/*
   New Perspectives on HTML, XHTML, and DHTML
   Tutorial 12
   Tutorial Case

   Author: ECMcCarron
   Date:   10/25/09

   Function List:
   calendar(calendarDay)
      Creates the calendar table for the month specified in the
      calendarDay parameter. The current date is highlighted in 
      the table.

   writeCalTitle(calendarDay)
      Writes the title row in the calendar table

   writeDayTitle()
      Writes the weekday title rows in the calendar table

   daysInMonth(calendarDay)
      Returns the number of days in the month from calendarDay

   writeCalDays(calendarDay)
      Writes the daily rows in the calendar table, highlighting
      calendarDay

*/


function calendar(calendarDay) {
	if (calendarDay == null) calDate=new Date()
	else calDate = new Date(calendarDay);
	// var calDate = new Date("October 25, 2009");
	document.write("<table id='calendar_table'>");
	writeCalTitle(calDate);
	writeDayNames();
	writeCalDays(calDate);
	document.write("</table>");
}

function writeCalTitle(calendarDay) {
	
	var monthName = new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");
	var thisMonth=calendarDay.getMonth();
	var thisYear=calendarDay.getFullYear();
	
	document.write("<tr>");
	document.write("<th id='calendar_head' colspan='7'>");
	document.write(monthName[thisMonth]+" "+thisYear);
	document.write("</th>");
	document.write("</tr>");
}

function writeDayNames() {
	var dayName = new Array("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat");
	document.write("<tr>");
	for (var i = 0;i<dayName.length;i++) {
		document.write("<th class='calendar_weekdays'> "+dayName[i]+"</th>");
	}
	document.write("</tr>");
}

function daysInMonth(calendarDay) {
	var thisYear = calendarDay.getFullYear();
	var thisMonth = calendarDay.getMonth();
	var dayCount = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
	if (thisYear % 4 == 0) {
		if ((thisYear % 100 != 0) || (thisYear % 400 == 0)) {
			dayCount[1] = 29; // this is a leap year
		} 
	}
	return dayCount[thisMonth]; // return the number of days in the month
}

function writeCalDays(calendarDay) {
	var currentDay = calendarDay.getDate();
	// determine the starting day of the week
	var dayCount = 1;
	var totalDays = daysInMonth(calendarDay);
	calendarDay.setDate(1);  // set datw to the first day of the month
	var weekDay = calendarDay.getDay();  // the day of the week of the first day
	// write blank cells preceeding the starting day
	document.write("<tr>");
	for (var i = 0; i < weekDay; i++) {
		document.write("<td></td>");
	}
	// write cells for each day of the month
	while (dayCount <= totalDays) {
		// write the table rows and cells
		if (weekDay == 0) document.write("<tr>");
		
		if (dayCount == currentDay) {
			// highlight the current day
			document.write("<td class='calendar_dates' id='calendar_today'>"+dayCount+"</td>");
		} else {
			// display the day as usual
			document.write("<td class='calendar_dates'>"+dayCount+"</td>");
		}			
		if (weekDay == 6) document.write("</tr>");
		// move to the next day
		dayCount++;
		calendarDay.setDate(dayCount);
		weekDay = calendarDay.getDay();
		
	}
	document.write("</tr>");
}