'use client';

import { useState, useEffect, useRef } from 'react';
import { ChevronLeft, ChevronRight, Calendar as CalendarIcon, Globe, X } from 'lucide-react';
import {
  gregorianToEthiopian,
  ethiopianToGregorian,
  formatEthiopianDate,
  getDaysInEthiopianMonth,
  ETHIOPIAN_MONTHS,
  type EthiopianDate,
} from '@/lib/ethiopian-calendar';
import { format } from 'date-fns';

interface ModernDatePickerProps {
  value?: Date;
  onChange: (date: Date) => void;
  minDate?: Date;
  maxDate?: Date;
  placeholder?: string;
}

export default function ModernDatePicker({
  value,
  onChange,
  minDate,
  maxDate,
  placeholder = 'Select date',
}: ModernDatePickerProps) {
  const [isOpen, setIsOpen] = useState(false);
  const [isMobileView, setIsMobileView] = useState(false);
  const [calendarType, setCalendarType] = useState<'gregorian' | 'ethiopian'>('gregorian');
  const [viewMonth, setViewMonth] = useState(value?.getMonth() ?? new Date().getMonth());
  const [viewYear, setViewYear] = useState(value?.getFullYear() ?? new Date().getFullYear());

  const initialEthDate = gregorianToEthiopian(value || new Date());
  const [ethViewMonth, setEthViewMonth] = useState(initialEthDate.month);
  const [ethViewYear, setEthViewYear] = useState(initialEthDate.year);
  const containerRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const check = () => setIsMobileView(window.innerWidth < 768);
    check();
    window.addEventListener('resize', check);
    return () => window.removeEventListener('resize', check);
  }, []);

  useEffect(() => {
    if (value) {
      setViewMonth(value.getMonth());
      setViewYear(value.getFullYear());
      const ethDate = gregorianToEthiopian(value);
      setEthViewMonth(ethDate.month);
      setEthViewYear(ethDate.year);
    }
  }, [value]);

  // Lock body scroll when modal is open (both mobile and desktop modal)
  useEffect(() => {
    if (isOpen) {
      document.body.style.overflow = 'hidden';
    } else {
      document.body.style.overflow = '';
    }
    return () => { document.body.style.overflow = ''; };
  }, [isOpen]);

  const toggleCalendarType = () => {
    const newType = calendarType === 'gregorian' ? 'ethiopian' : 'gregorian';
    const ref = value || new Date();
    if (newType === 'ethiopian') {
      const ethDate = gregorianToEthiopian(ref);
      setEthViewMonth(ethDate.month);
      setEthViewYear(ethDate.year);
    } else {
      setViewMonth(ref.getMonth());
      setViewYear(ref.getFullYear());
    }
    setCalendarType(newType);
  };

  const handleDateSelect = (date: Date) => {
    onChange(date);
    setIsOpen(false);
  };

  const handleEthiopianDateSelect = (ethDate: EthiopianDate) => {
    handleDateSelect(ethiopianToGregorian(ethDate));
  };

  const renderGregorianCalendar = () => {
    const daysInMonth = new Date(viewYear, viewMonth + 1, 0).getDate();
    const firstDay = new Date(viewYear, viewMonth, 1).getDay();
    const days: (number | null)[] = Array(firstDay).fill(null);
    for (let d = 1; d <= daysInMonth; d++) days.push(d);
    const monthNames = ['January','February','March','April','May','June','July','August','September','October','November','December'];

