import { useEffect, useRef, useState } from 'react';
import type { Patient } from 'fhir/r4';
import { usePatientServiceContext } from '../../../services/PatientService';
import { useActiveEncounterContext } from './ActiveEncounterContext';
import { formatFhirHumanName } from '../../../utils/fhirHumanName';

/**
 * sub-task 5a - the ACTIVE encounter's patient, hoisted out of `FloatingEncounterNotes` so a
 * later consumer (the meeting-window notes panel) INHERITS the render-time identity gate rather than
 * re-deriving the cross-patient write bug sub-task 3's review found.
 *
 * `enabled` matters: this hook is mounted app-wide by consumers that may never be visible, so without
 * the gate every encounter switch fires a patient fetch even for practitioners who never open the pane.
 */
export const useActiveEncounterPatient = (enabled: boolean) => {
    const { active } = useActiveEncounterContext();
    const { fetchPatient } = usePatientServiceContext();
    const [patient, setPatient] = useState<Patient | undefined>();
    const token = useRef(0);
    const patientId = active?.item.patientId;

    useEffect(() => {
        const mine = ++token.current;
        // Skip entirely while no consumer is showing - this is mounted app-wide, so without the gate
        // every encounter switch fetches a patient for practitioners who never open the pane.
        if (!patientId || !enabled) { setPatient(undefined); return; }
        void fetchPatient(patientId)
            .then((p) => { if (mine === token.current) setPatient(p); })
            .catch(() => { if (mine === token.current) setPatient(undefined); });
    }, [patientId, enabled, fetchPatient]);

    // RENDER-TIME identity gate, not an effect. `patient` always lags `active` by at least one
    // commit, and pairing a stale patient with the new encounter is a wrong-name title AND a
    // wrong-subject clinical write. An effect cannot fix it - the first committed frame is already wrong.
    const current = patient?.id === patientId ? patient : undefined;
    const resolved = current ? formatFhirHumanName(current.name) : undefined;
    const name = resolved || active?.item.patientName || 'this patient';

    return { patient: current, name };
};