import type { Coding, HealthcareService } from 'fhir/r4';
import type { ServiceCategory } from './serviceCategories';

// The practice category (service taxonomy code) a service was added under. Not every category has a
// verified standard category coding, so services are grouped under their category by this.
export const SERVICE_PRACTICE_CATEGORY_EXTENSION_URL =
    'https://akashichealthrecords.com/fhir/StructureDefinition/service-practice-category';

export const servicePracticeCategoryOf = (service: HealthcareService | null | undefined): string | undefined =>
    service?.extension?.find((extension) => extension.url === SERVICE_PRACTICE_CATEGORY_EXTENSION_URL)?.valueCode;

export const applyServicePracticeCategory = (service: HealthcareService, code: string | undefined): HealthcareService => {
    const others = (service.extension ?? []).filter((extension) => extension.url !== SERVICE_PRACTICE_CATEGORY_EXTENSION_URL);
    const extension = code ? [...others, { url: SERVICE_PRACTICE_CATEGORY_EXTENSION_URL, valueCode: code }] : others;
    const next: HealthcareService = { ...service, extension };
    if (extension.length === 0) delete next.extension;
    return next;
};

const codingKey = (coding: Coding) => `${coding.system}|${coding.code}`;

// Swaps the taxonomy-managed standard category coding for another; codings the taxonomy does not manage stay.
export const replaceStandardCategory = (
    service: HealthcareService, categories: ServiceCategory[], next: Coding | undefined,
): HealthcareService => {
    const managed = new Set(categories.flatMap((category) =>
        (category.standardCategory ? [codingKey(category.standardCategory)] : [])));
    const kept = (service.category ?? []).flatMap((concept) => {
        const coding = (concept.coding ?? []).filter((item) => !managed.has(codingKey(item)));
        if (coding.length === (concept.coding ?? []).length) return [concept];
        return coding.length > 0 ? [{ ...concept, coding }] : [];
    });
    const category = next ? [...kept, { coding: [next] }] : kept;
    const result: HealthcareService = { ...service, category };
    if (category.length === 0) delete result.category;
    return result;
};