/*
    This sample code is provided by Annsa Ltd. for information only.
*/

// Simple helper to return the "exMaxLen" attribute for
// the specified field.  Using "getAttribute" won't work
// with Firefox.
function GetMaxLength(targetField)
{
    return targetField.exMaxLen;
}

//
// Limit the text input in the specified field.
//
function LimitInput(targetField, sourceEvent)
{
	var isPermittedKeystroke;
	var enteredKeystroke;
	var maximumFieldLength;
	var currentFieldLength;
	var inputAllowed = true;
	var selectionLength = parseInt(GetSelectionLength(targetField));
	
	if ( GetMaxLength(targetField) != null )
	{
	    // Get the current and maximum field length
	    currentFieldLength = parseInt(targetField.value.length);
		maximumFieldLength = parseInt(GetMaxLength(targetField));

		// Allow non-printing, arrow and delete keys
        enteredKeystroke = window.event ? sourceEvent.keyCode : sourceEvent.which;
		isPermittedKeystroke = ((enteredKeystroke < 32)								// Non printing
					          ||(enteredKeystroke >= 33 && enteredKeystroke <= 40)	// Page Up, Down, Home, End, Arrow
					          ||(enteredKeystroke == 46))							// Delete

		// Decide whether the keystroke is allowed to proceed
		if ( !isPermittedKeystroke )
		{
			if ( ( currentFieldLength - selectionLength ) >= maximumFieldLength ) 
			{
				inputAllowed = false;
			}
		}
		
		// Force a trim of the textarea contents if necessary
		if ( currentFieldLength > maximumFieldLength )
		{
			targetField.value = targetField.value.substring(0, maximumFieldLength)
		}
	}   
	
	sourceEvent.returnValue = inputAllowed;
	return (inputAllowed);
}

//
// Limit the text input in the specified field.
//
function LimitPaste(targetField, sourceEvent)
{
	var clipboardText;
	var resultantLength;
	var maximumFieldLength;
	var currentFieldLength;
	var pasteAllowed = true;
	var selectionLength = GetSelectionLength(targetField);

	if ( GetMaxLength(targetField) != null )
	{
	    // Get the current and maximum field length
	    currentFieldLength = parseInt(targetField.value.length);
		maximumFieldLength = parseInt(GetMaxLength(targetField));

		clipboardText = window.clipboardData.getData("Text");
		if (clipboardText == null)
		{
		    pasteAllowed = false;
		}
		else
		{
		    resultantLength = currentFieldLength + clipboardText.length - selectionLength;
		    if ( resultantLength > maximumFieldLength)
		    {
			    pasteAllowed = false;
		    }	
		}
	}	
	
	sourceEvent.returnValue = pasteAllowed;
	return (pasteAllowed);
}

//
// Returns the number of selected characters in 
// the specified element
//
function GetSelectionLength(targetField)
{
	if ( targetField.selectionStart == undefined )
	{
		return document.selection.createRange().text.length;
	}
	else
	{
		return (targetField.selectionEnd - targetField.selectionStart);
	}
}