import { useEffect, useMemo, useState } from "react";
import type { Appointment, Location } from "fhir/r4";
import { useHttpService } from "../services/HttpService.tsx";
import { environment } from "../environments/environment.ts";
import { appointmentLocationId } from "../utils/appointmentDirections";

/**
 * The practice's loaded Locations plus each appointment's own site from another practice, read under
 * that practice's organization so a patient's booking elsewhere keeps its address and Directions.
 */
export const useAppointmentSites = (
  appointments: readonly Appointment[],
  locations: readonly Location[],
  practiceIdOf: (appointment: Appointment) => string | undefined,
): Location[] => {
  const { get } = useHttpService();
  const [fetched, setFetched] = useState<Record<string, Location>>({});

  const missing = useMemo(() => {
    const known = new Set(locations.map((location) => location.id));
    const wanted = new Map<string, string>();
    for (const appointment of appointments) {
      const id = appointmentLocationId(appointment);
      const practiceId = practiceIdOf(appointment);
      if (id && practiceId && !known.has(id)) wanted.set(id, practiceId);
    }
    return [...wanted].sort(([a], [b]) => a.localeCompare(b));
  }, [appointments, locations, practiceIdOf]);
  const missingKey = missing.map(([id, practiceId]) => `${id}@${practiceId}`).join(",");

  useEffect(() => {
    const toRead = missing.filter(([id]) => !fetched[id]);
    if (toRead.length === 0) return;
    let cancelled = false;
    void Promise.all(toRead.map(async ([id, practiceId]) => {
      try {
        return await get<Location>(`${environment.fhirBaseApi}/Location/${id}`, { organizationId: practiceId });
      } catch {
        // Without the site the panel keeps the booking's own place name; nothing is claimed about it.
        return undefined;
      }
    })).then((results) => {
      if (cancelled) return;
      const found = results.filter((location): location is Location => Boolean(location?.id));
      if (found.length) setFetched((previous) => ({ ...previous, ...Object.fromEntries(found.map((l) => [l.id!, l])) }));
    });
    return () => { cancelled = true; };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [missingKey, get]);

  return useMemo(() => [...locations, ...Object.values(fetched)], [locations, fetched]);
};

export default useAppointmentSites;