implemented federation

internal/domain/federation/inbox.go

@@ -0,0 +1,113 @@
+package federation
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"time"
+
+	"xorm.io/xorm"
+
+	"github.com/forgeo/forgebucket/internal/models"
+)
+
+// Receive persists an inbound activity and dispatches it by type.
+// The caller is responsible for verifying the HTTP signature before calling this.
+func Receive(db *xorm.Engine, localActor *models.FederationActor, body []byte) error {
+	var activity map[string]any
+	if err := json.Unmarshal(body, &activity); err != nil {
+		return fmt.Errorf("parse activity: %w", err)
+	}
+
+	actType, _ := activity["type"].(string)
+	actorAPID, _ := activity["actor"].(string)
+
+	entry := &models.FederationActivity{
+		ActorAPID:   localActor.APID,
+		Type:        actType,
+		ObjectJSON:  string(body),
+		Direction:   "inbound",
+		RemoteActor: actorAPID,
+		Published:   time.Now().UTC(),
+	}
+	db.Insert(entry) //nolint:errcheck
+
+	switch actType {
+	case "Follow":
+		return handleFollow(db, localActor, activity, actorAPID)
+	case "Accept":
+		handleAccept(db, localActor, activity)
+	case "Undo":
+		handleUndo(db, localActor, activity)
+	default:
+		log.Printf("federation: received unhandled activity type %q from %s", actType, actorAPID)
+	}
+	return nil
+}
+
+// handleFollow auto-accepts all incoming Follow activities and sends an Accept
+// back to the sender's inbox.
+func handleFollow(db *xorm.Engine, localActor *models.FederationActor, follow map[string]any, followerAPID string) error {
+	if followerAPID == "" {
+		return fmt.Errorf("Follow activity missing actor field")
+	}
+
+	// Fetch the follower's remote actor to get their inbox URL.
+	remote, err := FetchActor(db, followerAPID)
+	if err != nil {
+		return fmt.Errorf("fetch follower actor: %w", err)
+	}
+	if remote.InboxURL == "" {
+		return fmt.Errorf("follower has no inbox URL")
+	}
+
+	// Build Accept activity.
+	accept := map[string]any{
+		"@context": "https://www.w3.org/ns/activitystreams",
+		"id":       localActor.APID + "/activities/accept-" + fmt.Sprint(time.Now().UnixNano()),
+		"type":     "Accept",
+		"actor":    localActor.APID,
+		"object":   follow,
+	}
+
+	// Deliver asynchronously so inbox handler returns quickly.
+	go func() {
+		if err := DeliverActivity(localActor, accept, remote.InboxURL); err != nil {
+			log.Printf("federation: deliver Accept to %s: %v", remote.InboxURL, err)
+			return
+		}
+		// Store the outbound Accept.
+		db.Insert(&models.FederationActivity{ //nolint:errcheck
+			ActorAPID:   localActor.APID,
+			Type:        "Accept",
+			ObjectJSON:  mustJSON(accept),
+			Direction:   "outbound",
+			RemoteActor: followerAPID,
+			Published:   time.Now().UTC(),
+		})
+		log.Printf("federation: accepted Follow from %s", followerAPID)
+	}()
+
+	return nil
+}
+
+func handleAccept(db *xorm.Engine, localActor *models.FederationActor, activity map[string]any) {
+	// A remote actor accepted our Follow. Nothing to store beyond the inbox entry.
+	log.Printf("federation: received Accept for actor %s", localActor.APID)
+}
+
+func handleUndo(db *xorm.Engine, localActor *models.FederationActor, activity map[string]any) {
+	// Common case: undo a Follow (unfollow).
+	obj, _ := activity["object"].(map[string]any)
+	if obj == nil {
+		return
+	}
+	if t, _ := obj["type"].(string); t == "Follow" {
+		log.Printf("federation: received Undo(Follow) for actor %s", localActor.APID)
+	}
+}
+
+func mustJSON(v any) string {
+	b, _ := json.Marshal(v)
+	return string(b)
+}