import { Parser, Quad_Predicate, Quad_Subject, Store, Term } from "n3";
export const EV = "http://bigasterisk.com/event#";
export const RDF = "http://www.w3.org/1999/02/22-rdf-syntax-ns#";

export function getLiteral(store: Store, graph: Term, subj: Quad_Subject, pred: Quad_Predicate, missing: string | null): string {
  let out = null;
  store.getObjects(subj, pred, graph).forEach((attr) => {
    out = attr.value;
  });
  if (!out) {
    if (missing === null) {
      throw new Error();
    }
    return missing;
  }
  return out;
}

export async function fetchGraph(url: string) {
  return await fetch(url, {
    method: "GET",
    headers: {
      Accept: "application/json",
      "X-Pomerium-Authorization": document.cookie.substring(document.cookie.indexOf("=") + 1),
    },
  });
}

export async function parseGraph(r: Response, done: (store: Store) => void) {
  const store = new Store();
  const n3txt = await r.text();
  const parser = new Parser({ format: "application/trig" });
  parser.parse(n3txt, (error, quad, prefixes) => {
    if (quad) {
      store.addQuad(quad);
    } else {
      done(store);
    }
  });
}