import type {
  CollectionDomainError,
  DomainCollection,
  DomainDescribeInput,
  DomainObjectResources,
} from "@/worker/objects/common/collection-types";

export interface CollectionDescribeSpec<
  TDb,
  TCollection extends DomainCollection,
  TObject,
  TResource extends { href: string; syncToken?: string },
  TError extends CollectionDomainError,
> {
  collectionKind: string;
  ensureCollection(db: TDb, subjectId: string, nowMs: number, collectionName: string): TCollection | null;
  homeResource(db: TDb): TResource;
  listCollections(db: TDb, subjectId: string, nowMs: number): TCollection[];
  collectionResource(db: TDb, collection: TCollection): TResource;
  objectByName(db: TDb, collectionId: string, objectName: string): TObject | undefined;
  objectResource(db: TDb, collection: TCollection, object: TObject): TResource;
  objectResources(db: TDb, collection: TCollection, maxResults: number): DomainObjectResources<TResource>;
  syncToken(seq: number): string;
  collectionNotFound(): TError;
  objectNotFound(): TError;
}

export function describeCollectionDomain<
  TDb,
  TCollection extends DomainCollection,
  TObject,
  TResource extends { href: string; syncToken?: string },
  TError extends CollectionDomainError,
>(
  db: TDb,
  input: DomainDescribeInput,
  spec: CollectionDescribeSpec<TDb, TCollection, TObject, TResource, TError>,
): { ok: true; resources: TResource[]; syncToken: string } | TError {
  if (input.kind === "home") {
    const collections = spec.listCollections(db, input.subjectId, input.nowMs);
    return {
      ok: true,
      resources: [spec.homeResource(db), ...collections.map((collection) => spec.collectionResource(db, collection))],
      syncToken: spec.syncToken(0),
    };
  }

  const collection = spec.ensureCollection(db, input.subjectId, input.nowMs, input.collectionName ?? "");
  if (!collection) return spec.collectionNotFound();
  if (input.kind === spec.collectionKind) {
    const resources = [spec.collectionResource(db, collection)];
    if (input.depth === "1") resources.push(...spec.objectResources(db, collection, input.maxResults).resources);
    return { ok: true, resources, syncToken: resources[0]!.syncToken ?? spec.syncToken(0) };
  }

  const object = spec.objectByName(db, collection.id, input.objectName ?? "");
  if (!object) return spec.objectNotFound();
  return { ok: true, resources: [spec.objectResource(db, collection, object)], syncToken: spec.syncToken(0) };
}