import React, { useState } from 'react';
import { Calendar, ChevronDown, Download, RefreshCw } from 'lucide-react';
import { Button } from './ui/button';
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuSeparator,
  DropdownMenuTrigger,
} from './ui/dropdown-menu';

/**
 * AddToCalendarButton Component
 * Universal calendar export button with support for:
 * - Google Calendar (web link)
 * - Microsoft Outlook (web link)
 * - Apple Calendar / Outlook Desktop (webcal:// subscription)
 * - Download .ics file (universal import)
 * - Subscribe to personal feed (auto-sync)
 */
export default function AddToCalendarButton({
  event = null,  // Single event object { id, title, description, start_at, end_at, location }
  showSubscribe = false,  // Show "Subscribe to My Events" option
  variant = "default",  // Button variant: default, outline, ghost
  size = "default"  // Button size: default, sm, lg
}) {
  const [isOpen, setIsOpen] = useState(false);
  const backendUrl = process.env.REACT_APP_BACKEND_URL || 'http://localhost:8000';

  // Format datetime for Google Calendar (YYYYMMDDTHHMMSSZ)
  const formatGoogleDate = (dateString) => {
    const date = new Date(dateString);
    return date.toISOString().replace(/[-:]/g, '').replace(/\.\d{3}/, '');
  };

  // Generate Google Calendar URL
  const getGoogleCalendarUrl = () => {
    if (!event) return null;

    const params = new URLSearchParams({
      action: 'TEMPLATE',
      text: event.title,
      dates: `${formatGoogleDate(event.start_at)}/${formatGoogleDate(event.end_at)}`,
      details: event.description || '',
      location: event.location || '',
    });

    return `https://calendar.google.com/calendar/render?${params.toString()}`;
  };

  // Generate Microsoft Outlook Web URL
  const getOutlookWebUrl = () => {
    if (!event) return null;

    const startDate = new Date(event.start_at).toISOString();
    const endDate = new Date(event.end_at).toISOString();

    const params = new URLSearchParams({
      path: '/calendar/action/compose',
      rru: 'addevent',
      subject: event.title,
      startdt: startDate,
      enddt: endDate,
      body: event.description || '',
      location: event.location || '',
    });

    return `https://outlook.live.com/calendar/0/deeplink/compose?${params.toString()}`;
  };

  // Get .ics download URL
  const getIcsDownloadUrl = () => {
    if (!event) return null;
    return `${backendUrl}/api/events/${event.id}/download.ics`;
  };

  // Get webcal:// subscription URL (for Apple Calendar / Outlook Desktop)
  const getWebcalUrl = () => {
    // Convert http:// to webcal://
    const webcalUrl = backendUrl.replace(/^https?:\/\//, 'webcal://');
    return `${webcalUrl}/api/calendars/subscribe.ics`;
  };

  // Get all events download URL
  const getAllEventsUrl = () => {
    return `${backendUrl}/api/calendars/all-events.ics`;
  };

  // Handle calendar action
  const handleCalendarAction = (action) => {
    setIsOpen(false);

    switch (action) {
      case 'google':
        window.open(getGoogleCalendarUrl(), '_blank');
        break;
      case 'outlook':
        window.open(getOutlookWebUrl(), '_blank');
        break;
      case 'apple':
        window.location.href = getWebcalUrl();
        break;
      case 'download':
        window.open(getIcsDownloadUrl(), '_blank');
        break;
      case 'subscribe':
        window.location.href = getWebcalUrl();
        break;
      case 'all-events':
        window.open(getAllEventsUrl(), '_blank');
        break;
      default:
        break;
    }
  };

  return (
    <DropdownMenu open={isOpen} onOpenChange={setIsOpen}>
      <DropdownMenuTrigger asChild>
        <Button variant={variant} size={size} className="bg-[var(--purple-lavender)] text-white hover:bg-[var(--purple-muted)] rounded-full gap-2 dark:hover:bg-brand-lavender dark:hover:text-brand-dark-lavender">
          <Calendar className="h-4 w-4" />
          Add to Calendar
          <ChevronDown className="h-4 w-4" />
        </Button>
      </DropdownMenuTrigger>

