Improve Follow pack timeline loading logic in the Universe view

Signed-off-by: Daniel D’Aquino <daniel@daquino.me>

damus.xcodeproj/project.pbxproj

@@ -1161,6 +1161,9 @@
 		D72A2D022AD9C136002AFF62 /* EventViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72A2CFF2AD9B66B002AFF62 /* EventViewTests.swift */; };
 		D72A2D052AD9C1B5002AFF62 /* MockDamusState.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72A2D042AD9C1B5002AFF62 /* MockDamusState.swift */; };
 		D72A2D072AD9C1FB002AFF62 /* MockProfiles.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72A2D062AD9C1FB002AFF62 /* MockProfiles.swift */; };
+		D72C01312E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72C01302E78C0FB00AACB67 /* CondensedProfilePicturesViewModel.swift */; };
+		D72C01322E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72C01302E78C0FB00AACB67 /* CondensedProfilePicturesViewModel.swift */; };
+		D72C01332E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72C01302E78C0FB00AACB67 /* CondensedProfilePicturesViewModel.swift */; };
 		D72E12782BEED22500F4F781 /* Array.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72E12772BEED22400F4F781 /* Array.swift */; };
 		D72E127A2BEEEED000F4F781 /* NostrFilterTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72E12792BEEEED000F4F781 /* NostrFilterTests.swift */; };
 		D7315A2A2ACDF3B70036E30A /* DamusCacheManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7315A292ACDF3B70036E30A /* DamusCacheManager.swift */; };
@@ -2607,6 +2610,7 @@
 		D72A2CFF2AD9B66B002AFF62 /* EventViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EventViewTests.swift; sourceTree = "<group>"; };
 		D72A2D042AD9C1B5002AFF62 /* MockDamusState.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MockDamusState.swift; sourceTree = "<group>"; };
 		D72A2D062AD9C1FB002AFF62 /* MockProfiles.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MockProfiles.swift; sourceTree = "<group>"; };
+		D72C01302E78C0FB00AACB67 /* CondensedProfilePicturesViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CondensedProfilePicturesViewModel.swift; sourceTree = "<group>"; };
 		D72E12772BEED22400F4F781 /* Array.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Array.swift; sourceTree = "<group>"; };
 		D72E12792BEEEED000F4F781 /* NostrFilterTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NostrFilterTests.swift; sourceTree = "<group>"; };
 		D7315A292ACDF3B70036E30A /* DamusCacheManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DamusCacheManager.swift; sourceTree = "<group>"; };
@@ -4301,6 +4305,7 @@
 		5C78A7922E3036F800CF177D /* Models */ = {
 			isa = PBXGroup;
 			children = (
+				D72C01302E78C0FB00AACB67 /* CondensedProfilePicturesViewModel.swift */,
 				4C3BEFD12819DB9B00B3DE84 /* ProfileModel.swift */,
 				4C363A912825FCF2006E126D /* ProfileUpdate.swift */,
 			);
@@ -5783,6 +5788,7 @@
 				D706C5AF2D5D31C20027C627 /* AutoSaveIndicatorView.swift in Sources */,
 				6439E014296790CF0020672B /* ProfilePicImageView.swift in Sources */,
 				4CE6DF1627F8DEBF00C66700 /* RelayConnection.swift in Sources */,
+				D72C01312E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */,
 				4C1253682A76D2470004F4B8 /* MuteNotify.swift in Sources */,
 				4CDA128C29EB19C40006FA5A /* LocalNotification.swift in Sources */,
 				4C3BEFD6281D995700B3DE84 /* ActionBarModel.swift in Sources */,
@@ -6385,6 +6391,7 @@
 				82D6FC082CD99F7900C925F4 /* ProfileZapLinkView.swift in Sources */,
 				D71AD8FE2CEC176A002E2C3C /* AppAccessibilityIdentifiers.swift in Sources */,
 				82D6FC092CD99F7900C925F4 /* AboutView.swift in Sources */,
+				D72C01332E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */,
 				82D6FC0A2CD99F7900C925F4 /* ProfileName.swift in Sources */,
 				82D6FC0B2CD99F7900C925F4 /* ProfilePictureSelector.swift in Sources */,
 				82D6FC0C2CD99F7900C925F4 /* EditMetadataView.swift in Sources */,
@@ -6940,6 +6947,7 @@
 				D703D7502C6709F500A400EA /* NdbTxn.swift in Sources */,
 				D703D77E2C670C1100A400EA /* NostrKind.swift in Sources */,
 				D73E5F972C6AA7B7007EB227 /* SuggestedHashtagsView.swift in Sources */,
+				D72C01322E78C10500AACB67 /* CondensedProfilePicturesViewModel.swift in Sources */,
 				D703D7B22C6710AF00A400EA /* ContentParsing.swift in Sources */,
 				D703D7522C670A1400A400EA /* Log.swift in Sources */,
 				D73E5E1B2C6A9672007EB227 /* LikeCounter.swift in Sources */,

