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

/**
 * The practice a resource was written at.
 *
 * FHIR HAS NO FIELD FOR THIS. `serviceProvider`, `managingOrganization` and `performer` each answer a
 * narrower question on one resource type, and most types answer it not at all - so every resource the
 * product writes carries this extension, and it is the one answer that works the same everywhere.
 *
 * Reach for it wherever a practice is named beside a person or a record. A practitioner is never shown
 * without their organization: a patient can hold clinicians at several practices, and the name alone
 * does not say which one this is.
 */
export const CREATED_AT_ORGANIZATION_EXTENSION =
    'https://akashichealthrecords.com/fhir/extensions/createdAtOrganization';

type ResourceWithExtensions = {
    extension?: Array<{ url?: string; valueReference?: Reference }>;
};

/**
 * The organization the extension points at, id and display name.
 *
 * BOTH, NOT ONE. The id is what a row filters or navigates on; the name is what a reader sees. A
 * caller that only wants the name reads `.name` - it does not have to know the reference's shape.
 */
export const createdAtOrganization = (
    resource?: ResourceWithExtensions,
): { id?: string; name?: string } => {
    const reference = (resource?.extension ?? []).find(
        (extension) => extension.url === CREATED_AT_ORGANIZATION_EXTENSION,
    )?.valueReference;

    return {
        id: reference?.reference?.split('/').pop() || undefined,
        name: reference?.display?.trim() || undefined,
    };
};