Optimize UI performance with message caching and List view

- Convert BitchatMessage from struct to class for efficient caching
- Cache formatted AttributedStrings to avoid expensive regex on every render
- Replace ScrollView+LazyVStack with native List for better cell reuse
- Implement message windowing (show last 100 messages for performance)
- Add LazyLinkPreviewView that defers loading for 0.5s to improve scroll performance

These optimizations significantly improve scroll performance, especially with large message lists.

bitchat/Protocols/BitchatProtocol.swift

@@ -929,7 +929,7 @@ enum DeliveryStatus: Codable, Equatable {
     }
 }
 
-struct BitchatMessage: Codable, Equatable {
+class BitchatMessage: Codable {
     let id: String
     let sender: String
     let content: String
@@ -942,6 +942,23 @@ struct BitchatMessage: Codable, Equatable {
     let mentions: [String]?  // Array of mentioned nicknames
     var deliveryStatus: DeliveryStatus? // Delivery tracking
     
+    // Cached formatted text (not included in Codable)
+    private var _cachedFormattedText: [String: AttributedString] = [:]
+    
+    func getCachedFormattedText(isDark: Bool) -> AttributedString? {
+        return _cachedFormattedText["\(isDark)"]
+    }
+    
+    func setCachedFormattedText(_ text: AttributedString, isDark: Bool) {
+        _cachedFormattedText["\(isDark)"] = text
+    }
+    
+    // Codable implementation
+    enum CodingKeys: String, CodingKey {
+        case id, sender, content, timestamp, isRelay, originalSender
+        case isPrivate, recipientNickname, senderPeerID, mentions, deliveryStatus
+    }
+    
     init(id: String? = nil, sender: String, content: String, timestamp: Date, isRelay: Bool, originalSender: String? = nil, isPrivate: Bool = false, recipientNickname: String? = nil, senderPeerID: String? = nil, mentions: [String]? = nil, deliveryStatus: DeliveryStatus? = nil) {
         self.id = id ?? UUID().uuidString
         self.sender = sender
@@ -957,6 +974,23 @@ struct BitchatMessage: Codable, Equatable {
     }
 }
 
+// Equatable conformance for BitchatMessage
+extension BitchatMessage: Equatable {
+    static func == (lhs: BitchatMessage, rhs: BitchatMessage) -> Bool {
+        return lhs.id == rhs.id &&
+               lhs.sender == rhs.sender &&
+               lhs.content == rhs.content &&
+               lhs.timestamp == rhs.timestamp &&
+               lhs.isRelay == rhs.isRelay &&
+               lhs.originalSender == rhs.originalSender &&
+               lhs.isPrivate == rhs.isPrivate &&
+               lhs.recipientNickname == rhs.recipientNickname &&
+               lhs.senderPeerID == rhs.senderPeerID &&
+               lhs.mentions == rhs.mentions &&
+               lhs.deliveryStatus == rhs.deliveryStatus
+    }
+}
+
 protocol BitchatDelegate: AnyObject {
     func didReceiveMessage(_ message: BitchatMessage)
     func didConnectToPeer(_ peerID: String)

bitchat/ViewModels/ChatViewModel.swift

@@ -938,9 +938,15 @@ class ChatViewModel: ObservableObject {
     }
     
     func formatMessageAsText(_ message: BitchatMessage, colorScheme: ColorScheme) -> AttributedString {
+        // Check cache first
+        let isDark = colorScheme == .dark
+        if let cachedText = message.getCachedFormattedText(isDark: isDark) {
+            return cachedText
+        }
+        
+        // Not cached, format the message
         var result = AttributedString()
         
-        let isDark = colorScheme == .dark
         let primaryColor = isDark ? Color.green : Color(red: 0, green: 0.5, blue: 0)
         let secondaryColor = primaryColor.opacity(0.7)
         
@@ -1075,6 +1081,9 @@ class ChatViewModel: ObservableObject {
             result.append(content.mergingAttributes(contentStyle))
         }
         
+        // Cache the formatted text
+        message.setCachedFormattedText(result, isDark: isDark)
+        
         return result
     }
     
@@ -2223,21 +2232,17 @@ extension ChatViewModel: BitchatDelegate {
         if let index = messages.firstIndex(where: { $0.id == messageID }) {
             let currentStatus = messages[index].deliveryStatus
             if !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) {
-                var updatedMessage = messages[index]
+                messages[index].deliveryStatus = status
-                updatedMessage.deliveryStatus = status
-                messages[index] = updatedMessage
             }
         }
         
