// Document GoogleCal.js

/* 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(handleGDError);
  // load the code.google.com developer calendar
  loadDeveloperCalendar();
}

/**
 * Loads the Google Developers Event Calendar
 */
function loadDeveloperCalendar() {
  loadCalendarByAddress('coralginesta@gmail.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) {
  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(5);

  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) {
}

/**
 * Callback function for the Google data JS client library to call with a feed 
 * of events retrieved.
 * 
 *
 * @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]);
  }
  
  var div = document.createElement('div');
  /* 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() + "/" + (startJSDate.getMonth() + 1);
        dateString = dateString + "/" + startJSDate.getFullYear();
    if (!startDateTime.isDateOnly()) {
      dateString += "   (" + (startJSDate.getHours()) + ":" + 
          padNumber(startJSDate.getMinutes()) + ")";
    }
    
    var pevent = document.createElement('p');
    
    var strong = document.createElement('strong');
    strong.appendChild(document.createTextNode(dateString));
    pevent.appendChild(strong);
    pevent.appendChild(document.createElement('br'));
    pevent.appendChild(document.createTextNode(title));
    /* if we have a link to the event, create an 'a' element */
    if (entryLinkHref != null) {
      entryLink = document.createElement('a');
      entryLink.setAttribute('href', entryLinkHref);
      entryLink.setAttribute('target', '_blank');
      entryLink.appendChild(document.createTextNode('+ info'));
      pevent.appendChild(document.createElement('br'));
      pevent.appendChild(entryLink);
    }
    div.appendChild(pevent);
  }
  eventDiv.appendChild(div);
}

google.setOnLoadCallback(init);