import 'package:flutter/material.dart';

import '../core/theme/context_tokens.dart';
import '../core/theme/app_tokens.dart';
import '../core/theme/app_dims.g.dart';
import '../core/utils/dialog_util.dart';
import '../core/theme/app_fonts.dart';

/// 年/月/日 滚轮日期选择面板（对齐原型单一真源 .wheel-pop / datewheel.js）。
/// 三列纯数字（年 4 位、月/日补零两位，等宽字体），中间高亮带 = .wheel-center，
/// 居中项为 primary 加粗 16px；底部「今天」+「确定」，无取消（点外部取消）。
///
/// 本体是自包含的 248px 卡片（Material 描边+阴影），既可放进锚定浮层（单据/生产日期，
/// 挂在字段下方，对齐原型 datewheel.js 的 pop 定位），也可放进居中弹窗（范围选择）。
/// 「确定」时回调 [onCommit]；「今天」仅在面板内滚动到今天，不提交。
class WheelDatePanel extends StatefulWidget {
  final DateTime initial;
  final ValueChanged<DateTime> onCommit;

  /// 可选标题（范围选择用「起始/结束日期」区分）；空则不渲染（对齐原型无标题）。
  final String title;

  const WheelDatePanel({
    super.key,
    required this.initial,
    required this.onCommit,
    this.title = '',
  });

  @override
  State<WheelDatePanel> createState() => _WheelDatePanelState();
}

const double _kItem = 36; // .wheel-item 行高
const double _kColsH = 180; // .wheel-cols 高度（5 行）
const double _kWidth = 248; // .wheel-pop 宽度

String _pad2(int n) => n.toString().padLeft(2, '0');
int _daysIn(int y, int m) => DateTime(y, m + 1, 0).day; // m: 1-12

class _WheelDatePanelState extends State<WheelDatePanel> {
  late final List<int> _years; // now-15 .. now+2（对齐 datewheel.js）
  late int _yIdx, _mIdx, _dIdx;
  late final FixedExtentScrollController _yCtrl, _mCtrl, _dCtrl;

  int get _year => _years[_yIdx];
  int get _month => _mIdx + 1;

  @override
  void initState() {
    super.initState();
    final now = DateTime.now();
    _years = [for (var y = now.year - 15; y <= now.year + 2; y++) y];
    final v = widget.initial;
    _yIdx = _years.indexOf(v.year);
    if (_yIdx < 0) _yIdx = _years.indexOf(now.year);
    if (_yIdx < 0) _yIdx = 0;
    _mIdx = (v.month - 1).clamp(0, 11);
    _dIdx = (v.day - 1).clamp(0, _daysIn(v.year, v.month) - 1);
    _yCtrl = FixedExtentScrollController(initialItem: _yIdx);
    _mCtrl = FixedExtentScrollController(initialItem: _mIdx);
    _dCtrl = FixedExtentScrollController(initialItem: _dIdx);
  }

  @override
  void dispose() {
    _yCtrl.dispose();
    _mCtrl.dispose();
    _dCtrl.dispose();
    super.dispose();
  }

  // 年/月变化后重算当月天数，超界则回夹并吸附。
  void _onYearOrMonth() {
    final n = _daysIn(_year, _month);
    if (_dIdx > n - 1) {
      _dIdx = n - 1;
      _dCtrl.jumpToItem(_dIdx);
    }
    setState(() {});
  }

