import 'dart:convert';
import 'dart:io';

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

class ApiException implements Exception {
  const ApiException(this.code, this.message);

  final int code;
  final String message;

  @override
  String toString() => message;
}

class ApiClient {
  ApiClient(
    this._tokenProvider, {
    http.Client? client,
    String? baseUrl,
  }) : _client = client ?? http.Client(),
       baseUrl =
           baseUrl ??
           const String.fromEnvironment(
             'API_BASE_URL',
             defaultValue: 'http://10.0.2.2:12426',
           );

  final String baseUrl;
  final String Function() _tokenProvider;
  final http.Client _client;

  Future<Object?> get(String path, {bool authenticated = true}) =>
      _send('GET', path, authenticated: authenticated);

  Future<Object?> post(
    String path, {
    Map<String, Object?>? body,
    bool authenticated = true,
  }) => _send('POST', path, body: body, authenticated: authenticated);

  Future<Object?> put(String path, {Map<String, Object?>? body}) => _send('PUT', path, body: body);

  Future<Object?> delete(String path, {Map<String, Object?>? body}) =>
      _send('DELETE', path, body: body);

  Future<Object?> _send(
    String method,
    String path, {
    Map<String, Object?>? body,
    bool authenticated = true,
  }) async {
    final request = http.Request(method, Uri.parse('$baseUrl$path'));
    request.headers[HttpHeaders.acceptHeader] = 'application/json';
    if (authenticated) {
      final token = _tokenProvider();
      if (token.isNotEmpty) request.headers[HttpHeaders.authorizationHeader] = token;
    }
    if (body != null) {
      request.headers[HttpHeaders.contentTypeHeader] = 'application/json; charset=UTF-8';
      request.body = jsonEncode(body);
    }
    final streamed = await _client.send(request);
    final response = await http.Response.fromStream(streamed);
    if (response.statusCode < 200 || response.statusCode >= 300) {
      throw ApiException(response.statusCode, '网络请求失败（${response.statusCode}）');
    }
    final decoded = jsonDecode(response.body);
    if (decoded is! Map<String, Object?>) {
      throw const ApiException(500, '服务端响应格式错误');
    }
    final code = (decoded['code'] as num?)?.toInt() ?? 500;
    if (code != 0) {
      throw ApiException(code, decoded['message'] as String? ?? '操作失败');
    }
    return decoded['details'];
  }
}

Map<String, Object?> jsonMap(Object? value) {
  if (value is Map<String, Object?>) return value;
  if (value is Map) return value.map((key, item) => MapEntry(key.toString(), item));
  throw const ApiException(500, '服务端数据格式错误');
}

List<Map<String, Object?>> jsonList(Object? value) {
  if (value is! List) return const [];
  return value.map<Map<String, Object?>>(jsonMap).toList(growable: false);
}