import { calendarDateInZone, viewerTimeZone } from '../../utils/practiceTimezone';

// The server's day is a UTC calendar day; its instant, when sent, is shown on the given clock (billing passes the
// practice's), else the viewer's. A day alone is parsed as a local calendar day, never a UTC instant.
export const chargeDateLabel = (day: string, instant?: string | null, timeZone?: string): string => {
    const options: Intl.DateTimeFormatOptions = { day: 'numeric', month: 'long', year: 'numeric' };
    const at = instant ? new Date(instant) : null;
    if (at && !Number.isNaN(at.getTime())) return at.toLocaleDateString(undefined, { ...options, timeZone });
    return new Date(`${day}T00:00:00`).toLocaleDateString(undefined, options);
};

/** The day `chargeDateLabel` names, as `YYYY-MM-DD`, for a page that formats its dates its own way. */
export const chargeDay = (day: string, instant?: string | null, timeZone?: string): string => {
    const at = instant ? new Date(instant) : null;
    if (!at || Number.isNaN(at.getTime())) return day;
    return calendarDateInZone(at, timeZone ?? viewerTimeZone());
};