[feature] Forward-compatibility with Approval objects (#3807)

* vendor

* [feature] Forward-compatibility with Approval objects

* vendor the thing

* fix leetle bug

* lil syntax tweak for beloved kimb

3 files changed, 70 insertions, 43 deletions

diff --git a/internal/ap/activitystreams.go b/internal/ap/activitystreams.go
index 50955ce2c..3851d0efb 100644
--- a/internal/ap/activitystreams.go
+++ b/internal/ap/activitystreams.go
@@ -97,6 +97,11 @@ const (
 	// Not in the AS spec, just used internally to indicate
 	// that we don't *yet* know what type of Object something is.
 	ObjectUnknown = "Unknown"
+
+	// Extensions and unofficial additions.
+	ObjectLikeApproval     = "LikeApproval"
+	ObjectReplyApproval    = "ReplyApproval"
+	ObjectAnnounceApproval = "AnnounceApproval"
 )
 
 // isActivity returns whether AS type name is of an Activity (NOT IntransitiveActivity).
diff --git a/internal/ap/interfaces.go b/internal/ap/interfaces.go
index fdd5e4a0b..acc799640 100644
--- a/internal/ap/interfaces.go
+++ b/internal/ap/interfaces.go
@@ -128,16 +128,13 @@ func ToPollOptionable(t vocab.Type) (PollOptionable, bool) {
 }
 
 // IsAccept returns whether AS vocab type name
-// is something that can be cast to Accept.
+// is something that can be cast to Acceptable.
 func IsAcceptable(typeName string) bool {
 	return typeName == ActivityAccept
 }
 
-// ToAcceptable safely tries to cast vocab.Type as vocab.ActivityStreamsAccept.
-//
-// TODO: Add additional "Accept" types here, eg., "ApproveReply" from
-// https://codeberg.org/fediverse/fep/src/branch/main/fep/5624/fep-5624.md
-func ToAcceptable(t vocab.Type) (vocab.ActivityStreamsAccept, bool) {
+// ToAcceptable safely tries to cast vocab.Type as Acceptable.
+func ToAcceptable(t vocab.Type) (Acceptable, bool) {
 	acceptable, ok := t.(vocab.ActivityStreamsAccept)
 	if !ok || !IsAcceptable(t.GetTypeName()) {
 		return nil, false
@@ -145,6 +142,28 @@ func ToAcceptable(t vocab.Type) (vocab.ActivityStreamsAccept, bool) {
 	return acceptable, true
 }
 
+// IsApprovable returns whether AS vocab type name
+// is something that can be cast to Approvable.
+func IsApprovable(typeName string) bool {
+	switch typeName {
+	case ObjectLikeApproval,
+		ObjectReplyApproval,
+		ObjectAnnounceApproval:
+		return true
+	default:
+		return false
+	}
+}
+
+// ToAcceptable safely tries to cast vocab.Type as Approvable.
+func ToApprovable(t vocab.Type) (Approvable, bool) {
+	approvable, ok := t.(Approvable)
+	if !ok || !IsApprovable(t.GetTypeName()) {
+		return nil, false
+	}
+	return approvable, true
+}
+
 // Activityable represents the minimum activitypub interface for representing an 'activity'.
 // (see: IsActivityable() for types implementing this, though you MUST make sure to check
 // the typeName as this bare interface may be implementable by non-Activityable types).
@@ -247,6 +266,19 @@ type PollOptionable interface {
 // interface for representing an Accept.
 type Acceptable interface {
 	Activityable
+
+	WithTarget
+	WithResult
+}
+
+// Approvable represents the minimum activitypub interface
+// for a LikeApproval, ReplyApproval, or AnnounceApproval.
+type Approvable interface {
+	vocab.Type
+
+	WithAttributedTo
+	WithObject
+	WithTarget
 }
 
 // Attachmentable represents the minimum activitypub interface for representing a 'mediaAttachment'. (see: IsAttachmentable).
@@ -708,3 +740,9 @@ type WithApprovedBy interface {
 	GetGoToSocialApprovedBy() vocab.GoToSocialApprovedByProperty
 	SetGoToSocialApprovedBy(vocab.GoToSocialApprovedByProperty)
 }
+
+// WithVotersCount represents an activity or object the result property.
+type WithResult interface {
+	GetActivityStreamsResult() vocab.ActivityStreamsResultProperty
+	SetActivityStreamsResult(vocab.ActivityStreamsResultProperty)
+}
diff --git a/internal/ap/resolve.go b/internal/ap/resolve.go
index 76a8809c3..82a242710 100644
--- a/internal/ap/resolve.go
+++ b/internal/ap/resolve.go
@@ -198,48 +198,12 @@ func ResolveCollectionPage(ctx context.Context, body io.ReadCloser) (CollectionP
 	return ToCollectionPageIterator(t)
 }
 
-// ResolveAcceptable tries to resolve the given reader
-// into an ActivityStreams Acceptable representation.
-func ResolveAcceptable(
-	ctx context.Context,
-	body io.ReadCloser,
-) (Acceptable, error) {
-	// Get "raw" map
-	// destination.
-	raw := getMap()
-	// Release.
-	defer putMap(raw)
-
-	// Decode data as JSON into 'raw' map
-	// and get the resolved AS vocab.Type.
-	// (this handles close of given body).
-	t, err := decodeType(ctx, body, raw)
-	if err != nil {
-		return nil, gtserror.SetWrongType(err)
-	}
-
-	// Attempt to cast as acceptable.
-	acceptable, ok := ToAcceptable(t)
-	if !ok {
-		err := gtserror.Newf("cannot resolve vocab type %T as acceptable", t)
-		return nil, gtserror.SetWrongType(err)
-	}
-
-	return acceptable, nil
-}
-
 // emptydest is an empty JSON decode
 // destination useful for "noop" decodes
 // to check underlying reader is empty.
 var emptydest = &struct{}{}
 
-// decodeType tries to read and parse the data
-// at provided io.ReadCloser as a JSON ActivityPub
-// type, failing if not parseable as JSON or not
-// resolveable as one of our known AS types.
-//
-// NOTE: this function handles closing
-// given body when it is finished with.
+// decodeType is the package-internal version of DecodeType.
 //
 // The given map pointer will also be populated with
 // the 'raw' JSON data, for further processing.
@@ -284,3 +248,23 @@ func decodeType(
 
 	return t, nil
 }
+
+// DecodeType tries to read and parse the data
+// at provided io.ReadCloser as a JSON ActivityPub
+// type, failing if not parseable as JSON or not
+// resolveable as one of our known AS types.
+//
+// NOTE: this function handles closing
+// given body when it is finished with.
+func DecodeType(
+	ctx context.Context,
+	body io.ReadCloser,
+) (vocab.Type, error) {
+	// Get "raw" map
+	// destination.
+	raw := getMap()
+	// Release.
+	defer putMap(raw)
+
+	return decodeType(ctx, body, raw)
+}