add android server chat and multi chat;update android server page

lib/models/chat_model.dart

@@ -1,3 +1,5 @@
+import 'dart:convert';
+
 import 'package:dash_chat/dash_chat.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_hbb/pages/chat_page.dart';
@@ -6,39 +8,65 @@ import 'model.dart';
 import 'native_model.dart';
 
 class ChatModel with ChangeNotifier {
-  final List<ChatMessage> _messages = [];
+  // -1作为客户端模式的id，客户端模式下此id唯一
+  // 其它正整数的id，来自被控服务器模式下的其他客户端的id，每个客户端有不同的id
+  // 注意 此id和peer_id不同，服务端模式下的id等同于conn的顺序累加id
+  static final clientModeID = -1;
+
+  final Map<int, List<ChatMessage>> _messages = Map()..[clientModeID] = [];
 
   final ChatUser me = ChatUser(
-    name:"me",
+    uid:"",
+    name: "me",
+    customProperties: Map()..["id"] = clientModeID
   );
 
+  var _currentID = clientModeID;
+
   get messages => _messages;
 
-  receive(String text){
+  get currentID => _currentID;
+
+  receive(int id, String text) {
     if (text.isEmpty) return;
     // first message show overlay icon
-    if (iconOverlayEntry == null){
+    if (iconOverlayEntry == null) {
       showChatIconOverlay();
     }
-    _messages.add(ChatMessage(text: text, user: ChatUser(
-      name:FFI.ffiModel.pi.username,
-      uid: FFI.getId(),
-    )));
+    if(!_messages.containsKey(id)){
+      _messages[id] = [];
+    }
+    // TODO  peer info
+    _messages[id]?.add(ChatMessage(
+        text: text,
+        user: ChatUser(
+          name: FFI.ffiModel.pi.username,
+          uid: FFI.getId(),
+        )));
+    _currentID = id;
     notifyListeners();
   }
 
-  send(ChatMessage message){
-    _messages.add(message);
-    if(message.text != null && message.text!.isNotEmpty){
-      PlatformFFI.setByName("chat",message.text!);
+  send(ChatMessage message) {
+    if (message.text != null && message.text!.isNotEmpty) {
+      _messages[_currentID]?.add(message);
+      if (_currentID == clientModeID) {
+        PlatformFFI.setByName("chat_client_mode", message.text!);
+      } else {
+        final msg = Map()
+          ..["id"] = _currentID
+          ..["text"] = message.text!;
+        PlatformFFI.setByName("chat_server_mode", jsonEncode(msg));
+      }
     }
     notifyListeners();
   }
 
-  release(){
+  release() {
     hideChatIconOverlay();
     hideChatWindowOverlay();
+    _messages.forEach((key, value) => value.clear());
     _messages.clear();
     notifyListeners();
   }
-}
+}