Fix conversation context topic fallback

server/im_http.go

@@ -4088,7 +4088,11 @@ func serveIMConversationContext(wrt http.ResponseWriter, req *http.Request) {
 		writeIMError(wrt, req, http.StatusMethodNotAllowed, 30002, imReasonMethodNotAllowed, "method not allowed", nil)
 		return
 	}
-	topic, peer := normalizeP2PConversationTopic(topic, principal.Uid)
+	topic, peer, err := resolveConversationContextTopic(principal, topic)
+	if err != nil {
+		writeIMRelationError(wrt, req, err)
+		return
+	}
 	if topic == "" || peer.IsZero() {
 		writeIMError(wrt, req, http.StatusBadRequest, 30000, imReasonMalformedRequest, "malformed request", map[string]any{"field": "topic"})
 		return
@@ -9996,6 +10000,37 @@ func normalizeP2PConversationTopic(topic string, uid types.Uid) (string, types.U
 	return topic, peer
 }
 
+func resolveConversationContextTopic(principal *imPrincipal, topic string) (string, types.Uid, error) {
+	normalized, peer := normalizeP2PConversationTopic(topic, principal.Uid)
+	if normalized != "" && !peer.IsZero() {
+		return normalized, peer, nil
+	}
+	topic = strings.TrimSpace(topic)
+	if types.GetTopicCat(topic) != types.TopicCatP2P {
+		return "", types.ZeroUid, nil
+	}
+	if _, _, err := types.ParseP2P(topic); err != nil {
+		return "", types.ZeroUid, nil
+	}
+	cursor := ""
+	for {
+		items, nextCursor, err := store.Relations.ListFriends(principal.TenantID, principal.Uid, "", "", cursor, 100)
+		if err != nil {
+			return "", types.ZeroUid, err
+		}
+		for _, item := range items {
+			if strings.TrimSpace(item.Friendship.Topic) == topic && !item.Friendship.PeerID.IsZero() {
+				return topic, item.Friendship.PeerID, nil
+			}
+		}
+		if nextCursor == "" {
+			break
+		}
+		cursor = nextCursor
+	}
+	return "", types.ZeroUid, nil
+}
+
 func normalizeConversationSettingsTopic(topic string, uid types.Uid) string {
 	if normalized, peer := normalizeP2PConversationTopic(topic, uid); !peer.IsZero() {
 		return normalized

server/im_http_test.go

@@ -5736,6 +5736,39 @@ func TestServeIMConversationContextAcceptsUserTopic(t *testing.T) {
 	}
 }
 
+func TestServeIMConversationContextAcceptsFriendListTopicFallback(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+	expectIMBearer(t, ctrl, "token-1", 7, 1)
+	oldRelations := store.Relations
+	peer := types.Uid(2)
+	legacyTopic := types.Uid(2).P2PName(types.Uid(3))
+	store.Relations = &testRelationsStore{friends: []types.FriendListItem{{
+		Friendship: types.Friendship{
+			TenantID: 7,
+			UserID:   types.Uid(1),
+			PeerID:   peer,
+			Status:   types.RelationshipFriend,
+			Topic:    legacyTopic,
+		},
+	}}}
+	defer func() { store.Relations = oldRelations }()
+
+	req := httptest.NewRequest(http.MethodGet, "/v1/im/conversations/"+legacyTopic+"/context", nil)
+	req.Header.Set("Authorization", "Bearer token-1")
+	rec := httptest.NewRecorder()
+
+	serveIMConversationContext(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status: got %d, want %d; body=%s", rec.Code, http.StatusOK, rec.Body.String())
+	}
+	data := decodeIMHTTPResponse(t, rec).Data.(map[string]any)
+	if data["topic"] != legacyTopic || data["peer_user_id"] != peer.UserId() {
+		t.Fatalf("unexpected context response: %#v", data)
+	}
+}
+
 func TestNormalizeP2PConversationTopicParsesTinodeTopic(t *testing.T) {
 	user := types.Uid(1)
 	peer := types.Uid(2)