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

/// 调用示例：
/// DateTime? picked = await BottomDateTimePicker.showDate(
///   context,
///   allowFuture: true,  // 添加此参数允许选择未来时间
///   minTimeStr: '2025-08-20 08:30', // 可选：不允许选择早于此时间
/// );
/// if (picked != null) {
///   print('用户选择的时间：$picked');
/// }
class BottomDateTimePicker {
  static Future<DateTime?> showDate(
      BuildContext context, {
        bool allowFuture = false,
        String? minTimeStr, // 新增：可选起始时间格式 'yyyy-MM-dd HH:mm'
      }) {
    return showModalBottomSheet<DateTime>(
      context: context,
      backgroundColor: Colors.white,
      isScrollControlled: true,
      shape: const RoundedRectangleBorder(
        borderRadius: BorderRadius.vertical(top: Radius.circular(12)),
      ),
      builder: (_) => _InlineDateTimePickerContent(
        allowFuture: allowFuture,
        minTimeStr: minTimeStr,
      ),
    );
  }
}

class _InlineDateTimePickerContent extends StatefulWidget {
  final bool allowFuture; // 允许未来
  final String? minTimeStr; // 新增：最小允许时间字符串 'yyyy-MM-dd HH:mm'

  const _InlineDateTimePickerContent({
    Key? key,
    this.allowFuture = false,
    this.minTimeStr,
  }) : super(key: key);

  @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> hours = List.generate(24, (i) => i);
  final List<int> minutes = List.generate(60, (i) => i);

  // 动态天数列表（根据年月变化）
  late List<int> days;

  // 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;

  DateTime? _minTime; // 解析后的最小允许时间（如果有）

  @override
  void initState() {
    super.initState();

    // 解析 minTimeStr（若提供）
    _minTime = _parseMinTime(widget.minTimeStr);

    // 选择初始时间：取 DateTime.now() 与 _minTime 的较大者（确保初始选中合法）
    final now = DateTime.now();
    DateTime initial = now;
    if (_minTime != null && _minTime!.isAfter(initial)) {
      initial = _minTime!;
    }

    selectedYear = initial.year;
    selectedMonth = initial.month;
    selectedDay = initial.day;
    selectedHour = initial.hour;
    selectedMinute = initial.minute;

    // 初始化天数列表
    days = _getDaysInMonth(selectedYear, selectedMonth);

    // controllers 初始项索引需在范围内
    yearCtrl = FixedExtentScrollController(
        initialItem: years.indexOf(selectedYear).clamp(0, years.length - 1));
    monthCtrl = FixedExtentScrollController(initialItem: (selectedMonth - 1).clamp(0, months.length - 1));
    dayCtrl = FixedExtentScrollController(initialItem: (selectedDay - 1).clamp(0, days.length - 1));
    hourCtrl = FixedExtentScrollController(initialItem: selectedHour.clamp(0, hours.length - 1));
    minuteCtrl = FixedExtentScrollController(initialItem: selectedMinute.clamp(0, minutes.length - 1));

    // 如果初始时间小于 minTime（理论上不会，因为我们取了较大者），再修正一次
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _enforceConstraintsAndUpdateControllers();
    });
  }

  // 根据年月获取当月天数
  List<int> _getDaysInMonth(int year, int month) {
    final lastDay = DateUtils.getDaysInMonth(year, month);
    return List.generate(lastDay, (i) => i + 1);
  }

  // 解析 'yyyy-MM-dd HH:mm' 返回 DateTime 或 null
  DateTime? _parseMinTime(String? s) {
    if (s == null || s.trim().isEmpty) return null;
    try {
      final trimmed = s.trim();
      final parts = trimmed.split(' ');
      final dateParts = parts[0].split('-').map((e) => int.parse(e)).toList();
      final timeParts = (parts.length > 1)
          ? parts[1].split(':').map((e) => int.parse(e)).toList()
          : [0, 0];
      final year = dateParts[0];
      final month = dateParts[1];
      final day = dateParts[2];
      final hour = (timeParts.isNotEmpty) ? timeParts[0] : 0;
      final minute = (timeParts.length > 1) ? timeParts[1] : 0;
      return DateTime(year, month, day, hour, minute);
    } catch (e) {
      // 解析失败则忽略
      debugPrint('parseMinTime failed for "$s": $e');
      return null;
    }
  }

  // 更新天数列表并调整选中日期
  void _updateDays({bool jumpDay = true}) {
    final newDays = _getDaysInMonth(selectedYear, selectedMonth);
    final isDayValid = selectedDay <= newDays.length;

    setState(() {
      days = newDays;
      if (!isDayValid) {
        selectedDay = newDays.last;
        if (jumpDay) dayCtrl.jumpToItem(selectedDay - 1);
      }
    });
  }

  // 检查并限制时间：
  // 1) 优先检查 _minTime（如果存在），不允许早于 _minTime
  // 2) 如果没有 _minTime，则根据 allowFuture 决定是否限制到 now
  // 注意：_minTime 优先级高于 allowFuture（如果 _minTime 在未来，会选择 _minTime）
  void _enforceConstraintsAndUpdateControllers() {
    final picked = DateTime(selectedYear, selectedMonth, selectedDay, selectedHour, selectedMinute);

    // 1) 最小时间约束（优先）
    if (_minTime != null && picked.isBefore(_minTime!)) {
      final m = _minTime!;
      selectedYear = m.year;
      selectedMonth = m.month;
      selectedDay = m.day;
      selectedHour = m.hour;
      selectedMinute = m.minute;

      // 更新天数列表与控制器索引
      _updateDays(jumpDay: false);
      yearCtrl.jumpToItem(years.indexOf(selectedYear));
      monthCtrl.jumpToItem(selectedMonth - 1);
      dayCtrl.jumpToItem(selectedDay - 1);
      hourCtrl.jumpToItem(selectedHour);
      minuteCtrl.jumpToItem(selectedMinute);
      return;
    }

    // 2) 禁止选择未来（当 allowFuture == false 且没有 minTime 或 minTime <= now）
    if (!widget.allowFuture) {
      final now = DateTime.now();
      // 如果 minTime 存在并大于 now，我们已在上面处理（minTime 优先），所以这里处理的是普通情况
      if (picked.isAfter(now)) {
        selectedYear = now.year;
        selectedMonth = now.month;
        selectedDay = now.day;
        selectedHour = now.hour;
        selectedMinute = now.minute;

        _updateDays(jumpDay: false);
        yearCtrl.jumpToItem(years.indexOf(selectedYear));
        monthCtrl.jumpToItem(selectedMonth - 1);
        dayCtrl.jumpToItem(selectedDay - 1);
        hourCtrl.jumpToItem(selectedHour);
        minuteCtrl.jumpToItem(selectedMinute);
        return;
      }
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 330,
      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];
                      _updateDays();
                      _enforceConstraintsAndUpdateControllers();
                    });
                  },
                ),

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

                // 日
                _buildPicker(
                  controller: dayCtrl,
                  items: days.map((e) => e.toString().padLeft(2, '0')).toList(),
                  onSelected: (idx) {
                    setState(() {
                      // 防护：idx 可能超出当前 days 长度（极小概率）
                      final safeIdx = idx.clamp(0, days.length - 1);
                      selectedDay = days[safeIdx];
                      _enforceConstraintsAndUpdateControllers();
                    });
                  },
                ),

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

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

  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]));
        },
      ),
    );
  }
}