/**
 * @class Ext.DomHelper
 * 
The DomHelper class provides a layer of abstraction from DOM and transparently supports creating
 * elements via DOM or using HTML fragments. It also has the ability to create HTML fragment templates
 * from your DOM building code.
 *
 * 
DomHelper element specification object
 * 
A specification object is used when creating elements. Attributes of this object
 * are assumed to be element attributes, except for 4 special attributes:
 * 

 * 
tag : 
The tag name of the element
 * 
children : or cn
An array of the
 * same kind of element definition objects to be created and appended. These can be nested
 * as deep as you want.
 * 
cls : 
The class attribute of the element.
 * This will end up being either the "class" attribute on a HTML fragment or className
 * for a DOM node, depending on whether DomHelper is using fragments or DOM.
 * 
html : 
The innerHTML for the element
 * 

 *
 * 
Insertion methods
 * 
Commonly used insertion methods:
 * 

 * 
{@link #append} : 

 * 
{@link #insertBefore} : 

 * 
{@link #insertAfter} : 

 * 
{@link #overwrite} : 

 * 
{@link #createTemplate} : 

 * 
{@link #insertHtml} : 

 * 

 *
 * 
Example
 * 
This is an example, where an unordered list with 3 children items is appended to an existing
 * element with id 'my-div':

 

var dh = Ext.DomHelper; // create shorthand alias
// specification object
var spec = {
    id: 'my-ul',
    tag: 'ul',
    cls: 'my-list',
    // append children after creating
    children: [     // may also specify 'cn' instead of 'children'
        {tag: 'li', id: 'item0', html: 'List Item 0'},
        {tag: 'li', id: 'item1', html: 'List Item 1'},
        {tag: 'li', id: 'item2', html: 'List Item 2'}
    ]
};
var list = dh.append(
    'my-div', // the context element 'my-div' can either be the id or the actual node
    spec      // the specification object
);
 

 * 
Element creation specification parameters in this class may also be passed as an Array of
 * specification objects. This can be used to insert multiple sibling nodes into an existing
 * container very efficiently. For example, to add more list items to the example above:

dh.append('my-ul', [
    {tag: 'li', id: 'item3', html: 'List Item 3'},
    {tag: 'li', id: 'item4', html: 'List Item 4'}
]);
 * 

 *
 * 
Templating
 * 
The real power is in the built-in templating. Instead of creating or appending any elements,
 * {@link #createTemplate} returns a Template object which can be used over and over to
 * insert new elements. Revisiting the example above, we could utilize templating this time:
 * 

// create the node
var list = dh.append('my-div', {tag: 'ul', cls: 'my-list'});
// get template
var tpl = dh.createTemplate({tag: 'li', id: 'item{0}', html: 'List Item {0}'});

for(var i = 0; i < 5, i++){
    tpl.append(list, [i]); // use template to append to the actual node
}
 * 

 * 
An example using a template:

var html = '{2}';

var tpl = new Ext.DomHelper.createTemplate(html);
tpl.append('blog-roll', ['link1', 'http://www.jackslocum.com/', "Jack's Site"]);
tpl.append('blog-roll', ['link2', 'http://www.dustindiaz.com/', "Dustin's Site"]);
 * 

 *
 * 
The same example using named parameters:

var html = '{text}';

var tpl = new Ext.DomHelper.createTemplate(html);
tpl.append('blog-roll', {
    id: 'link1',
    url: 'http://www.jackslocum.com/',
    text: "Jack's Site"
});
tpl.append('blog-roll', {
    id: 'link2',
    url: 'http://www.dustindiaz.com/',
    text: "Dustin's Site"
});
 * 

 *
 * 
Compiling Templates
 * 
Templates are applied using regular expressions. The performance is great, but if
 * you are adding a bunch of DOM elements using the same template, you can increase
 * performance even further by {@link Ext.Template#compile "compiling"} the template.
 * The way "{@link Ext.Template#compile compile()}" works is the template is parsed and
 * broken up at the different variable points and a dynamic function is created and eval'ed.
 * The generated function performs string concatenation of these parts and the passed
 * variables instead of using regular expressions.
 * 

var html = '{text}';

var tpl = new Ext.DomHelper.createTemplate(html);
tpl.compile();

