/**
 * Written by Neil Crosby. 
 * http://www.workingwith.me.uk/
 *
 * Use this wherever you want, but please keep this comment at the top of this file.
 **/
var css = {
    /**
    * Returns an array containing references to all elements
    * of a given tag type within a certain node which have a given class
    *
    * @param node		the node to start from 
    *					(e.g. document, 
    *						  getElementById('whateverStartpointYouWant')
    *					)
    * @param searchClass the class we're wanting
    *					(e.g. 'some_class')
    * @param tag		 the tag that the found elements are allowed to be
    *					(e.g. '*', 'div', 'li')
    **/
    getElementsByClass: function(node, searchClass, tag) {
        var classElements = new Array();
        var els = node.getElementsByTagName(tag);
        var elsLen = els.length;
        var pattern = new RegExp("(^|\\s)" + searchClass + "(\\s|$)");


        for (var i = 0, j = 0; i < elsLen; i++) {
            if (this.elementHasClass(els[i], searchClass)) {
                classElements[j] = els[i];
                j++;
            }
        }
        return classElements;
    },

    getFirstElementByClass: function(node, searchClass, tag) {
        var classElements = new Array();
        var els = node.getElementsByTagName(tag);
        var elsLen = els.length;
        var pattern = new RegExp("(^|\\s)" + searchClass + "(\\s|$)");


        for (var i = 0, j = 0; i < elsLen; i++) {
            if (this.elementHasClass(els[i], searchClass)) {
                classElements[j] = els[i];
                break;
            }
        }
        return classElements;
    },

    getElementsByIdStr: function(node, searchIdStr, tag) {
        var idElements = new Array();
        var els = node.getElementsByTagName(tag);
        var elsLen = els.length;
        var pattern = new RegExp("(^|\\s)" + searchIdStr + "(\\s|$)");


        for (var i = 0, j = 0; i < elsLen; i++) {
            if (this.elementHasIdStr(els[i], searchIdStr)) {
                idElements[j] = els[i];
                j++;
            }
        }
        return idElements;
    },
    /**
    * PRIVATE.  Returns an array containing all the classes applied to this
    * element.
    *
    * Used internally by elementHasClass(), addClassToElement() and 
    * removeClassFromElement().
    **/
    privateGetClassArray: function(el) {
        return el.className.split(' ');
    },

    /**
    * PRIVATE.  Creates a string from an array of class names which can be used 
    * by the className function.
    *
    * Used internally by addClassToElement().
    **/
    privateCreateClassString: function(classArray) {
        return classArray.join(' ');
    },

    /**
    * Returns true if the given element has been assigned the given class.
    **/
    elementHasClass: function(el, classString) {
        if (!el) {
            return false;
        }

        var regex = new RegExp('\\b' + classString + '\\b');
        if (el.className.match(regex)) {
            return true;
        }

        return false;
    },

    elementHasIdStr: function(el, idString) {
        if (!el) {
            return false;
        }

        var regex = new RegExp('\\b' + idString + '\\b');
        if (el.id.match(regex)) {
            return true;
        }

        return false;
    },

    /**
    * Adds classString to the classes assigned to the element with id equal to
    * idString.
    **/
    addClassToId: function(idString, classString) {
        this.addClassToElement($(idString), classString);
    },

    /**
    * Adds classString to the classes assigned to the given element.
    * If the element already has the class which was to be added, then
    * it is not added again.
    **/
    addClassToElement: function(el, classString) {
        var classArray = this.privateGetClassArray(el);

        if (this.elementHasClass(el, classString)) {
            return; // already has element so don't need to add it
        }

        classArray.push(classString);

        el.className = this.privateCreateClassString(classArray);
    },

    /**
    * Removes the given classString from the list of classes assigned to the
    * element with id equal to idString
    **/
    removeClassFromId: function(idString, classString) {
        this.removeClassFromElement($(idString), classString);
    },

    /**
    * Removes the given classString from the list of classes assigned to the
    * given element.  If the element has the same class assigned to it twice, 
    * then only the first instance of that class is removed.
    **/
    removeClassFromElement: function(el, classString) {
        var classArray = this.privateGetClassArray(el);

        for (x in classArray) {
            if (classArray.hasOwnProperty(x)) {
                if (classString == classArray[x]) {
                    classArray[x] = '';
                    break;
                }
            }
        }

        el.className = this.privateCreateClassString(classArray);
    }
};