twschiller/open-synthesis

/*
 * Open Synthesis, an open platform for intelligence analysis
 * Copyright (C) 2016 Open Synthesis Contributors. See CONTRIBUTING.md
 * file at the top-level directory of this distribution.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

// Adapted from: https://github.com/django-notifications/django-notifications/blob/master/notifications/static/notifications/notify.js

// sessionStorage key for the last known number of unread notifications
const NOTIFICATION_KEY = "unread_notifications";
const NOTIFY_REFRESH_PERIOD_MILLIS = 15 * 1000;
const MAX_RETRIES = 5;

/**
 * Returns a function that queries the number of unread notifications and sets the text of badge to the number.
 *
 * Re-queries the server every NOTIFY_REFRESH_PERIOD_MILLIS milliseconds. Stops querying the server if more than
 * MAX_RETRIES consecutive requests fail.
 *
 * @param badge the badge JQuery selector
 * @param {string} url the url to request
 * @returns {Function} function that updates the unread notification count
 */
function fetch_api_data(badge, url) {
  let consecutiveMisfires = 0;
  return function () {
    $.get(url, function (data) {
      consecutiveMisfires = 0;
      badge.text(data.unread_count);
      window.sessionStorage.setItem(NOTIFICATION_KEY, data.unread_count);
    })
      .fail(function () {
        consecutiveMisfires++;
      })
      .always(function () {
        if (consecutiveMisfires <= MAX_RETRIES) {
          setTimeout(fetch_api_data(badge, url), NOTIFY_REFRESH_PERIOD_MILLIS);
        } else {
          badge.text("!");
          badge.prop("title", "No connection to server");
        }
      });
  };
}

// NOTE: in practice, there will only be one element that has a data-notify-api-url attribute
$("[data-notify-api-url]").each(function (index, badge) {
  const elt = $(badge);
  setTimeout(fetch_api_data(elt, elt.data("notify-api-url")), 1000);
  const previous = window.sessionStorage.getItem(NOTIFICATION_KEY);
  if (previous != null) {
    elt.text(previous);
  }
});