import React, { useState, useEffect, useCallback } from 'react';
import { useNavigate } from 'react-router-dom';
import { Button } from '@/components/ui/button';
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuLabel,
  DropdownMenuSeparator,
  DropdownMenuTrigger,
} from '@/components/ui/dropdown-menu';
import { ScrollArea } from '@/components/ui/scroll-area';
import {
  Bell,
  MessageSquare,
  DollarSign,
  CheckCircle2,
  XCircle,
  AlertTriangle,
  Star,
  Loader2,
  CheckCheck,
} from 'lucide-react';
import { useAuth } from '@/contexts/AuthContext';
import { supabase } from '@/lib/supabase';

interface Notification {
  id: string;
  user_id: string;
  type: string;
  title: string;
  message: string;
  reference_type?: string;
  reference_id?: string;
  is_read: boolean;
  created_at: string;
}

export function NotificationBell() {
  const navigate = useNavigate();
  const { user } = useAuth();
  const [notifications, setNotifications] = useState<Notification[]>([]);
  const [unreadCount, setUnreadCount] = useState(0);
  const [loading, setLoading] = useState(true);
  const [isOpen, setIsOpen] = useState(false);

  // Fetch notifications
  const fetchNotifications = useCallback(async () => {
    if (!user) return;

    try {
      const { data, error } = await supabase
        .from('p2p_notifications')
        .select('*')
        .eq('user_id', user.id)
        .order('created_at', { ascending: false })
        .limit(20);

      if (error) throw error;

      setNotifications(data || []);
      setUnreadCount(data?.filter(n => !n.is_read).length || 0);
    } catch (error) {
      console.error('Fetch notifications error:', error);
    } finally {
      setLoading(false);
    }
  }, [user]);

  // Initial fetch
  useEffect(() => {
    fetchNotifications();
  }, [fetchNotifications]);

  // Real-time subscription
  useEffect(() => {
    if (!user) return;

    const channel = supabase
      .channel(`notifications-${user.id}`)
      .on(
        'postgres_changes',
        {
          event: 'INSERT',
          schema: 'public',
          table: 'p2p_notifications',
          filter: `user_id=eq.${user.id}`,
        },
        (payload) => {
          const newNotif = payload.new as Notification;
          setNotifications(prev => [newNotif, ...prev.slice(0, 19)]);
          setUnreadCount(prev => prev + 1);
        }
      )
      .subscribe();

    return () => {
      supabase.removeChannel(channel);
    };
  }, [user]);

  // Mark as read
  const markAsRead = async (notificationId: string) => {
    try {
      await supabase
        .from('p2p_notifications')
        .update({ is_read: true })
        .eq('id', notificationId);

      setNotifications(prev =>
        prev.map(n => n.id === notificationId ? { ...n, is_read: true } : n)
      );
      setUnreadCount(prev => Math.max(0, prev - 1));
    } catch (error) {
      console.error('Mark as read error:', error);
    }
  };

  // Mark all as read
  const markAllAsRead = async () => {
    if (!user) return;

    try {
      await supabase
        .from('p2p_notifications')
        .update({ is_read: true })
        .eq('user_id', user.id)
        .eq('is_read', false);

      setNotifications(prev => prev.map(n => ({ ...n, is_read: true })));
      setUnreadCount(0);
    } catch (error) {
      console.error('Mark all as read error:', error);
    }
  };

  // Handle notification click
  const handleClick = (notification: Notification) => {
    // Mark as read
    if (!notification.is_read) {
      markAsRead(notification.id);
    }

    // Navigate to reference
    if (notification.reference_type === 'trade' && notification.reference_id) {
      navigate(`/p2p/trade/${notification.reference_id}`);
      setIsOpen(false);
    }
  };

  // Get icon for notification type
  const getIcon = (type: string) => {
    switch (type) {
      case 'new_message':
        return <MessageSquare className="w-4 h-4 text-blue-400" />;
      case 'payment_sent':
        return <DollarSign className="w-4 h-4 text-yellow-400" />;
      case 'payment_confirmed':
        return <CheckCircle2 className="w-4 h-4 text-green-400" />;
      case 'trade_cancelled':
        return <XCircle className="w-4 h-4 text-gray-400" />;
      case 'dispute_opened':
        return <AlertTriangle className="w-4 h-4 text-red-400" />;
      case 'new_rating':
        return <Star className="w-4 h-4 text-yellow-400" />;
      case 'new_order':
        return <DollarSign className="w-4 h-4 text-green-400" />;
      default:
        return <Bell className="w-4 h-4 text-gray-400" />;
    }
  };