damus/Core/Nostr/RelayPool.swift

@@ -44,6 +44,10 @@ class RelayPool {
     private let network_monitor_queue = DispatchQueue(label: "io.damus.network_monitor")
     private var last_network_status: NWPath.Status = .unsatisfied
     
+    /// The limit of maximum concurrent subscriptions. Any subscriptions beyond this limit will be paused until subscriptions clear
+    /// This is to avoid error states and undefined behaviour related to hitting subscription limits on the relays, by letting those wait instead — with the principle that slower is better than broken.
+    static let MAX_CONCURRENT_SUBSCRIPTION_LIMIT = 10   // This number is only an educated guess at this point.
+
     func close() {
         disconnect()
         relays = []
@@ -102,10 +106,17 @@ class RelayPool {
     }
 
     @MainActor
-    func register_handler(sub_id: String, handler: @escaping (RelayURL, NostrConnectionEvent) -> ()) {
+    func register_handler(sub_id: String, handler: @escaping (RelayURL, NostrConnectionEvent) -> ()) async {
+        while handlers.count > Self.MAX_CONCURRENT_SUBSCRIPTION_LIMIT {
+            Log.debug("%s: Too many subscriptions, waiting for subscription pool to clear", for: .networking, sub_id)
+            try? await Task.sleep(for: .seconds(1))
+        }
+        Log.debug("%s: Subscription pool cleared", for: .networking, sub_id)
         for handler in handlers {
             // don't add duplicate handlers
             if handler.sub_id == sub_id {
+                assertionFailure("Duplicate handlers are not allowed. Proper error handling for this has not been built yet.")
+                Log.error("Duplicate handlers are not allowed. Error handling for this has not been built yet.", for: .networking)
                 return
             }
         }

damus/Features/Onboarding/Views/SaveKeysView.swift

@@ -142,7 +142,7 @@ struct SaveKeysView: View {
             add_rw_relay(self.pool, relay)
         }
 
-        self.pool.register_handler(sub_id: "signup", handler: handle_event)
+        Task { await self.pool.register_handler(sub_id: "signup", handler: handle_event) }
 
         self.loading = true
         

damus/Features/Profile/Models/CondensedProfilePicturesViewModel.swift

@@ -0,0 +1,42 @@
+//
+//  CondensedProfilePicturesViewModel.swift
+//  damus
+//
+//  Created by Daniel D’Aquino on 2025-09-15.
+//
+import Combine
+import Foundation
+
+class CondensedProfilePicturesViewModel: ObservableObject {
+    let state: DamusState
+    let pubkeys: [Pubkey]
+    let maxPictures: Int
+    var shownPubkeys: [Pubkey] {
+        return Array(pubkeys.prefix(maxPictures))
+    }
+    var loadingTask: Task<Void, Never>? = nil
+    
+    init(state: DamusState, pubkeys: [Pubkey], maxPictures: Int) {
+        self.state = state
+        self.pubkeys = pubkeys
+        self.maxPictures = min(maxPictures, pubkeys.count)
+    }
+    
+    func load() {
+        loadingTask?.cancel()
+        loadingTask = Task { try? await loadingTask() }
+    }
+    
+    func loadingTask() async throws {
+        let filter = NostrFilter(kinds: [.metadata], authors: shownPubkeys)
+        let _ = await state.nostrNetwork.reader.query(filters: [filter])
+        for await _ in state.nostrNetwork.reader.streamNotesUntilEndOfStoredEvents(filters: [filter]) {
+            // NO-OP, we just need it to be loaded into NostrDB.
+            try Task.checkCancellation()
+        }
+        DispatchQueue.main.async {
+            // Cause the view to re-render with the newly loaded profiles
+            self.objectWillChange.send()
+        }
+    }
+}

damus/Features/Profile/Views/CondensedProfilePicturesView.swift

@@ -8,26 +8,26 @@
 import SwiftUI
 
 struct CondensedProfilePicturesView: View {
-    let state: DamusState
+    let model: CondensedProfilePicturesViewModel
-    let pubkeys: [Pubkey]
-    let maxPictures: Int
 
