import type { BaseOption, VariantOption } from "@ben-to/builder/domain";

export type RecipesIndex = Readonly<{
  bases: ReadonlyArray<BaseOption>;
  variants: ReadonlyArray<VariantOption>;
}>;

const isRecord = (value: unknown): value is Record<string, unknown> =>
  typeof value === "object" && value !== null;

export const fetchRecipesIndex = async (
  catalogUrl = "/recipes/catalog.json"
): Promise<RecipesIndex> => {
  const response = await fetch(catalogUrl, { headers: { Accept: "application/json" } });
  if (!response.ok) {
    throw new Error(`Failed to load recipe catalog (${response.status})`);
  }

  const payload: unknown = await response.json();
  if (!isRecord(payload)) {
    throw new Error("Invalid recipe catalog payload");
  }

  const bases = payload.bases;
  const variants = payload.variants;
  if (!Array.isArray(bases) || !Array.isArray(variants)) {
    throw new Error("Invalid recipe catalog shape");
  }

  return Object.freeze({
    bases: Object.freeze(bases as BaseOption[]),
    variants: Object.freeze(variants as VariantOption[])
  });
};