var datePickerDivID = "datepicker";
var iFrameDivID = "datepickeriframe";

var defaultDateSeparator = "";
var defaultDateFormat = "ymd";
var dateSeparator = defaultDateSeparator;
var dateFormat = defaultDateFormat;

function displayDatePicker(dateFieldName, displayBelowThisObject, dtFormat, dtSep) {
	var targetDateField = document.getElementsByName(dateFieldName).item(0);
 
	// if we weren't told what node to display the datepicker beneath, just display it
	// beneath the date field we're updating
	if (!displayBelowThisObject)
		displayBelowThisObject = targetDateField;
 
	// if a date separator character was given, update the dateSeparator variable
	if (dtSep)
		dateSeparator = dtSep;
	else
		dateSeparator = defaultDateSeparator;
 
	// if a date format was given, update the dateFormat variable
	if (dtFormat)
		dateFormat = dtFormat;
	else
		dateFormat = defaultDateFormat;
 
	var x = displayBelowThisObject.offsetLeft;
	var y = displayBelowThisObject.offsetTop + displayBelowThisObject.offsetHeight ;
 
	// deal with elements inside tables and such
	var parent = displayBelowThisObject;
	while (parent.offsetParent) {
		parent = parent.offsetParent;
		x += parent.offsetLeft;
		y += parent.offsetTop ;
	}
 
	drawDatePicker(targetDateField, x, y);
}


/**
Draw the datepicker object (which is just a table with calendar elements) at the
specified x and y coordinates, using the targetDateField object as the input tag
that will ultimately be populated with a date.

This function will normally be called by the displayDatePicker function.
*/
function drawDatePicker(targetDateField, x, y) {
	var dt = getFieldDate(targetDateField.value );
 
	// the datepicker table will be drawn inside of a <div> with an ID defined by the
	// global datePickerDivID variable. If such a div doesn't yet exist on the HTML
	// document we're working with, add one.
	if (!document.getElementById(datePickerDivID)) {
		// don't use innerHTML to update the body, because it can cause global variables
		// that are currently pointing to objects on the page to have bad references
		//document.body.innerHTML += "<div id='" + datePickerDivID + "' class='dpDiv'></div>";
		var newNode = document.createElement("div");
		newNode.setAttribute("id", datePickerDivID);
		newNode.setAttribute("class", "dpDiv");
		newNode.setAttribute("style", "visibility: hidden;");
		document.body.appendChild(newNode);
	}
 
	// move the datepicker div to the proper x,y coordinate and toggle the visiblity
	var pickerDiv = document.getElementById(datePickerDivID);
	pickerDiv.style.position = "absolute";
	pickerDiv.style.left = x + "px";
	pickerDiv.style.top = y + "px";
	pickerDiv.style.visibility = (pickerDiv.style.visibility == "visible" ? "hidden" : "visible");
	pickerDiv.style.display = (pickerDiv.style.display == "block" ? "none" : "block");
	pickerDiv.style.zIndex = 10000;
 
	// draw the datepicker table
	refreshDatePicker(targetDateField.name, dt.getFullYear(), dt.getMonth(), dt.getDate());
}


/**
This is the function that actually draws the datepicker calendar.
*/
function refreshDatePicker(dateFieldName, year, month, day) {
	// if no arguments are passed, use today's date; otherwise, month and year
	// are required (if a day is passed, it will be highlighted later)
	var thisDay = new Date();
 
	if ((month >= 0) && (year > 0)) {
		thisDay = new Date(year, month, 1);
	} else {
		day = thisDay.getDate();
		thisDay.setDate(1);
	}
 
	// the calendar will be drawn as a table
	// you can customize the table elements with a global CSS style sheet,
	// or by hardcoding style and formatting elements below
	var crlf = "\r\n";
	var TABLE = "<table cols=7 class='dpTable'>" + crlf;
	var xTABLE = "</table>" + crlf;
	var TR = "<tr class='dpTR'>";
	var TR_title = "<tr class='dpTitleTR'>";
	var TR_days = "<tr class='dpDayTR'>";
	var TR_todaybutton = "<tr class='dpTodayButtonTR'>";
	var xTR = "</tr>" + crlf;
	var TD = "<td class='dpTD' onMouseOut='this.className=\"dpTD\";' onMouseOver=' this.className=\"dpTDHover\";' ";		// leave this tag open, because we'll be adding an onClick event
	var TD_title = "<td colspan=5 class='dpTitleTD'>";
	var TD_buttons = "<td class='dpButtonTD'>";
	var TD_todaybutton = "<td colspan=7 class='dpTodayButtonTD'>";
	var TD_days = "<td class='dpDayTD'>";
	var TD_selected = "<td class='dpDayHighlightTD' onMouseOut='this.className=\"dpDayHighlightTD\";' onMouseOver='this.className=\"dpTDHover\";' ";		// leave this tag open, because we'll be adding an onClick event
	var xTD = "</td>" + crlf;
	var DIV_title = "<div class='dpTitleText'>";
	var DIV_selected = "<div class='dpDayHighlight'>";
	var xDIV = "</div>";
 
