add timeline paging for older messages

crates/nip29/src/lib.rs

@@ -21,6 +21,7 @@ pub(crate) static LOCAL_KEYS: LazyLock<Keys> = LazyLock::new(Keys::generate);
 const LIST_SUBSCRIPTION: &str = "nip29-list";
 const GROUP_PREFIX: &str = "grp-";
 const BROWSE_PREFIX: &str = "brw-";
+const PAGE_PREFIX: &str = "pg-";
 const BROWSE_LIMIT: usize = 500;
 const BROWSE_TIMEOUT: Duration = Duration::from_secs(10);
 
@@ -67,9 +68,20 @@ fn browse_subscription(relay: &RelayUrl) -> SubscriptionId {
     SubscriptionId::new(format!("{BROWSE_PREFIX}{:08x}", hasher.finish() as u32))
 }
 
+fn page_subscription(key: &GroupKey) -> SubscriptionId {
+    SubscriptionId::new(format!("{PAGE_PREFIX}{:08x}", key.uniq_id() as u32))
+}
+
+fn is_page(id: &SubscriptionId) -> bool {
+    id.as_str().starts_with(PAGE_PREFIX)
+}
+
 fn is_own_subscription(id: &SubscriptionId) -> bool {
     let id = id.as_str();
-    id == LIST_SUBSCRIPTION || id.starts_with(GROUP_PREFIX) || id.starts_with(BROWSE_PREFIX)
+    id == LIST_SUBSCRIPTION
+        || id.starts_with(GROUP_PREFIX)
+        || id.starts_with(BROWSE_PREFIX)
+        || id.starts_with(PAGE_PREFIX)
 }
 
 impl EventEmitter<GroupsEvent> for GroupsRegistry {}
@@ -259,6 +271,22 @@ impl GroupsRegistry {
         self.browse.get(&browse_subscription(relay))
     }
 
+    pub fn load_more(&mut self, key: &GroupKey, cx: &mut Context<Self>) {
+        let Some(group) = self.group(key, cx) else {
+            return;
+        };
+
+        if group.read(cx).loading_more() || group.read(cx).oldest().is_none() {
+            return;
+        }
+
+        self.routes.insert(page_subscription(key), key.clone());
+
+        group.update(cx, |group, cx| {
+            group.load_page(cx);
+        });
+    }
+
     pub fn leave(&mut self, key: &GroupKey, cx: &mut Context<Self>) {
         let Some(group) = self.group(key, cx) else {
             return;
@@ -394,9 +422,11 @@ impl GroupsRegistry {
 
     fn forget(&mut self, key: GroupKey, cx: &mut Context<Self>) {
         let id = subscription_id(&key);
+        let page = page_subscription(&key);
         let cache_tag = key.cache_tag();
 
         self.routes.remove(&id);
+        self.routes.remove(&page);
         self.observers.remove(&key);
         self.groups.retain(|group| group.read(cx).key() != &key);
         self.list.remove(&key);
@@ -405,8 +435,10 @@ impl GroupsRegistry {
         let client = nostr.read(cx).client();
 
         self.tasks.push(cx.background_spawn(async move {
-            if let Err(error) = client.unsubscribe(&id).await {
-                log::warn!("nip29: unsubscribing {id} failed: {error}");
+            for id in [id, page] {
+                if let Err(error) = client.unsubscribe(&id).await {
+                    log::warn!("nip29: unsubscribing {id} failed: {error}");
+                }
             }
 
             let filter = Filter::new()
@@ -595,6 +627,18 @@ impl GroupsRegistry {
             return;
         };
 
+        if is_page(&id) {
+            self.routes.remove(&id);
+
+            if let Some(group) = self.group(&key, cx) {
+                group.update(cx, |group, cx| {
+                    group.page_finished(cx);
+                });
+            }
+
+            return;
+        }
+
         let Some(group) = self.group(&key, cx) else {
             return;
         };
@@ -620,6 +664,22 @@ impl GroupsRegistry {
             return;
         };
 
+        if is_page(&id) {
+            self.routes.remove(&id);
+            log::warn!(
+                "nip29: loading older messages in {} was refused: {reason}",
+                key.id()
+            );
+
+            if let Some(group) = self.group(&key, cx) {
+                group.update(cx, |group, cx| {
+                    group.page_finished(cx);
+                });
+            }
+
+            return;
+        }
+
         let Some(group) = self.group(&key, cx) else {
             return;
         };