  void _goToday() {
    final now = DateTime.now();
    final yi = _years.indexOf(now.year);
    if (yi >= 0) _yIdx = yi;
    _mIdx = now.month - 1;
    _dIdx = now.day - 1;
    const d = Duration(milliseconds: 250);
    _yCtrl.animateToItem(_yIdx, duration: d, curve: Curves.easeOut);
    _mCtrl.animateToItem(_mIdx, duration: d, curve: Curves.easeOut);
    _dCtrl.animateToItem(_dIdx, duration: d, curve: Curves.easeOut);
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    final t = context.tokens;
    final days = _daysIn(_year, _month);
    return Material(
      color: t.surface,
      elevation: 6,
      borderRadius: BorderRadius.circular(AppDims.rMd),
      child: Container(
        width: _kWidth,
        padding: const EdgeInsets.all(8),
        decoration: BoxDecoration(
          border: Border.all(color: t.border),
          borderRadius: BorderRadius.circular(AppDims.rMd),
        ),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            if (widget.title.isNotEmpty)
              Padding(
                padding: const EdgeInsets.fromLTRB(4, 2, 4, 8),
                child: Align(
                  alignment: Alignment.centerLeft,
                  child: Text(widget.title,
                      style: TextStyle(
                          fontSize: AppDims.fsTitle,
                          fontWeight: FontWeight.w600,
                          color: t.heading)),
                ),
              ),
            // 三列滚轮 + 中间高亮带
            SizedBox(
              height: _kColsH,
              child: Stack(
                children: [
                  Positioned(
                    left: 4,
                    right: 4,
                    top: (_kColsH - _kItem) / 2,
                    height: _kItem,
                    child: IgnorePointer(
                      child: Container(
                        decoration: BoxDecoration(
                          color: t.bg,
                          borderRadius: BorderRadius.circular(AppDims.rMd),
                          border: Border(
                            top: BorderSide(color: t.border),
                            bottom: BorderSide(color: t.border),
                          ),
                        ),
                      ),
                    ),
                  ),
                  Row(
                    children: [
                      _col(t, _yCtrl, _years.length,
                          (i) => _years[i].toString(), _yIdx, (i) {
                        _yIdx = i;
                        _onYearOrMonth();
                      }),
                      _col(t, _mCtrl, 12, (i) => _pad2(i + 1), _mIdx, (i) {
                        _mIdx = i;
                        _onYearOrMonth();
                      }),
                      _col(t, _dCtrl, days, (i) => _pad2(i + 1), _dIdx,
                          (i) => setState(() => _dIdx = i)),
                    ],
                  ),
                ],
              ),
            ),
            // 底栏：今天（左） / 确定（右，无取消，点外部取消）
            Container(
              margin: const EdgeInsets.only(top: 6),
              padding: const EdgeInsets.fromLTRB(4, 8, 4, 2),
              decoration: BoxDecoration(
                border: Border(top: BorderSide(color: t.borderSubtle)),
              ),
              child: Row(
                children: [
                  InkWell(
                    onTap: _goToday,
                    borderRadius: BorderRadius.circular(AppDims.rSm),
                    child: Padding(
                      padding: const EdgeInsets.symmetric(
                          horizontal: 10, vertical: 4),
                      child: Text('今天',
                          style: TextStyle(
                              fontSize: AppDims.fsSm, color: t.muted)),
                    ),
                  ),
                  const Spacer(),
                  InkWell(
                    onTap: () =>
                        widget.onCommit(DateTime(_year, _month, _dIdx + 1)),
                    borderRadius: BorderRadius.circular(AppDims.rSm),
                    child: Container(
                      padding: const EdgeInsets.symmetric(
                          horizontal: 16, vertical: 5),
                      decoration: BoxDecoration(
                        color: t.primary,
                        borderRadius: BorderRadius.circular(AppDims.rSm),
                      ),
                      child: Text('确定',
                          style: TextStyle(
                              fontSize: AppDims.fsSm,
                              color: t.onPrimary,
                              fontWeight: FontWeight.w600)),
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _col(
    AppTokens t,
    FixedExtentScrollController ctrl,
    int count,
    String Function(int) label,
    int selIdx,
    ValueChanged<int> onSel,
  ) {
    return Expanded(
      child: ListWheelScrollView.useDelegate(
        controller: ctrl,
        itemExtent: _kItem,
        physics: const FixedExtentScrollPhysics(),
        diameterRatio: 100, // 近似平面，去掉滚轮弧度
        perspective: 0.0001,
        onSelectedItemChanged: onSel,
        childDelegate: ListWheelChildBuilderDelegate(
          childCount: count,
          builder: (c, i) {
            final on = i == selIdx;
            return Center(
              child: Text(
                label(i),
                style: TextStyle(
                  fontFamily: AppFonts.mono,
                  fontFamilyFallback: AppFonts.monoFallback,
                  fontSize: on ? 16 : AppDims.fsBody,
                  fontWeight: on ? FontWeight.w700 : FontWeight.w400,
                  color: on ? t.primary : t.muted,
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

/// 居中弹窗形式（范围选择用）。锚定字段的用法见 DsDateCell（直接嵌 WheelDatePanel 到浮层）。
Future<DateTime?> showWheelDatePicker(
  BuildContext context, {
  DateTime? initial,
  String title = '',
}) {
  return showAppDialog<DateTime>(
    context: context,
    builder: (dctx) => Align(
      alignment: Alignment.center,
      child: WheelDatePanel(
        initial: initial ?? DateTime.now(),
        title: title,
        onCommit: (d) => Navigator.of(dctx).pop(d),
      ),
    ),
  );
}

/// 范围选择：先选起始日、再选结束日；任一取消则返回 null。
Future<DateTimeRange?> showWheelDateRange(
  BuildContext context, {
  DateTimeRange? initial,
}) async {
  final start = await showWheelDatePicker(context,
      initial: initial?.start, title: '起始日期');
  if (start == null || !context.mounted) return null;
  final end = await showWheelDatePicker(context,
      initial: initial?.end ?? start, title: '结束日期');
  if (end == null) return null;
  return end.isBefore(start)
      ? DateTimeRange(start: end, end: start)
      : DateTimeRange(start: start, end: end);
}