      <DropdownMenuContent align="end" className="w-64">
        {event && (
          <>
            {/* Single Event Export Options */}
            <div className="px-2 py-1.5 text-sm font-semibold text-[var(--purple-ink)]">
              Add This Event
            </div>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('google')}
              className="cursor-pointer"
            >
              <svg className="h-4 w-4 mr-2" viewBox="0 0 24 24" fill="currentColor">
                <path d="M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm-1 17.93c-3.95-.49-7-3.85-7-7.93 0-.62.08-1.21.21-1.79L9 15v1c0 1.1.9 2 2 2v1.93zm6.9-2.54c-.26-.81-1-1.39-1.9-1.39h-1v-3c0-.55-.45-1-1-1H8v-2h2c.55 0 1-.45 1-1V7h2c1.1 0 2-.9 2-2v-.41c2.93 1.19 5 4.06 5 7.41 0 2.08-.8 3.97-2.1 5.39z" />
              </svg>
              Google Calendar
            </DropdownMenuItem>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('outlook')}
              className="cursor-pointer"
            >
              <svg className="h-4 w-4 mr-2" viewBox="0 0 24 24" fill="currentColor">
                <path d="M7 2h14v20H7V2zm7 11c0 2.761-2.239 5-5 5H2c-.552 0-1-.448-1-1s.448-1 1-1h7c1.657 0 3-1.343 3-3V9c0-1.657-1.343-3-3-3H2c-.552 0-1-.448-1-1s.448-1 1-1h7c2.761 0 5 2.239 5 5v4z" />
              </svg>
              Outlook Web
            </DropdownMenuItem>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('apple')}
              className="cursor-pointer"
            >
              <svg className="h-4 w-4 mr-2" viewBox="0 0 24 24" fill="currentColor">
                <path d="M17.05 20.28c-.98.95-2.05.8-3.08.35-1.09-.46-2.09-.48-3.24 0-1.44.62-2.2.44-3.06-.35C2.79 15.25 3.51 7.59 9.05 7.31c1.35.07 2.29.74 3.08.8 1.18-.24 2.31-.93 3.57-.84 1.51.12 2.65.72 3.4 1.8-3.12 1.87-2.38 5.98.48 7.13-.57 1.5-1.31 2.99-2.54 4.09l.01-.01zM12.03 7.25c-.15-2.23 1.66-4.07 3.74-4.25.29 2.58-2.34 4.5-3.74 4.25z" />
              </svg>
              Apple Calendar
            </DropdownMenuItem>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('download')}
              className="cursor-pointer"
            >
              <Download className="h-4 w-4 mr-2" />
              Download .ics File
            </DropdownMenuItem>

            {showSubscribe && <DropdownMenuSeparator />}
          </>
        )}

        {showSubscribe && (
          <>
            {/* Subscription Options */}
            <div className="px-2 py-1.5 text-sm font-semibold text-[var(--purple-ink)]">
              Calendar Feeds
            </div>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('subscribe')}
              className="cursor-pointer"
            >
              <RefreshCw className="h-4 w-4 mr-2" />
              Subscribe to My Events
              <div className="text-xs text-brand-purple  mt-0.5">
                Auto-syncs your RSVP'd events
              </div>
            </DropdownMenuItem>

            <DropdownMenuItem
              onClick={() => handleCalendarAction('all-events')}
              className="cursor-pointer"
            >
              <Download className="h-4 w-4 mr-2" />
              Download All Events
              <div className="text-xs text-brand-purple  mt-0.5">
                One-time import of all upcoming events
              </div>
            </DropdownMenuItem>
          </>
        )}

        {!event && !showSubscribe && (
          <div className="px-2 py-6 text-center text-sm text-brand-purple ">
            No event selected
          </div>
        )}
      </DropdownMenuContent>
    </DropdownMenu>
  );
}