import { useMemo } from 'react';
import { Link } from 'react-router-dom';
import { Bell } from 'lucide-react';
import { formatDistanceToNow } from 'date-fns';
import {
  Popover,
  PopoverContent,
  PopoverTrigger,
} from '@/components/ui/popover';
import {
  useNotifications,
  useUnreadCount,
  useMarkNotificationsRead,
} from '../api/queries';
import type { Notification } from '../../../shared/types';

const KIND_LABELS: Record<string, string> = {
  ASSIGNED: 'assigned to you',
  MENTION: 'mentioned you',
  RESOLVED: 'was resolved',
  TICKET_CREATED: 'was created',
  STATUS_CHANGED: 'status changed',
  COMMENT: 'new comment',
};

interface NotifData {
  displayId?: string;
  title?: string;
  byName?: string;
}

function renderSummary(n: Notification): { label: string; href: string } {
  const data = (n.data ?? {}) as NotifData;
  const action = KIND_LABELS[n.kind] ?? n.kind.toLowerCase();
  const label = data.title
    ? `${data.title} — ${action}`
    : `Ticket ${action}`;
  const href = data.displayId ? `/${data.displayId}` : '/notifications';
  return { label, href };
}

export default function NotificationsBell() {
  const { data: unreadCount = 0 } = useUnreadCount();
  const { data: notifications = [] } = useNotifications();
  const markRead = useMarkNotificationsRead();

  const latest = useMemo(() => notifications.slice(0, 8), [notifications]);

  return (
    <Popover>
      <PopoverTrigger asChild>
        <button
          type="button"
          aria-label="Notifications"
          className="relative p-2 rounded-md text-muted-foreground hover:text-foreground hover:bg-accent transition-colors"
        >
          <Bell size={18} />
          {unreadCount > 0 && (
            <span className="absolute top-1 right-1 min-w-[1rem] h-4 px-1 rounded-full bg-destructive text-destructive-foreground text-[10px] font-semibold flex items-center justify-center">
              {unreadCount > 99 ? '99+' : unreadCount}
            </span>
          )}
        </button>
      </PopoverTrigger>
      <PopoverContent align="end" className="w-80 p-0">
        <div className="flex items-center justify-between px-3 py-2 border-b">
          <span className="text-sm font-semibold">Notifications</span>
          {unreadCount > 0 && (
            <button
              onClick={() => markRead.mutate({ all: true })}
              className="text-xs text-primary hover:underline"
            >
              Mark all read
            </button>
          )}
        </div>
        <div className="max-h-96 overflow-auto">
          {latest.length === 0 ? (
            <p className="px-3 py-6 text-center text-xs text-muted-foreground">
              You&apos;re all caught up
            </p>
          ) : (
            latest.map((n) => {
              const { label, href } = renderSummary(n);
              const unread = !n.readAt;
              return (
                <Link
                  key={n.id}
                  to={href}
                  onClick={() => unread && markRead.mutate({ ids: [n.id] })}
                  className={`flex flex-col gap-1 px-3 py-2 text-sm border-b last:border-b-0 hover:bg-accent transition-colors ${
                    unread ? 'bg-primary/5' : ''
                  }`}
                >
                  <span className="line-clamp-2">{label}</span>
                  <span className="text-xs text-muted-foreground">
                    {formatDistanceToNow(new Date(n.createdAt), { addSuffix: true })}
                  </span>
                </Link>
              );
            })
          )}
        </div>
        <Link
          to="/notifications"
          className="block px-3 py-2 text-center text-xs text-primary hover:underline border-t"
        >
          View all notifications
        </Link>
      </PopoverContent>
    </Popover>
  );
}