From 915b18789f002fa8f4c50fe1e626d34cc47c5c9b Mon Sep 17 00:00:00 2001
From: fiaxh <git@lightrise.org>
Date: Fri, 13 Jun 2025 19:38:49 +0200
Subject: Disregard SFS fallback messages even without source attachment given
 a full-body fallback indication

---
 libdino/src/entity/message.vala                           |  2 +-
 libdino/src/service/stateless_file_sharing.vala           |  6 ++++++
 libdino/src/util/send_message.vala                        |  5 +++--
 xmpp-vala/src/module/xep/0428_fallback_indication.vala    |  7 +++----
 xmpp-vala/src/module/xep/0447_stateless_file_sharing.vala | 10 ++++++++++
 5 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/libdino/src/entity/message.vala b/libdino/src/entity/message.vala
index 7e15cfe4..4de17125 100644
--- a/libdino/src/entity/message.vala
+++ b/libdino/src/entity/message.vala
@@ -212,7 +212,7 @@ public class Message : Object {
 
         var fallbacks = new ArrayList<Xep.FallbackIndication.Fallback>();
         foreach (string ns_uri in fallbacks_by_ns.keys) {
-            fallbacks.add(new Xep.FallbackIndication.Fallback(ns_uri, fallbacks_by_ns[ns_uri].to_array()));
+            fallbacks.add(new Xep.FallbackIndication.Fallback(ns_uri, fallbacks_by_ns[ns_uri]));
         }
         this.fallbacks = fallbacks;
         this.markups = markups;
diff --git a/libdino/src/service/stateless_file_sharing.vala b/libdino/src/service/stateless_file_sharing.vala
index 9d3c53ab..15e1ddfe 100644
--- a/libdino/src/service/stateless_file_sharing.vala
+++ b/libdino/src/service/stateless_file_sharing.vala
@@ -156,6 +156,12 @@ public class Dino.StatelessFileSharing : StreamInteractionModule, Object {
                     return true;
                 }
             }
+
+            // Don't process messages that are fallback for legacy clients
+            if (Xep.StatelessFileSharing.is_sfs_fallback_message(stanza)) {
+                return true;
+            }
+
             return false;
         }
     }
diff --git a/libdino/src/util/send_message.vala b/libdino/src/util/send_message.vala
index 8312cf17..c320bf7b 100644
--- a/libdino/src/util/send_message.vala
+++ b/libdino/src/util/send_message.vala
@@ -26,9 +26,10 @@ namespace Dino {
             out_message.body = fallback + out_message.body;
 
             // Store fallback location
-            var fallback_location = new Xep.FallbackIndication.FallbackLocation.partial_body(0, (int)fallback.char_count());
+            var fallback_locations = new ArrayList<Xep.FallbackIndication.FallbackLocation>();
+            fallback_locations.add(new Xep.FallbackIndication.FallbackLocation.partial_body(0, (int)fallback.char_count()));
             var fallback_list = new ArrayList<Xep.FallbackIndication.Fallback>();
-            fallback_list.add(new Xep.FallbackIndication.Fallback(Xep.Replies.NS_URI, new Xep.FallbackIndication.FallbackLocation[] { fallback_location }));
+            fallback_list.add(new Xep.FallbackIndication.Fallback(Xep.Replies.NS_URI, fallback_locations));
             out_message.set_fallbacks(fallback_list);
 
             // Adjust markups to new prefix
diff --git a/xmpp-vala/src/module/xep/0428_fallback_indication.vala b/xmpp-vala/src/module/xep/0428_fallback_indication.vala
index 3cad689b..d07ec9be 100644
--- a/xmpp-vala/src/module/xep/0428_fallback_indication.vala
+++ b/xmpp-vala/src/module/xep/0428_fallback_indication.vala
@@ -6,10 +6,9 @@ namespace Xmpp.Xep.FallbackIndication {
 
     public class Fallback {
         public string ns_uri { get; set; }
-        public FallbackLocation[] locations;
+        public Gee.List<FallbackLocation> locations;
 
-
-        public Fallback(string ns_uri, FallbackLocation[] locations) {
+        public Fallback(string ns_uri, Gee.List<FallbackLocation> locations) {
             this.ns_uri = ns_uri;
             this.locations = locations;
         }
@@ -73,7 +72,7 @@ namespace Xmpp.Xep.FallbackIndication {
                 }
             }
             if (locations.is_empty) continue;
-            ret.add(new Fallback(ns_uri, locations.to_array()));
+            ret.add(new Fallback(ns_uri, locations));
         }
 
         return ret;
diff --git a/xmpp-vala/src/module/xep/0447_stateless_file_sharing.vala b/xmpp-vala/src/module/xep/0447_stateless_file_sharing.vala
index 63cab59f..86da6a3a 100644
--- a/xmpp-vala/src/module/xep/0447_stateless_file_sharing.vala
+++ b/xmpp-vala/src/module/xep/0447_stateless_file_sharing.vala
@@ -44,6 +44,16 @@ namespace Xmpp.Xep.StatelessFileSharing {
         return ret;
     }
 
+    public static bool is_sfs_fallback_message(MessageStanza message) {
+        Gee.List<FallbackIndication.Fallback> fallbacks = Xep.FallbackIndication.get_fallbacks(message);
+        foreach (var fallback in fallbacks) {
+            if (fallback.ns_uri == StatelessFileSharing.NS_URI && fallback.locations.any_match((it) => it.is_whole)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     // Currently only returns a single http source
     private static Gee.List<Source>? get_sources(StanzaNode sources_node) {
         string? url = HttpSchemeForUrlData.get_url(sources_node);
-- 
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