    return (
      <div className="p-4">
        <div className="flex items-center justify-between mb-4">
          <button type="button" onClick={() => { if (viewMonth === 0) { setViewMonth(11); setViewYear(y => y - 1); } else setViewMonth(m => m - 1); }} className="p-2 hover:bg-gray-100 dark:hover:bg-gray-700 rounded-lg transition-colors">
            <ChevronLeft className="w-5 h-5 text-gray-600 dark:text-gray-400" />
          </button>
          <span className="font-semibold text-base text-gray-900 dark:text-gray-100">{monthNames[viewMonth]} {viewYear}</span>
          <button type="button" onClick={() => { if (viewMonth === 11) { setViewMonth(0); setViewYear(y => y + 1); } else setViewMonth(m => m + 1); }} className="p-2 hover:bg-gray-100 dark:hover:bg-gray-700 rounded-lg transition-colors">
            <ChevronRight className="w-5 h-5 text-gray-600 dark:text-gray-400" />
          </button>
        </div>
        <div className="grid grid-cols-7 gap-1 mb-2">
          {['Su','Mo','Tu','We','Th','Fr','Sa'].map(d => (
            <div key={d} className="text-center text-xs font-semibold text-gray-400 py-2">{d}</div>
          ))}
        </div>
        <div className="grid grid-cols-7 gap-1">
          {days.map((day, i) => {
            if (day === null) return <div key={`e-${i}`} />;
            const date = new Date(viewYear, viewMonth, day);
            const isSelected = value && date.getDate() === value.getDate() && date.getMonth() === value.getMonth() && date.getFullYear() === value.getFullYear();
            const isToday = date.toDateString() === new Date().toDateString();
            const isDisabled = (minDate && date < new Date(minDate.getFullYear(), minDate.getMonth(), minDate.getDate())) || (maxDate && date > new Date(maxDate.getFullYear(), maxDate.getMonth(), maxDate.getDate()));
            return (
              <button key={day} type="button" onClick={() => !isDisabled && handleDateSelect(date)} disabled={!!isDisabled}
                className={`aspect-square flex items-center justify-center text-sm rounded-lg transition-all
                  ${isSelected ? 'bg-primary text-white font-semibold shadow-md scale-105' : ''}
                  ${isToday && !isSelected ? 'border-2 border-primary text-primary font-semibold' : ''}
                  ${!isSelected && !isToday && !isDisabled ? 'hover:bg-gray-100 dark:hover:bg-gray-700 text-gray-700 dark:text-gray-300' : ''}
                  ${isDisabled ? 'text-gray-300 dark:text-gray-600 cursor-not-allowed' : ''}`}>
                {day}
              </button>
            );
          })}
        </div>
      </div>
    );
  };

  const renderEthiopianCalendar = () => {
    const daysInMonth = getDaysInEthiopianMonth(ethViewYear, ethViewMonth);
    const firstDate = ethiopianToGregorian({ year: ethViewYear, month: ethViewMonth, day: 1 });
    const firstDayOfWeek = firstDate.getDay();
    const daysWithOffset: (number | null)[] = Array(firstDayOfWeek).fill(null);
    for (let d = 1; d <= daysInMonth; d++) daysWithOffset.push(d);
    const monthName = ETHIOPIAN_MONTHS[ethViewMonth - 1] || `Month ${ethViewMonth}`;

