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

/*
 * THE PATIENT'S TIME LIST IS DRAWN ON THE PATIENT'S CLOCK (option B, Spencer 2026-08-10), so a picked
 * label such as "2:00 PM" is a time on that clock. The availability windows are real instants rendered in
 * the viewer's zone, and the held slots are checked the same way; the stored instant has to be read on
 * that clock too. Reading it as practice time stored a New York patient's 2:00 PM as 3:00 PM against a
 * Chicago practice, and let 11:00 AM land on a visit already held at noon.
 *
 * `clock` defaults to the viewer's zone and exists so a test can name one.
 */
export function pickedTimeInstant(dateStr: string, timeStr: string, clock: string = viewerTimeZone()): Date {
    return zonedWallClockToInstant(dateStr, timeStr, clock);
}

type HeldSlot = { start?: string; end?: string; status?: string };

const minutesOf = (hhmm: string): number => {
    const [hours, minutes] = hhmm.split(':').map(Number);
    return hours * 60 + minutes;
};

/**
 * Busy [startMin, endMin) ranges, in minutes of the day on `clock`, for the slots that begin on `dateStr`
 * as read on that clock. The day is the patient's day, not the UTC one: an evening hold in New York is
 * already tomorrow in UTC and used to drop off the list it blocks.
 */
export function heldRangesOnDate(
    slots: HeldSlot[],
    dateStr: string,
    clock: string = viewerTimeZone(),
): { startMin: number; endMin: number }[] {
    return slots
        .filter((slot) => slot.start && String(slot.status ?? '').includes('busy'))
        .filter((slot) => calendarDateInZone(new Date(slot.start as string), clock) === dateStr)
        .map((slot) => {
            const start = new Date(slot.start as string);
            const startMin = minutesOf(wallClockInZone(start, clock));
            if (!slot.end) return { startMin, endMin: startMin + 1 };
            const end = new Date(slot.end);
            // A hold that runs past midnight blocks the rest of this day.
            const endMin = calendarDateInZone(end, clock) === dateStr ? minutesOf(wallClockInZone(end, clock)) : 24 * 60;
            return { startMin, endMin: Math.max(endMin, startMin + 1) };
        });
}