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

function summary(str, maxlen) {
  if (str.length > maxlen)
    return str.substring(0, maxlen-1) + "...";
  else
    return str
}

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('e56f43aa4mf13euil2lpq5odoo@group.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) {
  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(3);

  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('Error at line ' + e.lineNumber +
          ' in ' + e.fileName + '\n' +
          'Message: ' + 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('Root cause: HTTP error ' + status + ' with status text of: ' + 
            statusText);
    }
  } else {
    alert(e.toString());
  }
}

/**
 * Callback function for the Google data JS client library to call with a feed 
 * of events retrieved.
 *
 * Creates a definition 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 definition list */
  var dl = document.createElement('dl');
  /* set the calendarTitle div with the name of the calendar, if such a div exists */
  var titleDiv = document.getElementById('calendarTitle')
  if (titleDiv != null)
      titleDiv.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 contents = summary(entry.getContent().getText(), 150);
    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();
    }


    /* The title bar dt, and div that goes in it. Using a div to make sure it inherits all the nice css things. */
    var dt = document.createElement('dt');
    var titleDiv = document.createElement('div');
    titleDiv.setAttribute('class', 'calendarentry-title');


    /* First take care of the title. */
    var titleBold = document.createElement('b');

    /* if we have a link to the event, create an 'a' element. Otherwise get a text node with the title */
    if (entryLinkHref != null) {
      entryLink = document.createElement('a');
      entryLink.setAttribute('href', entryLinkHref);
      entryLink.appendChild(document.createTextNode(title));
      titleTextElem = entryLink
    } else {
      titleTextElem = document.createTextNode(title)
    }

    titleBold.appendChild(titleTextElem);


    /* Next take care of the date. */
    var dateItalics = document.createElement('i');
    var dateBold = document.createElement('b');
    var dateString = (startJSDate.getMonth() + 1) + "/" + startJSDate.getDate() + "/" + startJSDate.getFullYear();

    if (!startDateTime.isDateOnly()) {
      dateString += " " + startJSDate.getHours() + ":" + 
          padNumber(startJSDate.getMinutes());
    }

    dateItalics.appendChild(document.createTextNode(dateString));
    dateBold.appendChild(dateItalics);


    /* Put the title bar together, title and date */
    titleDiv.appendChild(titleBold);
    titleDiv.appendChild(document.createTextNode(' - '));
    titleDiv.appendChild(dateBold);
    dt.appendChild(titleDiv);

    /* append the title bar list item onto the definition list */
    dl.appendChild(dt);


    /* finally, put the content */
    var dt = document.createElement('dt');
    var contentElement = document.createElement('div');
    contentElement.setAttribute('class', 'calendarentry-contents');
    contentElement.appendChild(document.createTextNode(contents));
    dt.appendChild(contentElement);
    dl.appendChild(dt);

  }
  eventDiv.appendChild(dl);
}

google.setOnLoadCallback(init);