handle group delete events by purging local state

crates/nip29/src/group.rs

@@ -485,6 +485,18 @@ impl Group {
         cx.notify();
     }
 
+    pub(crate) fn forget(&mut self, id: EventId, cx: &mut Context<Self>) {
+        self.window.remove(id);
+
+        if !self.index.remove(&id) {
+            return;
+        }
+
+        self.messages.retain(|message| message.id != id);
+        cx.emit(GroupEvent::Updated);
+        cx.notify();
+    }
+
     pub(crate) fn eose(&mut self, cx: &mut Context<Self>) {
         self.loading = false;
         cx.emit(GroupEvent::Eose);

crates/nip29/src/lib.rs

@@ -506,8 +506,12 @@ impl GroupsRegistry {
             key.clone(),
             cx.subscribe(&group, |this, group, event, cx| match event {
                 GroupEvent::Sent(event) => {
-                    let key = group.read(cx).key().clone();
-                    this.reload(key, Some(event.clone()), cx);
+                    if event.kind == Kind::GroupDeleteEvent {
+                        this.forget_event(group, event.clone(), cx);
+                    } else {
+                        let key = group.read(cx).key().clone();
+                        this.reload(key, Some(event.clone()), cx);
+                    }
                 }
                 GroupEvent::Updated => {
                     this.refresh_entry(group, cx);
@@ -676,6 +680,40 @@ impl GroupsRegistry {
         }));
     }
 
+    fn forget_event(&mut self, group: Entity<Group>, event: Event, cx: &mut Context<Self>) {
+        let Some(target) = event.tags.event_ids().next() else {
+            return;
+        };
+
+        let key = group.read(cx).key().clone();
+        let cache_tag = key.cache_tag();
+
+        let nostr = NostrRegistry::global(cx);
+        let client = nostr.read(cx).client();
+
+        let purge = cx.background_spawn(async move {
+            let filter = Filter::new()
+                .kind(Kind::ApplicationSpecificData)
+                .identifier(target.to_hex())
+                .custom_tag(SingleLetterTag::LOWERCASE_R, cache_tag);
+
+            client.database().delete(filter).await
+        });
+
+        self.tasks.push(cx.spawn(async move |this, cx| {
+            if let Err(error) = purge.await {
+                log::warn!("nip29: dropping the deleted envelope failed: {error}");
+            }
+            this.update(cx, |this, cx| {
+                group.update(cx, |group, cx| {
+                    group.forget(target, cx);
+                });
+                this.reload(key, Some(event), cx);
+            })
+            .ok();
+        }));
+    }
+
     fn handle_event(&mut self, id: SubscriptionId, event: Event, cx: &mut Context<Self>) {
         if id == list_subscription_id() {
             match GroupList::parse(&event) {

crates/nip29/src/protocol.rs

@@ -819,6 +819,10 @@ impl TimelineWindow {
         self.0.truncate(TIMELINE_WINDOW);
     }
 
+    pub fn remove(&mut self, id: EventId) {
+        self.0.retain(|event| event.id != id);
+    }
+
     pub fn previous_tag(&self, me: PublicKey) -> Option<Tag> {
         let references: Vec<String> = self
             .0