# Yahoo! UI Library

### yuiloader 2.5.0

Yahoo! UI Library > yuiloader > yuiloader.js (source view)

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    /**
     * Provides dynamic loading for the YUI library.  It includes the dependency
     * info for the library, and will automatically pull in dependencies for
     * the modules requested.  It supports rollup files (such as utilities.js
     * and yahoo-dom-event.js), and will automatically use these when
     * appropriate in order to minimize the number of http connections
     * required to load all of the dependencies.
     *
     * @module yuiloader
     * @namespace YAHOO.util
     */

    /**
     * YUILoader provides dynamic loading for YUI.
     * @class YAHOO.util.YUILoader
     * @todo
     *      version management, automatic sandboxing
     */
    (function() {

        var Y=YAHOO, util=Y.util, lang=Y.lang, env=Y.env;

        var YUI = {

            dupsAllowed: {'yahoo': true, 'get': true},

            /*
             * The library metadata for the current release  The is the default
             * value for YAHOO.util.YUILoader.moduleInfo
             * @property YUIInfo
             * @static
             */
            info: {

        'base': 'http://yui.yahooapis.com/2.5.0/build/',

        'skin': {
            'defaultSkin': 'sam',
            'base': 'assets/skins/',
            'path': 'skin.css',
            'rollup': 3
        },

        'moduleInfo': {

            'animation': {
                'type': 'js',
                'path': 'animation/animation-min.js',
                'requires': ['dom', 'event']
            },

            'autocomplete': {
                'type': 'js',
                'path': 'autocomplete/autocomplete-min.js',
                'requires': ['dom', 'event'],
                'optional': ['connection', 'animation'],
                'skinnable': true
            },

            'base': {
                'type': 'css',
                'path': 'base/base-min.css'
            },

            'button': {
                'type': 'js',
                'path': 'button/button-min.js',
                'requires': ['element'],
                'optional': ['menu'],
                'skinnable': true
            },

            'calendar': {
                'type': 'js',
                'path': 'calendar/calendar-min.js',
                'requires': ['event', 'dom'],
                'skinnable': true
            },

            'charts': {
                'type': 'js',
                'path': 'charts/charts-experimental-min.js',
                'requires': ['element', 'json', 'datasource']
            },

            'colorpicker': {
                'type': 'js',
                'path': 'colorpicker/colorpicker-min.js',
                'requires': ['slider', 'element'],
                'optional': ['animation'],
                'skinnable': true
            },

            'connection': {
                'type': 'js',
                'path': 'connection/connection-min.js',
                'requires': ['event']
            },

            'container': {
                'type': 'js',
                'path': 'container/container-min.js',
                'requires': ['dom', 'event'],
                // button is optional, but creates a circular dep
                //'optional': ['dragdrop', 'animation', 'connection', 'connection', 'button'],
                'optional': ['dragdrop', 'animation', 'connection'],
                'supersedes': ['containercore'],
                'skinnable': true
            },

            'containercore': {
                'type': 'js',
                'path': 'container/container_core-min.js',
                'requires': ['dom', 'event'],
                'pkg': 'container'
            },

            'cookie': {
                'type': 'js',
                'path': 'cookie/cookie-beta-min.js',
                'requires': ['yahoo']
            },

            'datasource': {
                'type': 'js',
                'path': 'datasource/datasource-beta-min.js',
                'requires': ['event'],
                'optional': ['connection']
            },

            'datatable': {
                'type': 'js',
                'path': 'datatable/datatable-beta-min.js',
                'requires': ['element', 'datasource'],
                'optional': ['calendar', 'dragdrop'],
                'skinnable': true
            },

            'dom': {
                'type': 'js',
                'path': 'dom/dom-min.js',
                'requires': ['yahoo']
            },

            'dragdrop': {
                'type': 'js',
                'path': 'dragdrop/dragdrop-min.js',
                'requires': ['dom', 'event']
            },

            'editor': {
                'type': 'js',
                'path': 'editor/editor-beta-min.js',
                'requires': ['menu', 'element', 'button'],
                'optional': ['animation', 'dragdrop'],
                'skinnable': true
            },

