"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { useRouter } from "next/navigation";
import Link from "next/link";
import { BellIcon } from "lucide-react";
import { Button } from "@/components/ui/button";
import {
  DropdownMenu,
  DropdownMenuContent,
  DropdownMenuItem,
  DropdownMenuLabel,
  DropdownMenuSeparator,
  DropdownMenuTrigger,
} from "@/components/ui/dropdown-menu";
import { cn } from "@/lib/utils";
import { notificationLabel } from "@/lib/notifications";
import {
  markAllNotificationsRead,
  markNotificationsRead,
} from "@/app/(frontend)/notifications/actions";

interface NotificationItem {
  id: number;
  type?: string | null;
  title: string;
  message?: string | null;
  link?: string | null;
  read: boolean;
  createdAt: string;
}

function timeAgo(iso: string): string {
  const diff = Date.now() - new Date(iso).getTime();
  const minutes = Math.floor(diff / 60000);
  if (minutes < 1) return "just now";
  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`;
}

const POLL_MS = 30_000;

export function NotificationsBell() {
  const router = useRouter();
  const [notifications, setNotifications] = useState<NotificationItem[]>([]);
  const [open, setOpen] = useState(false);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(false);
  const intervalRef = useRef<ReturnType<typeof setInterval> | null>(null);

  const unreadCount = notifications.filter((n) => !n.read).length;

  const fetchNotifications = useCallback(async () => {
    try {
      const res = await fetch("/api/user-notifications?limit=12&sort=-createdAt", {
        cache: "no-store",
      });
      if (!res.ok) throw new Error("Failed to fetch");
      const data = (await res.json()) as { docs?: NotificationItem[] };
      setNotifications(data.docs ?? []);
      setError(false);
    } catch {
      setError(true);
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => {
    void fetchNotifications();
    intervalRef.current = setInterval(() => void fetchNotifications(), POLL_MS);
    return () => {
      if (intervalRef.current) clearInterval(intervalRef.current);
    };
  }, [fetchNotifications]);

  async function handleItemClick(item: NotificationItem) {
    if (!item.read) {
      await markNotificationsRead([item.id]);
      setNotifications((prev) => prev.map((n) => (n.id === item.id ? { ...n, read: true } : n)));
    }
    if (item.link) {
      router.push(item.link);
      setOpen(false);
    }
  }

  async function handleMarkAll() {
    if (unreadCount === 0) return;
    await markAllNotificationsRead();
    setNotifications((prev) => prev.map((n) => (n.read ? n : { ...n, read: true })));
  }

  return (
    <DropdownMenu open={open} onOpenChange={setOpen}>
      <DropdownMenuTrigger asChild>
        <Button variant="ghost" size="icon" className="relative" aria-label="Notifications">
          <BellIcon className="size-5" />
          {unreadCount > 0 && (
            <span className="absolute -right-0.5 -top-0.5 flex size-4 items-center justify-center rounded-full bg-red-500 text-[10px] font-semibold text-white">
              {unreadCount > 9 ? "9+" : unreadCount}
            </span>
          )}
        </Button>
      </DropdownMenuTrigger>
      <DropdownMenuContent align="end" className="w-80 sm:w-96">
        <div className="flex items-center justify-between pr-1">
          <DropdownMenuLabel className="pb-1">Notifications</DropdownMenuLabel>
          {unreadCount > 0 && (
            <button
              onClick={() => void handleMarkAll()}
              className="text-xs text-muted-foreground hover:text-foreground"
            >
              Mark all read
            </button>
          )}
        </div>
        <DropdownMenuSeparator />
        <div className="max-h-96 overflow-y-auto">
          {loading ? (
            <p className="px-3 py-6 text-center text-sm text-muted-foreground">Loading...</p>
          ) : error ? (
            <p className="px-3 py-6 text-center text-sm text-red-400">
              Could not load notifications.
            </p>
          ) : notifications.length === 0 ? (
            <p className="px-3 py-6 text-center text-sm text-muted-foreground">
              No notifications yet.
            </p>
          ) : (
            notifications.map((item) => (
              <DropdownMenuItem
                key={item.id}
                className={cn(
                  "flex flex-col items-start gap-1 py-2.5",
                  !item.read && "bg-accent/50",
                )}
                onClick={() => void handleItemClick(item)}
              >
                <span className="flex w-full items-center justify-between gap-2">
                  <span className="text-sm font-medium">
                    {!item.read && (
                      <span className="mr-1.5 inline-block size-1.5 rounded-full bg-blue-500 align-middle" />
                    )}
                    {item.title}
                  </span>
                  <span className="shrink-0 text-[10px] text-muted-foreground">
                    {timeAgo(item.createdAt)}
                  </span>
                </span>
                {item.message && (
                  <span className="w-full text-xs text-muted-foreground">{item.message}</span>
                )}
                <span className="text-[10px] text-muted-foreground/70">
                  {notificationLabel(item.type)}
                </span>
              </DropdownMenuItem>
            ))
          )}
        </div>
        <DropdownMenuSeparator />
        <DropdownMenuItem asChild>
          <Link href="/notifications" className="justify-center text-sm font-medium">
            View all
          </Link>
        </DropdownMenuItem>
      </DropdownMenuContent>
    </DropdownMenu>
  );
}