import ReactDatePicker from 'react-datepicker';
import { de } from 'date-fns/locale';
import { Calendar as CalendarIcon, Clock } from 'lucide-react';
import { forwardRef } from 'react';
import { createPortal } from 'react-dom';
import 'react-datepicker/dist/react-datepicker.css';

// Renders the calendar popper into document.body so it never affects the form
// layout (prevents the "everything shifts down + auto-scroll" bug).
const PopperContainer = ({ children }) => createPortal(children, document.body);

/**
 * Custom DateTimePicker that reads the app's CSS variables and
 * fully matches whatever theme is active.
 *
 * Props:
 *   value      – ISO datetime string (or '')
 *   onChange   – (isoString) => void
 *   label      – string
 *   required   – bool
 *   minDate    – Date | null
 *   icon       – 'calendar' (default) | 'clock'
 */
export default function DateTimePicker({
  value,
  onChange,
  label,
  required = false,
  minDate = null,
  icon = 'calendar',
}) {
  const selected = value ? new Date(value) : null;

  const handleChange = (date) => {
    if (!date) { onChange(''); return; }
    // Produce local datetime string yyyy-MM-ddTHH:mm
    const y = date.getFullYear();
    const mo = String(date.getMonth() + 1).padStart(2, '0');
    const d = String(date.getDate()).padStart(2, '0');
    const h = String(date.getHours()).padStart(2, '0');
    const mi = String(date.getMinutes()).padStart(2, '0');
    onChange(`${y}-${mo}-${d}T${h}:${mi}`);
  };

  const Icon = icon === 'clock' ? Clock : CalendarIcon;

  return (
    <div className="dtp-wrapper">
      {label && (
        <label className="block text-sm font-medium text-th-text mb-1.5">
          {label}{required && ' *'}
        </label>
      )}
      <div className="dtp-input-wrap">
        <Icon size={15} className="dtp-icon" />
        <ReactDatePicker
          selected={selected}
          onChange={handleChange}
          showTimeSelect
          timeFormat="HH:mm"
          timeIntervals={15}
          dateFormat="dd.MM.yyyy  HH:mm"
          locale={de}
          minDate={minDate}
          required={required}
          popperPlacement="bottom-start"
          popperContainer={PopperContainer}
          popperModifiers={[
            { name: 'offset', options: { offset: [0, 4] } },
            { name: 'preventOverflow', options: { rootBoundary: 'viewport', tether: false, altAxis: true } },
          ]}
          customInput={<CustomInput />}
          calendarClassName="dtp-calendar"
          dayClassName={(date) => 'dtp-day'}
          timeClassName={() => 'dtp-time-item'}
          renderCustomHeader={CalendarHeader}
          wrapperClassName="dtp-dp-wrapper"
        />
      </div>
    </div>
  );
}

// ── Custom Input ─────────────────────────────────────────────────────────────
const CustomInput = forwardRef(({ value, onClick, onClear, ...rest }, ref) => (
  <button
    ref={ref}
    type="button"
    onClick={onClick}
    className="dtp-custom-input"
    {...rest}
  >
    <span className={value ? 'dtp-value' : 'dtp-placeholder'}>
      {value || 'Datum & Uhrzeit wählen …'}
    </span>
  </button>
));
CustomInput.displayName = 'CustomInput';

// ── Custom Header ─────────────────────────────────────────────────────────────
function CalendarHeader({
  date,
  decreaseMonth, increaseMonth,
  prevMonthButtonDisabled, nextMonthButtonDisabled,
}) {
  const label = date.toLocaleString('de', { month: 'long', year: 'numeric' });
  return (
    <div className="dtp-header">
      <button
        type="button"
        onClick={decreaseMonth}
        disabled={prevMonthButtonDisabled}
        className="dtp-nav-btn"
        aria-label="Vorheriger Monat"
      >
        ‹
      </button>
      <span className="dtp-month-label">{label}</span>
      <button
        type="button"
        onClick={increaseMonth}
        disabled={nextMonthButtonDisabled}
        className="dtp-nav-btn"
        aria-label="Nächster Monat"
      >
        ›
      </button>
    </div>
  );
}