1 files changed, 89 insertions, 0 deletions
diff --git a/internal/federation/federatingdb/undo.go b/internal/federation/federatingdb/undo.go
new file mode 100644
index 000000000..8ca681bb2
--- /dev/null
+++ b/internal/federation/federatingdb/undo.go
@@ -0,0 +1,89 @@
+package federatingdb
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/go-fed/activity/streams"
+	"github.com/go-fed/activity/streams/vocab"
+	"github.com/sirupsen/logrus"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
+)
+
+func (f *federatingDB) Undo(ctx context.Context, undo vocab.ActivityStreamsUndo) error {
+	l := f.log.WithFields(
+		logrus.Fields{
+			"func":   "Undo",
+			"asType": undo.GetTypeName(),
+		},
+	)
+	m, err := streams.Serialize(undo)
+	if err != nil {
+		return err
+	}
+	b, err := json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	l.Debugf("received UNDO asType %s", string(b))
+
+	targetAcctI := ctx.Value(util.APAccount)
+	if targetAcctI == nil {
+		l.Error("UNDO: target account wasn't set on context")
+		return nil
+	}
+	targetAcct, ok := targetAcctI.(*gtsmodel.Account)
+	if !ok {
+		l.Error("UNDO: target account was set on context but couldn't be parsed")
+		return nil
+	}
+
+	undoObject := undo.GetActivityStreamsObject()
+	if undoObject == nil {
+		return errors.New("UNDO: no object set on vocab.ActivityStreamsUndo")
+	}
+
+	for iter := undoObject.Begin(); iter != undoObject.End(); iter = iter.Next() {
+		switch iter.GetType().GetTypeName() {
+		case string(gtsmodel.ActivityStreamsFollow):
+			// UNDO FOLLOW
+			ASFollow, ok := iter.GetType().(vocab.ActivityStreamsFollow)
+			if !ok {
+				return errors.New("UNDO: couldn't parse follow into vocab.ActivityStreamsFollow")
+			}
+			// make sure the actor owns the follow
+			if !sameActor(undo.GetActivityStreamsActor(), ASFollow.GetActivityStreamsActor()) {
+				return errors.New("UNDO: follow actor and activity actor not the same")
+			}
+			// convert the follow to something we can understand
+			gtsFollow, err := f.typeConverter.ASFollowToFollow(ASFollow)
+			if err != nil {
+				return fmt.Errorf("UNDO: error converting asfollow to gtsfollow: %s", err)
+			}
+			// make sure the addressee of the original follow is the same as whatever inbox this landed in
+			if gtsFollow.TargetAccountID != targetAcct.ID {
+				return errors.New("UNDO: follow object account and inbox account were not the same")
+			}
+			// delete any existing FOLLOW
+			if err := f.db.DeleteWhere([]db.Where{{Key: "uri", Value: gtsFollow.URI}}, &gtsmodel.Follow{}); err != nil {
+				return fmt.Errorf("UNDO: db error removing follow: %s", err)
+			}
+			// delete any existing FOLLOW REQUEST
+			if err := f.db.DeleteWhere([]db.Where{{Key: "uri", Value: gtsFollow.URI}}, &gtsmodel.FollowRequest{}); err != nil {
+				return fmt.Errorf("UNDO: db error removing follow request: %s", err)
+			}
+			l.Debug("follow undone")
+			return nil
+		case string(gtsmodel.ActivityStreamsLike):
+			// UNDO LIKE
+		case string(gtsmodel.ActivityStreamsAnnounce):
+			// UNDO BOOST/REBLOG/ANNOUNCE
+		}
+	}
+
+	return nil
+}