feat: Implement ChatView model and integrate chat service for conversation management

Author: AdamLBS

lib/models/chat_view.dart

@@ -0,0 +1,67 @@
+import 'package:intl/intl.dart';
+
+class ChatView {
+  final String id;
+  final String chatType;
+  final String? partnerUserId;
+  final String? partnerUsername;
+  final String? name; // for group chats
+  final String? lastMessageId;
+  final String? lastMessagePreview;
+  final DateTime updatedAt;
+  final String displayName;
+
+  ChatView({
+    required this.id,
+    required this.chatType,
+    this.partnerUserId,
+    this.partnerUsername,
+    this.name,
+    this.lastMessageId,
+    this.lastMessagePreview,
+    required this.updatedAt,
+    this.displayName = '',
+  });
+
+  factory ChatView.fromJson(Map<String, dynamic> json) {
+    return ChatView(
+      id: json['id'] ?? '',
+      chatType: json['chat_type'] ?? 'direct',
+      partnerUserId: json['partner_user_id'],
+      partnerUsername: json['partner_username'],
+      name: json['name'],
+      lastMessageId: json['last_message_id'],
+      lastMessagePreview: json['last_message_preview'],
+      updatedAt: DateTime.parse(json['updated_at']),
+      displayName: json['name'] ?? json['partner_username'] ?? '',
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'chat_type': chatType,
+      'partner_user_id': partnerUserId,
+      'partner_username': partnerUsername,
+      'name': name,
+      'last_message_id': lastMessageId,
+      'last_message_preview': lastMessagePreview,
+      'updated_at': updatedAt.toIso8601String(),
+    };
+  }
+
+  /// Optional helper: format the last update nicely for UI
+  String get formattedDate {
+    return DateFormat('dd/MM HH:mm').format(updatedAt);
+  }
+
+  /// Optional helper: title shown in chat list
+  String get displayTitle {
+    if (chatType == 'group') return name ?? 'Group chat';
+    return partnerUsername ?? 'Unknown';
+  }
+
+  String get previewText {
+    return lastMessagePreview ?? 'Secure session established 🔒';
+  }
+}

lib/models/session.dart

@@ -1,62 +1,28 @@
 import 'dart:convert';
-import 'dart:typed_data';
 
 class Session {
   final String id;
   final String chatId;
   final String senderDeviceId;
   final String receiverDeviceId;
-  final Uint8List rootKey;
-  final Uint8List? sendChainKey;
-  final Uint8List? recvChainKey;
-  final int sendCounter;
-  final int recvCounter;
-  final Uint8List ratchetPub;
-  final Uint8List? ratchetPriv;
-  final Uint8List? lastRemotePub;
   final DateTime createdAt;
   final DateTime updatedAt;
 
   Session({
-     this.id = '',
-     this.chatId = '',
+    this.id = '',
+    this.chatId = '',
     required this.senderDeviceId,
     required this.receiverDeviceId,
-    required this.rootKey,
-    this.sendChainKey,
-    this.recvChainKey,
-    this.sendCounter = 0,
-    this.recvCounter = 0,
-    required this.ratchetPub,
-    this.ratchetPriv,
-    this.lastRemotePub,
     required this.createdAt,
     required this.updatedAt,
   });
-  
 
   factory Session.fromJson(Map<String, dynamic> json) {
     return Session(
-      id: json['id'],
-      chatId: json['chat_id'],
+      id: json['id'] ?? '',
+      chatId: json['chat_id'] ?? '',
       senderDeviceId: json['sender_device_id'],
       receiverDeviceId: json['receiver_device_id'],
-      rootKey: base64Decode(json['root_key']),
-      sendChainKey: json['send_chain_key'] != null
-          ? base64Decode(json['send_chain_key'])
-          : null,
-      recvChainKey: json['recv_chain_key'] != null
-          ? base64Decode(json['recv_chain_key'])
-          : null,
-      sendCounter: json['send_counter'] ?? 0,
-      recvCounter: json['recv_counter'] ?? 0,
-      ratchetPub: base64Decode(json['ratchet_pub']),
-      ratchetPriv: json['ratchet_priv'] != null
-          ? base64Decode(json['ratchet_priv'])
-          : null,
-      lastRemotePub: json['last_remote_pub'] != null
-          ? base64Decode(json['last_remote_pub'])
-          : null,
       createdAt: DateTime.parse(json['created_at']),
       updatedAt: DateTime.parse(json['updated_at']),
     );
@@ -68,30 +34,17 @@ class Session {
       'chat_id': chatId,
       'sender_device_id': senderDeviceId,
       'receiver_device_id': receiverDeviceId,
-      'root_key': base64Encode(rootKey),
-      if (sendChainKey != null)
-        'send_chain_key': base64Encode(sendChainKey!),
-      if (recvChainKey != null)
-        'recv_chain_key': base64Encode(recvChainKey!),
-      'send_counter': sendCounter,
-      'recv_counter': recvCounter,
-      'ratchet_pub': base64Encode(ratchetPub),
-      if (ratchetPriv != null)
-        'ratchet_priv': base64Encode(ratchetPriv!),
-      if (lastRemotePub != null)
-        'last_remote_pub': base64Encode(lastRemotePub!),
       'created_at': createdAt.toIso8601String(),
       'updated_at': updatedAt.toIso8601String(),
     };
   }
+
+  /// This JSON is used when confirming a pending session with the node.
+  /// Only non-sensitive metadata is uploaded — the actual ratchet keys remain client-side.
   Map<String, dynamic> toConfirmJson() {
-  return {
-    "sender_device_id": senderDeviceId,
-    "receiver_device_id": receiverDeviceId,
-    "root_key": base64Encode(rootKey),
-    "ratchet_pub": base64Encode(ratchetPub),
-    if (lastRemotePub != null)
-      "last_remote_pub": base64Encode(lastRemotePub!),
-  };
-}
+    return {
+      'sender_device_id': senderDeviceId,
+      'receiver_device_id': receiverDeviceId,
+    };
+  }
 }