import { useMemo, useState } from 'react';
import { CalendarDays, ChevronLeft, ChevronRight, Clock3, X } from 'lucide-react';

type DateTimeInputProps = {
  label?: string;
  value: string;
  onChange: (value: string) => void;
  placeholder?: string;
};

const weekDays = ['一', '二', '三', '四', '五', '六', '日'];

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 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,
    };
  });
}

function splitDateTime(value: string) {
  const [date = '', time = ''] = value.split('T');
  return { date, time };
}

export function DateTimeInput({ label, value, onChange, placeholder = '选择定时发送时间' }: DateTimeInputProps) {
  const { date, time } = splitDateTime(value);
  const [open, setOpen] = useState(false);
  const [viewDate, setViewDate] = useState(() => parseDate(date) ?? new Date());
  const calendarDays = useMemo(() => getCalendarDays(viewDate), [viewDate]);

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

  function updateDate(nextDate: string) {
    onChange(`${nextDate}T${time || '09:00'}`);
  }

  function updateTime(nextTime: string) {
    onChange(`${date || formatDate(new Date())}T${nextTime}`);
  }

  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 ? 'ui-date-range-trigger--filled' : ''].filter(Boolean).join(' ')}
        onClick={() => setOpen((current) => !current)}
        type="button"
      >
        <CalendarDays size={16} />
        <span>{value ? `${date} ${time}` : placeholder}</span>
        {value ? (
          <span
            aria-label="清空定时发送时间"
            className="ui-date-range__clear"
            onClick={(event) => {
              event.stopPropagation();
              onChange('');
            }}
            role="button"
            tabIndex={0}
          >
            <X size={14} />
          </span>
        ) : null}
      </button>
      {open ? (
        <div className="ui-date-range-popover ui-date-time-popover">
          <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) => (
                <button
                  className={[
                    'ui-calendar__day',
                    item.inCurrentMonth ? '' : 'ui-calendar__day--muted',
                    item.dateString === date ? 'ui-calendar__day--selected' : '',
                  ].filter(Boolean).join(' ')}
                  key={item.dateString}
                  onClick={() => updateDate(item.dateString)}
                  type="button"
                >
                  {item.date.getDate()}
                </button>
              ))}
            </div>
          </div>
          <label className="ui-time-picker">
            <span><Clock3 size={15} /> 发送时间</span>
            <input onChange={(event) => updateTime(event.target.value)} type="time" value={time || '09:00'} />
          </label>
          <div className="ui-date-range-actions">
            <button onClick={() => onChange('')} type="button">清空</button>
            <button disabled={!value} onClick={() => setOpen(false)} type="button">确定</button>
          </div>
        </div>
      ) : null}
    </div>
  );
}