/* 
 * Auto Expanding Text Area (1.2.2)
 * by Chrys Bader (www.chrysbader.com)
 * chrysb@gmail.com
 *
 * Special thanks to:
 * Jake Chapa - jake@hybridstudio.com
 * John Resig - jeresig@gmail.com
 *
 * Copyright (c) 2008 Chrys Bader (www.chrysbader.com)
 * Dual licensed under the MIT (MIT-LICENSE.txt)
 * and GPL (GPL-LICENSE.txt) licenses.
 *
 *
 * NOTE: This script requires jQuery to work.  Download jQuery at www.jquery.com
 *
 */
 
(function(jQuery) {
		  
	var self = null;
 
	jQuery.fn.autogrow = function(o)
	{	
		return this.each(function() {
			new jQuery.autogrow(this, o);
		});
	};
	

    /**
     * The autogrow object.
     *
     * @constructor
     * @name jQuery.autogrow
     * @param Object e The textarea to create the autogrow for.
     * @param Hash o A set of key/value pairs to set as configuration properties.
     * @cat Plugins/autogrow
     */
	
	jQuery.autogrow = function (e, o)
	{
		this.options		  	= o || {};
		this.dummy			  	= null;
		this.interval	 	  	= null;
		this.line_height	  	= this.options.lineHeight || parseInt(jQuery(e).css('line-height'));
		this.min_height		  	= this.options.minHeight || parseInt(jQuery(e).css('min-height'));
		this.max_height		  	= this.options.maxHeight || parseInt(jQuery(e).css('max-height'));;
		this.textarea		  	= jQuery(e);
		
		if(this.line_height == NaN)
		  this.line_height = 0;
		
		// Only one textarea activated at a time, the one being used
		this.init();
	};
	
	jQuery.autogrow.fn = jQuery.autogrow.prototype = {
    autogrow: '1.2.2'
    };
	
	var setSelectionRange = function(input, selectionStart, selectionEnd) {
        if (input.setSelectionRange) {
            input.focus();
            input.setSelectionRange(selectionStart, selectionEnd);
        }
        else if (input.createTextRange) {
            var range = input.createTextRange();
            range.collapse(true);
            range.moveEnd('character', selectionEnd);
            range.moveStart('character', selectionStart);
            range.select();
        }
    }

    var setCaretToPos = function(input, pos) {
        setSelectionRange(input, pos, pos);
    }
    
    var findFirstDiff = function(in1, in2) {
        var min = in1.length > in2.length ? in2.length : in1.length;
        for (var i = 0; i < min; ++i) {
            if (in1[i] != in2[i]) {
                return i;
            }
        }
        return min == in1.length ? in2.length - 1 : in1.length - 1;
    }
    
    var getCurrentPosition = function(textarea, dummy){
	    // Strip HTML tags
	    var html = textarea.val().replace(/(<|>)/g, '');
    	
	    // IE is different, as per usual
	    if ($.browser.msie)
	    {
		    html = html.replace(/\n/g, '<BR>new');
	    }
	    else
	    {
		    html = html.replace(/\n/g, '<br>new');
	    }
	    
	    return findFirstDiff(dummy.html(), html) + 1;
    }
	
 	jQuery.autogrow.fn.extend = jQuery.autogrow.extend = jQuery.extend;
	
	jQuery.autogrow.fn.extend({
						 
		init: function() {			
			var self = this;			
			this.textarea.css({overflow: 'hidden', display: 'block'});
			this.textarea.bind('focus', function() { self.startExpand() } ).bind('blur', function() { self.stopExpand() });
			this.checkExpand();	
		},
						 
		startExpand: function() {				
		  var self = this;
			this.interval = window.setInterval(function() {self.checkExpand()}, 400);
		},
		
		stopExpand: function() {
			clearInterval(this.interval);	
		},
		
		checkExpand: function() {
			
			if (this.dummy == null)
			{
				this.dummy = jQuery('<div></div>');
				this.dummy.css({
												'font-size'  : this.textarea.css('font-size'),
												'font-family': this.textarea.css('font-family'),
												'width'      : this.textarea.css('width'),
												'padding'    : this.textarea.css('padding'),
												'line-height': this.line_height + 'px',
												'overflow-x' : 'hidden',
												'position'   : 'absolute',
												'top'        : 0,
												'left'		 : -9999
												}).appendTo('body');
			}
			
			// Strip HTML tags
			var html = this.textarea.val().replace(/(<|>)/g, '');
			
			// IE is different, as per usual
			if ($.browser.msie)
			{
				html = html.replace(/\n/g, '<BR>new');
			}
			else
			{
				html = html.replace(/\n/g, '<br>new');
			}
			
			if (this.dummy.html() != html)
			{
				this.dummy.html(html);	
				
				if (this.max_height > 0 && (this.dummy.height() + this.line_height > this.max_height))
				{
					this.textarea.css('overflow-y', 'auto');	
				}
				else
				{
					this.textarea.css('overflow-y', 'hidden');
					if (this.textarea.height() < this.dummy.height() + this.line_height || (this.dummy.height() < this.textarea.height()))
					{	
					    var $textarea = this.textarea;
					    var $dummy = this.dummy;
						this.textarea.animate({height: (this.dummy.height() + this.line_height) + 'px'}, { duration:100, 
						    step:function(){
						        setCaretToPos($textarea.get(0), getCurrentPosition($textarea, $dummy));
						    },
						    complete:function(){
						        setCaretToPos($textarea.get(0), getCurrentPosition($textarea, $dummy));
						    }});
					}
				}
			}
		}
						 
	 });
})(jQuery);