollection(t)
+	case ActorApplication, ActorGroup, ActorOrganization, ActorPerson, ActorService:
+		return serializeAccountable(t, true)
+	case ActivityUpdate:
+		return serializeWithObject(t)
+	default:
+		// No custom serializer necessary.
+		return streams.Serialize(t)
+	}
+}
+
+// serializeOrderedCollection is a custom serializer for an ActivityStreamsOrderedCollection.
 // Unlike the standard streams.Serialize function, this serializer normalizes the orderedItems
 // value to always be an array/slice, regardless of how many items are contained therein.
 //
@@ -33,32 +61,146 @@ import (
 // See:
 //   - https://github.com/go-fed/activity/issues/139
 //   - https://github.com/mastodon/mastodon/issues/24225
-func SerializeOrderedCollection(orderedCollection vocab.ActivityStreamsOrderedCollection) (map[string]interface{}, error) {
+func serializeOrderedCollection(orderedCollection vocab.Type) (map[string]interface{}, error) {
 	data, err := streams.Serialize(orderedCollection)
 	if err != nil {
 		return nil, err
 	}
 
-	return data, normalizeOrderedCollectionData(data)
-}
-
-func normalizeOrderedCollectionData(rawOrderedCollection map[string]interface{}) error {
-	orderedItems, ok := rawOrderedCollection["orderedItems"]
+	orderedItems, ok := data["orderedItems"]
 	if !ok {
-		return errors.New("no orderedItems set on OrderedCollection")
+		// No 'orderedItems', nothing to change.
+		return data, nil
 	}
 
 	if _, ok := orderedItems.([]interface{}); ok {
 		// Already slice.
-		return nil
+		return data, nil
 	}
 
-	orderedItemsString, ok := orderedItems.(string)
-	if !ok {
-		return errors.New("orderedItems was neither slice nor string")
-	}
+	// Coerce single-object to slice.
+	data["orderedItems"] = []interface{}{orderedItems}
 
-	rawOrderedCollection["orderedItems"] = []string{orderedItemsString}
-
-	return nil
+	return data, nil
+}
+
+// SerializeAccountable is a custom serializer for any Accountable type.
+// This serializer rewrites the 'attachment' value of the Accountable, if
+// present, to always be an array/slice.
+//
+// While this is not strictly necessary in json-ld terms, most other fedi
+// implementations look for attachment to be an array of PropertyValue (field)
+// entries, and will not parse single-entry, non-array attachments on accounts
+// properly.
+//
+// If the accountable is being serialized as a top-level object (eg., for serving
+// in response to an account dereference request), then includeContext should be
+// set to true, so as to include the json-ld '@context' entries in the data.
+// If the accountable is being serialized as part of another object (eg., as the
+// object of an activity), then includeContext should be set to false, as the
+// @context entry should be included on the top-level/wrapping activity/object.
+func serializeAccountable(accountable vocab.Type, includeContext bool) (map[string]interface{}, error) {
+	var (
+		data map[string]interface{}
+		err  error
+	)
+
+	if includeContext {
+		data, err = streams.Serialize(accountable)
+	} else {
+		data, err = accountable.Serialize()
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	attachment, ok := data["attachment"]
+	if !ok {
+		// No 'attachment', nothing to change.
+		return data, nil
+	}
+
+	if _, ok := attachment.([]interface{}); ok {
+		// Already slice.
+		return data, nil
+	}
+
+	// Coerce single-object to slice.
+	data["attachment"] = []interface{}{attachment}
+
+	return data, nil
+}
+
+func serializeWithObject(t vocab.Type) (map[string]interface{}, error) {
+	withObject, ok := t.(WithObject)
+	if !ok {
+		return nil, fmt.Errorf("serializeWithObject: could not resolve %T to WithObject", t)
+	}
+
+	data, err := streams.Serialize(t)
+	if err != nil {
+		return nil, err
+	}
+
+	object := withObject.GetActivityStreamsObject()
+	if object == nil {
+		// Nothing to do, bail early.
+		return data, nil
+	}
+
+	objectLen := object.Len()
+	if objectLen == 0 {
+		// Nothing to do, bail early.
+		return data, nil
+	}
+
+	// The thing we already serialized has objects
+	// on it, so we should see if we need to custom
+	// serialize any of those objects, and replace
+	// them on the data map as necessary.
+	objects := make([]interface{}, 0, objectLen)
+	for iter := object.Begin(); iter != object.End(); iter = iter.Next() {
+		if iter.IsIRI() {
+			// Plain IRIs don't need custom serialization.
+			objects = append(objects, iter.GetIRI().String())
+			continue
+		}
+
+		var (
+			objectType = iter.GetType()
+			objectSer  map[string]interface{}
+		)
+
+		if objectType == nil {
+			// This is awkward.
+			return nil, fmt.Errorf("serializeWithObject: could not resolve object iter %T to vocab.Type", iter)
+		}
+
+		switch objectType.GetTypeName() {
+		case ActorApplication, ActorGroup, ActorOrganization, ActorPerson, ActorService:
+			// @context will be included in wrapping type already,
+			// we don't need to include it in the object itself.
+			objectSer, err = serializeAccountable(objectType, false)
+		default:
+			// No custom serializer for this type; serialize as normal.
+			objectSer, err = objectType.Serialize()
+		}
+
+		if err != nil {
+			return nil, err
+		}
+
+		objects = append(objects, objectSer)
+	}
+
+	if objectLen == 1 {
+		// Unnest single object.
+		data["object"] = objects[0]
+	} else {
+		// Array of objects.
+		data["object"] = objects
+	}
+
+	return data, nil
 }