import type { Appointment, CodeableConcept, HealthcareService } from 'fhir/r4';
import { selectedServiceIdOf } from './booking/selectedServiceRef';

/**
 * The visit's catalogue service: the one it recorded choosing, else the only one whose type shares a code, or ''.
 * Never guessed: a code two services share leaves an older visit with its own label.
 */
export const visitServiceIdFor = (appointment: Appointment | undefined, services: HealthcareService[]): string => {
    const recorded = selectedServiceIdOf(appointment);
    if (recorded) return services.some((service) => service.id === recorded) ? recorded : '';
    const codes = new Set(
        (appointment?.serviceType ?? [])
            .flatMap((concept) => (concept.coding ?? []).map((coding) => coding.code))
            .filter((code): code is string => Boolean(code)),
    );
    if (codes.size === 0) return '';
    const matches = services.filter((service) =>
        (service.type ?? []).some((t) => (t.coding ?? []).some((c) => c.code && codes.has(c.code))),
    );
    return matches.length === 1 ? matches[0].id ?? '' : '';
};

/** What the visit says it was booked for, read from the visit itself. */
export const bookedServiceLabel = (appointment: Appointment | undefined): string | undefined => {
    const [concept] = appointment?.serviceType ?? [];
    return concept?.text || concept?.coding?.find((c) => c.display)?.display || undefined;
};

/**
 * The service fields an edit writes. A service nobody changed stays exactly as booked, whether or not the
 * form matched it to the catalogue: an edit to the time must not erase it, nor restate it in today's coding.
 */
export const serviceFieldsToSave = (args: {
    selectedService: HealthcareService | undefined;
    appointment: Appointment | undefined;
    isEditMode: boolean;
    serviceTouched: boolean;
}): { serviceType: CodeableConcept[] | undefined; serviceCategory: CodeableConcept[] | undefined } => {
    if (args.isEditMode && !args.serviceTouched) {
        return { serviceType: args.appointment?.serviceType, serviceCategory: args.appointment?.serviceCategory };
    }
    if (args.selectedService) return { serviceType: args.selectedService.type, serviceCategory: args.selectedService.category };
    return { serviceType: undefined, serviceCategory: undefined };
};

/** The services the desk may choose now: the practice's active ones, and an edited visit's own current service. */
export const deskSelectableServices = (services: HealthcareService[], currentServiceId: string | undefined): HealthcareService[] =>
    services.filter((service) => service.active !== false || (Boolean(currentServiceId) && service.id === currentServiceId));

/** Why the desk may not send this service, or undefined: a switched-off service stays only as the visit's own. */
export const inactiveSelectionRefusal = (args: {
    selectedService: HealthcareService | undefined;
    currentServiceId: string | undefined;
    isEditMode: boolean;
}): string | undefined => {
    const { selectedService, currentServiceId, isEditMode } = args;
    if (!selectedService || selectedService.active !== false) return undefined;
    if (isEditMode && currentServiceId && selectedService.id === currentServiceId) return undefined;
    return `${selectedService.name ?? 'This service'} is no longer offered by the practice. Choose another service.`;
};