import 'dart:convert';
import 'package:crypto/crypto.dart';
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';

/// ChatGPT-Next-Web / Free2GPT clones (`/api/generate` + md5 sign).
class Free2Gpt extends BaseProvider {
  @override
  String get name => 'Free2Gpt';

  @override
  bool get working => true;

  @override
  List<String> get models => ['gpt-3.5-turbo', 'gpt-4o-mini', 'gemini'];

  @override
  String get defaultModel => 'gpt-3.5-turbo';

  static const _hosts = [
    'https://chat.free2gpt.xyz',
    'https://chatz.free2gpt.xyz',
    'https://gpt.aifree.site',
    'https://chat.aifree.site',
    'https://gemini.free2gpt.com',
  ];

  @override
  Stream<String> createAsyncGenerator(
    String model,
    List<Message> messages, {
    bool stream = false,
  }) async* {
    Object? last;
    for (final host in _hosts) {
      try {
        yield await _generate(host, messages);
        return;
      } catch (e) {
        last = e;
      }
    }
    throw Exception('Free2Gpt failed: $last');
  }

  Future<String> _generate(String host, List<Message> messages) async {
    final lastUser = getLastUserMessage(messages);
    final t = DateTime.now().millisecondsSinceEpoch;
    final sign = md5.convert(utf8.encode('$t:$lastUser:undefined')).toString();
    final payload = jsonEncode({
      'messages': toOpenAiMessages(messages),
      'time': t,
      'pass': null,
      'sign': sign,
    });

    final urls = [
      '$host/api/generate',
      '$host/api/openai/v1/chat/completions',
    ];
    Object? last;
    for (final url in urls) {
      try {
        final req = http.Request('POST', Uri.parse(url));
        req.headers.addAll(browserHeaders(
          origin: host,
          referer: '$host/',
          contentType: 'application/json',
        ));
        req.body = payload;
        final res = await g4fHttp.send(req).timeout(const Duration(seconds: 14));
        if (res.statusCode != 200) {
          last = 'HTTP ${res.statusCode}';
          continue;
        }
        final raw = utf8.decode(await res.stream.toBytes().timeout(const Duration(seconds: 14)));
        final openai = extractOpenAiMessage(raw);
        if (openai != null && looksLikeModelOutput(openai)) return openai.trim();
        final sse = extractAllSseContent(raw).join();
        if (looksLikeModelOutput(sse)) return sse.trim();
        if (looksLikeModelOutput(raw)) return raw.trim();
        last = 'unusable';
      } catch (e) {
        last = e;
      }
    }
    throw Exception('$host failed: $last');
  }
}