/**
 * 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.
 *
 * Copyright (c) 2006 Neil Crosby
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 **/
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;
    },


    /**
     * 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;
    },

    /**
     * Adds classString to the classes assigned to the element with id equal to
     * idString.
     **/
    addClassToId: function(idString, classString) {
        this.addClassToElement(document.getElementById(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(document.getElementById(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 (classString == classArray[x]) {
                classArray[x] = '';
                break;
            }
        }

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