import { utcToZonedTime, zonedTimeToUtc } from "date-fns-tz";

export const TERMS = ["winter", "spring", "fall"] as const;
export type Term = typeof TERMS[number];
export const DATE_FORMAT = "MMMM dd yyyy HH:mm";

// https://www.typescriptlang.org/docs/handbook/2/narrowing.html#using-type-predicates
export function isTerm(x: string): x is Term {
  return TERMS.some((term) => x === term);
}

export function capitalize(str: string) {
  return str.slice(0, 1).toUpperCase() + str.slice(1);
}

// Converts a date to local time
export function getLocalDateFromEST(date: Date): Date {
  return utcToZonedTime(
    // The date parameter is in EST
    zonedTimeToUtc(date, "America/Toronto"),
    Intl.DateTimeFormat().resolvedOptions().timeZone
  );
}