//... use template like normal
 * 

 *
 * 
Performance Boost
 * 
DomHelper will transparently create HTML fragments when it can. Using HTML fragments instead
 * of DOM can significantly boost performance.
 * 
Element creation specification parameters may also be strings. If {@link #useDom} is false,
 * then the string is used as innerHTML. If {@link #useDom} is true, a string specification
 * results in the creation of a text node. Usage:
 * 

Ext.DomHelper.useDom = true; // force it to use DOM; reduces performance
 * 
 * @singleton
 */
Ext.DomHelper = function(){
    var tempTableEl = null,
    	emptyTags = /^(?:br|frame|hr|img|input|link|meta|range|spacer|wbr|area|param|col)$/i,
    	tableRe = /^table|tbody|tr|td$/i,
    	pub,
    	// kill repeat to save bytes
    	afterbegin = "afterbegin",
    	afterend = "afterend",
    	beforebegin = "beforebegin",
    	beforeend = "beforeend",
    	ts = '',
        te = '',
        tbs = ts+'',
        tbe = ''+te,
        trs = tbs + '',
        tre = ''+tbe;

    // private
    function doInsert(el, o, returnElement, pos, sibling, append){
        var newNode = pub.insertHtml(pos, Ext.getDom(el), createHtml(o));
        return returnElement ? Ext.get(newNode, true) : newNode;
    }

    // build as innerHTML where available
    function createHtml(o){
	    var b = "",
	    	attr,
	    	val,
	    	key,
	    	keyVal,
	    	cn;

        if(typeof o == 'string'){
            b = o;
        } else if (Ext.isArray(o)) {
	        Ext.each(o, function(v) {
                b += createHtml(v);
            });
        } else {
	        b += "<" + (o.tag = o.tag || "div");
            Ext.iterate(o, function(attr, val){
                if(!/tag|children|cn|html$/i.test(attr)){
                    if (Ext.isObject(val)) {
                        b += " " + attr + "='";
                        Ext.iterate(val, function(key, keyVal){
                            b += key + ":" + keyVal + ";";
                        });
                        b += "'";
                    }else{
                        b += " " + ({cls : "class", htmlFor : "for"}[attr] || attr) + "='" + val + "'";
                    }
                }
            });
	        // Now either just close the tag or try to add children and close the tag.
	        if (emptyTags.test(o.tag)) {
	            b += "/>";
	        } else {
	            b += ">";
	            if ((cn = o.children || o.cn)) {
	                b += createHtml(cn);
	            } else if(o.html){
	                b += o.html;
	            }
	            b += "";
        	}
        }
        return b;
    }

    function ieTable(depth, s, h, e){
        tempTableEl.innerHTML = [s, h, e].join('');
        var i = -1,
        	el = tempTableEl;
        while(++i < depth){
            el = el.firstChild;
        }
        return el;
    }

    /**
     * @ignore
     * Nasty code for IE's broken table implementation
     */
    function insertIntoTable(tag, where, el, html) {
	    var node,
        	before;

        tempTableEl = tempTableEl || document.createElement('div');

  	    if(tag == 'td' && (where == afterbegin || where == beforeend) ||
  	       !/td|tr|tbody/i.test(tag) && (where == beforebegin || where == afterend)) {
            return;
        }
        before = where == beforebegin ? el :
		 		 where == afterend ? el.nextSibling :
				 where == afterbegin ? el.firstChild : null;

        if (where == beforebegin || where == afterend) {
        	el = el.parentNode;
    	}

        if (tag == 'td' || (tag == "tr" && (where == beforeend || where == afterbegin))) {
	        node = ieTable(4, trs, html, tre);
        } else if ((tag == "tbody" && (where == beforeend || where == afterbegin)) ||
        		   (tag == "tr" && (where == beforebegin || where == afterend))) {
	        node = ieTable(3, tbs, html, tbe);
        } else {
	     	node = ieTable(2, ts, html, te);
        }
        el.insertBefore(node, before);
        return node;
    }


    pub = {
	    
/**
	     * Returns the markup for the passed Element(s) config.
	     * @param {Object} o The DOM object spec (and children)
	     * @return {String}
	     */
	    markup : function(o){
	        return createHtml(o);
	    },

