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 'webview_base_provider.dart';

/// Duck.ai / DuckDuckGo chat. REST first; WebView executes the JS anti-bot hash.
class DuckDuckGo extends WebViewBaseProvider {
  @override
  String get name => 'DuckDuckGo';

  @override
  bool get working => true;

  @override
  List<String> get models => [
        'gpt-5.6-luna',
        'gpt-5.4-mini',
        'claude-haiku-4-5',
        'mistralai/Mistral-Small-24B-Instruct-2501',
        'meta-llama/Llama-4-Scout',
      ];

  @override
  String get defaultModel => 'gpt-5.6-luna';

  @override
  String get baseUrl => 'https://duckduckgo.com/';

  @override
  String get apiEndpoint => 'https://duckduckgo.com/duckchat/v1/chat';

  static const _statusUrl = 'https://duckduckgo.com/duckchat/v1/status';
  static const _chatUrl = 'https://duckduckgo.com/duckchat/v1/chat';

  @override
  Stream<String> createAsyncGenerator(
    String model,
    List<Message> messages, {
    bool stream = false,
  }) async* {
    try {
      await for (final chunk in _tryRest(model, messages, stream: stream)) {
        yield chunk;
      }
      return;
    } catch (_) {
      // 418 challenge — fall through to a real browser context.
    }
    await for (final chunk in super.createAsyncGenerator(model, messages, stream: stream)) {
      yield chunk;
    }
  }

  Stream<String> _tryRest(
    String model,
    List<Message> messages, {
    required bool stream,
  }) async* {
      final statusReq = http.Request('GET', Uri.parse(_statusUrl));
      statusReq.headers.addAll(browserHeaders(
        origin: 'https://duckduckgo.com',
        referer: 'https://duckduckgo.com/',
        accept: 'application/json',
        extra: {'x-vqd-accept': '1'},
      ));
      final statusRes = await g4fHttp.send(statusReq).timeout(const Duration(seconds: 12));
      final vqd4 = statusRes.headers['x-vqd-4'];
      final hash1 = statusRes.headers['x-vqd-hash-1'];
      await statusRes.stream.drain();
      if (vqd4 == null || vqd4.isEmpty) {
        throw Exception('DuckDuckGo: no x-vqd-4 (challenge required)');
      }

      final chatReq = http.Request('POST', Uri.parse(_chatUrl));
      chatReq.headers.addAll(browserHeaders(
        origin: 'https://duckduckgo.com',
        referer: 'https://duckduckgo.com/',
        contentType: 'application/json',
        accept: 'text/event-stream',
        extra: {
          'x-vqd-4': vqd4,
          if (hash1 != null && hash1.isNotEmpty) 'x-vqd-hash-1': hash1,
        },
      ));
      chatReq.body = jsonEncode({
        'model': models.contains(model) ? model : defaultModel,
        'messages': toOpenAiMessages(messages),
        'canUseTools': false,
        'canUseApproxLocation': false,
      });

      final chatRes = await g4fHttp.send(chatReq).timeout(const Duration(seconds: 25));
      if (chatRes.statusCode != 200) {
        throw Exception('DuckDuckGo chat ${chatRes.statusCode}');
      }

      final collected = StringBuffer();
      await for (final line in splitSseLines(chatRes.stream.transform(utf8.decoder))) {
        final trimmed = line.trim();
        if (trimmed.isEmpty || !trimmed.startsWith('data:')) continue;
        final content = extractSseContent(trimmed.substring(5).trim());
        if (content != null && content.isNotEmpty) {
          collected.write(content);
          if (stream) yield content;
        }
      }
      final text = collected.toString();
      if (!looksLikeModelOutput(text)) {
        throw Exception('DuckDuckGo empty/challenge response');
      }
      if (!stream) yield text;
  }

  @override
  String buildJsFetchCode(String model, List<Message> messages, bool stream) {
    final messagesJson = jsonEncode(toOpenAiMessages(messages));
    final modelJson = jsonEncode(models.contains(model) ? model : defaultModel);
    return '''
      (async function() {
        const status = await fetch('https://duckduckgo.com/duckchat/v1/status', {
          headers: { 'x-vqd-accept': '1', 'Accept': 'application/json' }
        });
        let vqd4 = status.headers.get('x-vqd-4') || '';
        let hash1 = status.headers.get('x-vqd-hash-1') || '';
        if (hash1) {
          try {
            let src = hash1;
            try { src = atob(hash1); } catch (e) {}
            if (src.includes('function') || src.trim().startsWith('(')) {
              const result = await (0, eval)(src);
              const value = (typeof result === 'function') ? await result() : result;
              hash1 = btoa(JSON.stringify(value));
            }
          } catch (e) {
            return JSON.stringify({error: 'hash failed: ' + e});
          }
        }
        const headers = {
          'Content-Type': 'application/json',
          'Accept': 'text/event-stream'
        };
        if (vqd4) headers['x-vqd-4'] = vqd4;
        if (hash1) headers['x-vqd-hash-1'] = hash1;
        const resp = await fetch('https://duckduckgo.com/duckchat/v1/chat', {
          method: 'POST',
          headers,
          body: JSON.stringify({
            model: $modelJson,
            messages: $messagesJson,
            canUseTools: false,
            canUseApproxLocation: false
          })
        });
        const body = await resp.text();
        return JSON.stringify({status: resp.status, body: body});
      })();
    ''';
  }

  @override
  String parseResponse(String rawResponse) {
    try {
      final json = jsonDecode(rawResponse);
      if (json is Map && json['error'] != null) {
        throw Exception(json['error']);
      }
      final body = json is Map ? (json['body']?.toString() ?? rawResponse) : rawResponse;
      final text = extractAllSseContent(body).join();
      if (!looksLikeModelOutput(text)) {
        throw Exception('DuckDuckGo WebView unusable: ${body.substring(0, body.length.clamp(0, 180))}');
      }
      return text;
    } catch (e) {
      if (e.toString().contains('DuckDuckGo')) rethrow;
      final text = extractAllSseContent(rawResponse).join();
      if (looksLikeModelOutput(text)) return text;
      throw Exception('Failed to parse DuckDuckGo: $e');
    }
  }
}