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

/**
 * Which agency provided this person, read off the role they hold.
 *
 * The server writes this tag in the same operation that writes the assignment row, so the practice can
 * answer "why is this person here?" from the role itself without a second lookup. This file is the
 * client's READER of that tag; the server's own reader is `agencyThatProvided` in
 * `utils/agencyAssignment.ts`.
 *
 * The system string must match the server's byte for byte. A drifted character reads as "nobody was
 * provided by an agency" forever - every row looks like ordinary staff and nothing errors, which is the
 * defect this exists to end rather than a new way to cause it.
 *
 * NOT A SECOND SOURCE OF TRUTH. The assignment row is authoritative and is what revocation acts on; this
 * tag is the same fact recorded where a reader can see it. The cascade's safety argument rests on the two
 * being independent and having to agree, so a third record of the same thing would be one more thing to
 * drift.
 */
export const AGENCY_PROVIDED_TAG_SYSTEM =
    'https://akashichealthrecords.com/fhir/tags/agencyProvidedBy';

/** The contractor id that provided this role, or undefined for somebody the practice hired itself. */
export const agencyThatProvided = (role: PractitionerRole | undefined): string | undefined =>
    role?.meta?.tag?.find((tag) => tag.system === AGENCY_PROVIDED_TAG_SYSTEM)?.code;

/**
 * The agency behind any of a person's roles.
 *
 * A person holds several roles and only the agency-provided one carries the tag, so this asks all of
 * them rather than the first. Undefined means no role says an agency provided them - which is left
 * SILENT by every caller: absence of the tag is not a statement that somebody is internal, because
 * nobody wrote that.
 */
export const agencyThatProvidedAny = (
    roles: readonly (PractitionerRole | undefined)[] | undefined,
): string | undefined => {
    for (const role of roles ?? []) {
        const contractorId = agencyThatProvided(role);
        if (contractorId) return contractorId;
    }
    return undefined;
};