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

/**
 * DOES THIS PRACTICE HAVE A CARE RELATIONSHIP WITH THIS PATIENT?
 *
 * Not a permission check - the server owns that, and this must never be read as one. It answers a
 * narrower question the CHART can answer for itself, so a clinician can be told why every clinical list
 * on an otherwise complete-looking chart is refusing.
 *
 * WHAT THE SERVER ACTUALLY DOES, which this mirrors and deliberately under-claims against. A
 * practitioner is granted the clinical axis when they are the patient's direct `generalPractitioner`, OR
 * when `generalPractitioner` names their organization. Failing both, execution falls through to the
 * AFFILIATION branch, which grants the visibility axis only - the name, the age, the phone number. That
 * is the two-axis model working, and it is why the chart opens and then every list refuses.
 *
 * MEASURED, 2026-08-30: a patient with `generalPractitioner: -` returned 403 on Condition and
 * DiagnosticReport while Flag and Provenance returned 200, in the same session, seconds apart. The
 * difference is not the resource type; it is that those two routes require patient access and the others
 * do not.
 */

/** Every reference on the patient, as `Type/id` strings. */
const referencesOf = (patient: Patient | undefined): string[] =>
    (patient?.generalPractitioner ?? [])
        .map((reference) => reference.reference)
        .filter((reference): reference is string => Boolean(reference));

/**
 * True ONLY when we can be certain no care relationship exists.
 *
 * FAILS SILENT, NOT LOUD, and that asymmetry is the whole design. A false negative costs a sentence
 * that could have been shown; a false positive tells a clinician their practice has no relationship with
 * a patient it may well be treating, on a chart that is refusing for some other reason entirely. The
 * second is a statement about the practice's own records and it must not be guessed.
 *
 * So it stays silent whenever it cannot decide:
 *
 * no patient loaded yet -> silent, the answer is not knowable
 * no organization in context -> silent, there is nothing to compare against
 * ANY Practitioner reference -> silent. The server grants on a direct practitioner link, and this
 * layer cannot tell whether that practitioner is a colleague here.
 * A named GP we cannot place is exactly the case to say nothing about
 * this organization is named -> silent, the relationship plainly exists
 *
 * It speaks only for a patient whose `generalPractitioner` is empty, or names other ORGANIZATIONS and
 * this one is not among them. In both of those the absence is a fact about the record rather than a gap
 * in what this screen can see.
 */
export const practiceHasNoCareRelationship = (
    patient: Patient | undefined,
    organizationId: string | undefined,
): boolean => {
    if (!patient || !organizationId) return false;

    const references = referencesOf(patient);

    // A direct practitioner link may be a colleague at this practice. Undecidable here, so say nothing.
    if (references.some((reference) => reference.startsWith('Practitioner/'))) return false;

    return !references.includes(`Organization/${organizationId}`);
};