// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// ignore_for_file: implementation_imports

import 'dart:math' as math;

import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/src/cupertino/picker.dart';

// Values derived from https://developer.apple.com/design/resources/ and on iOS
// simulators with "Debug View Hierarchy".
const double _kItemExtent = 56.0;
// From the picker's intrinsic content size constraint.
const double _kPickerWidth = 380.0;
const bool _kUseMagnifier = true;
// const double _kMagnification = 2.35 / 2.1;
const double _kMagnification = 1.06;
const double _kDatePickerPadSize = 12.0;
// The density of a date picker is different from a generic picker.
// Eyeballed from iOS.
const double _kSqueeze = 1.25;

const TextStyle _kDefaultPickerTextStyle = TextStyle(
  letterSpacing: -0.83,
);

TextStyle _themeTextStyle(BuildContext context, {bool isValid = true}) {
  return isValid
      ? const TextStyle(color: Colors.black, fontSize: 24)
      : TextStyle(color: Colors.grey[700], fontSize: 22);
}

void _animateColumnControllerToItem(
    FixedExtentScrollController controller, int targetItem) {
  controller.animateToItem(
    targetItem,
    curve: Curves.easeInOut,
    duration: const Duration(milliseconds: 200),
  );
}

const Widget _startSelectionOverlay = CupertinoPickerDefaultSelectionOverlay(
  capEndEdge: false,
  background: Colors.transparent,
);
const Widget _centerSelectionOverlay = CupertinoPickerDefaultSelectionOverlay(
  capStartEdge: false,
  capEndEdge: false,
  background: Colors.transparent,
);
const Widget _endSelectionOverlay = CupertinoPickerDefaultSelectionOverlay(
  capStartEdge: false,
  background: Colors.transparent,
);

// Lays out the date picker based on how much space each single column needs.
//
// Each column is a child of this delegate, indexed from 0 to number of columns - 1.
// Each column will be padded horizontally by 12.0 both left and right.
//
// The picker will be placed in the center, and the leftmost and rightmost
// column will be extended equally to the remaining width.
class _DatePickerLayoutDelegate extends MultiChildLayoutDelegate {
  _DatePickerLayoutDelegate({
    required this.columnWidths,
    required this.textDirectionFactor,
    required this.maxWidth,
  });

  // The list containing widths of all columns.
  final List<double> columnWidths;

  // textDirectionFactor is 1 if text is written left to right, and -1 if right to left.
  final int textDirectionFactor;

  // The max width the children should reach to avoid bending outwards.
  final double maxWidth;

  @override
  void performLayout(Size size) {
    double remainingWidth = maxWidth < size.width ? maxWidth : size.width;

    double currentHorizontalOffset = (size.width - remainingWidth) / 2;

    for (int i = 0; i < columnWidths.length; i++) {
      remainingWidth -= columnWidths[i] + _kDatePickerPadSize * 2;
    }

    for (int i = 0; i < columnWidths.length; i++) {
      final int index =
          textDirectionFactor == 1 ? i : columnWidths.length - i - 1;

      double childWidth = columnWidths[index] + _kDatePickerPadSize * 2;
      if (index == 0 || index == columnWidths.length - 1) {
        childWidth += remainingWidth / 2;
      }

      // We can't actually assert here because it would break things badly for
      // semantics, which will expect that we laid things out here.
      assert(() {
        if (childWidth < 0) {
          FlutterError.reportError(
            FlutterErrorDetails(
              exception: FlutterError(
                'Insufficient horizontal space to render the '
                'CupertinoDatePicker because the parent is too narrow at '
                '${size.width}px.\n'
                'An additional ${-remainingWidth}px is needed to avoid '
                'overlapping columns.',
              ),
            ),
          );
        }
        return true;
      }());
      layoutChild(index,
          BoxConstraints.tight(Size(math.max(0.0, childWidth), size.height)));
      positionChild(index, Offset(currentHorizontalOffset, 0.0));

      currentHorizontalOffset += childWidth;
    }
  }

  @override
  bool shouldRelayout(_DatePickerLayoutDelegate oldDelegate) {
    return columnWidths != oldDelegate.columnWidths ||
        textDirectionFactor != oldDelegate.textDirectionFactor;
  }
}