    return (
      <div className="p-4">
        <div className="flex items-center justify-between mb-4">
          <button type="button" onClick={() => { if (ethViewMonth === 1) { setEthViewMonth(13); setEthViewYear(y => y - 1); } else setEthViewMonth(m => m - 1); }} className="p-2 hover:bg-gray-100 dark:hover:bg-gray-700 rounded-lg transition-colors">
            <ChevronLeft className="w-5 h-5 text-gray-600 dark:text-gray-400" />
          </button>
          <span className="font-semibold text-base text-gray-900 dark:text-gray-100">{monthName} {ethViewYear}</span>
          <button type="button" onClick={() => { if (ethViewMonth === 13) { setEthViewMonth(1); setEthViewYear(y => y + 1); } else setEthViewMonth(m => m + 1); }} className="p-2 hover:bg-gray-100 dark:hover:bg-gray-700 rounded-lg transition-colors">
            <ChevronRight className="w-5 h-5 text-gray-600 dark:text-gray-400" />
          </button>
        </div>
        <div className="grid grid-cols-7 gap-1 mb-2">
          {['Su','Mo','Tu','We','Th','Fr','Sa'].map(d => (
            <div key={d} className="text-center text-xs font-semibold text-gray-400 py-2">{d}</div>
          ))}
        </div>
        <div className="grid grid-cols-7 gap-1">
          {daysWithOffset.map((day, i) => {
            if (day === null) return <div key={`e-${i}`} />;
            const ethDate: EthiopianDate = { year: ethViewYear, month: ethViewMonth, day };
            const gregDate = ethiopianToGregorian(ethDate);
            const isSelected = value && gregDate.getDate() === value.getDate() && gregDate.getMonth() === value.getMonth() && gregDate.getFullYear() === value.getFullYear();
            const todayEth = gregorianToEthiopian(new Date());
            const isToday = ethDate.day === todayEth.day && ethDate.month === todayEth.month && ethDate.year === todayEth.year;
            let isDisabled = false;
            if (minDate) {
              const [mY, mM, mD] = [minDate.getFullYear(), minDate.getMonth(), minDate.getDate()];
              const [gY, gM, gD] = [gregDate.getFullYear(), gregDate.getMonth(), gregDate.getDate()];
              if (gY < mY || (gY === mY && gM < mM) || (gY === mY && gM === mM && gD < mD)) isDisabled = true;
            }
            if (maxDate && !isDisabled) {
              const [mY, mM, mD] = [maxDate.getFullYear(), maxDate.getMonth(), maxDate.getDate()];
              const [gY, gM, gD] = [gregDate.getFullYear(), gregDate.getMonth(), gregDate.getDate()];
              if (gY > mY || (gY === mY && gM > mM) || (gY === mY && gM === mM && gD > mD)) isDisabled = true;
            }
            return (
              <button key={day} type="button" onClick={() => !isDisabled && handleEthiopianDateSelect(ethDate)} disabled={isDisabled}
                className={`aspect-square flex items-center justify-center text-sm rounded-lg transition-all
                  ${isSelected ? 'bg-primary text-white font-semibold shadow-md scale-105' : ''}
                  ${isToday && !isSelected ? 'border-2 border-primary text-primary font-semibold' : ''}
                  ${!isSelected && !isToday && !isDisabled ? 'hover:bg-gray-100 dark:hover:bg-gray-700 text-gray-700 dark:text-gray-300' : ''}
                  ${isDisabled ? 'text-gray-300 dark:text-gray-600 cursor-not-allowed' : ''}`}>
                {day}
              </button>
            );
          })}
        </div>
      </div>
    );
  };

  const calendarFooter = value && (
    <div className="border-t border-gray-200 dark:border-gray-700 p-3 bg-gray-50 dark:bg-gray-800/60 space-y-1.5">
      <div className="flex items-center justify-between text-xs">
        <span className="text-gray-500 dark:text-gray-400">Gregorian:</span>
        <span className="font-medium text-gray-700 dark:text-gray-300">{format(value, 'MMMM d, yyyy')}</span>
      </div>
      <div className="flex items-center justify-between text-xs">
        <span className="text-gray-500 dark:text-gray-400">Ethiopian:</span>
        <span className="font-medium text-gray-700 dark:text-gray-300">{formatEthiopianDate(gregorianToEthiopian(value))}</span>
      </div>
    </div>
  );

  // Shared modal content (used by both mobile and desktop)
  const modalContent = (
    <div className="flex flex-col h-full">
      {/* Header row: title + close */}
      <div className="flex items-center justify-between px-4 py-4 border-b border-gray-100 dark:border-gray-800 flex-shrink-0">
        <div className="flex items-center gap-2">
          <CalendarIcon className="w-4 h-4 text-primary" />
          <h2 className="text-base font-bold text-gray-900 dark:text-white">Select Date</h2>
        </div>
        <button
          type="button"
          onClick={() => setIsOpen(false)}
          className="w-9 h-9 flex items-center justify-center rounded-full hover:bg-gray-100 dark:hover:bg-gray-800 transition-colors"
        >
          <X className="w-5 h-5 text-gray-500 dark:text-gray-400" />
        </button>
      </div>

