/* Loads the Google data JavaScript client library */
google.load("gdata", "1");

function init() {
  // init the Google data JS client library with an error handler
  google.gdata.client.init();
  // load the code.google.com developer calendar
  loadDeveloperCalendar();
}

/**
* Loads the Google Developers Event Calendar
*/
function loadDeveloperCalendar() {
  loadCalendarByAddress('cu4onf92g7i49qprtf299tqqac%40');
}

/**
* Adds a leading zero to a single-digit number.  Used for displaying dates.
*/
function padNumber(num) {
  if (num <= 9) {
    return "0" + num;
  }
  return num;
}

/**
* Determines the full calendarUrl based upon the calendarAddress
* argument and calls loadCalendar with the calendarUrl value.
*
* @param {string} calendarAddress is the email-style address for the calendar
*/
function loadCalendarByAddress(calendarAddress) {
  var calendarUrl = 'http://www.google.com/calendar/feeds/' +
                    calendarAddress +
                    '/public/full';
  loadCalendar(calendarUrl);
}

/**
* Uses Google data JS client library to retrieve a calendar feed from the specified
* URL.  The feed is controlled by several query parameters and a callback 
* function is called to process the feed results.
*
* @param {string} calendarUrl is the URL for a public calendar feed
*/
function loadCalendar(calendarUrl) {
  var service = new 
      google.gdata.calendar.CalendarService('gdata-js-client-samples-simple');
  var query = new google.gdata.calendar.CalendarEventQuery(calendarUrl);
  query.setOrderBy('starttime');
  query.setSortOrder('ascending');
  query.setFutureEvents(true);
  query.setSingleEvents(true);
  query.setMaxResults(10);

  service.getEventsFeed(query, listEvents, '');
}

function listEvents(feedRoot) {
  var entries = feedRoot.feed.getEntries();
  var eventDiv = document.getElementById('events');
  if (eventDiv.childNodes.length > 0) {
    eventDiv.removeChild(eventDiv.childNodes[0]);
  }
  /* create a new unordered list */
  var ul = document.createElement('ul');
  /* set the calendarTitle div with the name of the calendar */
  document.getElementById('calendarTitle').innerHTML =
    "Calendar: " + feedRoot.feed.title.$t;
  /* loop through each event in the feed */
  var len = entries.length;
  for (var i = 0; i < len; i++) {
    var entry = entries[i];
    var title = entry.getTitle().getText();
    var startDateTime = null;
    var startJSDate = null;
    var times = entry.getTimes();
    if (times.length > 0) {
      startDateTime = times[0].getStartTime();
      startJSDate = startDateTime.getDate();
    }
    var entryLinkHref = null;
    if (entry.getHtmlLink() != null) {
      entryLinkHref = entry.getHtmlLink().getHref();
    }
    var dateString = (startJSDate.getMonth() + 1) + "/" + startJSDate.getDate();
    if (!startDateTime.isDateOnly()) {
      dateString += " " + startJSDate.getHours() + ":" +
          padNumber(startJSDate.getMinutes());
    }
    var li = document.createElement('li');

    /* if we have a link to the event, create an 'a' element */
    if (entryLinkHref != null) {
      entryLink = document.createElement('a');
      entryLink.setAttribute('href', entryLinkHref);
      entryLink.appendChild(document.createTextNode(title));
      li.appendChild(entryLink);
      li.appendChild(document.createTextNode(' - ' + dateString));
    } else {
      li.appendChild(document.createTextNode(title + ' - ' + dateString));
    }

    /* append the list item onto the unordered list */
    ul.appendChild(li);
  }
  eventDiv.appendChild(ul);
}

google.setOnLoadCallback(init);