add client chat page & chat overlay window

lib/models/chat_model.dart

@@ -1,5 +1,44 @@
+import 'package:dash_chat/dash_chat.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_hbb/pages/chat_page.dart';
+
+import 'model.dart';
+import 'native_model.dart';
 
 class ChatModel with ChangeNotifier {
+  final List<ChatMessage> _messages = [];
 
+  final ChatUser me = ChatUser(
+    name:"me",
+  );
+
+  get messages => _messages;
+
+  receive(String text){
+    if (text.isEmpty) return;
+    // first message show overlay icon
+    if (iconOverlayEntry == null){
+      showChatIconOverlay();
+    }
+    _messages.add(ChatMessage(text: text, user: ChatUser(
+      name:FFI.ffiModel.pi.username,
+      uid: FFI.getId(),
+    )));
+    notifyListeners();
+  }
+
+  send(ChatMessage message){
+    _messages.add(message);
+    if(message.text != null && message.text!.isNotEmpty){
+      PlatformFFI.setByName("chat",message.text!);
+    }
+    notifyListeners();
+  }
+
+  release(){
+    hideChatIconOverlay();
+    hideChatWindowOverlay();
+    _messages.clear();
+    notifyListeners();
+  }
 }