/// ============================================================
/// 【QuestionPlanCountDown】单题建议作答时长倒计时
/// （1:1 迁移 Vue classExercises/QuestionPlanCountDown.vue，
///  底层由 uview up-count-down 换为 Flutter Timer.periodic）
///
/// 对外方法（`GlobalKey<QuestionPlanCountDownState>` 调用）：
///   start / pause / reset / getRemainTime（毫秒）
/// autoStart：initState 后自动开始；到点只触发一次 onFinish(key)。
/// ============================================================
library;

import 'dart:async';

import 'package:flutter/material.dart';

class QuestionPlanCountDown extends StatefulWidget {
  const QuestionPlanCountDown({
    super.key,
    this.questionKey,
    required this.timeMs,
    this.format = 'mm:ss',
    this.onFinish,
    this.textStyle,
  });

  final Object? questionKey;

  /// 剩余总时长（毫秒）
  final int timeMs;

  /// 'mm:ss'（本页另有 HH:mm:ss 的动态格式，按是否含 HH 切换）
  final String format;
  final ValueChanged<Object?>? onFinish;
  final TextStyle? textStyle;

  @override
  State<QuestionPlanCountDown> createState() => QuestionPlanCountDownState();
}

class QuestionPlanCountDownState extends State<QuestionPlanCountDown> {
  Timer? _timer;
  late int _remainMs;
  bool _finished = false;

  @override
  void initState() {
    super.initState();
    _remainMs = widget.timeMs;
    // autoStart
    start();
  }

  @override
  void didUpdateWidget(covariant QuestionPlanCountDown oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.timeMs != widget.timeMs) {
      reset();
      start();
    }
  }

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

  void start() {
    if (_timer != null) return;
    _timer = Timer.periodic(const Duration(milliseconds: 200), (_) {
      if (!mounted) return;
      _remainMs -= 200;
      if (_remainMs <= 0) {
        _remainMs = 0;
        pause();
        if (!_finished) {
          _finished = true;
          widget.onFinish?.call(widget.questionKey);
        }
      }
      setState(() {});
    });
  }

  void pause() {
    _timer?.cancel();
    _timer = null;
  }

  /// 重置回初始时长并暂停（与 uview reset 行为一致，调用方需再 start）
  void reset() {
    pause();
    _remainMs = widget.timeMs;
    _finished = false;
    if (mounted) setState(() {});
  }

  /// 剩余毫秒
  int getRemainTime() => _remainMs < 0 ? 0 : _remainMs;

  String _two(int v) => v < 10 ? '0$v' : '$v';

  String get _display {
    // 展示向上取整：刚开始显示完整秒
    final seconds = (_remainMs / 1000).ceil().clamp(0, 1 << 31);
    final h = seconds ~/ 3600;
    final m = (seconds % 3600) ~/ 60;
    final s = seconds % 60;
    if (widget.format.contains('HH')) {
      return '${_two(h)}:${_two(m)}:${_two(s)}';
    }
    return '${_two(m)}:${_two(s)}';
  }

  @override
  Widget build(BuildContext context) {
    // 字体的 ascent/descent 度量让文字视觉偏下，整体上移 2px 校正
    return Transform.translate(
      offset: const Offset(0, -2),
      child: Text(
        _display,
        style: widget.textStyle ??
            const TextStyle(
              color: Colors.white,
              fontSize: 12,
              fontWeight: FontWeight.w500,
            ),
      ),
    );
  }
}