current-time

export type DateFormat = "iso" | "human" | "unix";

export interface TimeDescription {
  local_datetime: string;
  weekday: string;
  timezone: string;
  locale: string;
  iso_utc: string;
  unix_seconds: number;
  formatted: string;
}

export function describeTime(
  date: Date,
  timezone: string,
  locale: string,
  format: DateFormat,
): TimeDescription {
  const tz = timezone || Intl.DateTimeFormat().resolvedOptions().timeZone;
  const loc = locale || Intl.DateTimeFormat().resolvedOptions().locale;

  const machineParts = new Intl.DateTimeFormat("en-CA", {
    timeZone: tz,
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    minute: "2-digit",
    second: "2-digit",
    hour12: false,
    weekday: "long",
    timeZoneName: "longOffset",
  }).formatToParts(date);
  const get = (t: string) => machineParts.find((p) => p.type === t)?.value ?? "";

  const local_datetime = `${get("year")}-${get("month")}-${get("day")} ${get("hour")}:${get("minute")}:${get("second")}`;
  const weekday = get("weekday");
  const offset = (get("timeZoneName") || "").replace(/^GMT/, "") || "Z";

  let formatted: string;
  switch (format) {
    case "iso":
      formatted = `${get("year")}-${get("month")}-${get("day")}T${get("hour")}:${get("minute")}:${get("second")}${offset}`;
      break;
    case "human":
      formatted = new Intl.DateTimeFormat(loc, {
        timeZone: tz,
        dateStyle: "full",
        timeStyle: "long",
      }).format(date);
      break;
    case "unix":
      formatted = String(Math.floor(date.getTime() / 1000));
      break;
  }

  return {
    local_datetime,
    weekday,
    timezone: tz,
    locale: loc,
    iso_utc: date.toISOString(),
    unix_seconds: Math.floor(date.getTime() / 1000),
    formatted,
  };
}

export function isValidTimezone(tz: string): boolean {
  try {
    new Intl.DateTimeFormat("en-US", { timeZone: tz }).format(new Date());
    return true;
  } catch {
    return false;
  }
}