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

/**
 * Loads the Google Developers Event Calendar
 */
function loadDeveloperCalendar() {
  loadCalendarByAddress('developer-calendar@google.com');
}

/**
 * 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) {
  /* aktiver Kalender ist Rehren Dopplekopf */
  var calendarUrl = 'http://www.google.com/calendar/feeds/a9hdi0del1fgl86i0tvlag72rs@group.calendar.google.com/public/full'
  /* var calendarUrl = 'http://www.google.com/calendar/feeds/4r2dmkb3rh55p47q5faus0ldd4@group.calendar.google.com/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('AMensching-GCal-js');
  var query = new google.gdata.calendar.CalendarEventQuery(calendarUrl);
  query.setOrderBy('starttime');
  query.setSortOrder('ascending');
  query.setSingleEvents(true);
  query.setMaxResults(1);
  
  var today=new Date();
  var von=today.getFullYear() + '-' + padNumber(today.getMonth()+1) + '-' + padNumber(today.getDate()) + 'T00:00:00.00-00:00';
  var bis=today.getFullYear() + '-' + padNumber(today.getMonth()+1) + '-' + padNumber(today.getDate()) + 'T23:59:59.99-00:00';      
  var startMin = google.gdata.DateTime.fromIso8601(von);
  var startMax = google.gdata.DateTime.fromIso8601(bis);
    
  query.setMinimumStartTime(startMin);
  query.setMaximumStartTime(startMax); 
 
  
  
  service.getEventsFeed(query, listEvents, handleGDError);
}

/**
 * Callback function for the Google data JS client library to call when an error
 * occurs during the retrieval of the feed.  Details available depend partly
 * on the web browser, but this shows a few basic examples. In the case of
 * a privileged environment using ClientLogin authentication, there may also
 * be an e.type attribute in some cases.
 *
 * @param {Error} e is an instance of an Error 
 */
function handleGDError(e) {
  document.getElementById('jsSourceFinal').setAttribute('style', 
      'display:none');
  if (e instanceof Error) {
    /* alert with the error line number, file and message */
    alert('Fehler in Zeile ' + e.lineNumber +
          ' in ' + e.fileName + '\n' +
          'Nachricht: ' + e.message);
    /* if available, output HTTP error code and status text */
    if (e.cause) {
      var status = e.cause.status;
      var statusText = e.cause.statusText;
      alert('Ursache: HTTP Fehler ' + status + ' mit Status Text: ' + 
            statusText);
    }
  } else {
    alert(e.toString());
  }
}


function getMonthString(monthIndex)
{
	var month=new Array(13)
	month[1]="Januar"
	month[2]="Februar"
	month[3]="März"
	month[4]="April"
	month[5]="Mai"
	month[6]="Juni"
	month[7]="Juli"
	month[8]="August"
	month[9]="September"
	month[10]="Oktober"
	month[11]="November"
	month[12]="Dezember"
	
	return month[monthIndex];
}




/**
 * Callback function for the Google data JS client library to call with a feed 
 * of events retrieved.
 *
 * Creates an unordered list of events in a human-readable form.  This list of
 * events is added into a div called 'events'.  The title for the calendar is
 * placed in a div called 'calendarTitle'
 *
 * @param {json} feedRoot is the root of the feed, containing all entries 
 */ 
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.getDate()) + "." + getMonthString((startJSDate.getMonth() + 1)) + " " + startJSDate.getFullYear();
    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);