flutter_desktop_online_state: refactor connection page

Signed-off-by: fufesou <shuanglongchen@yeah.net>

flutter/lib/models/peer_model.dart

@@ -0,0 +1,89 @@
+import 'package:flutter/foundation.dart';
+import '../../common.dart';
+
+class Peer {
+  final String id;
+  final String username;
+  final String hostname;
+  final String platform;
+  final List<dynamic> tags;
+  bool online = false;
+
+  Peer.fromJson(String id, Map<String, dynamic> json)
+      : id = id,
+        username = json['username'] ?? '',
+        hostname = json['hostname'] ?? '',
+        platform = json['platform'] ?? '',
+        tags = json['tags'] ?? [];
+
+  Peer({
+    required this.id,
+    required this.username,
+    required this.hostname,
+    required this.platform,
+    required this.tags,
+  });
+
+  Peer.loading()
+      : this(
+            id: '...',
+            username: '...',
+            hostname: '...',
+            platform: '...',
+            tags: []);
+}
+
+class Peers extends ChangeNotifier {
+  late String _name;
+  late var _peers;
+  static const cbQueryOnlines = 'callback_query_onlines';
+
+  Peers(String name, List<Peer> peers) {
+    _name = name;
+    _peers = peers;
+    gFFI.ffiModel.platformFFI.registerEventHandler(cbQueryOnlines, _name,
+        (evt) {
+      _updateOnlineState(evt);
+    });
+  }
+
+  List<Peer> get peers => _peers;
+
+  @override
+  void dispose() {
+    gFFI.ffiModel.platformFFI.unregisterEventHandler(cbQueryOnlines, _name);
+    super.dispose();
+  }
+
+  Peer getByIndex(int index) {
+    if (index < _peers.length) {
+      return _peers[index];
+    } else {
+      return Peer.loading();
+    }
+  }
+
+  int getPeersCount() {
+    return _peers.length;
+  }
+
+  void _updateOnlineState(Map<String, dynamic> evt) {
+    evt['onlines'].split(',').forEach((online) {
+      for (var i = 0; i < _peers.length; i++) {
+        if (_peers[i].id == online) {
+          _peers[i].online = true;
+        }
+      }
+    });
+
+    evt['offlines'].split(',').forEach((offline) {
+      for (var i = 0; i < _peers.length; i++) {
+        if (_peers[i].id == offline) {
+          _peers[i].online = false;
+        }
+      }
+    });
+
+    notifyListeners();
+  }
+}