            'element': {
                'type': 'js',
                'path': 'element/element-beta-min.js',
                'requires': ['dom', 'event']
            },

            'event': {
                'type': 'js',
                'path': 'event/event-min.js',
                'requires': ['yahoo']
            },

            'fonts': {
                'type': 'css',
                'path': 'fonts/fonts-min.css'
            },

            'get': {
                'type': 'js',
                'path': 'get/get-min.js',
                'requires': ['yahoo']
            },

            'grids': {
                'type': 'css',
                'path': 'grids/grids-min.css',
                'requires': ['fonts'],
                'optional': ['reset']
            },

            'history': {
                'type': 'js',
                'path': 'history/history-min.js',
                'requires': ['event']
            },

             'imagecropper': {
                 'type': 'js',
                 'path': 'imagecropper/imagecropper-beta-min.js',
                 'requires': ['dom', 'event', 'dragdrop', 'element', 'resize'],
                 'skinnable': true
             },

             'imageloader': {
                'type': 'js',
                'path': 'imageloader/imageloader-min.js',
                'requires': ['event', 'dom']
             },

             'json': {
                'type': 'js',
                'path': 'json/json-min.js',
                'requires': ['yahoo']
             },

             'layout': {
                 'type': 'js',
                 'path': 'layout/layout-beta-min.js',
                 'requires': ['dom', 'event', 'element'],
                 'optional': ['animation', 'dragdrop', 'resize', 'selector'],
                 'skinnable': true
             },

            'logger': {
                'type': 'js',
                'path': 'logger/logger-min.js',
                'requires': ['event', 'dom'],
                'optional': ['dragdrop'],
                'skinnable': true
            },

            'menu': {
                'type': 'js',
                'path': 'menu/menu-min.js',
                'requires': ['containercore'],
                'skinnable': true
            },

            'profiler': {
                'type': 'js',
                'path': 'profiler/profiler-beta-min.js',
                'requires': ['yahoo']
            },

            'profilerviewer': {
                'type': 'js',
                'path': 'profilerviewer/profilerviewer-beta-min.js',
                'requires': ['yuiloader', 'element'],
                'skinnable': true
            },

            'reset': {
                'type': 'css',
                'path': 'reset/reset-min.css'
            },

            'reset-fonts-grids': {
                'type': 'css',
                'path': 'reset-fonts-grids/reset-fonts-grids.css',
                'supersedes': ['reset', 'fonts', 'grids', 'reset-fonts'],
                'rollup': 3
            },

            'reset-fonts': {
                'type': 'css',
                'path': 'reset-fonts/reset-fonts.css',
                'supersedes': ['reset', 'fonts'],
                'rollup': 2
            },

             'resize': {
                 'type': 'js',
                 'path': 'resize/resize-beta-min.js',
                 'requires': ['dom', 'event', 'dragdrop', 'element'],
                 'optional': ['animation'],
                 'skinnable': true
             },

            'selector': {
                'type': 'js',
                'path': 'selector/selector-beta-min.js',
                'requires': ['yahoo', 'dom']
            },

            'simpleeditor': {
                'type': 'js',
                'path': 'editor/simpleeditor-beta-min.js',
                'requires': ['element'],
                'optional': ['containercore', 'menu', 'button', 'animation', 'dragdrop'],
                'skinnable': true,
                'pkg': 'editor'
            },

            'slider': {
                'type': 'js',
                'path': 'slider/slider-min.js',
                'requires': ['dragdrop'],
                'optional': ['animation']
            },

            'tabview': {
                'type': 'js',
                'path': 'tabview/tabview-min.js',
                'requires': ['element'],
                'optional': ['connection'],
                'skinnable': true
            },

            'treeview': {
                'type': 'js',
                'path': 'treeview/treeview-min.js',
                'requires': ['event'],
                'skinnable': true
            },

            'uploader': {
                'type': 'js',
                'path': 'uploader/uploader-experimental.js',
                'requires': ['yahoo']
            },

            'utilities': {
                'type': 'js',
                'path': 'utilities/utilities.js',
                'supersedes': ['yahoo', 'event', 'dragdrop', 'animation', 'dom', 'connection', 'element', 'yahoo-dom-event'],
                'rollup': 6
            },

