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

export type ConditionStatusKind = 'clinical' | 'verification';

const SYSTEMS: Record<ConditionStatusKind, string> = {
    clinical: 'http://terminology.hl7.org/CodeSystem/condition-clinical',
    verification: 'http://terminology.hl7.org/CodeSystem/condition-ver-status',
};

const LABELS: Record<ConditionStatusKind, Record<string, string>> = {
    clinical: { active: 'Active', recurrence: 'Recurrence', relapse: 'Relapse', inactive: 'Inactive', remission: 'Remission', resolved: 'Resolved' },
    verification: {
        unconfirmed: 'Unconfirmed', provisional: 'Provisional', differential: 'Differential',
        confirmed: 'Confirmed', refuted: 'Refuted', 'entered-in-error': 'Entered in error',
    },
};

/**
 * A Condition's clinical or verification status as recorded: its own text or display first, then the standard label of
 * a code from that status's own code system. Any other code is shown as recorded, never given a meaning, and a status
 * that was not recorded says so rather than implying one.
 */
export const conditionStatusText = (concept: CodeableConcept | undefined | null, kind: ConditionStatusKind): string => {
    const text = concept?.text?.trim();
    if (text) return text;
    const codings = (concept?.coding ?? []).filter((coding) => coding?.code?.trim() || coding?.display?.trim());
    const known = codings.find((coding) => coding.system === SYSTEMS[kind] && coding.code && Object.prototype.hasOwnProperty.call(LABELS[kind], coding.code));
    if (known) return known.display?.trim() || LABELS[kind][known.code as string];
    const shown = codings.find((coding) => coding.display?.trim());
    if (shown) return (shown.display as string).trim();
    const code = codings[0]?.code?.trim();
    return code ? `Recorded as "${code}", not a recognised ${kind} status` : 'Not recorded';
};