     init(state: DamusState, pubkeys: [Pubkey], maxPictures: Int) {
-        self.state = state
+        self.model = CondensedProfilePicturesViewModel(state: state, pubkeys: pubkeys, maxPictures: maxPictures)
-        self.pubkeys = pubkeys
-        self.maxPictures = min(maxPictures, pubkeys.count)
     }
 
     var body: some View {
         // Using ZStack to make profile pictures floating and stacked on top of each other.
         ZStack {
-            ForEach((0..<maxPictures).reversed(), id: \.self) { index in
+            ForEach((0..<model.maxPictures).reversed(), id: \.self) { index in
-                ProfilePicView(pubkey: pubkeys[index], size: 32.0, highlight: .none, profiles: state.profiles, disable_animation: state.settings.disable_animation)
+                ProfilePicView(pubkey: model.pubkeys[index], size: 32.0, highlight: .none, profiles: model.state.profiles, disable_animation: model.state.settings.disable_animation)
                     .offset(x: CGFloat(index) * 20)
             }
         }
         // Padding is needed so that other components drawn adjacent to this view don't get drawn on top.
-        .padding(.trailing, CGFloat((maxPictures - 1) * 20))
+        .padding(.trailing, CGFloat((model.maxPictures - 1) * 20))
+        .onAppear {
+            self.model.load()
+        }
+        
     }
 }
 

damus/Features/Search/Models/SearchHomeModel.swift

@@ -10,9 +10,11 @@ import Foundation
 /// The data model for the SearchHome view, typically something global-like
 class SearchHomeModel: ObservableObject {
     var events: EventHolder
+    var followPackEvents: EventHolder
     @Published var loading: Bool = false
 
     var seen_pubkey: Set<Pubkey> = Set()
+    var follow_pack_seen_pubkey: Set<Pubkey> = Set()
     let damus_state: DamusState
     let base_subid = UUID().description
     let follow_pack_subid = UUID().description
@@ -25,6 +27,9 @@ class SearchHomeModel: ObservableObject {
         self.events = EventHolder(on_queue: { ev in
             preload_events(state: damus_state, events: [ev])
         })
+        self.followPackEvents = EventHolder(on_queue: { ev in
+            preload_events(state: damus_state, events: [ev])
+        })
     }
     
     func get_base_filter() -> NostrFilter {
@@ -40,6 +45,12 @@ class SearchHomeModel: ObservableObject {
         self.objectWillChange.send()
     }
     
+    @MainActor
+    func reload() async {
+        self.events.reset()
+        await self.load()
+    }
+    
     func load() async {
         DispatchQueue.main.async {
             self.loading = true
@@ -51,16 +62,23 @@ class SearchHomeModel: ObservableObject {
         var follow_list_filter = NostrFilter(kinds: [.follow_list])
         follow_list_filter.until = UInt32(Date.now.timeIntervalSince1970)
         
-        for await noteLender in damus_state.nostrNetwork.reader.streamNotesUntilEndOfStoredEvents(filters: [get_base_filter(), follow_list_filter], to: to_relays) {
+        for await noteLender in damus_state.nostrNetwork.reader.streamNotesUntilEndOfStoredEvents(filters: [follow_list_filter], to: to_relays) {
+            await noteLender.justUseACopy({ await self.handleFollowPackEvent($0) })
+        }
+        
+        for await noteLender in damus_state.nostrNetwork.reader.streamNotesUntilEndOfStoredEvents(filters: [get_base_filter()], to: to_relays) {
             await noteLender.justUseACopy({ await self.handleEvent($0) })
         }
         
+        guard let txn = NdbTxn(ndb: damus_state.ndb) else { return }
+        let allEvents = events.all_events + followPackEvents.all_events
+        let task = load_profiles(context: "universe", load: .from_events(allEvents), damus_state: damus_state, txn: txn)
+        
+        try? await task?.value
+        
         DispatchQueue.main.async {
             self.loading = false
         }
-        
-        guard let txn = NdbTxn(ndb: damus_state.ndb) else { return }
-        load_profiles(context: "universe", load: .from_events(events.all_events), damus_state: damus_state, txn: txn)
     }
     