            'yahoo': {
                'type': 'js',
                'path': 'yahoo/yahoo-min.js'
            },

            'yahoo-dom-event': {
                'type': 'js',
                'path': 'yahoo-dom-event/yahoo-dom-event.js',
                'supersedes': ['yahoo', 'event', 'dom'],
                'rollup': 3
            },

            'yuiloader': {
                'type': 'js',
                'path': 'yuiloader/yuiloader-beta-min.js'
            },

            'yuitest': {
                'type': 'js',
                'path': 'yuitest/yuitest-min.js',
                'requires': ['logger'],
                'skinnable': true
            }
        }
    }
     ,

            ObjectUtil: {
                appendArray: function(o, a) {
                    if (a) {
                        for (var i=0; i<a.length; i=i+1) {
                            o[a[i]] = true;
                        }
                    }
                },

                keys: function(o, ordered) {
                    var a=[], i;
                    for (i in o) {
                        if (lang.hasOwnProperty(o, i)) {
                            a.push(i);
                        }
                    }

                    return a;
                }
            },

            ArrayUtil: {

                appendArray: function(a1, a2) {
                    Array.prototype.push.apply(a1, a2);
                    /*
                    for (var i=0; i<a2.length; i=i+1) {
                        a1.push(a2[i]);
                    }
                    */
                },

                indexOf: function(a, val) {
                    for (var i=0; i<a.length; i=i+1) {
                        if (a[i] === val) {
                            return i;
                        }
                    }

                    return -1;
                },

                toObject: function(a) {
                    var o = {};
                    for (var i=0; i<a.length; i=i+1) {
                        o[a[i]] = true;
                    }

                    return o;
                },

                /*
                 * Returns a unique array.  Does not maintain order, which is fine
                 * for this application, and performs better than it would if it
                 * did.
                 */
                uniq: function(a) {
                    return YUI.ObjectUtil.keys(YUI.ArrayUtil.toObject(a));
                }
            }
        };

        YAHOO.util.YUILoader = function(o) {

            /**
             * Internal callback to handle multiple internal insert() calls
             * so that css is inserted prior to js
             * @property _internalCallback
             * @private
             */
            this._internalCallback = null;

            /**
             * Use the YAHOO environment listener to detect script load.  This
             * is only switched on for Safari 2.x and below.
             * @property _useYahooListener
             * @private
             */
            this._useYahooListener = false;

            /**
             * Callback that will be executed when the loader is finished
             * with an insert
             * @method onSuccess
             * @type function
             */
            this.onSuccess = null;

            /**
             * Callback that will be executed if there is a failure
             * @method onFailure
             * @type function
             */
            this.onFailure = Y.log;

            /**
             * Callback that will be executed each time a new module is loaded
             * @method onProgress
             * @type function
             */
            this.onProgress = null;

            /**
             * The execution scope for all callbacks
             * @property scope
             * @default this
             */
            this.scope = this;

            /**
             * Data that is passed to all callbacks
             * @property data
             */
            this.data = null;

            /**
             * The name of the variable in a sandbox or script node
             * (for external script support in Safari 2.x and earlier)
             * to reference when the load is complete.  If this variable
             * is not available in the specified scripts, the operation will
             * fail.
             * @property varName
             * @type string
             */
            this.varName = null;

            /**
             * The base directory.
             * @property base
             * @type string
             * @default http://yui.yahooapis.com/[YUI VERSION]/build/
             */
            this.base = YUI.info.base;

            /**
             * A list of modules that should not be loaded, even if
             * they turn up in the dependency tree
             * @property ignore
             * @type string[]
             */
            this.ignore = null;

            /**
             * A list of modules that should always be loaded, even
             * if they have already been inserted into the page.
             * @property force
             * @type string
             */
            this.force = null;

            /**
             * Should we allow rollups
             * @property allowRollup
             * @type boolean
             * @default true
             */
            this.allowRollup = true;

