// examples/versions.ts
import { JsonPointer } from 'json-ptr';

export type SupportedVersion = '1.0' | '1.1';

interface PrimaryGuestNamePointers {
  name: JsonPointer;
  surname: JsonPointer;
  honorific: JsonPointer;
}
const versions: Record<SupportedVersion, PrimaryGuestNamePointers> = {
  '1.0': {
    name: JsonPointer.create('/guests/0/name'),
    surname: JsonPointer.create('/guests/0/surname'),
    honorific: JsonPointer.create('/guests/0/honorific'),
  },
  '1.1': {
    name: JsonPointer.create('/primary/primaryGuest/name'),
    surname: JsonPointer.create('/primary/primaryGuest/surname'),
    honorific: JsonPointer.create('/primary/primaryGuest/honorific'),
  }
};

interface Reservation extends Record<string, unknown> {
  version?: SupportedVersion;
}

/**
 * Gets the primary guest's name from the specified reservation.
 * @param reservation a reservation, either version 1.0 or bearing a `version`
 * property indicating the version.
 */
function primaryGuestName(reservation: Reservation): string {
  const pointers = versions[reservation.version || '1.0'];
  if (!pointers) {
    throw new Error(`Unsupported reservation version: ${reservation.version}`);
  }
  const name = pointers.name.get(reservation) as string;
  const surname = pointers.surname.get(reservation) as string;
  const honorific = pointers.honorific.get(reservation) as string;
  const names: string[] = [];
  if (honorific) names.push(honorific);
  if (name) names.push(name);
  if (surname) names.push(surname);
  return names.join(' ');
}

// The original layout of a reservation (only the parts relevant to our example)
const reservationV1: Reservation = {
  guests: [{
    name: 'Wilbur',
    surname: 'Finkle',
    honorific: 'Mr.'
  }, {
    name: 'Wanda',
    surname: 'Finkle',
    honorific: 'Mrs.'
  }, {
    name: 'Wilma',
    surname: 'Finkle',
    honorific: 'Miss',
    child: true,
    age: 12
  }]
  // ...
};

// The new layout of a reservation (only the parts relevant to our example)
const reservationV1_1: Reservation = {
  version: '1.1',
  primary: {
    primaryGuest: {
      name: 'Wilbur',
      surname: 'Finkle',
      honorific: 'Mr.'
    },
    additionalGuests: [{
      name: 'Wanda',
      surname: 'Finkle',
      honorific: 'Mrs.'
    }, {
      name: 'Wilma',
      surname: 'Finkle',
      honorific: 'Miss',
      child: true,
      age: 12
    }]
    // ...
  }
  // ...
};

console.log(primaryGuestName(reservationV1));
console.log(primaryGuestName(reservationV1_1));