import 'dart:convert';
import 'package:http/http.dart' as http;
import '../http_client.dart';
import '../http_util.dart';
import '../models.dart';
import '../sse.dart';
import 'base_provider.dart';

/// OpenAI-compatible `/v1/chat/completions` client used by several free proxies.
class OpenAiCompatProvider extends BaseProvider {
  OpenAiCompatProvider({
    required this.providerName,
    required this.apiBase,
    required this.fallbackModel,
    List<String>? supportedModels,
    this.apiKey,
    this.extraHeaders = const {},
  }) : supportedModels = supportedModels ?? [fallbackModel];

  final String providerName;
  final String apiBase;
  final String fallbackModel;
  final List<String> supportedModels;
  final String? apiKey;
  final Map<String, String> extraHeaders;

  @override
  String get name => providerName;

  @override
  bool get working => true;

  @override
  List<String> get models => supportedModels;

  @override
  String get defaultModel => fallbackModel;

  String get chatUrl {
    final base = apiBase.endsWith('/') ? apiBase.substring(0, apiBase.length - 1) : apiBase;
    if (base.endsWith('/chat/completions')) return base;
    return '$base/chat/completions';
  }

  @override
  Stream<String> createAsyncGenerator(
    String model,
    List<Message> messages, {
    bool stream = false,
  }) async* {
    final payload = <String, dynamic>{
      'model': models.contains(model) ? model : defaultModel,
      'messages': toOpenAiMessages(messages),
      'stream': false,
      'temperature': 0.8,
    };

    final headers = browserHeaders(
      contentType: 'application/json',
      accept: 'application/json',
      extra: {
        if (apiKey != null && apiKey!.isNotEmpty) 'Authorization': 'Bearer $apiKey',
        ...extraHeaders,
      },
    );

    final req = http.Request('POST', Uri.parse(chatUrl));
    req.headers.addAll(headers);
    req.body = jsonEncode(payload);

    final response = await g4fHttp.send(req).timeout(requestTimeout);
    if (response.statusCode < 200 || response.statusCode >= 300) {
      final err = await response.stream.bytesToString();
      throw Exception(
        '$name returned ${response.statusCode}: ${err.substring(0, err.length.clamp(0, 240))}',
      );
    }

    final body = utf8.decode(await response.stream.toBytes());
    final fromJson = extractOpenAiMessage(body);
    final fromSse = extractAllSseContent(body).join();
    final text = (fromJson != null && looksLikeModelOutput(fromJson))
        ? fromJson
        : fromSse;
    if (!looksLikeModelOutput(text)) {
      throw Exception('$name returned unusable body');
    }
    yield text;
  }
}