import json5 from "json5";
import Resource from "terriajs-cesium/Source/Core/Resource";
import JsonValue from "./Json";

const defaultHeaders = {
  Accept: "application/json5,application/json;q=0.8,*/*;q=0.01"
};

/*
 * A modified version of Cesium's loadJson function, supporting the more flexible JSON5 specification.
 */
export default function loadJson5(
  urlOrResource: string | Resource,
  headers?: { [key: string]: string }
): Promise<JsonValue> {
  let resource: Resource;
  if (urlOrResource instanceof Resource) {
    resource = urlOrResource;
  } else {
    resource = new Resource({
      url: urlOrResource,
      headers: {
        ...defaultHeaders,
        ...headers
      }
    });
  }

  const promise = resource.fetchText()!;
  return promise.then(function (value: string) {
    return json5.parse(value);
  });
}

// Use these headers if passing a Cesium Resource to loadJson5
loadJson5.defaultHeaders = defaultHeaders;