/// Different display modes of [CupertinoDatePicker].
///
/// See also:
///
///  * [CupertinoDatePicker], the class that implements different display modes
///    of the iOS-style date picker.
///  * [CupertinoPicker], the class that implements a content agnostic spinner UI.
enum CupertinoDatePickerMode {
  /// Mode that shows the date in hour, minute, and (optional) an AM/PM designation.
  /// The AM/PM designation is shown only if [CupertinoDatePicker] does not use 24h format.
  /// Column order is subject to internationalization.
  ///
  /// Example: ` 4 | 14 | PM `.
  time,

  /// Mode that shows the date in month, day of month, and year.
  /// Name of month is spelled in full.
  /// Column order is subject to internationalization.
  ///
  /// Example: ` July | 13 | 2012 `.
  date,

  /// Mode that shows the date as day of the week, month, day of month and
  /// the time in hour, minute, and (optional) an AM/PM designation.
  /// The AM/PM designation is shown only if [CupertinoDatePicker] does not use 24h format.
  /// Column order is subject to internationalization.
  ///
  /// Example: ` Fri Jul 13 | 4 | 14 | PM `
  dateAndTime,
}

// Different types of column in CupertinoDatePicker.
enum _PickerColumnType {
  // Day of month column in date mode.
  dayOfMonth,
  // Month column in date mode.
  month,
  // Year column in date mode.
  year,
}

/// A date picker widget in iOS style.
///
/// There are several modes of the date picker listed in [CupertinoDatePickerMode].
///
/// The class will display its children as consecutive columns. Its children
/// order is based on internationalization, or the [dateOrder] property if specified.
///
/// Example of the picker in date mode:
///
///  * US-English: `| July | 13 | 2012 |`
///  * Vietnamese: `| 13 | Tháng 7 | 2012 |`
///
/// Can be used with [showCupertinoModalPopup] to display the picker modally at
/// the bottom of the screen.
///
/// Sizes itself to its parent and may not render correctly if not given the
/// full screen width. Content texts are shown with
/// [CupertinoTextThemeData.dateTimePickerTextStyle].
///
/// {@tool dartpad}
/// This sample shows how to implement CupertinoDatePicker with different picker modes.
/// We can provide initial dateTime value for the picker to display. When user changes
/// the drag the date or time wheels, the picker will call onDateTimeChanged callback.
///
/// CupertinoDatePicker can be displayed directly on a screen or in a popup.
///
/// ** See code in examples/api/lib/cupertino/date_picker/cupertino_date_picker.0.dart **
/// {@end-tool}
///
/// See also:
///
///  * [CupertinoTimerPicker], the class that implements the iOS-style timer picker.
///  * [CupertinoPicker], the class that implements a content agnostic spinner UI.
///  * <https://developer.apple.com/design/human-interface-guidelines/ios/controls/pickers/>
class VCustomCupertinoDatePicker extends StatefulWidget {
  /// Constructs an iOS style date picker.
  ///
  /// [mode] is one of the mode listed in [CupertinoDatePickerMode] and defaults
  /// to [CupertinoDatePickerMode.dateAndTime].
  ///
  /// [onDateTimeChanged] is the callback called when the selected date or time
  /// changes and must not be null. When in [CupertinoDatePickerMode.time] mode,
  /// the year, month and day will be the same as [initialDateTime]. When in
  /// [CupertinoDatePickerMode.date] mode, this callback will always report the
  /// start time of the currently selected day.
  ///
  /// [initialDateTime] is the initial date time of the picker. Defaults to the
  /// present date and time and must not be null. The present must conform to
  /// the intervals set in [minimumDate], [maximumDate], [minimumYear], and
  /// [maximumYear].
  ///
  /// [minimumDate] is the minimum selectable [DateTime] of the picker. When set
  /// to null, the picker does not limit the minimum [DateTime] the user can pick.
  /// In [CupertinoDatePickerMode.time] mode, [minimumDate] should typically be
  /// on the same date as [initialDateTime], as the picker will not limit the
  /// minimum time the user can pick if it's set to a date earlier than that.
  ///
  /// [maximumDate] is the maximum selectable [DateTime] of the picker. When set
  /// to null, the picker does not limit the maximum [DateTime] the user can pick.
  /// In [CupertinoDatePickerMode.time] mode, [maximumDate] should typically be
  /// on the same date as [initialDateTime], as the picker will not limit the
  /// maximum time the user can pick if it's set to a date later than that.
  ///
  /// [minimumYear] is the minimum year that the picker can be scrolled to in
  /// [CupertinoDatePickerMode.date] mode. Defaults to 1 and must not be null.
  ///
  /// [maximumYear] is the maximum year that the picker can be scrolled to in
  /// [CupertinoDatePickerMode.date] mode. Null if there's no limit.
  ///
  /// [minuteInterval] is the granularity of the minute spinner. Must be a
  /// positive integer factor of 60.
  ///
  /// [use24hFormat] decides whether 24 hour format is used. Defaults to false.
  ///
  /// [dateOrder] determines the order of the columns inside [CupertinoDatePicker] in date mode.
  /// Defaults to the locale's default date format/order.
  VCustomCupertinoDatePicker({
    super.key,
    required this.onDateTimeChanged,
    DateTime? initialDateTime,
    this.minimumDate,
    this.maximumDate,
    this.minimumYear = 1,
    this.maximumYear,
    this.minuteInterval = 1,
    this.backgroundColor,
  })  : initialDateTime = initialDateTime ?? DateTime.now(),
        assert(
          minuteInterval > 0 && 60 % minuteInterval == 0,
          'minute interval is not a positive integer factor of 60',
        ) {
    assert(
      this.initialDateTime.minute % minuteInterval == 0,
      'initial minute is not divisible by minute interval',
    );
  }

