Cu.import("resource://gre/modules/PromiseUtils.jsm");

const PREF_FREC_DECAY_RATE_DEF = 0.975;

/**
 * Promises that the frecency has been changed, and is the new value.
 *
 * @param {nsIURI} expectedURI The URI to check frecency for.
 * @param {Number} expectedFrecency The expected frecency for the URI.
 * @returns {Promise} A promise which is resolved when the URI is seen.
 */
function promiseFrecencyChanged(expectedURI, expectedFrecency) {
  let deferred = PromiseUtils.defer();
  let obs = new NavHistoryObserver();
  obs.onFrecencyChanged =
    (uri, newFrecency, guid, hidden, visitDate) => {
      PlacesUtils.history.removeObserver(obs);
      Assert.ok(!!uri, "uri should not be null");
      Assert.ok(uri.equals(NetUtil.newURI(expectedURI)), "uri should be the expected one");
      Assert.equal(newFrecency, expectedFrecency, "Frecency should be the expected one");
      deferred.resolve();
    };
  PlacesUtils.history.addObserver(obs, false);
  return deferred.promise;
}

/**
 * Promises that the many frecencies changed notification has been seen.
 *
 * @returns {Promise} A promise which is resolved when the notification is seen.
 */
function promiseManyFrecenciesChanged() {
  let deferred = PromiseUtils.defer();
  let obs = new NavHistoryObserver();
  obs.onManyFrecenciesChanged = () => {
    PlacesUtils.history.removeObserver(obs);
    Assert.ok(true);
    deferred.resolve();
  };
  PlacesUtils.history.addObserver(obs, false);
  return deferred.promise;
}

add_task(function* setup() {
  Services.prefs.setCharPref("places.frecency.decayRate", PREF_FREC_DECAY_RATE_DEF);
});

add_task(function* test_frecency_decay() {
  let unvisitedBookmarkFrecency = Services.prefs.getIntPref("places.frecency.unvisitedBookmarkBonus");

  // Add a bookmark and check its frecency.
  let url = "http://example.com/b";
  let promiseOne = promiseFrecencyChanged(url, unvisitedBookmarkFrecency);
  yield PlacesUtils.bookmarks.insert({
    url,
    parentGuid: PlacesUtils.bookmarks.unfiledGuid
  });
  yield promiseOne;

  // Trigger DecayFrecency.
  let promiseMany = promiseManyFrecenciesChanged();
  PlacesUtils.history.QueryInterface(Ci.nsIObserver)
             .observe(null, "idle-daily", "");
  yield promiseMany;

  // Now check the new frecency is correct.
  let newFrecency = yield PlacesTestUtils.frecencyInDB(url);

  Assert.equal(newFrecency, Math.round(unvisitedBookmarkFrecency * PREF_FREC_DECAY_RATE_DEF),
               "Frecencies should match");
});
