import 'dart:convert';
import 'dart:io';

class Deepseek {
  final String apiKey;
  Deepseek({required this.apiKey});

  Stream<String> chat(String prompt) async* {
    final client = HttpClient();
    try {
      final request = await client
          .postUrl(Uri.parse('https://api.deepseek.com/chat/completions'));

      // 设置流式请求头
      request.headers
        ..set('Content-Type', 'application/json')
        ..set('Authorization', 'Bearer $apiKey')
        ..set('Accept', 'text/event-stream');

      // 构建请求体
      final requestBody = jsonEncode({
        'model': 'deepseek-chat',
        'stream': true,
        'messages': [
          {'role': 'user', 'content': prompt}
        ]
      });

      // 写入请求体
      request.add(utf8.encode(requestBody));
      final response = await request.close();

      // 检查状态码
      if (response.statusCode != 200) {
        throw Exception('API请求失败: ${response.statusCode}');
      }

      // 处理流数据
      String buffer = '';
      await for (final chunk in response.transform(utf8.decoder)) {
        buffer += chunk;

        // 分割完整事件（假设使用SSE格式）
        while (buffer.contains('\n\n')) {
          final eventEnd = buffer.indexOf('\n\n');
          final event = buffer.substring(0, eventEnd);
          buffer = buffer.substring(eventEnd + 2);

          if (event.startsWith('data: ')) {
            final dataContent = event.substring(6);
            // 增加有效性检查
            if (dataContent == '[DONE]') {
              // print('流式传输结束');
              continue; // 跳过特殊结束标记
            }
            final jsonData = jsonDecode(event.substring(6));
            yield jsonData['choices'][0]['delta']['content'];
          }
        }
      }
    } finally {
      client.close();
    }
  }
}