//Constructor
function calendar(id,d,p,e,path){					//e = add by me -> events (array)
	this.id = id;									//id
	this.dateObject = d;							//data curenta; usually: d = new Date();
	this.pix = p;									//array of images [typeof: Image]
	this.write = writeCalendar;
	this.length = getLength;						//28,29,30,31 -> days of the month
	this.month = d.getMonth();						//0..11
	this.date = d.getDate();						//1..31 -> day of the month
	this.day = d.getDay();							//0..6	-> day of the week
	this.year = d.getFullYear();					//year
	this.getFormattedDate = getFormattedDate;
	//get the first day of the month's day
	d.setDate(1);									//ex: d=2008-09-16; d.setDate(1) -> 2008-09-01
	this.firstDay = d.getDay();						//
	//then reset the date object to the correct date
	d.setDate(this.date);							//
	this.e = e;
	this.path = path;
}

var days = new Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
var months = new Array('January','February','March','April','May','June','July','August','September','October','November','December');

//ex return: "Tuesday, September 16, 2008"
function getFormattedDate(){
	return days[this.day] + ', ' + months[this.month] + ' ' + this.date + ', ' + this.year;
	//return this.month + '/' + this.date + '/' + this.year;
}

function writeCalendar(){
	var calString = '<div id="calContainer" align="center">';
	//write month and year at top of table
	calString += '<table id="cal' + this.id + '" cellspacing="0" width="200" style="border:1px black solid;">';
	//write the image – comment out to hide images
	//calString += '<tr><th colspan="7"><img src="' + this.pix[this.month].src + '"/></th></tr>';
	//write the month
	calString += '<tr><th colspan="7" class="month">' + months[this.month] + ', ' + this.year + '</th></tr>';
	//write a row containing days of the week
	calString += '<tr>';
	
	for(i=0;i<days.length;i++){
		calString += '<th class="dayHeader">' + days[i].substring(0,3) + '</th>';
	}
	
	//write the body of the calendar
	calString += '<tr>';
	//create 6 rows so that the calendar doesn't resize
	for(j=0;j<42;j++){
		var displayNum = (j-this.firstDay+1);
		
		y = this.year;		
		m = this.month+1;
		s = y+'-'+with_prefix(m)+'-'+with_prefix(displayNum);
		
		
		if(j<this.firstDay){
			//write the leading empty cells
			calString += '<td class="empty">&nbsp;</td>';
		}else if( (displayNum<=this.length()) && in_date(s, this.e) ){
			calString += '<td id="' + this.id +'selected" class="date"><a href="'+ this.path + '?date=' + s +'">'+ displayNum + '</a></td>';
		}else if(displayNum > this.length()){
			//Empty cells at bottom of calendar
			calString += '<td>&nbsp;</td>';
		}else{
			//the rest of the numbered cells
			calString += '<td id="" class="days">' + displayNum + '</td>';
		}
		if(j%7==6){
			calString += '</tr><tr>';
		}
	}
	//close the last number row
	calString += '</tr>';
	//write the nav row
	calString += '<tr>';
	calString += '<td class="nav" style="text-decoration:underline;" onClick="changeMonth(-12,\'' + this.id + '\')">&lt;</td>';
	calString += '<td class="nav" onClick="changeMonth(-1,\'' + this.id + '\')">&lt;</td>';
	calString += '<td class="month" colspan="3">&nbsp;</td>';
	calString += '<td class="nav" onClick="changeMonth(1,\'' + this.id + '\')">&gt;</td>';
	calString += '<td class="nav" style="text-decoration:underline;text-align:right;" onClick="changeMonth(12,\'' + this.id + '\')">&gt;</td>';
	calString += '</tr>';
	
	calString += '</table>';
	calString += '</div>';
	return calString;
}

//returns the numbers of the days in a month
//?? this.dateObject.getFullYear() -> I don't understand the adressing mode
function getLength(){
	//thirty days has September...
	switch(this.month){
		case 1:
			if((this.dateObject.getFullYear()%4==0&&this.dateObject.getFullYear()%100!=0)||this.dateObject.getFullYear()%400==0)
				return 29; //leap year
			else
				return 28;
		case 3:
			return 30;
		case 5:
			return 30;
		case 8:
			return 30;
		case 10:
			return 30
		default:
			return 31;
	}
}


//?? eval, className
//td = object; cal = id
function changeDate(td,cal){
	//Some JavaScript trickery
	//Change the cal argument to the existing calendar object
	//This is why the first argument in the constructor must match the variable name
	//The cal reference also allows for multiple calendars on a page
	
	cal = eval(cal);
	document.getElementById(cal.id + "selected").className = "days";
	document.getElementById(cal.id + "selected").id = "";
	td.className = "date";
	td.id = cal.id + "selected";
	//set the calendar object to the new date
	cal.dateObject.setDate(td.firstChild.nodeValue);
	cal = new calendar(cal.id,cal.dateObject,cal.pix);
	//here is where you could react to a date change - I'll just display the formatted date
	alert(cal.getFormattedDate());
}

function changeMonth(mo,cal){	
	//more trickery!
	
	cal = eval(cal);
	//The Date object is smart enough to know that it should roll over in December
	//when going forward and in January when going back
	cal.dateObject.setMonth(cal.dateObject.getMonth() + mo);
	cal = new calendar(cal.id,cal.dateObject,cal.pix,cal.e,cal.path);
	//cal.formattedDate = cal.getFormattedDate();		//?? what is the meaning of this line
	document.getElementById('calContainer').innerHTML = cal.write();
}


/* convert "s" from string to date */
function to_date(s, d)
{
	var year = s.substring(0, 4);
	var month = s.substring(5, 7);
	var day = s.substring(8);
	d = new Date(year, month, day);
	return d;
}

/*
* my_date = string
* verify if "my_date" date is in vector "v"
*/
function in_date(my_date, v)
{
	var d = new Date();
	d = to_date(my_date, d);
	
	var start = new Date();
	var end = new Date();
		
	var ok = false;
	for (i = 0; i < v.length; i = i + 2)
	{		
		start = to_date(v[i], start);
		end = to_date(v[i+1], end);
		
		if (start <= d && d <= end)
		{
			ok = true;
			break;
		}
	}
	return ok;
}

function with_prefix(n)
{
	s = n+'';
	if (n<=9)
		s = '0'+n;
	return s;
}