            /**
             * A filter to apply to result urls.  This filter will modify the default
             * path for all modules.  The default path for the YUI library is the
             * minified version of the files (e.g., event-min.js).  The filter property
             * can be a predefined filter or a custom filter.  The valid predefined
             * filters are:
             * <dl>
             *  <dt>DEBUG</dt>
             *  <dd>Selects the debug versions of the library (e.g., event-debug.js).
             *      This option will automatically include the logger widget</dd>
             *  <dt>RAW</dt>
             *  <dd>Selects the non-minified version of the library (e.g., event.js).
             * </dl>
             * You can also define a custom filter, which must be an object literal
             * containing a search expression and a replace string:
             * <pre>
             *  myFilter: &#123;
             *      'searchExp': "-min\\.js",
             *      'replaceStr': "-debug.js"
             *  &#125;
             * </pre>
             * @property filter
             * @type string|{searchExp: string, replaceStr: string}
             */
            this.filter = null;

            /**
             * The list of requested modules
             * @property required
             * @type {string: boolean}
             */
            this.required = {};

            /**
             * The library metadata
             * @property moduleInfo
             */
            this.moduleInfo = lang.merge(YUI.info.moduleInfo);

            /**
             * List of rollup files found in the library metadata
             * @property rollups
             */
            this.rollups = null;

            /**
             * Whether or not to load optional dependencies for
             * the requested modules
             * @property loadOptional
             * @type boolean
             * @default false
             */
            this.loadOptional = false;

            /**
             * All of the derived dependencies in sorted order, which
             * will be populated when either calculate() or insert()
             * is called
             * @property sorted
             * @type string[]
             */
            this.sorted = [];

            /**
             * Set when beginning to compute the dependency tree.
             * Composed of what YAHOO reports to be loaded combined
             * with what has been loaded by the tool
             * @propery loaded
             * @type {string: boolean}
             */
            this.loaded = {};

            /**
             * Flag to indicate the dependency tree needs to be recomputed
             * if insert is called again.
             * @property dirty
             * @type boolean
             * @default true
             */
            this.dirty = true;

            /**
             * List of modules inserted by the utility
             * @property inserted
             * @type {string: boolean}
             */
            this.inserted = {};

            /**
             * Provides the information used to skin the skinnable components.
             * The following skin definition would result in 'skin1' and 'skin2'
             * being loaded for calendar (if calendar was requested), and
             * 'sam' for all other skinnable components:
             *
             *   <code>
             *   skin: {
             *
             *      // The default skin, which is automatically applied if not
             *      // overriden by a component-specific skin definition.
             *      // Change this in to apply a different skin globally
             *      defaultSkin: 'sam',
             *
             *      // This is combined with the loader base property to get
             *      // the default root directory for a skin. ex:
             *      // http://yui.yahooapis.com/2.3.0/build/assets/skins/sam/
             *      base: 'assets/skins/',
             *
             *      // The name of the rollup css file for the skin
             *      path: 'skin.css',
             *
             *      // The number of skinnable components requested that are
             *      // required before using the rollup file rather than the
             *      // individual component css files
             *      rollup: 3,
             *
             *      // Any component-specific overrides can be specified here,
             *      // making it possible to load different skins for different
             *      // components.  It is possible to load more than one skin
             *      // for a given component as well.
             *      overrides: {
             *          calendar: ['skin1', 'skin2']
             *      }
             *   }
             *   </code>
             *   @property skin
             */

            var self = this;

            env.listeners.push(function(m) {
                if (self._useYahooListener) {
                    //Y.log("YAHOO listener: " + m.name);
                    self.loadNext(m.name);
                }
            });

            this.skin = lang.merge(YUI.info.skin);

            this._config(o);

        };

        Y.util.YUILoader.prototype = {

            FILTERS: {
                RAW: {
                    'searchExp': "-min\\.js",
                    'replaceStr': ".js"
                },
                DEBUG: {
                    'searchExp': "-min\\.js",
                    'replaceStr': "-debug.js"
                }
            },

            SKIN_PREFIX: "skin-",

            _config: function(o) {

                if (!o) {
                    return;
                }

                // lang.augmentObject(this, o);

                // apply config values
                for (var i in o) {
                    if (lang.hasOwnProperty(o, i)) {
                        switch (i) {
                            case "require":
                                this.require(o[i]);
                                break;