	    
/**
	     * Inserts an HTML fragment into the DOM.
	     * @param {String} where Where to insert the html in relation to el - beforeBegin, afterBegin, beforeEnd, afterEnd.
	     * @param {HTMLElement} el The context element
	     * @param {String} html The HTML fragmenet
	     * @return {HTMLElement} The new node
	     */
	    insertHtml : function(where, el, html){
	        var hash = {},
	        	hashVal,
 	        	setStart,
	        	range,
	        	frag,
	        	rangeEl,
	        	rs;

	        where = where.toLowerCase();
	        // add these here because they are used in both branches of the condition.
	        hash[beforebegin] = ['BeforeBegin', 'previousSibling'];
	        hash[afterend] = ['AfterEnd', 'nextSibling'];

	        if (el.insertAdjacentHTML) {
	            if(tableRe.test(el.tagName) && (rs = insertIntoTable(el.tagName.toLowerCase(), where, el, html))){
	            	return rs;
	            }
	            // add these two to the hash.
	            hash[afterbegin] = ['AfterBegin', 'firstChild'];
	            hash[beforeend] = ['BeforeEnd', 'lastChild'];
	            if ((hashVal = hash[where])) {
		        	el.insertAdjacentHTML(hashVal[0], html);
	            	return el[hashVal[1]];
	            }
	        } else {
		        range = el.ownerDocument.createRange();
		        setStart = "setStart" + (/end/i.test(where) ? "After" : "Before");
		        if (hash[where]) {
			     	range[setStart](el);
			     	frag = range.createContextualFragment(html);
			     	el.parentNode.insertBefore(frag, where == beforebegin ? el : el.nextSibling);
			     	return el[(where == beforebegin ? "previous" : "next") + "Sibling"];
		        } else {
			        rangeEl = (where == afterbegin ? "first" : "last") + "Child";
			        if (el.firstChild) {
				        range[setStart](el[rangeEl]);
				        frag = range.createContextualFragment(html);
                        if(where == afterbegin){
                            el.insertBefore(frag, el.firstChild);
                        }else{
                            el.appendChild(frag);
                        }
			        } else {
		 	            el.innerHTML = html;
	 	            }
	 	            return el[rangeEl];
		        }
	        }
	        throw 'Illegal insertion point -> "' + where + '"';
	    },

	    
/**
	     * Creates new DOM element(s) and inserts them before el.
	     * @param {Mixed} el The context element
	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
	     * @return {HTMLElement/Ext.Element} The new node
	     */
	    insertBefore : function(el, o, returnElement){
	        return doInsert(el, o, returnElement, beforebegin);
	    },

	    
/**
	     * Creates new DOM element(s) and inserts them after el.
	     * @param {Mixed} el The context element
	     * @param {Object} o The DOM object spec (and children)
	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
	     * @return {HTMLElement/Ext.Element} The new node
	     */
	    insertAfter : function(el, o, returnElement){
	        return doInsert(el, o, returnElement, afterend, "nextSibling");
	    },

	    
/**
	     * Creates new DOM element(s) and inserts them as the first child of el.
	     * @param {Mixed} el The context element
	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
	     * @return {HTMLElement/Ext.Element} The new node
	     */
	    insertFirst : function(el, o, returnElement){
	        return doInsert(el, o, returnElement, afterbegin, "firstChild");
	    },

	    
/**
	     * Creates new DOM element(s) and appends them to el.
	     * @param {Mixed} el The context element
	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
	     * @return {HTMLElement/Ext.Element} The new node
	     */
	    append : function(el, o, returnElement){
		    return doInsert(el, o, returnElement, beforeend, "", true);
	    },

	    
/**
	     * Creates new DOM element(s) and overwrites the contents of el with them.
	     * @param {Mixed} el The context element
	     * @param {Object/String} o The DOM object spec (and children) or raw HTML blob
	     * @param {Boolean} returnElement (optional) true to return a Ext.Element
	     * @return {HTMLElement/Ext.Element} The new node
	     */
	    overwrite : function(el, o, returnElement){
	        el = Ext.getDom(el);
	        el.innerHTML = createHtml(o);
	        return returnElement ? Ext.get(el.firstChild) : el.firstChild;
	    },

	    createHtml : createHtml
    };
    return pub;
}();