import { useMemo, useState } from 'react';
import { CalendarDays, ChevronLeft, ChevronRight, X } from 'lucide-react';

export type DateRangeValue = {
  start?: string;
  end?: string;
};

type DateRangeInputProps = {
  label?: string;
  value: DateRangeValue;
  onChange: (value: DateRangeValue) => void;
};

const weekDays = ['一', '二', '三', '四', '五', '六', '日'];
const presets = [
  { label: '今天', days: 0 },
  { label: '近7天', days: 6 },
  { label: '近30天', days: 29 },
];

function formatDate(date: Date) {
  const year = date.getFullYear();
  const month = String(date.getMonth() + 1).padStart(2, '0');
  const day = String(date.getDate()).padStart(2, '0');
  return `${year}-${month}-${day}`;
}

function parseDate(value?: string) {
  if (!value) {
    return undefined;
  }

  const [year, month, day] = value.split('-').map(Number);
  return new Date(year, month - 1, day);
}

function getMonthLabel(date: Date) {
  return `${date.getFullYear()}年${date.getMonth() + 1}月`;
}

function isSameDate(left: Date, right?: Date) {
  if (!right) {
    return false;
  }

  return formatDate(left) === formatDate(right);
}

function getCalendarDays(viewDate: Date) {
  const year = viewDate.getFullYear();
  const month = viewDate.getMonth();
  const firstDate = new Date(year, month, 1);
  const firstWeekday = (firstDate.getDay() + 6) % 7;
  const startDate = new Date(year, month, 1 - firstWeekday);

  return Array.from({ length: 42 }, (_, index) => {
    const date = new Date(startDate);
    date.setDate(startDate.getDate() + index);
    return {
      date,
      dateString: formatDate(date),
      inCurrentMonth: date.getMonth() === month,
    };
  });
}

export function DateRangeInput({ label, value, onChange }: DateRangeInputProps) {
  const [open, setOpen] = useState(false);
  const [viewDate, setViewDate] = useState(() => parseDate(value.start) ?? new Date());
  const startDate = parseDate(value.start);
  const endDate = parseDate(value.end);

  const calendarDays = useMemo(() => getCalendarDays(viewDate), [viewDate]);

  const displayValue = useMemo(() => {
    if (value.start && value.end) {
      return `${value.start} 至 ${value.end}`;
    }

    if (value.start) {
      return `${value.start} 至 ...`;
    }

    return '选择提交时间区间';
  }, [value.end, value.start]);

  function moveMonth(offset: number) {
    setViewDate((current) => new Date(current.getFullYear(), current.getMonth() + offset, 1));
  }

  function applyPreset(days: number) {
    const end = new Date();
    const start = new Date();
    start.setDate(end.getDate() - days);
    onChange({ start: formatDate(start), end: formatDate(end) });
    setViewDate(start);
  }

  function selectDate(dateString: string) {
    if (!value.start || value.end) {
      onChange({ start: dateString, end: undefined });
      return;
    }

    if (dateString < value.start) {
      onChange({ start: dateString, end: value.start });
      return;
    }

    onChange({ start: value.start, end: dateString });
  }

  return (
    <div className="ui-field ui-date-range-field">
      {label ? <span className="ui-field__label">{label}</span> : null}
      <button
        className={['ui-date-range-trigger', open ? 'ui-date-range-trigger--open' : '', value.start || value.end ? 'ui-date-range-trigger--filled' : ''].filter(Boolean).join(' ')}
        onClick={() => setOpen((current) => !current)}
        type="button"
      >
        <CalendarDays size={16} />
        <span>{displayValue}</span>
        {value.start || value.end ? (
          <span
            aria-label="清空时间区间"
            className="ui-date-range__clear"
            onClick={(event) => {
              event.stopPropagation();
              onChange({});
            }}
            onKeyDown={(event) => {
              if (event.key === 'Enter' || event.key === ' ') {
                event.preventDefault();
                event.stopPropagation();
                onChange({});
              }
            }}
            role="button"
            tabIndex={0}
          >
            <X size={14} />
          </span>
        ) : null}
      </button>
      {open ? (
        <div className="ui-date-range-popover">
          <div className="ui-date-range-presets">
            {presets.map((item) => (
              <button key={item.label} onClick={() => applyPreset(item.days)} type="button">{item.label}</button>
            ))}
          </div>
          <div className="ui-calendar">
            <div className="ui-calendar__header">
              <button aria-label="上个月" onClick={() => moveMonth(-1)} type="button">
                <ChevronLeft size={16} />
              </button>
              <strong>{getMonthLabel(viewDate)}</strong>
              <button aria-label="下个月" onClick={() => moveMonth(1)} type="button">
                <ChevronRight size={16} />
              </button>
            </div>
            <div className="ui-calendar__weekdays">
              {weekDays.map((day) => <span key={day}>{day}</span>)}
            </div>
            <div className="ui-calendar__grid">
              {calendarDays.map((item) => {
                const isStart = isSameDate(item.date, startDate);
                const isEnd = isSameDate(item.date, endDate);
                const isInRange = Boolean(startDate && endDate && item.date > startDate && item.date < endDate);

                return (
                  <button
                    className={[
                      'ui-calendar__day',
                      item.inCurrentMonth ? '' : 'ui-calendar__day--muted',
                      isStart ? 'ui-calendar__day--start' : '',
                      isEnd ? 'ui-calendar__day--end' : '',
                      isInRange ? 'ui-calendar__day--range' : '',
                    ].filter(Boolean).join(' ')}
                    key={item.dateString}
                    onClick={() => selectDate(item.dateString)}
                    type="button"
                  >
                    {item.date.getDate()}
                  </button>
                );
              })}
            </div>
          </div>
          <div className="ui-date-range-actions">
            <button onClick={() => onChange({})} type="button">清空</button>
            <button disabled={!value.start} onClick={() => setOpen(false)} type="button">确定</button>
          </div>
        </div>
      ) : null}
    </div>
  );
}