import 'package:flutter_secure_storage/flutter_secure_storage.dart';

import '../auth/session_store.dart';
import 'models.dart';
import 'order_api.dart';

/// 授权管理：本地缓存用于主界面展示到期时间；识别入口强制服务端校验。
/// 缓存按手机号隔离（键含账号），切换账号不会读到上一账号的到期时间。
class LicenseService {
  static const _storage = FlutterSecureStorage();

  final OrderApi orderApi;
  final SessionStore sessionStore;

  LicenseService({required this.orderApi, required this.sessionStore});

  /// 主界面展示/启动加载：先读本账号本地缓存，有效则直接用；
  /// 无效或缺失时询问服务端（网络失败按缓存兜底，未登录按过期处理）。
  Future<LicenseStatus> check() async {
    final phone = await sessionStore.readPhone();
    if (phone == null) return const LicenseStatus(active: false);

    final cached = await _readCache(phone);
    final now = DateTime.now();
    if (cached != null && cached.expiresAt!.isAfter(now)) return cached;

    if (await sessionStore.readToken() == null) {
      return const LicenseStatus(active: false);
    }
    try {
      final remote = await orderApi.fetchLicense();
      try {
        if (remote.active && remote.expiresAt != null) {
          await _writeCache(phone, remote.expiresAt!);
        } else if (!remote.active) {
          await _clearCache(phone);
        }
      } catch (_) {
        // 本地缓存不可用不影响授权状态展示
      }
      return remote;
    } on OrderApiException {
      return cached ?? const LicenseStatus(active: false);
    }
  }

  /// 识别入口强制校验：必须走服务端且 active 才放行，失败即抛错（不进相机）
  Future<LicenseStatus> verifyServer() async {
    if (await sessionStore.readToken() == null) {
      throw const SessionExpiredException();
    }
    return orderApi.fetchLicense();
  }

  /// 支付成功后立即刷新（清缓存强制走服务端，避免旧授权干扰）
  Future<LicenseStatus> refresh() async {
    final phone = await sessionStore.readPhone();
    if (phone != null) await _clearCache(phone);
    return orderApi.fetchLicense();
  }

  Future<LicenseStatus?> _readCache(String phone) async {
    try {
      final raw = await _storage.read(key: _cacheKey(phone));
      final t = raw == null ? null : DateTime.tryParse(raw);
      if (t == null || !t.isAfter(DateTime.now())) return null;
      return LicenseStatus(active: true, expiresAt: t);
    } catch (_) {
      return null;
    }
  }

  Future<void> _writeCache(String phone, DateTime expiresAt) =>
      _storage.write(key: _cacheKey(phone), value: expiresAt.toIso8601String());

  Future<void> _clearCache(String phone) => _storage.delete(key: _cacheKey(phone));

  static String _cacheKey(String phone) => 'license_expires_at:$phone';
}