import type { ContactPoint, Patient } from 'fhir/r4';

export interface SignupDetails {
    /** E.164, as the signup form validated it. */
    phone?: string;
    /** YYYY-MM-DD. */
    birthDate?: string;
}

// The phone and date of birth typed at signup, for the one address they were typed for. Held in memory like the
// sign-in handoff, so they never reach the URL or storage and are gone after this visit.
let held: { email: string; details: SignupDetails } | undefined;

const sameAddress = (a: string, b: string) => a.trim().toLowerCase() === b.trim().toLowerCase();

/** An existing account's signup resumed: what was typed is kept for that address only. */
export const rememberSignupDetails = (email: string, details: SignupDetails) => {
    held = { email: email.trim(), details };
};

/** The details for this signed-in address, once; anything held for another address is dropped, never handed over. */
export const takeSignupDetailsFor = (signedInEmail: string): SignupDetails | undefined => {
    const taken = held;
    held = undefined;
    return taken && signedInEmail && sameAddress(taken.email, signedInEmail) ? taken.details : undefined;
};

/** The date of birth typed at signup, for this signed-in address only, read without handing the details over. */
export const signupBirthDateFor = (signedInEmail: string): string | undefined =>
    held && signedInEmail && sameAddress(held.email, signedInEmail) ? held.details.birthDate : undefined;

/**
 * The home record with only what it lacks filled in from signup: a phone when it has none, a date of birth when it
 * has none. Undefined when there is nothing to add. The phone is added as a plain number: an email verified at
 * signup says nothing about the phone, so it is neither marked verified nor opted into texts.
 */
export const missingDetailsPatch = (patient: Patient, details: SignupDetails): Patient | undefined => {
    const telecom: ContactPoint[] = patient.telecom ?? [];
    const addPhone = Boolean(details.phone) && !telecom.some((point) => point.system === 'phone' && point.value);
    const addBirthDate = Boolean(details.birthDate) && !patient.birthDate;
    if (!addPhone && !addBirthDate) return undefined;
    return {
        ...patient,
        ...(addPhone ? { telecom: [...telecom, { system: 'phone', value: details.phone as string }] } : {}),
        ...(addBirthDate ? { birthDate: details.birthDate } : {}),
    };
};