flutter-template/lib/core/utils/sms_countdown_mixin.dart

import 'dart:async';

import 'package:flutter/widgets.dart';

/// 短信验证码倒计时 mixin — 抽自 phone_add / old_phone_verify 重复模板。
///
/// 用法（任意 [State] 子类，包含 ConsumerState）：
/// ```dart
/// class _MyPageState extends ConsumerState<MyPage>
///     with SmsCountdownMixin<MyPage> {
///
///   Future<void> _sendCode() async {
///     await repo.sendSms(phone);
///     startSmsCountdown(); // 默认 60s
///   }
///
///   @override
///   Widget build(BuildContext context) {
///     final text = isSmsCountingDown ? '${smsCountdown}s 后重发' : '发送验证码';
///     ...
///   }
/// }
/// ```
///
/// dispose 时自动 cancel Timer，子类 `super.dispose()` 即可。
mixin SmsCountdownMixin<T extends StatefulWidget> on State<T> {
  int _countdown = 0;
  Timer? _timer;

  /// 当前剩余秒数（0 = 未运行）
  int get smsCountdown => _countdown;

  /// 是否正在倒计时
  bool get isSmsCountingDown => _countdown > 0;

  /// 启动倒计时（重复调用会取消上一个 Timer 重新开始）。
  void startSmsCountdown({int seconds = 60}) {
    _timer?.cancel();
    setState(() => _countdown = seconds);
    _timer = Timer.periodic(const Duration(seconds: 1), (t) {
      if (!mounted) {
        t.cancel();
        return;
      }
      setState(() {
        _countdown -= 1;
        if (_countdown <= 0) t.cancel();
      });
    });
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }
}