import { Organization } from 'fhir/r4';

// ---------------------------------------------------------------------------
// - WHERE THIS PRACTICE'S INCOMING REFERRALS LAND.
//
// front-desk the receptionists handle referrals
// referral-workspace staff holding the referral coordinator role work them
//
// The same field is read by SENDING organizations: a practice that has designated a destination is one
// another practice can deliver to in-system, with no fax and no phone call. One field does both jobs.
//
// Mirrors the server's `utils/referralRoutingPolicy.ts` - this file is the client's READER, and the two
// must agree on the extension url byte for byte.
// ---------------------------------------------------------------------------

// There is no GET /R4/referral-routing-settings. The org's saved routing travels only on the Organization
// resource, as this extension. The server WRITES this exact url (setReferralRouting in its own copy of
// this file); the client READS it back here, so the literal MUST match character for character.
// A drifted character reads as "never saved" forever: the practice chooses a destination, the server
// stores it, and every reader still sees no designation.
export const ORG_REFERRAL_ROUTING_EXTENSION_URL =
    'https://akashichealthrecords.com/fhir/StructureDefinition/organization-referral-routing';

const DESTINATION_SUB_URL = 'destination';

export const REFERRAL_DESTINATIONS = {
    FRONT_DESK: 'front-desk',
    REFERRAL_WORKSPACE: 'referral-workspace',
} as const;

export type ReferralDestination =
    (typeof REFERRAL_DESTINATIONS)[keyof typeof REFERRAL_DESTINATIONS];

const VALID_DESTINATIONS: readonly string[] = Object.values(REFERRAL_DESTINATIONS);

export const isReferralDestination = (value: unknown): value is ReferralDestination =>
    typeof value === 'string' && VALID_DESTINATIONS.includes(value);

export interface ReferralRoutingPolicy {
    /**
 * OPTIONAL, AND THERE IS DELIBERATELY NO DEFAULT VALUE - the same rule as the server's copy, and it
 * is the load-bearing one.
 *
 * *"A routing setting nobody filled in is the same as not being on the system, because the sending
 * side falls back to fax anyway."* Undefined means the practice has never chosen, and a sending org
 * must read that as *"we cannot deliver in-system here"*.
 *
 * Defaulting to `front-desk` would make every practice advertise, from the day this ships, that it
 * accepts in-system referrals - delivering them into queues nobody has been told to watch. A referral
 * that silently lands somewhere unwatched is strictly worse than a fax, because the sender believes it
 * arrived.
 */
    destination?: ReferralDestination;
}

/** A practice that has never opened the setting has no destination - not a default one. */
export const DEFAULT_REFERRAL_ROUTING_POLICY: ReferralRoutingPolicy = {};

/**
 * Pure reader - mirrors the server's `resolveEffectiveReferralRouting` exactly (same extension url, same
 * child url, same treatment of an unrecognised code), so every surface seeds from whatever the practice
 * last saved rather than from a second opinion assembled locally.
 */
export function resolveOrgReferralRouting(organization?: Organization | null): ReferralRoutingPolicy {
    const ext = organization?.extension?.find((e) => e.url === ORG_REFERRAL_ROUTING_EXTENSION_URL);
    if (!ext) return { ...DEFAULT_REFERRAL_ROUTING_POLICY };

    const destination = (ext.extension ?? []).find((e) => e.url === DESTINATION_SUB_URL)?.valueCode;

    // An unrecognised stored value reads as "never chosen" rather than being passed through - a code
    // this build does not know cannot be routed to, and showing it as a designation would tell an admin
    // their referrals are going somewhere that does not exist.
    return isReferralDestination(destination) ? { destination } : { ...DEFAULT_REFERRAL_ROUTING_POLICY };
}

/** Whether another practice could deliver a referral here in-system, rather than faxing it. */
export const acceptsInSystemReferrals = (organization?: Organization | null): boolean =>
    resolveOrgReferralRouting(organization).destination !== undefined;