// Utility composable for event date handling with timezone support.
// Pass `{ timeZone: event.displayTimezone }` to render in the event's TZ.
export const useEventDateUtils = () => {
  const DEFAULT_TIMEZONE = "America/Toronto";

  const formatDate = (date, options = {}) => {
    if (!date) return "";
    const dateObj = date instanceof Date ? date : new Date(date);
    if (isNaN(dateObj.getTime())) return "";
    const {
      month = "short",
      day = "numeric",
      year = "numeric",
      weekday,
      timeZone,
    } = options;

    return new Intl.DateTimeFormat("en-US", {
      ...(weekday && { weekday }),
      month,
      day,
      year,
      ...(timeZone && { timeZone }),
    }).format(dateObj);
  };

  const formatDateRange = (startDate, endDate, compact = false, timeZone) => {
    if (!startDate || !endDate) return "No dates";

    const start = new Date(startDate);
    const end = new Date(endDate);

    const tzOpts = timeZone ? { timeZone } : {};
    const startMonth = start.toLocaleDateString("en-US", { month: "short", ...tzOpts });
    const endMonth = end.toLocaleDateString("en-US", { month: "short", ...tzOpts });
    const startDay = Number(
      start.toLocaleDateString("en-US", { day: "numeric", ...tzOpts }),
    );
    const endDay = Number(
      end.toLocaleDateString("en-US", { day: "numeric", ...tzOpts }),
    );
    const year = Number(
      end.toLocaleDateString("en-US", { year: "numeric", ...tzOpts }),
    );
    const startMonthIdx = startMonth; // compared as label string
    const endMonthIdx = endMonth;
    const startYear = Number(
      start.toLocaleDateString("en-US", { year: "numeric", ...tzOpts }),
    );

    if (compact) {
      if (startMonthIdx === endMonthIdx && startYear === year) {
        return `${startMonth} ${startDay}-${endDay}`;
      }
      return `${startMonth} ${startDay} - ${endMonth} ${endDay}`;
    }

    if (startMonthIdx === endMonthIdx && startYear === year) {
      return `${startMonth} ${startDay}-${endDay}, ${year}`;
    } else if (startYear === year) {
      return `${startMonth} ${startDay} - ${endMonth} ${endDay}, ${year}`;
    } else {
      return `${formatDate(startDate, { timeZone })} - ${formatDate(endDate, { timeZone })}`;
    }
  };

  const isPastDate = (date) => {
    const dateObj = date instanceof Date ? date : new Date(date);
    return dateObj < new Date();
  };

  const isToday = (date, timeZone) => {
    const dateObj = date instanceof Date ? date : new Date(date);
    const today = new Date();
    const opts = { year: "numeric", month: "2-digit", day: "2-digit", ...(timeZone && { timeZone }) };
    return (
      dateObj.toLocaleDateString("en-US", opts) ===
      today.toLocaleDateString("en-US", opts)
    );
  };

  const formatTime = (date, includeSeconds = false, timeZone) => {
    const dateObj = date instanceof Date ? date : new Date(date);
    return new Intl.DateTimeFormat("en-US", {
      hour: "2-digit",
      minute: "2-digit",
      ...(includeSeconds && { second: "2-digit" }),
      ...(timeZone && { timeZone }),
    }).format(dateObj);
  };

  return {
    DEFAULT_TIMEZONE,
    // Legacy alias for callers that hard-coded the constant.
    TIMEZONE: DEFAULT_TIMEZONE,
    formatDate,
    formatDateRange,
    isPastDate,
    isToday,
    formatTime,
  };
};