  /// The initial date and/or time of the picker. Defaults to the present date
  /// and time and must not be null. The present must conform to the intervals
  /// set in [minimumDate], [maximumDate], [minimumYear], and [maximumYear].
  ///
  /// Changing this value after the initial build will not affect the currently
  /// selected date time.
  final DateTime initialDateTime;

  /// The minimum selectable date that the picker can settle on.
  ///
  /// When non-null, the user can still scroll the picker to [DateTime]s earlier
  /// than [minimumDate], but the [onDateTimeChanged] will not be called on
  /// these [DateTime]s. Once let go, the picker will scroll back to [minimumDate].
  ///
  /// In [CupertinoDatePickerMode.time] mode, a time becomes unselectable if the
  /// [DateTime] produced by combining that particular time and the date part of
  /// [initialDateTime] is earlier than [minimumDate]. So typically [minimumDate]
  /// needs to be set to a [DateTime] that is on the same date as [initialDateTime].
  ///
  /// Defaults to null. When set to null, the picker does not impose a limit on
  /// the earliest [DateTime] the user can select.
  final DateTime? minimumDate;

  /// The maximum selectable date that the picker can settle on.
  ///
  /// When non-null, the user can still scroll the picker to [DateTime]s later
  /// than [maximumDate], but the [onDateTimeChanged] will not be called on
  /// these [DateTime]s. Once let go, the picker will scroll back to [maximumDate].
  ///
  /// In [CupertinoDatePickerMode.time] mode, a time becomes unselectable if the
  /// [DateTime] produced by combining that particular time and the date part of
  /// [initialDateTime] is later than [maximumDate]. So typically [maximumDate]
  /// needs to be set to a [DateTime] that is on the same date as [initialDateTime].
  ///
  /// Defaults to null. When set to null, the picker does not impose a limit on
  /// the latest [DateTime] the user can select.
  final DateTime? maximumDate;

  /// Minimum year that the picker can be scrolled to in
  /// [CupertinoDatePickerMode.date] mode. Defaults to 1 and must not be null.
  final int minimumYear;

  /// Maximum year that the picker can be scrolled to in
  /// [CupertinoDatePickerMode.date] mode. Null if there's no limit.
  final int? maximumYear;

  /// The granularity of the minutes spinner, if it is shown in the current mode.
  /// Must be an integer factor of 60.
  final int minuteInterval;

  /// Callback called when the selected date and/or time changes. If the new
  /// selected [DateTime] is not valid, or is not in the [minimumDate] through
  /// [maximumDate] range, this callback will not be called.
  ///
  /// Must not be null.
  final ValueChanged<DateTime> onDateTimeChanged;

  /// Background color of date picker.
  ///
  /// Defaults to null, which disables background painting entirely.
  final Color? backgroundColor;

  @override
  State<StatefulWidget> createState() =>
      // ignore: no_logic_in_create_state
      _CupertinoDatePickerDateState();