  // Format time ago
  const formatTimeAgo = (dateString: string) => {
    const seconds = Math.floor((Date.now() - new Date(dateString).getTime()) / 1000);
    if (seconds < 60) return 'Just now';
    const minutes = Math.floor(seconds / 60);
    if (minutes < 60) return `${minutes}m ago`;
    const hours = Math.floor(minutes / 60);
    if (hours < 24) return `${hours}h ago`;
    const days = Math.floor(hours / 24);
    return `${days}d ago`;
  };

  if (!user) return null;

  return (
    <DropdownMenu open={isOpen} onOpenChange={setIsOpen}>
      <DropdownMenuTrigger asChild>
        <Button
          variant="ghost"
          size="sm"
          className="relative text-gray-400 hover:text-white"
        >
          <Bell className="w-5 h-5" />
          {unreadCount > 0 && (
            <span className="absolute -top-1 -right-1 w-5 h-5 flex items-center justify-center bg-red-500 text-white text-xs rounded-full">
              {unreadCount > 9 ? '9+' : unreadCount}
            </span>
          )}
        </Button>
      </DropdownMenuTrigger>

      <DropdownMenuContent
        align="end"
        className="w-80 bg-gray-900 border-gray-800"
      >
        <DropdownMenuLabel className="flex items-center justify-between">
          <span className="text-white">Notifications</span>
          {unreadCount > 0 && (
            <Button
              variant="ghost"
              size="sm"
              onClick={markAllAsRead}
              className="text-xs text-gray-400 hover:text-white h-auto py-1"
            >
              <CheckCheck className="w-3 h-3 mr-1" />
              Mark all read
            </Button>
          )}
        </DropdownMenuLabel>
        <DropdownMenuSeparator className="bg-gray-800" />

        <ScrollArea className="h-[300px]">
          {loading ? (
            <div className="flex items-center justify-center py-8">
              <Loader2 className="w-6 h-6 animate-spin text-gray-500" />
            </div>
          ) : notifications.length === 0 ? (
            <div className="flex flex-col items-center justify-center py-8 text-gray-500">
              <Bell className="w-8 h-8 mb-2" />
              <p className="text-sm">No notifications</p>
            </div>
          ) : (
            notifications.map((notification) => (
              <DropdownMenuItem
                key={notification.id}
                onClick={() => handleClick(notification)}
                className={`
                  flex items-start gap-3 p-3 cursor-pointer
                  ${!notification.is_read ? 'bg-gray-800/50' : ''}
                  hover:bg-gray-800
                `}
              >
                <div className="mt-0.5">{getIcon(notification.type)}</div>
                <div className="flex-1 min-w-0">
                  <p className={`text-sm ${!notification.is_read ? 'text-white font-medium' : 'text-gray-300'}`}>
                    {notification.title}
                  </p>
                  {notification.message && (
                    <p className="text-xs text-gray-500 truncate">
                      {notification.message}
                    </p>
                  )}
                  <p className="text-xs text-gray-600 mt-1">
                    {formatTimeAgo(notification.created_at)}
                  </p>
                </div>
                {!notification.is_read && (
                  <div className="w-2 h-2 bg-blue-500 rounded-full mt-1.5" />
                )}
              </DropdownMenuItem>
            ))
          )}
        </ScrollArea>

        {notifications.length > 0 && (
          <>
            <DropdownMenuSeparator className="bg-gray-800" />
            <DropdownMenuItem
              onClick={() => {
                navigate('/p2p/orders');
                setIsOpen(false);
              }}
              className="justify-center text-gray-400 hover:text-white cursor-pointer"
            >
              View all trades
            </DropdownMenuItem>
          </>
        )}
      </DropdownMenuContent>
    </DropdownMenu>
  );
}