import 'dart:async';
import 'dart:collection';
import 'dart:convert';
import 'dart:io';

import 'package:package_info_plus/package_info_plus.dart';

import '../network/api_client.dart';

/// 用户操作日志上报器（仅白名单邮箱用户启用）
///
/// 用法：
/// ```dart
/// ActionLogger.I.bindUser(userEmail);
/// ActionLogger.I.log('route_push', page: '/search/feed', detail: {...});
/// ```
///
/// 设计：
/// - 白名单：只有 email == 256kb@gmail.com 时启用，其他账号调用为 no-op
/// - 缓冲：本地 Queue 缓冲，达到 BATCH_SIZE 或超过 FLUSH_INTERVAL 自动批量上传
/// - 静默失败：网络错误/服务端 403 不重试不上抛，避免影响业务
class ActionLogger {
  ActionLogger._();
  static final ActionLogger I = ActionLogger._();

  /// 白名单邮箱（与后端 ALLOWED_EMAILS 保持一致）
  static const String _allowedEmail = '256kb@gmail.com';

  static const int _batchSize = 30;
  static const Duration _flushInterval = Duration(seconds: 10);
  static const int _maxQueueLen = 500; // 防止离线积压撑爆内存

  bool _enabled = false;
  String _userEmail = '';
  String _deviceInfo = '';
  String _appVersion = '';

  final Queue<Map<String, dynamic>> _queue = Queue();
  Timer? _flushTimer;
  bool _flushing = false;

  bool get enabled => _enabled;

  /// 登录成功后调用，开启上报；非白名单邮箱则关闭
  void bindUser(String? email) {
    _userEmail = email ?? '';
    _enabled = _userEmail.toLowerCase() == _allowedEmail;
    if (_enabled) {
      _initMeta();
      _startFlushTimer();
      log('log_session_start', page: 'app', detail: {'email': _userEmail});
    } else {
      _stopFlushTimer();
      _queue.clear();
    }
  }

  /// 登出/切换账号时调用
  void unbind() {
    if (_enabled) {
      log('log_session_end', page: 'app', detail: {'email': _userEmail});
      // 立即上传残余
      unawaited(flush());
    }
    _enabled = false;
    _userEmail = '';
    _stopFlushTimer();
    // 不清 queue：flush 已在飞，让它带完最后这批
  }

  Future<void> _initMeta() async {
    try {
      final info = await PackageInfo.fromPlatform();
      _appVersion = '${info.version}+${info.buildNumber}';
    } catch (_) {
      _appVersion = 'unknown';
    }
    _deviceInfo = '${Platform.operatingSystem} ${Platform.operatingSystemVersion}';
  }

  void _startFlushTimer() {
    _flushTimer?.cancel();
    _flushTimer = Timer.periodic(_flushInterval, (_) => unawaited(flush()));
  }

  void _stopFlushTimer() {
    _flushTimer?.cancel();
    _flushTimer = null;
  }

  /// 记一条日志。enabled=false 时直接 no-op
  void log(
    String action, {
    String page = '',
    Map<String, dynamic>? detail,
    String? detailRaw,
  }) {
    if (!_enabled) return;
    if (_queue.length >= _maxQueueLen) {
      _queue.removeFirst(); // 丢最老的，保留最新
    }
    _queue.add({
      'action': action,
      'page': page,
      'detail': detailRaw ?? (detail != null ? jsonEncode(detail) : ''),
      'device_info': _deviceInfo,
      'app_version': _appVersion,
      'client_ts': DateTime.now().millisecondsSinceEpoch,
    });
    if (_queue.length >= _batchSize) {
      unawaited(flush());
    }
  }

  /// 立即上传队列里的所有日志
  Future<void> flush() async {
    if (!_enabled || _flushing || _queue.isEmpty) return;
    _flushing = true;
    try {
      final batch = <Map<String, dynamic>>[];
      while (_queue.isNotEmpty && batch.length < 100) {
        batch.add(_queue.removeFirst());
      }
      await ApiClient.I.post<Map<String, dynamic>>(
        '/logs/action',
        data: {'items': batch},
      );
    } catch (_) {
      // 静默失败：上报通道绝不能影响业务
    } finally {
      _flushing = false;
    }
  }
}