AI 接入 V0.1

lib/models/ai.dart

@@ -0,0 +1,111 @@
+import 'json_util.dart';
+
+/// 会话列表项（不含消息）
+class ChatSessionItem {
+  final int id;
+  final String title;
+  final String updateTime;
+
+  const ChatSessionItem({
+    required this.id,
+    required this.title,
+    required this.updateTime,
+  });
+
+  factory ChatSessionItem.fromJson(Map<String, dynamic> json) {
+    return ChatSessionItem(
+      id: asInt(json['id']),
+      title: asNonEmpty(json['title'], '新对话'),
+      updateTime: formatDateTime(json['updateTime']),
+    );
+  }
+}
+
+/// 会话里的一条消息。工具调用的中间过程后端不入库，所以只有 user / assistant
+class ChatMessageItem {
+  final int id;
+  final String role;
+  final String content;
+
+  const ChatMessageItem({
+    required this.id,
+    required this.role,
+    required this.content,
+  });
+
+  bool get isUser => role == 'user';
+
+  factory ChatMessageItem.fromJson(Map<String, dynamic> json) {
+    return ChatMessageItem(
+      id: asInt(json['id']),
+      role: asString(json['role'], fallback: 'assistant'),
+      content: asString(json['content']),
+    );
+  }
+}
+
+/// 页面上的一个气泡。
+///
+/// 和 [ChatMessageItem] 的区别：这个没有 id、带 streaming 标记，
+/// 因为正在生成的那条回答还没落库。
+class ChatBubble {
+  final String role;
+  final String content;
+
+  /// 正在生成中（末尾会显示光标 / 工具提示）
+  final bool streaming;
+
+  const ChatBubble({
+    required this.role,
+    required this.content,
+    this.streaming = false,
+  });
+
+  const ChatBubble.user(String content) : this(role: 'user', content: content);
+
+  const ChatBubble.assistant(String content, {bool streaming = false})
+      : this(role: 'assistant', content: content, streaming: streaming);
+
+  bool get isUser => role == 'user';
+
+  ChatBubble copyWith({String? content, bool? streaming}) {
+    return ChatBubble(
+      role: role,
+      content: content ?? this.content,
+      streaming: streaming ?? this.streaming,
+    );
+  }
+
+  factory ChatBubble.fromItem(ChatMessageItem item) =>
+      ChatBubble(role: item.role, content: item.content);
+}
+
+/// SSE 事件类型
+enum AiEventType { delta, tool, done, error }
+
+/// 一次 SSE 事件。后端只会发这四种，见 AiChatService。
+class AiEvent {
+  final AiEventType type;
+
+  /// delta：本次新增的文本
+  final String? content;
+
+  /// tool：正在调用的工具名
+  final String? toolName;
+
+  /// done：会话 ID（新会话时后端才刚创建，App 要靠它接着聊）
+  final int? sessionId;
+
+  /// error：错误提示
+  final String? message;
+
+  const AiEvent._(this.type, {this.content, this.toolName, this.sessionId, this.message});
+
+  const AiEvent.delta(String content) : this._(AiEventType.delta, content: content);
+
+  const AiEvent.tool(String name) : this._(AiEventType.tool, toolName: name);
+
+  const AiEvent.done(int? sessionId) : this._(AiEventType.done, sessionId: sessionId);
+
+  const AiEvent.error(String message) : this._(AiEventType.error, message: message);
+}