import type { Address, Patient } from 'fhir/r4';
import type { IValueSet } from '../../services/ValueSetService';
import { readDemographics } from '../../components/FhirPatientDisplay/demographics';
import { telecomSlots, telecomUseSlots } from '../../components/FhirPatientDisplay/telecomSlots';
import { formatFhirHumanName } from '../fhirHumanName';
import { interpreterNeededLabel } from '../interpreterNeeded';
import { enrolledLabel } from '../tribalAffiliation';
import { formatPhoneNumber } from '../phoneNumber';
import { getAtPath } from './getAtPath';

/**
 * History bindings for profile fields that have no fixed position in a Patient: answers kept in
 * extensions (whose order in `Patient.extension` shifts whenever another one is added), repeats, and
 * the formatted name. Each is read by what it means, the same way the profile reads it, so a field's
 * history never picks up another extension that happens to sit at its old index.
 */
export const PROFILE_HISTORY = {
  name: 'profile:name',
  languages: 'profile:languages',
  preferredLanguage: 'profile:preferredLanguage',
  interpreterNeeded: 'profile:interpreterNeeded',
  interpreterAnswer: 'profile:interpreterAnswer',
  races: 'profile:races',
  detailedRaces: 'profile:detailedRaces',
  ethnicities: 'profile:ethnicities',
  detailedEthnicities: 'profile:detailedEthnicities',
  tribes: 'profile:tribes',
  enrolled: 'profile:enrolled',
  phone: 'profile:phone',
  email: 'profile:email',
} as const;

/** Address rows are shown by index, the same way How to reach you lists them. */
export const profileAddressHistory = (index: number): string => `profile:address:${index}`;

/** "1200 Gear Avenue, West Burlington, IA 52655". */
export const formatProfileAddress = (address: Address): string => {
  const region = [address.state, address.postalCode].filter(Boolean).join(' ');
  return [...(address.line ?? []), address.city, region].filter(Boolean).join(', ');
};

const ADDRESS_HISTORY = /^profile:address:(\d+)$/;

const phoneHistory = (patient: Patient): string[] | undefined => {
  const values = telecomSlots(patient.telecom, 'phone');
  const uses = telecomUseSlots(patient.telecom, 'phone');
  const slots = ([0, 1] as const)
    .filter((index) => values[index])
    .map((index) => {
      const formatted = formatPhoneNumber(values[index]);
      return uses[index] ? `${formatted} ${uses[index]}` : formatted;
    });
  return slots.length ? slots : undefined;
};

const emailHistory = (patient: Patient): string[] | undefined => {
  const values = telecomSlots(patient.telecom, 'email').filter(Boolean);
  return values.length ? values : undefined;
};

// An empty answer is absent, so a cleared list and a never-given one read alike as "(not set)".
const displays = (items: IValueSet[]): string[] | undefined =>
  items.length ? items.map((item) => item.display || item.code) : undefined;

const preferredLanguage = (patient: Patient): string | undefined => {
  const entries = patient.communication ?? [];
  const language = (entries.find((entry) => entry.preferred) ?? entries[0])?.language;
  return language?.coding?.[0]?.display || language?.text || language?.coding?.[0]?.code || undefined;
};

const READERS: Record<string, (patient: Patient) => unknown> = {
  [PROFILE_HISTORY.name]: (patient) => formatFhirHumanName(patient.name, { emptyText: '' }) || undefined,
  [PROFILE_HISTORY.languages]: (patient) => displays(readDemographics(patient).languages),
  [PROFILE_HISTORY.preferredLanguage]: preferredLanguage,
  // The patient's profile reads no answer as No, so its history does too; staff see the answer itself.
  [PROFILE_HISTORY.interpreterNeeded]: (patient) => interpreterNeededLabel(patient) ?? 'No',
  [PROFILE_HISTORY.interpreterAnswer]: (patient) => interpreterNeededLabel(patient),
  [PROFILE_HISTORY.races]: (patient) => displays(readDemographics(patient).races),
  [PROFILE_HISTORY.detailedRaces]: (patient) => displays(readDemographics(patient).detailedRaces),
  [PROFILE_HISTORY.ethnicities]: (patient) => displays(readDemographics(patient).ethnicities),
  [PROFILE_HISTORY.detailedEthnicities]: (patient) => displays(readDemographics(patient).detailedEthnicities),
  [PROFILE_HISTORY.tribes]: (patient) => displays(readDemographics(patient).tribes),
  [PROFILE_HISTORY.enrolled]: (patient) => {
    const demographics = readDemographics(patient);
    return enrolledLabel(demographics.tribes.length > 0, demographics.enrolled) || undefined;
  },
  [PROFILE_HISTORY.phone]: phoneHistory,
  [PROFILE_HISTORY.email]: emailHistory,
};

/** One version's value for a history binding: a profile meaning, or a plain path into the resource. */
export function readFieldValue(resource: unknown, path: string): unknown {
  const read = READERS[path];
  if (read) return resource && typeof resource === 'object' ? read(resource as Patient) : undefined;
  const addressMatch = path.match(ADDRESS_HISTORY);
  if (addressMatch && resource && typeof resource === 'object') {
    const address = (resource as Patient).address?.[Number(addressMatch[1])];
    return address ? formatProfileAddress(address) : undefined;
  }
  return getAtPath(resource, path);
}