import type { Communication } from 'fhir/r4';
import { hasReadReceiptForReference } from './readReceipts';

/**
 * Whom a read receipt names: the server's caller. A helper acting for someone is their link there, never the account
 * they signed in with; while that link is not known yet, nobody, so nothing is marked read in the wrong name.
 */
export const receiptReferenceOf = (
    user: { resourceType?: string; id?: string } | undefined,
    actingAs: { relatedPersonId?: string } | null | undefined,
): string | null => {
    if (actingAs) return actingAs.relatedPersonId ? `RelatedPerson/${actingAs.relatedPersonId}` : null;
    return user?.resourceType && user.id ? `${user.resourceType}/${user.id}` : null;
};

export const editionOf = (message: Communication): number | null => {
    const version = message.meta?.versionId;
    if (!version || !/^[0-9]+$/.test(version)) return null;
    const edition = Number(version);
    return Number.isSafeInteger(edition) ? edition : null;
};

/**
 * A receipt is confirmed only by what the save returned: the same message, carrying `reader`'s receipt, as a newer
 * edition than the one it was written on. Anything else, a missing or non-numeric edition included, is not proof.
 */
export const receiptConfirmed = (reader: string) => (sent: Communication, returned: Communication): boolean => {
    const before = editionOf(sent);
    const after = editionOf(returned);
    return returned.id === sent.id && before !== null && after !== null && after > before
        && hasReadReceiptForReference(returned, reader);
};