	// start generating the code for the calendar table
	var html = TABLE;
 
	// this is the title bar, which displays the month and the buttons to
	// go back to a previous month or forward to the next month
	html += TR_title;
	html += TD_buttons + getButtonCode(dateFieldName, thisDay, -1, "&lt;") + xTD;
	html += TD_title + DIV_title + monthArrayLong[ thisDay.getMonth()] + " " + thisDay.getFullYear() + xDIV + xTD;
	html += TD_buttons + getButtonCode(dateFieldName, thisDay, 1, "&gt;") + xTD;
	html += xTR;
 
	// this is the row that indicates which day of the week we're on
	html += TR_days;
	for(i = 0; i < dayArrayShort.length; i++)
		html += TD_days + dayArrayShort[i] + xTD;
	html += xTR;
 
	// now we'll start populating the table with days of the month
	html += TR;
 
	// first, the leading blanks
	for (i = 0; i < thisDay.getDay(); i++)
		html += TD + "&nbsp;" + xTD;
 
	// now, the days of the month
	do {
		dayNum = thisDay.getDate();
		TD_onclick = " onclick=\"updateDateField('" + dateFieldName + "', '" + getDateString(thisDay) + "');\">";
		
		if (dayNum == day)
			html += TD_selected + TD_onclick + DIV_selected + dayNum + xDIV + xTD;
		else
			html += TD + TD_onclick + dayNum + xTD;
		
		// if this is a Saturday, start a new row
		if (thisDay.getDay() == 6)
			html += xTR + TR;
		
		// increment the day
		thisDay.setDate(thisDay.getDate() + 1);
	} while (thisDay.getDate() > 1)
 
	// fill in any trailing blanks
	if (thisDay.getDay() > 0) {
		for (i = 6; i > thisDay.getDay(); i--)
			html += TD + "&nbsp;" + xTD;
	}
	html += xTR;
 
	// add a button to allow the user to easily return to today, or close the calendar
	var today = new Date();
	var todayString = "Today is " + dayArrayMed[today.getDay()] + ", " + monthArrayMed[ today.getMonth()] + " " + today.getDate();
	html += TR_todaybutton + TD_todaybutton;
	html += "<button class='dpTodayButton' onClick='refreshDatePicker(\"" + dateFieldName + "\");'>"+thisMonthBtn+"</button> ";
	html += "<button class='dpTodayButton' onClick='updateDateField(\"" + dateFieldName + "\");'>"+closeBtn+"</button>";
	html += xTD + xTR;
 
	// and finally, close the table
	html += xTABLE;
 
	document.getElementById(datePickerDivID).innerHTML = html;
	// add an "iFrame shim" to allow the datepicker to display above selection lists
	adjustiFrame();
}


/**
Convenience function for writing the code for the buttons that bring us back or forward
a month.
*/
function getButtonCode(dateFieldName, dateVal, adjust, label) {
	var newMonth = (dateVal.getMonth () + adjust) % 12;
	var newYear = dateVal.getFullYear() + parseInt((dateVal.getMonth() + adjust) / 12);
	if (newMonth < 0) {
		newMonth += 12;
		newYear += -1;
	}
 
	return "<button class='dpButton' onClick='refreshDatePicker(\"" + dateFieldName + "\", " + newYear + ", " + newMonth + ");'>" + label + "</button>";
}


/**
Convert a JavaScript Date object to a string, based on the dateFormat and dateSeparator
variables at the beginning of this script library.
*/
function getDateString(dateVal)
{
	var dayString = "00" + dateVal.getDate();
	var monthString = "00" + (dateVal.getMonth()+1);
	dayString = dayString.substring(dayString.length - 2);
	monthString = monthString.substring(monthString.length - 2);
 
	switch (dateFormat) {
		case "dmy" :
			return dayString + dateSeparator + monthString + dateSeparator + dateVal.getFullYear();
		case "ymd" :
			return (dateVal.getFullYear() + dateSeparator + monthString + dateSeparator + dayString).substr(2);
		case "mdy" :
		default :
			return monthString + dateSeparator + dayString + dateSeparator + dateVal.getFullYear();
	}
}


