import 'package:flutter/material.dart';
import 'calendar_utils.dart' show get2Weekdays, addDay, subtractDay, firstDayOfWeek;
import 'day_table_view.dart';

enum PageState {
  previous,
  current,
  next,
}

/// 一周的Days的PageView页面
class WeekPage extends StatefulWidget {
  const WeekPage({
    super.key,
    required this.selectedDate,
    required this.now,
    required this.isAutoSelect,
    this.onChangedSelectedDate,
    this.onChangedPage,
  });

  final DateTime now;
  final DateTime selectedDate;
  final bool isAutoSelect;

  final Function(DateTime)? onChangedSelectedDate; //选择日期变化的监听
  final Function(DateTime date, PageState state)? onChangedPage; //切换日期Page的监听

  final double height = 40 + 40 + 10;

  @override
  State<StatefulWidget> createState() => _WeekPageState();
}

class _WeekPageState extends State<WeekPage> {
  double get height => widget.height;
  final int initialPage = 999;
  List<int> pageCounts = [0, 1, 2];
  int currentPage = 1;
  late DateTime _currentPageDate;
  late DateTime _slectedDate;

  DateTime get now => widget.now;

  DateTime get selectedDate => widget.selectedDate;

  @override
  void initState() {
    super.initState();
    _currentPageDate = selectedDate;
    _slectedDate = selectedDate;
  }

  @override
  Widget build(BuildContext context) {
    return Flexible(
      child: AnimatedSize(
        duration: const Duration(milliseconds: 250),
        curve: Curves.easeInOut,
        alignment: Alignment.topCenter,
        child: SizedBox(
          height: height,
          child: pageViewBuilder(),
        ),
      ),
    );
  }

  //PageView的方式展示不同的星期，每周每一个Page
  Widget pageViewBuilder() {
    final PageController pageController = PageController(initialPage: initialPage);
    return PageView.builder(
      itemBuilder: (context, index) {
        final idx = _getIndex(index);
        return dayTable(idx);
      },
      onPageChanged: onPageChanged,
      controller: pageController,
    );
  }

  //两周的数据
  Widget dayTable(int index) {
    int at = pageCounts[index] - 1;
    final weekdays = get2Weekdays(now, at);
    return DayTableView(
      weekdays: weekdays,
      onSelect: (date) {
        setState(() {
          _slectedDate = date;
        });
        //主动点击之后回调
        widget.onChangedSelectedDate?.call(date);
      },
      selectedDate: _slectedDate,
      currentDate: now,
    );
  }

  //是否需要切换页面的时候自动选中
  void changeSelectedDate(int value) {
    if (_pageState(value) == PageState.next) {
      if (widget.isAutoSelect) {
        _slectedDate = addDay(selectedDate, 14);
        widget.onChangedSelectedDate?.call(_slectedDate);
      }
    } else {
      if (widget.isAutoSelect) {
        _slectedDate = subtractDay(selectedDate, 14);
        widget.onChangedSelectedDate?.call(_slectedDate);
      }
    }
  }

  //当切换页面的时候更新当前页面数据，返回当前页面第一条数据的日期
  void updateCurrentPageDate(int value) {
    final first = firstDayOfWeek(_currentPageDate);

    if (_pageState(value) == PageState.next) {
      _currentPageDate = addDay(first, 14);
      widget.onChangedPage?.call(_currentPageDate, PageState.next);
    } else {
      _currentPageDate = subtractDay(first, 14);
      widget.onChangedPage?.call(_currentPageDate, PageState.previous);
    }
  }

  void onPageChanged(int value) {
    changeSelectedDate(value);
    updateCurrentPageDate(value);

    int currentIndex = _getIndex(value);
    int leftIndex = (currentIndex - 1 < 0) ? pageCounts.length - 1 : currentIndex - 1;
    int rightIndex = (currentIndex + 1 > pageCounts.length - 1) ? 0 : currentIndex + 1;

    pageCounts[leftIndex] = pageCounts[currentIndex] - 1;
    pageCounts[rightIndex] = pageCounts[currentIndex] + 1;

    currentPage = pageCounts[currentIndex];
  }

  int _getIndex(int idx) {
    return (idx + 1) % pageCounts.length;
  }

  PageState _pageState(int idx) {
    final prePage = currentPage;
    final current = pageCounts[_getIndex(idx)];
    return (prePage < current) ? PageState.next : PageState.previous;
  }
}