         // Update in private chats
         var updatedPrivateChats = privateChats
-        for (peerID, var chatMessages) in updatedPrivateChats {
+        for (peerID, chatMessages) in updatedPrivateChats {
             if let index = chatMessages.firstIndex(where: { $0.id == messageID }) {
                 let currentStatus = chatMessages[index].deliveryStatus
                 if !shouldSkipUpdate(currentStatus: currentStatus, newStatus: status) {
-                    var updatedMessage = chatMessages[index]
+                    chatMessages[index].deliveryStatus = status
-                    updatedMessage.deliveryStatus = status
-                    chatMessages[index] = updatedMessage
                     updatedPrivateChats[peerID] = chatMessages
                 }
             }

bitchat/Views/ContentView.swift

@@ -163,18 +163,20 @@ struct ContentView: View {
     
     private func messagesView(privatePeer: String?) -> some View {
         ScrollViewReader { proxy in
-            ScrollView {
+            List {
-                LazyVStack(alignment: .leading, spacing: 2) {
+                let messages: [BitchatMessage] = {
-                    let messages: [BitchatMessage] = {
+                    if let privatePeer = privatePeer {
-                        if let privatePeer = privatePeer {
+                        let msgs = viewModel.getPrivateChatMessages(for: privatePeer)
-                            let msgs = viewModel.getPrivateChatMessages(for: privatePeer)
+                        return msgs
-                            return msgs
+                    } else {
-                        } else {
+                        return viewModel.messages
-                            return viewModel.messages
+                    }
-                        }
+                }()
-                    }()
+                
-                    
+                // Implement windowing - show last 100 messages for performance
-                    ForEach(messages, id: \.id) { message in
+                let windowedMessages = messages.suffix(100)
+                
+                ForEach(Array(windowedMessages), id: \.id) { message in
                         VStack(alignment: .leading, spacing: 4) {
                             // Check if current user is mentioned
                             let _ = message.mentions?.contains(viewModel.nickname) ?? false
@@ -208,24 +210,26 @@ struct ContentView: View {
                                         // Don't show link preview if the message is just the emoji
                                         let cleanContent = message.content.trimmingCharacters(in: .whitespacesAndNewlines)
                                         if cleanContent.hasPrefix("👇") {
-                                            LinkPreviewView(url: markdownLink.url, title: markdownLink.title)
+                                            LazyLinkPreviewView(
-                                                .padding(.top, 2)
+                                                url: markdownLink.url,
-                                                .id("\(message.id)-\(markdownLink.url.absoluteString)")
+                                                title: markdownLink.title,
+                                                id: "\(message.id)-\(markdownLink.url.absoluteString)"
+                                            )
                                         }
                                     } else {
                                         // Check for plain URLs
                                         let urls = message.content.extractURLs()
                                         ForEach(Array(urls.prefix(3).enumerated()), id: \.offset) { index, urlInfo in
-                                            LinkPreviewView(url: urlInfo.url, title: nil)
+                                            LazyLinkPreviewView(
-                                                .padding(.top, 2)
+                                                url: urlInfo.url,
-                                                .id("\(message.id)-\(urlInfo.url.absoluteString)")
+                                                title: nil,
+                                                id: "\(message.id)-\(urlInfo.url.absoluteString)"
+                                            )
                                         }
                                     }
                                 }
                             }
                         }
-                        .padding(.horizontal, 12)
-                        .padding(.vertical, 2)
                         .id(message.id)
                         .contentShape(Rectangle())
                         .onTapGesture {
@@ -236,10 +240,13 @@ struct ContentView: View {
                                 showMessageActions = true
                             }
                         }
+                        .listRowInsets(EdgeInsets(top: 2, leading: 12, bottom: 2, trailing: 12))
+                        .listRowSeparator(.hidden)
+                        .listRowBackground(backgroundColor)
                     }
-                }
-                .padding(.vertical, 8)
             }
+            .listStyle(.plain)
+            .scrollContentBackground(.hidden)
             .background(backgroundColor)
             .onTapGesture(count: 3) {
                 // Triple-tap to clear current chat
@@ -248,7 +255,9 @@ struct ContentView: View {
             .onChange(of: viewModel.messages.count) { _ in
                 if privatePeer == nil && !viewModel.messages.isEmpty {
                     withAnimation {
-                        proxy.scrollTo(viewModel.messages.last?.id, anchor: .bottom)
+                        // Scroll to last message in windowed view
+                        let lastId = viewModel.messages.suffix(100).last?.id
+                        proxy.scrollTo(lastId, anchor: .bottom)
                     }
                 }
             }
@@ -257,7 +266,9 @@ struct ContentView: View {
                    let messages = viewModel.privateChats[peerID],
                    !messages.isEmpty {
                     withAnimation {
-                        proxy.scrollTo(messages.last?.id, anchor: .bottom)
+                        // Scroll to last message in windowed view
+                        let lastId = messages.suffix(100).last?.id
+                        proxy.scrollTo(lastId, anchor: .bottom)
                     }
                 }
             }
@@ -940,6 +951,34 @@ struct MessageContentView: View {
     }
 }
 
+// Lazy loading wrapper for LinkPreviewView
+struct LazyLinkPreviewView: View {
+    let url: URL
+    let title: String?
+    let id: String
+    
+    @State private var shouldLoad = false
+    
+    var body: some View {
+        Group {
+            if shouldLoad {
+                LinkPreviewView(url: url, title: title)
+                    .padding(.top, 2)
+                    .id(id)
+            }
+        }
+        .onAppear {
+            // Delay loading to improve scroll performance
+            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
+                shouldLoad = true
+            }
+        }
+        .onDisappear {
+            shouldLoad = false
+        }
+    }
+}
+
 // Delivery status indicator view
 struct DeliveryStatusView: View {
     let status: DeliveryStatus