  // Estimate the minimum width that each column needs to layout its content.
  static double _getColumnWidth(
      _PickerColumnType columnType, BuildContext context) {
    switch (columnType) {
      case _PickerColumnType.year:
        return 132;
      case _PickerColumnType.month:
        return 90;
      case _PickerColumnType.dayOfMonth:
        return 110;
      default:
        return 0;
    }
  }
}

typedef _ColumnBuilder = Widget Function(double offAxisFraction,
    TransitionBuilder itemPositioningBuilder, Widget selectionOverlay);

class _CupertinoDatePickerDateState extends State<VCustomCupertinoDatePicker> {
  late int textDirectionFactor;

  // Alignment based on text direction. The variable name is self descriptive,
  // however, when text direction is rtl, alignment is reversed.
  late Alignment alignCenterLeft;
  late Alignment alignCenterRight;

  // The currently selected values of the picker.
  late int selectedDay;
  late int selectedMonth;
  late int selectedYear;

  // The controller of the day picker. There are cases where the selected value
  // of the picker is invalid (e.g. February 30th 2018), and this dayController
  // is responsible for jumping to a valid value.
  late FixedExtentScrollController dayController;
  late FixedExtentScrollController monthController;
  late FixedExtentScrollController yearController;

  bool isDayPickerScrolling = false;
  bool isMonthPickerScrolling = false;
  bool isYearPickerScrolling = false;

  bool get isScrolling =>
      isDayPickerScrolling || isMonthPickerScrolling || isYearPickerScrolling;

  // Estimated width of columns.
  Map<int, double> estimatedColumnWidths = <int, double>{};

  @override
  void initState() {
    super.initState();
    selectedDay = widget.initialDateTime.day;
    selectedMonth = widget.initialDateTime.month;
    selectedYear = widget.initialDateTime.year;

    dayController = FixedExtentScrollController(initialItem: selectedDay - 1);
    monthController =
        FixedExtentScrollController(initialItem: selectedMonth - 1);
    yearController = FixedExtentScrollController(initialItem: selectedYear);

    PaintingBinding.instance.systemFonts.addListener(_handleSystemFontsChange);
  }

  void _handleSystemFontsChange() {
    setState(() {
      // System fonts change might cause the text layout width to change.
      _refreshEstimatedColumnWidths();
    });
  }

  @override
  void dispose() {
    dayController.dispose();
    monthController.dispose();
    yearController.dispose();

    PaintingBinding.instance.systemFonts
        .removeListener(_handleSystemFontsChange);
    super.dispose();
  }

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

    textDirectionFactor =
        Directionality.of(context) == TextDirection.ltr ? 1 : -1;

    alignCenterLeft =
        textDirectionFactor == 1 ? Alignment.centerLeft : Alignment.centerRight;
    alignCenterRight =
        textDirectionFactor == 1 ? Alignment.centerRight : Alignment.centerLeft;

    _refreshEstimatedColumnWidths();
  }

  void _refreshEstimatedColumnWidths() {
    estimatedColumnWidths[_PickerColumnType.dayOfMonth.index] =
        VCustomCupertinoDatePicker._getColumnWidth(
            _PickerColumnType.dayOfMonth, context);
    estimatedColumnWidths[_PickerColumnType.month.index] =
        VCustomCupertinoDatePicker._getColumnWidth(
            _PickerColumnType.month, context);
    estimatedColumnWidths[_PickerColumnType.year.index] =
        VCustomCupertinoDatePicker._getColumnWidth(
            _PickerColumnType.year, context);
  }

  // The DateTime of the last day of a given month in a given year.
  // Let `DateTime` handle the year/month overflow.
  DateTime _lastDayInMonth(int year, int month) => DateTime(year, month + 1, 0);

  Widget _buildDayPicker(double offAxisFraction,
      TransitionBuilder itemPositioningBuilder, Widget selectionOverlay) {
    final int daysInCurrentMonth =
        _lastDayInMonth(selectedYear, selectedMonth).day;
    return NotificationListener<ScrollNotification>(
      onNotification: (ScrollNotification notification) {
        if (notification is ScrollStartNotification) {
          isDayPickerScrolling = true;
        } else if (notification is ScrollEndNotification) {
          isDayPickerScrolling = false;
          _pickerDidStopScrolling();
        }

