import { useEffect, useState } from "react";
import { getGreetingPeriod, type GreetingPeriod } from "./greeting";

// Checked frequently enough that a period rollover (e.g. 11:59 -> 12:00) is picked up
// within the Dashboard while the app stays open, without a page reload -- see section 9
// of the Fleet Ops final localization brief.
const CHECK_INTERVAL_MS = 30_000;

export function useGreetingPeriod(): GreetingPeriod {
  const [period, setPeriod] = useState<GreetingPeriod>(() => getGreetingPeriod());

  useEffect(() => {
    const id = setInterval(() => {
      setPeriod((current) => {
        const next = getGreetingPeriod();
        return next === current ? current : next;
      });
    }, CHECK_INTERVAL_MS);
    return () => clearInterval(id);
  }, []);

  return period;
}