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

var dayArrayShort = new Array('Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa');
var dayArrayMed = new Array('Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
var dayArrayLong = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday');
var monthArrayShort = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
var monthArrayMed = new Array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'June', 'July', 'Aug', 'Sept', 'Oct', 'Nov', 'Dec');
var monthArrayLong = new Array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');

// these variables define the date formatting we're expecting and outputting.
// If you want to use a different format by default, change the defaultDateSeparator
// and defaultDateFormat variables either here or on your HTML page.
var defaultDateSeparator = "/";        // common values would be "/" or "."
var defaultDateFormat = "mdy"    // valid values are "mdy", "dmy", and "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 + "\");'>this month</button> ";
    //html += "<p align='right'><button class='dpTodayButton' onClick='updateDateField(\"" + dateFieldName + "\");'>close</button></p>";
    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;
        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(dateString);
        } 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:

http://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) {
    }

}