        return false;
      },
      child: CupertinoPicker(
        scrollController: dayController,
        // offAxisFraction: offAxisFraction,
        itemExtent: _kItemExtent,
        useMagnifier: _kUseMagnifier,
        magnification: _kMagnification,
        backgroundColor: widget.backgroundColor,
        squeeze: _kSqueeze,
        onSelectedItemChanged: (int index) {
          selectedDay = index + 1;
          if (_isCurrentDateValid) {
            widget.onDateTimeChanged(
                DateTime(selectedYear, selectedMonth, selectedDay));
          }
        },
        looping: true,
        selectionOverlay: selectionOverlay,
        children: List<Widget>.generate(31, (int index) {
          final int day = index + 1;

          return itemPositioningBuilder(
            context,
            Text(
              "$day日",
              style:
                  _themeTextStyle(context, isValid: day <= daysInCurrentMonth),
            ),
          );
        }),
      ),
    );
  }

  Widget _buildMonthPicker(double offAxisFraction,
      TransitionBuilder itemPositioningBuilder, Widget selectionOverlay) {
    return NotificationListener<ScrollNotification>(
      onNotification: (ScrollNotification notification) {
        if (notification is ScrollStartNotification) {
          isMonthPickerScrolling = true;
        } else if (notification is ScrollEndNotification) {
          isMonthPickerScrolling = false;
          _pickerDidStopScrolling();
        }

        return false;
      },
      child: CupertinoPicker(
        scrollController: monthController,
        // offAxisFraction: offAxisFraction,
        itemExtent: _kItemExtent,
        useMagnifier: _kUseMagnifier,
        magnification: _kMagnification,
        backgroundColor: widget.backgroundColor,
        squeeze: _kSqueeze,
        onSelectedItemChanged: (int index) {
          selectedMonth = index + 1;
          if (_isCurrentDateValid) {
            widget.onDateTimeChanged(
                DateTime(selectedYear, selectedMonth, selectedDay));
          }
        },
        looping: true,
        selectionOverlay: selectionOverlay,
        children: List<Widget>.generate(12, (int index) {
          final int month = index + 1;
          final bool isInvalidMonth =
              (widget.minimumDate?.year == selectedYear &&
                      widget.minimumDate!.month > month) ||
                  (widget.maximumDate?.year == selectedYear &&
                      widget.maximumDate!.month < month);

          return itemPositioningBuilder(
            context,
            Text(
              "$month月",
              style: _themeTextStyle(context, isValid: !isInvalidMonth),
            ),
          );
        }),
      ),
    );
  }

  Widget _buildYearPicker(double offAxisFraction,
      TransitionBuilder itemPositioningBuilder, Widget selectionOverlay) {
    return NotificationListener<ScrollNotification>(
      onNotification: (ScrollNotification notification) {
        if (notification is ScrollStartNotification) {
          isYearPickerScrolling = true;
        } else if (notification is ScrollEndNotification) {
          isYearPickerScrolling = false;
          _pickerDidStopScrolling();
        }

        return false;
      },
      child: CupertinoPicker.builder(
        scrollController: yearController,
        itemExtent: _kItemExtent,
        // offAxisFraction: offAxisFraction,
        useMagnifier: _kUseMagnifier,
        magnification: _kMagnification,
        backgroundColor: widget.backgroundColor,
        onSelectedItemChanged: (int index) {
          selectedYear = index;
          if (_isCurrentDateValid) {
            widget.onDateTimeChanged(
                DateTime(selectedYear, selectedMonth, selectedDay));
          }
        },
        itemBuilder: (BuildContext context, int year) {
          if (year < widget.minimumYear) {
            return null;
          }

          if (widget.maximumYear != null && year > widget.maximumYear!) {
            return null;
          }

          final bool isValidYear = (widget.minimumDate == null ||
                  widget.minimumDate!.year <= year) &&
              (widget.maximumDate == null || widget.maximumDate!.year >= year);

          return itemPositioningBuilder(
            context,
            Text(
              "$year年",
              style: _themeTextStyle(context, isValid: isValidYear),
            ),
          );
        },
        selectionOverlay: selectionOverlay,
      ),
    );
  }

  bool get _isCurrentDateValid {
    // The current date selection represents a range [minSelectedData, maxSelectDate].
    final DateTime minSelectedDate =
        DateTime(selectedYear, selectedMonth, selectedDay);
    final DateTime maxSelectedDate =
        DateTime(selectedYear, selectedMonth, selectedDay + 1);

    final bool minCheck = widget.minimumDate?.isBefore(maxSelectedDate) ?? true;
    final bool maxCheck =
        widget.maximumDate?.isBefore(minSelectedDate) ?? false;

