import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

/// 调用示例：
/// DateTime? picked = await BottomDateTimePicker.show(context);
/// if (picked != null) {
///   print('用户选择的时间：$picked');
/// }
class BottomDateTimePicker {
  static Future<DateTime?> showDate(BuildContext context) {
    return showModalBottomSheet<DateTime>(
      context: context,
      backgroundColor: Colors.white,
      isScrollControlled: true,
      shape: const RoundedRectangleBorder(
        borderRadius: BorderRadius.vertical(top: Radius.circular(12)),
      ),
      builder: (_) => _InlineDateTimePickerContent(),
    );
  }
}

class _InlineDateTimePickerContent extends StatefulWidget {
  @override
  State<_InlineDateTimePickerContent> createState() => _InlineDateTimePickerContentState();
}

class _InlineDateTimePickerContentState extends State<_InlineDateTimePickerContent> {
  // 数据源
  final List<int> years = List.generate(101, (i) => 1970 + i);
  final List<int> months = List.generate(12, (i) => i + 1);
  final List<int> days = List.generate(31, (i) => i + 1);
  final List<int> hours = List.generate(24, (i) => i);
  final List<int> minutes = List.generate(60, (i) => i);

  // Controllers
  late FixedExtentScrollController yearCtrl;
  late FixedExtentScrollController monthCtrl;
  late FixedExtentScrollController dayCtrl;
  late FixedExtentScrollController hourCtrl;
  late FixedExtentScrollController minuteCtrl;

  // 当前选中值
  late int selectedYear;
  late int selectedMonth;
  late int selectedDay;
  late int selectedHour;
  late int selectedMinute;

  @override
  void initState() {
    super.initState();
    final now = DateTime.now();
    selectedYear = now.year;
    selectedMonth = now.month;
    selectedDay = now.day;
    selectedHour = now.hour;
    selectedMinute = now.minute;

    yearCtrl = FixedExtentScrollController(initialItem: years.indexOf(selectedYear));
    monthCtrl = FixedExtentScrollController(initialItem: selectedMonth - 1);
    dayCtrl = FixedExtentScrollController(initialItem: selectedDay - 1);
    hourCtrl = FixedExtentScrollController(initialItem: selectedHour);
    minuteCtrl = FixedExtentScrollController(initialItem: selectedMinute);
  }

  @override
  void dispose() {
    yearCtrl.dispose();
    monthCtrl.dispose();
    dayCtrl.dispose();
    hourCtrl.dispose();
    minuteCtrl.dispose();
    super.dispose();
  }

  void _checkAndClampToNow() {
    final picked = DateTime(selectedYear, selectedMonth, selectedDay, selectedHour, selectedMinute);
    final now = DateTime.now();
    if (picked.isAfter(now)) {
      // 回滚到当前时间
      selectedYear = now.year;
      selectedMonth = now.month;
      selectedDay = now.day;
      selectedHour = now.hour;
      selectedMinute = now.minute;

      // 更新各滚轮位置
      yearCtrl.jumpToItem(years.indexOf(selectedYear));
      monthCtrl.jumpToItem(selectedMonth - 1);
      dayCtrl.jumpToItem(selectedDay - 1);
      hourCtrl.jumpToItem(selectedHour);
      minuteCtrl.jumpToItem(selectedMinute);
    }
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 300,
      child: Column(
        children: [
          // 顶部按钮
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 6),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                TextButton(
                  onPressed: () => Navigator.of(context).pop(),
                  child: const Text("取消", style: TextStyle(color: Colors.grey)),
                ),
                TextButton(
                  onPressed: () {
                    final result = DateTime(
                      selectedYear,
                      selectedMonth,
                      selectedDay,
                      selectedHour,
                      selectedMinute,
                    );
                    Navigator.of(context).pop(result);
                  },
                  child: const Text("确定", style: TextStyle(color: Colors.blue)),
                ),
              ],
            ),
          ),
          const Divider(height: 1),

          // 五列数字滚轮
          Expanded(
            child: Row(
              children: [
                // 年
                _buildPicker(
                  controller: yearCtrl,
                  items: years.map((e) => e.toString()).toList(),
                  onSelected: (idx) {
                    setState(() {
                      selectedYear = years[idx];
                      _checkAndClampToNow();
                    });
                  },
                ),

                // 月
                _buildPicker(
                  controller: monthCtrl,
                  items: months.map((e) => e.toString().padLeft(2, '0')).toList(),
                  onSelected: (idx) {
                    setState(() {
                      selectedMonth = months[idx];
                      _checkAndClampToNow();
                    });
                  },
                ),

                // 日
                _buildPicker(
                  controller: dayCtrl,
                  items: days.map((e) => e.toString().padLeft(2, '0')).toList(),
                  onSelected: (idx) {
                    setState(() {
                      selectedDay = days[idx];
                      _checkAndClampToNow();
                    });
                  },
                ),

                // 时
                _buildPicker(
                  controller: hourCtrl,
                  items: hours.map((e) => e.toString().padLeft(2, '0')).toList(),
                  onSelected: (idx) {
                    setState(() {
                      selectedHour = hours[idx];
                      _checkAndClampToNow();
                    });
                  },
                ),

                // 分
                _buildPicker(
                  controller: minuteCtrl,
                  items: minutes.map((e) => e.toString().padLeft(2, '0')).toList(),
                  onSelected: (idx) {
                    setState(() {
                      selectedMinute = minutes[idx];
                      _checkAndClampToNow();
                    });
                  },
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildPicker({
    required FixedExtentScrollController controller,
    required List<String> items,
    required ValueChanged<int> onSelected,
  }) {
    return Expanded(
      child: CupertinoPicker.builder(
        scrollController: controller,
        itemExtent: 32,
        childCount: items.length,
        onSelectedItemChanged: onSelected,
        itemBuilder: (context, index) {
          return Center(child: Text(items[index]));
        },
      ),
    );
  }
}