import { useEffect, useRef } from "react";
import { useTranslation } from "react-i18next";
import { fetchDueReminders } from "@/api/diet.api";
import { isAuthenticated } from "@/store/authStore";

const POLL_MS = 60_000;
const notifiedKeys = new Set<string>();

function slotKey(id: number, date: string, hour: number, minute: number): string {
  return `${date}:${hour}:${minute}:${id}`;
}

export function useReminderNotifications(): void {
  const { t } = useTranslation();
  const permissionRef = useRef<NotificationPermission | "unsupported">("default");

  useEffect(() => {
    if (typeof Notification === "undefined") {
      permissionRef.current = "unsupported";
      return;
    }
    permissionRef.current = Notification.permission;
    if (Notification.permission === "default") {
      void Notification.requestPermission().then((p) => {
        permissionRef.current = p;
      });
    }
  }, []);

  useEffect(() => {
    if (!isAuthenticated()) return;

    const tick = async () => {
      if (permissionRef.current !== "granted") return;
      try {
        const due = await fetchDueReminders();
        const now = new Date();
        const date = now.toISOString().slice(0, 10);
        for (const r of due) {
          const key = slotKey(r.id, date, now.getHours(), now.getMinutes());
          if (notifiedKeys.has(key)) continue;
          notifiedKeys.add(key);
          new Notification(r.title, {
            body: r.message ?? t("diet.reminderNotificationBody"),
            tag: key,
          });
        }
      } catch {
        // ignore polling errors
      }
    };

    void tick();
    const id = window.setInterval(() => void tick(), POLL_MS);
    return () => window.clearInterval(id);
  }, [t]);
}