      {/* Toggle row: always full-width, clearly visible */}
      <div className="px-4 py-2.5 border-b border-gray-100 dark:border-gray-800 flex-shrink-0">
        <div className="flex rounded-lg overflow-hidden border-2 border-gray-200 dark:border-gray-700">
          <button
            type="button"
            onClick={() => calendarType !== 'gregorian' && toggleCalendarType()}
            className={`flex-1 flex items-center justify-center gap-1.5 py-2 text-xs font-semibold transition-colors ${
              calendarType === 'gregorian'
                ? 'bg-primary text-white'
                : 'bg-white dark:bg-gray-800 text-gray-500 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-gray-700'
            }`}
          >
            <Globe className="w-3.5 h-3.5" />
            Gregorian
          </button>
          <button
            type="button"
            onClick={() => calendarType !== 'ethiopian' && toggleCalendarType()}
            className={`flex-1 flex items-center justify-center gap-1.5 py-2 text-xs font-semibold transition-colors ${
              calendarType === 'ethiopian'
                ? 'bg-primary text-white'
                : 'bg-white dark:bg-gray-800 text-gray-500 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-gray-700'
            }`}
          >
            <Globe className="w-3.5 h-3.5" />
            Ethiopian
          </button>
        </div>
      </div>

      {/* Calendar body */}
      <div className="flex-1 overflow-y-auto">
        {calendarType === 'gregorian' ? renderGregorianCalendar() : renderEthiopianCalendar()}
        {calendarFooter}
      </div>
    </div>
  );

  return (
    <div className="relative" ref={containerRef}>
      {/* Trigger button */}
      <button
        type="button"
        onClick={() => setIsOpen(true)}
        className="w-full px-3.5 py-3.5 border-2 border-gray-200 dark:border-gray-700 rounded-xl focus:outline-none focus:ring-2 focus:ring-primary/30 focus:border-primary text-left flex items-center justify-between bg-white dark:bg-gray-800 hover:border-gray-300 dark:hover:border-gray-600 transition-all group"
      >
        <span className={`text-sm ${value ? 'text-gray-900 dark:text-gray-100 font-medium' : 'text-gray-400'}`}>
          {value ? format(value, 'EEE, MMM d, yyyy') : placeholder}
        </span>
        <CalendarIcon className="w-4 h-4 text-gray-400 group-hover:text-primary transition-colors flex-shrink-0" />
      </button>

      {isOpen && (
        <>

          {/* Mobile: full-screen takeover */}
          {isMobileView ? (
            <div
              className="fixed inset-0 z-[100] bg-white dark:bg-gray-900 flex flex-col"
              style={{ animation: 'mdp-slide-up 0.25s cubic-bezier(0.32,0.72,0,1)' }}
            >
              {modalContent}
            </div>
          ) : (
            /* Desktop: centred modal with backdrop */
            <>
              <div className="fixed inset-0 z-[99] bg-black/40 backdrop-blur-sm" onClick={() => setIsOpen(false)} />
              <div
                className="fixed inset-0 z-[100] flex items-center justify-center p-4 pointer-events-none"
              >
                <div
                  className="bg-white dark:bg-gray-900 rounded-2xl shadow-2xl border border-gray-200 dark:border-gray-700 w-full max-w-sm pointer-events-auto"
                  style={{ animation: 'mdp-scale-in 0.2s cubic-bezier(0.34,1.56,0.64,1)' }}
                >
                  {modalContent}
                </div>
              </div>
            </>
          )}

          <style>{`
            @keyframes mdp-slide-up {
              from { transform: translateY(100%); opacity: 0; }
              to   { transform: translateY(0);    opacity: 1; }
            }
            @keyframes mdp-scale-in {
              from { transform: scale(0.92); opacity: 0; }
              to   { transform: scale(1);    opacity: 1; }
            }
          `}</style>
        </>
      )}
    </div>
  );
}