import type { Appointment } from 'fhir/r4';

/**
 * HAS THE PRACTICE AGREED TO THIS APPOINTMENT YET?
 *
 * A booking made under review mode comes back `pending`, and one made under request-only comes back
 * `proposed`. Neither is a visit the practice has accepted; both are a time the patient asked for and
 * is holding while somebody looks.
 *
 * MEASURED 2026-09-15, booking as a patient at a practice in review mode. The receipt said "Until then
 * it shows as pending on your appointments." It did not: the appointments row printed the day, date,
 * time and location with no status at all, and the home card read "Next appointment", so the only place
 * the state existed was inside the detail panel nobody has a reason to open.
 *
 * WHY THAT IS WORSE THAN AN OMISSION. The whole point of review mode is that the practice can move or
 * refuse the time. A patient who reads "Next appointment" has been told it was agreed, and turns up.
 * The absence of a marker is carrying the message that the appointment is confirmed, which is the
 * convention against letting a screen speak by showing nothing.
 *
 * ONE PREDICATE, so a row, a card and a panel cannot disagree about the same appointment.
 */

const AWAITING: ReadonlySet<NonNullable<Appointment['status']>> = new Set([
    // Review mode: the slot is held and staff have to approve it.
    'pending',
    // Request-only: the patient has asked, and nothing is held until staff turn it into a booking.
    'proposed',
]);

export const isAwaitingPractice = (appointment: Appointment | undefined): boolean =>
    Boolean(appointment?.status && AWAITING.has(appointment.status));

/**
 * The short marker a row or a card carries, in the patient's words rather than the resource's.
 *
 * "Pending" alone is the status field read aloud, and it does not say pending on WHAT. What a patient
 * needs to know is that somebody else still has to say yes.
 */
export const AWAITING_PRACTICE_LABEL = 'Waiting for the practice to confirm';

/**
 * The sentence the detail panel leads with, which has room to say what happens next.
 *
 * It replaces a band that printed the raw status word in the same green the confirmed state uses - so
 * the one screen that did carry the state was colouring it as though the practice had agreed.
 */
export const AWAITING_PRACTICE_SENTENCE =
    'Waiting for the practice to confirm. Your time is held until they do, and they will let you know.';