/**
Convert a string to a JavaScript Date object.
*/
function getFieldDate(dateString) {
	var dateVal;
	var dArray;
	var d, m, y;
 
	try {
		dArray = splitDateString(dateString);
		if (dArray) {
			switch (dateFormat) {
				case "dmy" :
					d = parseInt(dArray[0], 10);
					m = parseInt(dArray[1], 10) - 1;
					y = parseInt(dArray[2], 10);
					break;
				case "ymd" :
					d = parseInt(dArray[2], 10);
					m = parseInt(dArray[1], 10) - 1;
					y = parseInt(dArray[0], 10);
					break;
				case "mdy" :
				default :
					d = parseInt(dArray[1], 10);
					m = parseInt(dArray[0], 10) - 1;
					y = parseInt(dArray[2], 10);
					break;
			}
			dateVal = new Date(y, m, d);
		} else if (dateString) {
			dateVal = new Date("20"+dateString.substr(0,2),dateString.substr(2,2)-1,dateString.substr(4,2));
		} else {
			dateVal = new Date();
		}
	} catch(e) {
		dateVal = new Date();
	}
 
	return dateVal;
}


/**
Try to split a date string into an array of elements, using common date separators.
If the date is split, an array is returned; otherwise, we just return false.
*/
function splitDateString(dateString) {
	var dArray;
	if (dateString.indexOf("/") >= 0)
		dArray = dateString.split("/");
	else if (dateString.indexOf(".") >= 0)
		dArray = dateString.split(".");
	else if (dateString.indexOf("-") >= 0)
		dArray = dateString.split("-");
	else if (dateString.indexOf("\\") >= 0)
		dArray = dateString.split("\\");
	else
		dArray = false;
 
	return dArray;
}

function updateDateField(dateFieldName, dateString)
{
	var targetDateField = document.getElementsByName (dateFieldName).item(0);
	if (dateString)
		targetDateField.value = dateString;
 
	var pickerDiv = document.getElementById(datePickerDivID);
	pickerDiv.style.visibility = "hidden";
	pickerDiv.style.display = "none";
 
	adjustiFrame();
	targetDateField.focus();
 
	// after the datepicker has closed, optionally run a user-defined function called
	// datePickerClosed, passing the field that was just updated as a parameter
	// (note that this will only run if the user actually selected a date from the datepicker)
	if ((dateString) && (typeof(datePickerClosed) == "function"))
		datePickerClosed(targetDateField);
}


/**
Use an "iFrame shim" to deal with problems where the datepicker shows up behind
selection list elements, if they're below the datepicker. The problem and solution are
described at:

ttp://dotnetjunkies.com/WebLog/jking/archive/2003/07/21/488.aspx
http://dotnetjunkies.com/WebLog/jking/archive/2003/10/30/2975.aspx
*/
function adjustiFrame(pickerDiv, iFrameDiv)
{
	// we know that Opera doesn't like something about this, so if we
	// think we're using Opera, don't even try
	var is_opera = (navigator.userAgent.toLowerCase().indexOf("opera") != -1);
	if (is_opera)
		return;
	
	// put a try/catch block around the whole thing, just in case
	try {
		if (!document.getElementById(iFrameDivID)) {
			// don't use innerHTML to update the body, because it can cause global variables
			// that are currently pointing to objects on the page to have bad references
			//document.body.innerHTML += "<iframe id='" + iFrameDivID + "' src='javascript:false;' scrolling='no' frameborder='0'>";
			var newNode = document.createElement("iFrame");
			newNode.setAttribute("id", iFrameDivID);
			newNode.setAttribute("src", "javascript:false;");
			newNode.setAttribute("scrolling", "no");
			newNode.setAttribute ("frameborder", "0");
			document.body.appendChild(newNode);
		}
		
		if (!pickerDiv)
			pickerDiv = document.getElementById(datePickerDivID);
		if (!iFrameDiv)
			iFrameDiv = document.getElementById(iFrameDivID);
		
		try {
			iFrameDiv.style.position = "absolute";
			iFrameDiv.style.width = pickerDiv.offsetWidth;
			iFrameDiv.style.height = pickerDiv.offsetHeight ;
			iFrameDiv.style.top = pickerDiv.style.top;
			iFrameDiv.style.left = pickerDiv.style.left;
			iFrameDiv.style.zIndex = pickerDiv.style.zIndex - 1;
			iFrameDiv.style.visibility = pickerDiv.style.visibility ;
			iFrameDiv.style.display = pickerDiv.style.display;
		} catch(e) {
		}
 
	} catch (ee) {
	}
 
}