Add useful view for note-not-found state in quoted notes

Changelog-Added: Added a view for quotes notes that could not be loaded, including actionable items
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>

damus/Features/Events/EventLoaderView.swift

@@ -15,7 +15,8 @@ struct EventLoaderView<Content: View>: View {
     let event_id: NoteId
     let relayHints: [RelayURL]
     @State var event: NostrEvent?
-    @State var subscription_uuid: String = UUID().description
+    @State private var eventNotFound: Bool = false
+    @State private var isReloading: Bool = false
     let content: (NostrEvent) -> Content
 
     /// Creates an event loader view.
@@ -34,6 +35,17 @@ struct EventLoaderView<Content: View>: View {
         _event = State(initialValue: event)
     }
 
+    /// Loads the event from nostrdb or the network using relay hints or the default relay pool.
+    ///
+    /// This method attempts to fetch the event via `nostrNetwork.reader.lookup`, which first checks
+    /// nostrdb for a cached copy, then queries the network if not found locally. Network queries use
+    /// either the specified relay hints (if provided) or the user's relay pool (if no hints are provided).
+    /// On success, sets `event` and clears `eventNotFound`. On failure, sets `eventNotFound` to true.
+    ///
+    /// Side effects:
+    /// - Updates `event` with the fetched event on success
+    /// - Updates `eventNotFound` flag based on the result
+    /// - Logs debug information when relay hints are used
     func load() async {
         let targetRelays = relayHints.isEmpty ? nil : relayHints
         #if DEBUG
@@ -42,7 +54,14 @@ struct EventLoaderView<Content: View>: View {
         }
         #endif
         let lender = try? await damus_state.nostrNetwork.reader.lookup(noteId: self.event_id, to: targetRelays)
-        lender?.justUseACopy({ event = $0 })
+        if let foundEvent = lender?.justGetACopy() {
+            event = foundEvent
+            eventNotFound = false
+        }
+        else {
+            // Handle nil case: event was not found
+            eventNotFound = true
+        }
         #if DEBUG
         if let targetRelays, !targetRelays.isEmpty {
             print("[relay-hints] EventLoaderView: Event \(event_id.hex().prefix(8))... loaded: \(event != nil)")
@@ -50,10 +69,27 @@ struct EventLoaderView<Content: View>: View {
         #endif
     }
     
+    /// Retries loading the event and displays loading state during the operation.
+    ///
+    /// This method sets the `isReloading` flag to true, calls `load()`, and resets
+    /// the flag when complete. It is typically triggered by user action (e.g., "Try Again" button).
+    ///
+    /// Side effects:
+    /// - Updates `isReloading` to true during the operation
+    /// - Delegates to `load()`, which updates `event` and `eventNotFound`
+    /// - Resets `isReloading` to false after completion
+    func retry() async {
+        isReloading = true
+        await load()
+        isReloading = false
+    }
+    
     var body: some View {
         VStack { 
             if let event {
                 self.content(event)
+            } else if eventNotFound {
+                not_found
             } else {
                 ProgressView().padding()
             }
@@ -65,6 +101,47 @@ struct EventLoaderView<Content: View>: View {
             await self.load()
         }
     }
+    
+    var not_found: some View {
+        VStack(spacing: 0) {
+            LoadableNostrEventView.SomethingWrong(
+                imageSystemName: "questionmark.app",
+                heading: NSLocalizedString("Note not found", comment: "Heading for the event loader view in a not found error state."),
+                description: NSLocalizedString("This note may have been deleted, or it might not be available on the relays you're connected to.", comment: "Text for the event loader view when it is unable to find the note the user is looking for"),
+                advice: NSLocalizedString("Try checking your internet connection, expanding your relay list, or contacting the person who quoted this note.", comment: "Tips on what to do if a quoted note cannot be found.")
+            )
+            
+            Button(action: {
+                Task {
+                    await retry()
+                }
+            }) {
+                HStack {
+                    if !isReloading {
+                        Image(systemName: "arrow.clockwise")
+                        Text("Try Again", comment: "Button label to retry loading a note that was not found")
+                    }
+                    else {
+                        ProgressView()
+                        Text("Retrying…", comment: "Button label for the retry-in-progress state when loading a note")
+                    }
+                }
+                .font(.headline)
+                .foregroundColor(.white)
+                .padding(.horizontal, 20)
+                .padding(.vertical, 12)
+                .background(Color.secondary)
+                .cornerRadius(10)
+            }
+            .disabled(isReloading)
+            .opacity(isReloading ? 0.6 : 1.0)
+            .padding(.bottom, 20)
+        }
+        .overlay(
+            RoundedRectangle(cornerRadius: 12)
+                .stroke(Color.secondary.opacity(0.3), lineWidth: 1)
+        )
+    }
 }