import * as R from "ramda";

function wrapEvent(target, name, obj) {
  target.addEventListener(name, obj);
}

function runOnceFor(object, flag, cb) {
  if (!object[flag]) {
    object[flag] = true;
    cb();
  }
}

let MISSING_CHANGE_URL = Symbol("missing_change_url");
export default function addChangeUrlEvent(window) {
  runOnceFor(window, MISSING_CHANGE_URL, () => {
    const changeUrlEventCreator = {
      lastLocation: null,
      handleEvent(_) {
        // interface for EventListener

        let { hash, host, hostname, origin, href, pathname, port, protocol } =
          window.location || {};
        // store in object for comparison
        const pushedLocation = {
          hash,
          host,
          hostname,
          origin,
          href,
          pathname,
          port,
          protocol
        };

        // only dispatch action when url has actually changed so same link can be clicked repeatedly.
        if (!R.equals(pushedLocation, this.lastLocation)) {
          var urlChangeEvent = new CustomEvent("urlchanged", {
            detail: pushedLocation
          });
          window.dispatchEvent(urlChangeEvent);
          this.lastLocation = pushedLocation;
        }
      }
    };

    // / make sure we fire urlchanged for these
    wrapEvent(window, "popstate", changeUrlEventCreator);
    wrapEvent(window, "pushstate", changeUrlEventCreator);
    wrapEvent(window, "replacestate", changeUrlEventCreator);
  });
}