import type { Document } from "@contentful/rich-text-types";

type GraphqlRichText = { json: Document; links?: unknown };

const isDocument = (v: unknown): v is Document =>
  !!v &&
  typeof v === "object" &&
  "nodeType" in (v as any) &&
  "content" in (v as any);

export const toDocument = (v: unknown | null | undefined): Document | null => {
  if (!v) return null;

  // REST/CDA Document
  if (isDocument(v)) return v;

  // GraphQL RichText { json: Document, links? }
  if (typeof v === "object" && v !== null && "json" in (v as any)) {
    const json = (v as GraphqlRichText).json;
    return isDocument(json) ? json : null;
  }

  return null;
};