/**
 * WHAT A PATIENT IS TOLD WHEN THE SERVICE STEP HAS NOTHING ON IT.
 *
 * MEASURED 2026-09-15 at a practice configured end to end: two active services, both attached to a
 * seated practitioner, both on a schedule block whose horizon covered that day. The patient was told
 * "<practice> hasn't added any bookable services yet. Please contact the office to schedule an
 * appointment." The wire returned both services, active. The sentence named the wrong subject, and the
 * only thing it offered was a telephone call to a practice that had done nothing wrong.
 *
 * THREE STATES REACH ONE EMPTY LIST AND THEY ARE NOT THE SAME FACT:
 *
 *   nothing to book from   no schedule block is open to patient self-booking at all
 *   nothing listed on it   blocks exist, and none of them carries a self-bookable service
 *   the first-visit gate   the practice requires a new patient consultation first, and no block
 *                          offering one is open to this patient
 *
 * Only the middle one is what the old sentence described, and it was said in all three. The third is
 * the one that produced the measurement above: the catalogue was full, and the gate had pinned the
 * choice to a consultation that no open block offered.
 *
 * WRITTEN FOR THE PATIENT, NOT THE OFFICE. `BLOCKER_COPY` says the same causes in an administrator's
 * words - "this schedule block", "self-booking is switched off" - which is right on the screen where
 * somebody can go and change them, and wrong here. A patient cannot act on a schedule block.
 */

/** Which of the three emptinesses the flow is in. Decided by the caller, which holds the inputs. */
export type NothingToOffer =
    /** No schedule block at this practice is open to patient self-booking. */
    | 'NO_SELF_BOOKABLE_SCHEDULE'
    /** Blocks are open, and none of them lists a service a patient may book. */
    | 'NO_SELF_BOOKABLE_SERVICE'
    /** A first visit must be a new patient consultation, and no open block offers one. */
    | 'FIRST_VISIT_NOT_OFFERED';

/**
 * The practice's name where there is one, and "This practice" where there is not - never an empty gap
 * and never the word "organization", which is ours and not theirs.
 */
const named = (practiceName: string | undefined): string => {
    const trimmed = practiceName?.trim();
    return trimmed ? trimmed : 'This practice';
};

/**
 * ONE SENTENCE PLUS ONE REMEDY, AND THE REMEDY IS THE SAME IN ALL THREE because it honestly is: none of
 * these is something the patient can route around inside the flow. What changes is that they are no
 * longer told something false on the way to the telephone.
 */
export const describeNothingToOffer = (
    state: NothingToOffer,
    practiceName: string | undefined,
): string => {
    const who = named(practiceName);
    switch (state) {
        case 'FIRST_VISIT_NOT_OFFERED':
            // Names the gate AND the gap, because the patient is otherwise told a practice they can see
            // has a full catalogue offers nothing. The gate is the practice's own policy and saying so
            // is what makes the emptiness make sense.
            return `Your first visit with ${who} has to be a new patient consultation, and none is `
                + 'open for online booking right now. Please contact the office to arrange it.';
        case 'NO_SELF_BOOKABLE_SCHEDULE':
            // "No times" rather than "no services": the catalogue is not what is missing, and sending
            // somebody to ask about services they can already see is what the old sentence did.
            return `${who} has no appointment times open for online booking right now. `
                + 'Please contact the office to schedule an appointment.';
        case 'NO_SELF_BOOKABLE_SERVICE':
        default:
            // The one case the original sentence described, kept close to its original words.
            return `${who} hasn't made any services available for online booking yet. `
                + 'Please contact the office to schedule an appointment.';
    }
};