var dayNames = new Array("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday");
var dayAbbrevs = new Array("S", "M", "T", "W", "T", "F", "S");
var firstDayOfWeek = 0;
var DEBUG = 1;

/* stolen from somebody's blog */

function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}

/* this function borrowed from prototype.js */
document.getElementsByClassName = function(className) {
  var children = document.getElementsByTagName('*') || document.all;
  var elements = new Array();

  for (var i = 0; i < children.length; i++) {
    var child = children[i];
    if (hasClass(child, className)) {
      elements.push(child);
    }
  }

  return elements;
}

  function hasClass (elt, cls) {
    var classNames = elt.className.split(' ');
    for (var j = 0; j < classNames.length; j++) {
      if (classNames[j] == cls) {
	return true;
      }
    }
    return false;
  }

function debug(message) {
  if (DEBUG)
    alert(message);
}

var globalDateHash = new Object();

function findHCalendarEvents () {
  if (!(document.getElementById && document.createElement)) {
    debug("No DOM!");
    return;
  }
  var outputDiv = document.getElementById('jhCalendar');
  if (outputDiv == null) {
    debug("jhCalendar not found!")
      return;
  }
    
  var events = document.getElementsByClassName("vevent");
  globalDateHash = new Object();
  for (var i = 0; i < events.length; i++) {
    processEvent(events[i]);
  }
  

  
  for (year in globalDateHash) {
    for (month in globalDateHash[year]) {
      var mt = makeMonthTable(globalDateHash[year][month], year, month);
      var firstChild = outputDiv.firstChild;
      //outputDiv.appendChild(mt);
      if(firstChild != null)
	{
	  outputDiv.replaceChild(mt, firstChild);
	}
      else
	{
	  outputDiv.appendChild(mt);
	}
    }
  }
}

function processEvent(ev) {
  var kids = ev.getElementsByTagName('*') || ev.all;
  var eventHash = {};
  var dateInfo;
  for (var i = 0; i < kids.length; i++) {
    var kid = kids[i];
    if (hasClass(kid, 'summary')) {
      eventHash.summary = kid.cloneNode(true); // true means a "deep" cloning
    } else if (hasClass(kid, 'dtstart')) {
      dateInfo = parseDT(kid);
    }
  }
  if (dateInfo == null) {
    debug("didn't find dtstart for " + ev);
    return;
  }
  if (globalDateHash[ dateInfo[0] ] == null)
    globalDateHash[ dateInfo[0] ] = new Object();
  if (globalDateHash[ dateInfo[0] ][ dateInfo[1] ] == null)
    globalDateHash[ dateInfo[0] ][ dateInfo[1] ] = new Object();
  if (globalDateHash[ dateInfo[0] ][ dateInfo[1] ][ dateInfo[2] ] == null)
    globalDateHash[ dateInfo[0] ][ dateInfo[1] ][ dateInfo[2] ] = new Array();
    
  globalDateHash[ dateInfo[0] ][ dateInfo[1] ][ dateInfo[2] ].push(eventHash);

  return;
}

function parseDT(dt) {
  var dtText;
  if (dt.nodeName == 'ABBR' && dt.title) {
    dtText = dt.title;
  } else {
    dtText = dt.firstChild.data;
  }
  var result = dtText.match( /^(\d{4})(\d{2})(\d{2})/ );
  if (result == null) {
    debug("didn't recognize DT: " + dtText);
  }
  
  return [result[1], result[2], result[3]];
}

var monthLength = new Array(31,28,31,30,31,30,31,31,30,31,30,31);

// TODO deal with leap year
getMonthLength = function(year, month) {
  return monthLength[month - 1];
}

  function makeMonthTable (monthHash, year, month) {
    currentMonthLength = getMonthLength(year, month);
  
    var today = new Date;
    var todayYear = today.getFullYear();
    var todayMonth = today.getMonth() + 1;
    var todayDay = today.getDate();
    
    var days = new Array(currentMonthLength+1); // We are going to index this array starting at 1.  Because I said so.
    for (var i = 1; i <= currentMonthLength; i++) {
      days[i] = document.createElement('TD');
      days[i].className = 'calDay';
      if (todayYear == year && todayMonth == month && todayDay == i) {
	days[i].className += ' calDayToday';
      }
      var dayLabel = document.createElement('DIV');
      dayLabel.className = 'calDayLabel';
      days[i].appendChild(dayLabel);
      dayLabel.appendChild(document.createTextNode(i));
    }
  
    // populate days here

    for (var day in monthHash) {
      var dayEvents = monthHash[day];
      for (var i = 0; i < dayEvents.length; i++) {
	  var eventDiv = document.createElement('DIV');
	  eventDiv.className = 'calEvent';
	  eventDiv.appendChild(dayEvents[i].summary);
	  dayTD = days[day-0];
	  dayTD.appendChild(eventDiv);
	  if (! hasClass(dayTD, 'calEventDay')) {
	    dayTD.className += ' calEventDay';
	  }
	}
    }
    
    var monthTable = document.createElement('TABLE');
    monthTable.className = 'calTable';
    var tbody = monthTable.appendChild(document.createElement("TBODY"));
  
    var titleRow = document.createElement('TR');
    tbody.appendChild(titleRow);
    var titleTD = document.createElement('TD');
    titleTD.setAttribute("colspan", 7);
    titleTD.className = 'calHeader';
  
    titleRow.appendChild(titleTD);
    titleTD.appendChild(document.createTextNode(month + "/" + year));
  
    var headerRow = document.createElement('TR');
    headerRow.className = 'calColumnHeader';
    tbody.appendChild(headerRow);
    for (var i = 0; i <= 6; i++) {
      var headerElement = document.createElement('TD');
      headerElement.className = 'calColumnHeader';
      headerElement.appendChild(document.createTextNode(dayNames[(i+firstDayOfWeek) % 7]));
      headerRow.appendChild(headerElement);
    }

    var miniHeaderRow = document.createElement('TR');
    miniHeaderRow.className = 'calAbbrevColumnHeader';
    tbody.appendChild(miniHeaderRow);
    for (var i = 0; i <= 6; i++) {
      var headerElement = document.createElement('TD');
      headerElement.className = 'calAbbrevColumnHeader';
      headerElement.appendChild(document.createTextNode(dayAbbrevs[(i+firstDayOfWeek) % 7]));
      miniHeaderRow.appendChild(headerElement);
    }
  
    var dateToCheck = new Date();
    dateToCheck.setYear(year);
    dateToCheck.setMonth(month-1);
    dateToCheck.setDate(1);
    var dayOfFirstOfMonth = dateToCheck.getDay();

    var row = tbody.appendChild(document.createElement("TR"));
    // We add 14 (could have gotten away with 7) so that we don't get (-3) % 7 == -3
    for (var i = 0; i < (dayOfFirstOfMonth - firstDayOfWeek + 14) % 7; i++) {
      var emptyDay = document.createElement('TD');
      emptyDay.className = 'calDay calEmptyDay';
      row.appendChild(emptyDay);
    }
  
    for (var i = 1; i <= currentMonthLength; i++) {
      if (row.childNodes.length == 7) {
	row = tbody.appendChild(document.createElement("TR"));
      }
      row.appendChild(days[i]);
    }
  
    while (row.childNodes.length < 7) {
      var emptyDay = document.createElement('TD');
      emptyDay.className = 'calDay calEmptyDay';
      row.appendChild(emptyDay);
    }
  
    return monthTable;
  }

addLoadEvent(findHCalendarEvents);