import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;

class AiService {
  static const _baseUrl = 'https://api.featherless.ai/v1';
  static const _apiKey =
      'rc_e10f49aaa4f7af03dcd9da115cfc12cc1988665e895955c11f77788ee5ad93c6';
  static const _model = 'Qwen/Qwen2.5-7B-Instruct';

  AiService._();
  static final instance = AiService._();

  Stream<String> streamChat({
    required String systemPrompt,
    required List<Map<String, String>> messages,
  }) async* {
    final client = http.Client();
    try {
      final request = http.Request(
        'POST',
        Uri.parse('$_baseUrl/chat/completions'),
      );
      request.headers.addAll({
        'Authorization': 'Bearer $_apiKey',
        'Content-Type': 'application/json',
      });
      request.body = jsonEncode({
        'model': _model,
        'messages': [
          {'role': 'system', 'content': systemPrompt},
          ...messages,
        ],
        'stream': true,
        'max_tokens': 2048,
        'temperature': 0.7,
      });

      final response = await client.send(request);
      if (response.statusCode != 200) {
        final body = await response.stream.bytesToString();
        String msg = 'API hatası ${response.statusCode}';
        try {
          final j = jsonDecode(body) as Map<String, dynamic>;
          msg = (j['error'] as Map?)?['message'] as String? ?? msg;
        } catch (_) {}
        throw Exception(msg);
      }

      final lines = response.stream
          .transform(utf8.decoder)
          .transform(const LineSplitter());

      await for (final line in lines) {
        if (!line.startsWith('data: ')) continue;
        final payload = line.substring(6).trim();
        if (payload == '[DONE]') break;
        try {
          final j = jsonDecode(payload) as Map<String, dynamic>;
          final choices = j['choices'] as List?;
          if (choices == null || choices.isEmpty) continue;
          final delta = choices.first['delta'] as Map<String, dynamic>?;
          final content = delta?['content'] as String?;
          if (content != null && content.isNotEmpty) yield content;
        } catch (_) {}
      }
    } finally {
      client.close();
    }
  }
}