     @MainActor
@@ -76,6 +94,20 @@ class SearchHomeModel: ObservableObject {
             }
         }
     }
+    
+    @MainActor
+    func handleFollowPackEvent(_ ev: NostrEvent) {
+        if ev.known_kind == .follow_list && should_show_event(state: damus_state, ev: ev) && !ev.is_reply() {
+            if !damus_state.settings.multiple_events_per_pubkey && follow_pack_seen_pubkey.contains(ev.pubkey) {
+                return
+            }
+            follow_pack_seen_pubkey.insert(ev.pubkey)
+            
+            if self.followPackEvents.insert(ev) {
+                self.objectWillChange.send()
+            }
+        }
+    }
 }
 
 func find_profiles_to_fetch<Y>(profiles: Profiles, load: PubkeysToLoad, cache: EventCache, txn: NdbTxn<Y>) -> [Pubkey] {
@@ -113,28 +145,23 @@ enum PubkeysToLoad {
     case from_keys([Pubkey])
 }
 
-func load_profiles<Y>(context: String, load: PubkeysToLoad, damus_state: DamusState, txn: NdbTxn<Y>) {
+func load_profiles<Y>(context: String, load: PubkeysToLoad, damus_state: DamusState, txn: NdbTxn<Y>) -> Task<Void, any Error>? {
     let authors = find_profiles_to_fetch(profiles: damus_state.profiles, load: load, cache: damus_state.events, txn: txn)
 
     guard !authors.isEmpty else {
-        return
+        return nil
     }
     
-    Task {
+    return Task {
         print("load_profiles[\(context)]: requesting \(authors.count) profiles from relay pool")
         let filter = NostrFilter(kinds: [.metadata], authors: authors)
         
-        for await item in damus_state.nostrNetwork.reader.subscribe(filters: [filter]) {
+        for await noteLender in damus_state.nostrNetwork.reader.streamNotesUntilEndOfStoredEvents(filters: [filter]) {
             let now = UInt64(Date.now.timeIntervalSince1970)
-            switch item {
+            try noteLender.borrow { event in
-            case .event(let lender):
-                lender.justUseACopy({ event in
                 if event.known_kind == .metadata {
                     damus_state.ndb.write_profile_last_fetched(pubkey: event.pubkey, fetched_at: now)
                 }
-                })
-            case .eose:
-                break
             }
         }
         

damus/Features/Search/Views/SearchHomeView.swift

@@ -54,7 +54,7 @@ struct SearchHomeView: View {
             loading: $model.loading,
             damus: damus_state,
             show_friend_icon: true,
-            filter:content_filter(FilterState.posts),
+            filter: content_filter(FilterState.posts),
             content: {
                 AnyView(VStack(alignment: .leading) {
                     HStack {
@@ -66,7 +66,7 @@ struct SearchHomeView: View {
                     .padding(.top)
                     .padding(.horizontal)
                     
-                    FollowPackTimelineView<AnyView>(events: model.events, loading: $model.loading, damus: damus_state, show_friend_icon: true,filter:content_filter(FilterState.follow_list)
+                    FollowPackTimelineView<AnyView>(events: model.followPackEvents, loading: $model.loading, damus: damus_state, show_friend_icon: true, filter: content_filter(FilterState.follow_list)
                     ).padding(.bottom)
                     
                     Divider()
@@ -83,20 +83,10 @@ struct SearchHomeView: View {
                 }.padding(.bottom, 50))
             }
         )
-        .refreshable {
-            // Fetch new information by unsubscribing and resubscribing to the relay
-            loadingTask?.cancel()
-            loadingTask = Task { await model.load() }
-        }
     }
     
     var SearchContent: some View {
         SearchResultsView(damus_state: damus_state, search: $search)
-            .refreshable {
-                // Fetch new information by unsubscribing and resubscribing to the relay
-                loadingTask?.cancel()
-                loadingTask = Task { await model.load() }
-            }
     }
     
     var MainContent: some View {
@@ -136,6 +126,12 @@ struct SearchHomeView: View {
         .onDisappear {
             loadingTask?.cancel()
         }
+        .refreshable {
+            // Fetch new information by unsubscribing and resubscribing to the relay
+            loadingTask?.cancel()
+            loadingTask = Task { await model.reload() }
+            try? await loadingTask?.value
+        }
     }
 }
 

damus/Shared/Utilities/EventHolder.swift

@@ -95,4 +95,10 @@ class EventHolder: ObservableObject, ScrollQueue {
         
         self.incoming = []
     }
+    
+    @MainActor
+    func reset() {
+        self.incoming = []
+        self.events = []
+    }
 }