    return minCheck && !maxCheck && minSelectedDate.day == selectedDay;
  }

  // One or more pickers have just stopped scrolling.
  void _pickerDidStopScrolling() {
    // Call setState to update the greyed out days/months/years, as the currently
    // selected year/month may have changed.
    setState(() {});

    if (isScrolling) {
      return;
    }

    // Whenever scrolling lands on an invalid entry, the picker
    // automatically scrolls to a valid one.
    final DateTime minSelectDate =
        DateTime(selectedYear, selectedMonth, selectedDay);
    final DateTime maxSelectDate =
        DateTime(selectedYear, selectedMonth, selectedDay + 1);

    final bool minCheck = widget.minimumDate?.isBefore(maxSelectDate) ?? true;
    final bool maxCheck = widget.maximumDate?.isBefore(minSelectDate) ?? false;

    if (!minCheck || maxCheck) {
      // We have minCheck === !maxCheck.
      final DateTime targetDate =
          minCheck ? widget.maximumDate! : widget.minimumDate!;
      _scrollToDate(targetDate);
      return;
    }

    // Some months have less days (e.g. February). Go to the last day of that month
    // if the selectedDay exceeds the maximum.
    if (minSelectDate.day != selectedDay) {
      final DateTime lastDay = _lastDayInMonth(selectedYear, selectedMonth);
      _scrollToDate(lastDay);
    }
  }

  void _scrollToDate(DateTime newDate) {
    SchedulerBinding.instance.addPostFrameCallback((Duration timestamp) {
      if (selectedYear != newDate.year) {
        _animateColumnControllerToItem(yearController, newDate.year);
      }

      if (selectedMonth != newDate.month) {
        _animateColumnControllerToItem(monthController, newDate.month - 1);
      }

      if (selectedDay != newDate.day) {
        _animateColumnControllerToItem(dayController, newDate.day - 1);
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    final List<_ColumnBuilder> pickerBuilders = <_ColumnBuilder>[
      _buildYearPicker,
      _buildMonthPicker,
      _buildDayPicker,
    ];
    final List<double> columnWidths = <double>[
      estimatedColumnWidths[_PickerColumnType.year.index]!,
      estimatedColumnWidths[_PickerColumnType.month.index]!,
      estimatedColumnWidths[_PickerColumnType.dayOfMonth.index]!,
    ];

    final List<Widget> pickers = <Widget>[];
    double totalColumnWidths = 4 * _kDatePickerPadSize;

    for (int i = 0; i < columnWidths.length; i++) {
      final double offAxisFraction = (i - 1) * 0.3 * textDirectionFactor;

      EdgeInsets padding = const EdgeInsets.only(right: _kDatePickerPadSize);
      if (textDirectionFactor == -1) {
        padding = const EdgeInsets.only(left: _kDatePickerPadSize);
      }

      Widget selectionOverlay = _centerSelectionOverlay;
      if (i == 0) {
        selectionOverlay = _startSelectionOverlay;
      } else if (i == columnWidths.length - 1) {
        selectionOverlay = _endSelectionOverlay;
      }

      totalColumnWidths += columnWidths[i] + (2 * _kDatePickerPadSize);

      pickers.add(LayoutId(
        id: i,
        child: pickerBuilders[i](
          offAxisFraction,
          (BuildContext context, Widget? child) {
            return Container(
              alignment: i == columnWidths.length - 1
                  ? alignCenterLeft
                  : alignCenterRight,
              padding: i == 0 ? null : padding,
              child: Container(
                alignment: i == 0 ? alignCenterLeft : alignCenterRight,
                width: columnWidths[i] + _kDatePickerPadSize,
                child: child,
              ),
            );
          },
          selectionOverlay,
        ),
      ));
    }

    final double maxPickerWidth =
        totalColumnWidths > _kPickerWidth ? totalColumnWidths : _kPickerWidth;

    return MediaQuery(
      data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0),
      child: DefaultTextStyle.merge(
        style: _kDefaultPickerTextStyle,
        child: CustomMultiChildLayout(
          delegate: _DatePickerLayoutDelegate(
            columnWidths: columnWidths,
            textDirectionFactor: textDirectionFactor,
            maxWidth: maxPickerWidth,
          ),
          children: pickers,
        ),
      ),
    );
  }
}