import 'dart:convert';

import 'package:flutter/foundation.dart' show visibleForTesting;
import 'package:http/http.dart' as http;

import '../models/appconfig.dart';
import 'ai_service.dart';

/// 语音纪要「Ask AI」用的文本大模型（OpenAI 兼容接口，客户端直连）。
///
/// 2026-09-17 起只读后台「第三方服务配置」里的 **`llm_qwen`**（通义千问），
/// 与服务端会议总结用的是同一家（服务端走 `llmv_qwen`）。火山（`llm_doubao`）
/// 已从后台删除，这里不再兜底、也不再退回 `OPENAI_*` 那几个老 env 键。
class DeapsoundAIService implements AiService {
  static const String svcId = 'llm_qwen';

  late final String baseUrl;
  late final String apiKey;
  late final String model;

  DeapsoundAIService() {
    apiKey = AppConfig.cred(svcId, 'api_key', '') ?? '';
    baseUrl = AppConfig.cred(svcId, 'base_url', '') ?? '';
    model = AppConfig.cred(svcId, 'model', '') ?? '';
  }

  /// 测试用：不读 AppConfig，只为验证 [chatUrl] 的拼接
  @visibleForTesting
  DeapsoundAIService.debugWithBaseUrl(String base)
      : baseUrl = base,
        apiKey = '',
        model = '';

  /// 后台 `llm_qwen.base_url` 填的是不带路径的根地址
  /// （`https://dashscope.aliyuncs.com/compatible-mode/v1`），这里补上
  /// `/chat/completions`；已经带了的原样用。
  Uri get chatUrl {
    var base = baseUrl.trim();
    while (base.endsWith('/')) {
      base = base.substring(0, base.length - 1);
    }
    if (!base.endsWith('/chat/completions')) base = '$base/chat/completions';
    return Uri.parse(base);
  }

  @override
  Future<String> sendMessage({
    required List<Map<String, String>> messages,
    String? systemPrompt,
    String? userProperties,
  }) async {
    final url = chatUrl;

    final headers = {
      'Content-Type': 'application/json',
      'Authorization': 'Bearer $apiKey',
    };

    final requestBody = {
      "model": model,
      "messages": messages,
    };

    try {
      final response = await http.post(
        url,
        headers: headers,
        body: jsonEncode(requestBody),
      );
      if (response.statusCode != 200) {
        throw Exception('Unknown error');
      }

      final result = jsonDecode(response.body);

      return result['choices'].first['message']['content'];
    } catch (e) {
      throw Exception('Unknown error');
    }
  }

  @override
  Stream sendMessageStream({
    required List<Map<String, String>> messages,
    String? systemPrompt,
    String? userProperties,
  }) async* {
    final client = http.Client();
    final url = chatUrl;

    final headers = {
      'Content-Type': 'application/json',
      'Authorization': 'Bearer $apiKey',
    };

    final requestBody = {
      "model": model,
      "messages": messages,
      "stream": true,
    };

    // ⚠️ 凭据来自 user_getappconfig_v3 的 llm_qwen；没拿到时 baseUrl 是空串，
    // Uri.parse('') 能过、client.send 才抛 "No host specified"。这里先给一句能看懂的。
    if (baseUrl.isEmpty || apiKey.isEmpty || model.isEmpty) {
      throw Exception(
          'AI 服务未配置（$svcId: base_url/api_key/model 缺失），请检查后台「第三方服务配置」');
    }

    try {
      final request = http.Request('POST', url)
        ..headers.addAll(headers)
        ..body = jsonEncode(requestBody);
      final response = await client.send(request);

      if (response.statusCode != 200) {
        // 把服务商的状态码和错误体带出去：401/403 是 key 不对、400 多半是 model 不存在，
        // 全压成 'Unknown error' 就只能靠猜。
        String body = '';
        try {
          body = await response.stream.bytesToString();
        } catch (_) {}
        if (body.length > 300) body = body.substring(0, 300);
        throw Exception('HTTP ${response.statusCode} $body');
      }

      await for (final chunk in response.stream
          .transform(utf8.decoder)
          .transform(const LineSplitter())) {
        if (chunk.isEmpty) continue;

        if (chunk.startsWith('data:')) {
          final jsonStr = chunk.substring(5).trim();
          if (jsonStr == '[DONE]') {
            break;
          }

          final data = jsonDecode(jsonStr);
          final content = data['choices'][0]['delta']['content'] ?? '';
          if (content.isNotEmpty) {
            yield content;
          }
        }
      }
    } catch (e) {
      // 原样抛出（上面 HTTP 分支已经带了状态码），不要再包一层 'Unknown error'
      rethrow;
    } finally {
      client.close();
    }
  }
}