import { useMemo } from "react";
import { isOrglessPatientsHost } from "../../../utils/hostedMount";
import { useAuthServiceContext, usePatientServiceContext } from "../../../services";
import {
  useFhirAllergyIntolerances,
  useFhirAppointments,
  useFhirFamilyMemberHistories,
  useFhirClinicalLists,
  useFhirCoverages,
  useFhirMedicationStatements,
  useFhirRelatedPersons,
} from "../../../hooks";
import {
  buildPatientSystemTasks,
  summarizePatientSystemTasks,
  type PatientSystemTaskSummary,
} from "../../../utils/patientSystemTasks.ts";

/**
 * - THE PATIENT'S OWN SETUP STEPS, COMPUTED ONCE FOR EVERY SURFACE THAT ASKS.
 *
 * It lived inside `PatientHomeBanner` and was private to it, which is why the home page could not
 * answer the only question it needed to: **is the banner already offering the patient something?**
 *
 * WHAT THAT COST. The banner listed five outstanding setup items, and the cell directly beneath it
 * read *"Nothing needs you yet"* - measured on the patient portal on 2026-09-13. Two surfaces, one
 * screen, opposite claims. It is the ninth UI convention exactly: **never let an absence carry a
 * message**, because a screen that speaks by showing nothing cannot distinguish the reasons for
 * nothing.
 *
 * ONE COMPUTATION, NOT TWO. Every input here comes from a service context that caches per patient, so
 * a second caller costs no second read and - the part that matters - **cannot arrive at a different
 * answer**. That is the same argument the page's own invoice provider makes about money: three
 * independent loads can disagree, and a screen quoting two numbers is worse than a slow one.
 */
const PRACTICE_SCOPED_SETUP_STEPS = new Set(["system-related-persons", "system-insurance", "system-first-appointment"]);

export const usePatientSetupSummary = (): PatientSystemTaskSummary | undefined => {
  const { currentUser } = useAuthServiceContext();
  const { patientState } = usePatientServiceContext();

  /**
 * - THIS CALL SITE USED TO STARVE THE THING IT CALLS.
 *
 * `buildPatientSystemTasks` computes five setup steps and was handed `medicationStatements: []`,
 * `allergyIntolerances: []` and a related-persons hook with `autoLoad: false`. Three of the five
 * could therefore never be anything but incomplete, so the maximum reachable was 2 of 5 and the
 * banner could never disappear - which is the one thing the spec requires of it, since disappearing
 * is the entire reason it is allowed to sit above the account summary.
 *
 * The completion logic was never wrong. Ed completed every item on his own laptop and the count
 * stayed at 1 of 5, which no test asked because none of them referenced these inputs at all.
 */
  // Caregivers and insurance are still read through a practice, so the org-less portal leaves those
  // two steps to the practice portals rather than waiting on reads it cannot make.
  const orgless = isOrglessPatientsHost();
  const { relatedPersonsList, relatedPersonsBundle } = useFhirRelatedPersons({ autoLoad: !orgless });
  const { medicationStatementsList, medicationStatementsBundle } = useFhirMedicationStatements();
  const { allergyIntolerancesList, allergyIntolerancesBundle } = useFhirAllergyIntolerances();
  const { coverageList, coveragesBundle } = useFhirCoverages({ autoLoad: !orgless });
  const {
    clinicalListsBundle,
    hasConfirmedNoCurrentMedications,
    hasConfirmedNoKnownAllergies,
    hasConfirmedNoKnownFamilyHistory,
    hasConfirmedNoRelatedPersons,
  } = useFhirClinicalLists();
  const { familyMemberHistoriesList, familyMemberHistoriesBundle } = useFhirFamilyMemberHistories();
  const { appointmentsList, appointmentsBundle } = useFhirAppointments({ autoLoad: !orgless });

  /**
 * HAVE THE READS ANSWERED YET? - and until they have, there is NO summary to offer.
 *
 * Every one of these lists is empty before its fetch resolves, and empty reads as *not done*. So a
 * summary built from them mid-flight tells a patient who has finished everything that they are at
 * 2 of 5, then corrects itself - asserting a count from data nobody has read, which is the same
 * defect as a screen reporting a zero it never measured.
 *
 * `undefined` is the answer for "not yet known", and both readers of this hook are built for it.
 * Not keyed on `loading`: that starts false and only rises after the first paint, so it says
 * "idle" during the exact window this guard exists for. A delivered bundle is the fact.
 */
  const readsAnswered = Boolean(
    (orgless || relatedPersonsBundle) && medicationStatementsBundle && allergyIntolerancesBundle && clinicalListsBundle
      && (orgless || coveragesBundle) && familyMemberHistoriesBundle && (orgless || appointmentsBundle),
  );

  return useMemo(() => {
    if (!readsAnswered) return undefined;
    const patient = patientState ?? (currentUser?.fhir?.resourceType === "Patient" ? currentUser.fhir : undefined);
    // Reads the tasks the system ALREADY computes and summarises them with the module's own
    // function. Deriving a second count here is the defect this app has shipped four times.
    const tasks = buildPatientSystemTasks({
        patient,
        relatedPersons: relatedPersonsList ?? [],
        medicationStatements: medicationStatementsList ?? [],
        allergyIntolerances: allergyIntolerancesList ?? [],
        coverages: coverageList ?? [],
        hasConfirmedNoCurrentMedications,
        hasConfirmedNoKnownAllergies,
        familyMemberHistories: familyMemberHistoriesList ?? [],
        hasConfirmedNoKnownFamilyHistory,
        hasConfirmedNoRelatedPersons,
        appointments: appointmentsList ?? [],
      });
    return summarizePatientSystemTasks(
      orgless ? tasks.filter((task) => !PRACTICE_SCOPED_SETUP_STEPS.has(task.id)) : tasks,
    );
  }, [
    orgless,
    readsAnswered,
    patientState,
    currentUser,
    relatedPersonsList,
    medicationStatementsList,
    allergyIntolerancesList,
    coverageList,
    hasConfirmedNoCurrentMedications,
    hasConfirmedNoKnownAllergies,
    familyMemberHistoriesList,
    hasConfirmedNoKnownFamilyHistory,
    hasConfirmedNoRelatedPersons,
    appointmentsList,
  ]);
};