// JavaScript Document

<!--
/*
 * Converts an xs:date or xs:dateTime formatted string into the local timezone
 * and outputs a human-readable form of this date or date/time.
 *
 * @param {string} gCalTime is the xs:date or xs:dateTime formatted string
 * @return {string} is the human-readable date or date/time string
 */
function formatGCalTime(gCalTime) { 
  // text for regex matches
	var remtxt = gCalTime;
 
	function consume(retxt) {
		var match = remtxt.match(new RegExp('^' + retxt));
		if (match) {
			remtxt = remtxt.substring(match[0].length);
			return match[0];
		}
		return '';
	}
 
  // minutes of correction between gCalTime and GMT
  var totalCorrMins = 0;
 
  var year = consume('\\d{4}');
  consume('-?');
  var month = consume('\\d{2}');
  consume('-?');
  var dateMonth = consume('\\d{2}');
  var timeOrNot = consume('T');
 
  // if a DATE-TIME was matched in the regex 
  if (timeOrNot == 'T') {
    var hours = consume('\\d{2}');
    consume(':?');
    var mins = consume('\\d{2}');
    consume('(:\\d{2})?(\\.\\d{3})?');
    var zuluOrNot = consume('Z');
 
    // if time from server is not already in GMT, calculate offset
    if (zuluOrNot != 'Z') {
      var corrPlusMinus = consume('[\\+\\-]');
      if (corrPlusMinus != '') {
        var corrHours = consume('\\d{2}');
        consume(':?');
        var corrMins = consume('\\d{2}');
        totalCorrMins = (corrPlusMinus=='-' ? 1 : -1) * 
            (Number(corrHours) * 60 + 
	    (corrMins=='' ? 0 : Number(corrMins)));
      }
    } 
 
    // get time since epoch and apply correction, if necessary
    // relies upon Date object to convert the GMT time to the local
    // timezone
    var originalDateEpoch = Date.UTC(year, month - 1, dateMonth, hours, mins);
    var gmtDateEpoch = originalDateEpoch + totalCorrMins * 1000 * 60;
    var ld = new Date(gmtDateEpoch);
 
    // date is originally in YYYY-MM-DD format
    // time is originally in a 24-hour format
    // this converts it to MM/DD hh:mm (AM|PM) 
    dateString = ld.getDate() + '/' + (ld.getMonth() + 1) + ' ' + 
        ((ld.getHours()>12)?(ld.getHours()-12):(ld.getHours()===0?12:
	ld.getHours())) + ':' + ((ld.getMinutes()<10)?('0' + 
	ld.getMinutes()):(ld.getMinutes())) + ' ' + 
	((ld.getHours()>=12)?'PM':'AM');
  } else {
    // if only a DATE was matched
    dateString =  parseInt(dateMonth, 10) + '/' + parseInt(month, 10);
  }
	return dateString;
}
 
/*
 * Creates an unordered list of events in a human-readable form
 *
 * @param {json} root is the root JSON-formatted content from GData
 * @param {string} divId is the div in which the events are added
 */ 
function listEvents(root, divId) {
	var feed = root.feed;
	var events = document.getElementById(divId);
 
	if (events.childNodes.length > 0) {
		events.removeChild(events.childNodes[0]);
	}	  
 
	// create a new unordered list
	var ul = document.createElement('ul');
 
	// loop through each event in the feed
	for (var i = 0; i < feed.entry.length; i++) {
		var entry = feed.entry[i];
		var title = entry.title.$t;
		var start = entry['gd$when'][0].startTime;
 
		// get the URL to link to the event
		for (var linki = 0; linki < entry['link'].length; linki++) {
			if (entry['link'][linki]['type'] == 'text/html' &&
				entry['link'][linki]['rel'] == 'alternate') {
				var entryLinkHref = entry['link'][linki]['href'];
			}
		}
 
		var dateString = formatGCalTime(start);
		var li = document.createElement('li');
 
		// if we have a link to the event, create an 'a' element
		if (typeof entryLinkHref != 'undefined') {
			entryLink = document.createElement('a');
			entryLink.setAttribute('href', 'events.asp'); //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);
	}
	events.appendChild(ul);
}
 
/**
 * Callback function for the GData json-in-script call
 * Inserts the supplied list of events into a div of a pre-defined name
 * 
 * @param {json} root is the JSON-formatted content from GData
 */ 
function insertAgenda(root) {
	listEvents(root, 'agenda');
}
//-->