                            case "filter":
                                var f = o[i];

                                if (typeof f === "string") {
                                    f = f.toUpperCase();

                                    // the logger must be available in order to use the debug
                                    // versions of the library
                                    if (f === "DEBUG") {
                                        this.require("logger");
                                    }

                                    this.filter = this.FILTERS[f];
                                } else {
                                    this.filter = f;
                                }

                                break;

                            default:
                                this[i] = o[i];
                        }
                    }
                }
            },

            /** Add a new module to the component metadata.
             * <dl>
             *     <dt>name:</dt>       <dd>required, the component name</dd>
             *     <dt>type:</dt>       <dd>required, the component type (js or css)</dd>
             *     <dt>path:</dt>       <dd>required, the path to the script from "base"</dd>
             *     <dt>requires:</dt>   <dd>the modules required by this component</dd>
             *     <dt>optional:</dt>   <dd>the optional modules for this component</dd>
             *     <dt>supersedes:</dt> <dd>the modules this component replaces</dd>
             *     <dt>rollup:</dt>     <dd>the number of superseded modules required for automatic rollup</dd>
             *     <dt>fullpath:</dt>   <dd>If fullpath is specified, this is used instead of the configured base + path</dd>
             *     <dt>skinnable:</dt>  <dd>flag to determine if skin assets should automatically be pulled in</dd>
             * </dl>
             * @method addModule
             * @param o An object containing the module data
             * @return {boolean} true if the module was added, false if
             * the object passed in did not provide all required attributes
             */
            addModule: function(o) {

                if (!o || !o.name || !o.type || (!o.path && !o.fullpath)) {
                    return false;
                }

                this.moduleInfo[o.name] = o;
                this.dirty = true;

                return true;
            },

            /**
             * Add a requirement for one or more module
             * @method require
             * @param what {string[] | string*} the modules to load
             */
            require: function(what) {
                var a = (typeof what === "string") ? arguments : what;

                this.dirty = true;

                for (var i=0; i<a.length; i=i+1) {
                    this.required[a[i]] = true;
                    var s = this.parseSkin(a[i]);
                    if (s) {
                        this._addSkin(s.skin, s.module);
                    }
                }
                YUI.ObjectUtil.appendArray(this.required, a);
            },

            /**
             * Adds the skin def to the module info
             * @method _addSkin
             * @private
             */
            _addSkin: function(skin, mod) {

                // Add a module definition for the skin rollup css
                var name = this.formatSkin(skin);
                if (!this.moduleInfo[name]) {
                    this.addModule({
                        'name': name,
                        'type': 'css',
                        'path': this.skin.base + skin + "/" + this.skin.path,
                        //'supersedes': '*',
                        'rollup': this.skin.rollup
                    });
                }

                // Add a module definition for the module-specific skin css
                if (mod) {
                    name = this.formatSkin(skin, mod);
                    if (!this.moduleInfo[name]) {
                        var mdef = this.moduleInfo[mod];
                        var pkg = mdef.pkg || mod;
                        this.addModule({
                            'name': name,
                            'type': 'css',
                            //'path': this.skin.base + skin + "/" + mod + ".css"
                            // 'path': mod + '/' + this.skin.base + skin + "/" + mod + ".css"
                            'path': pkg + '/' + this.skin.base + skin + "/" + mod + ".css"
                        });
                    }
                }
            },

            /**
             * Returns an object containing properties for all modules required
             * in order to load the requested module
             * @method getRequires
             * @param mod The module definition from moduleInfo
             */
            getRequires: function(mod) {
                if (!mod) {
                    return [];
                }

                if (!this.dirty && mod.expanded) {
                    return mod.expanded;
                }

                mod.requires=mod.requires || [];
                var i, d=[], r=mod.requires, o=mod.optional, info=this.moduleInfo, m;
                for (i=0; i<r.length; i=i+1) {
                    d.push(r[i]);
                    m = info[r[i]];
                    YUI.ArrayUtil.appendArray(d, this.getRequires(m));

                    // add existing skins for skinnable modules as well.  The only
                    // way to do this is go through the list of required items (this
                    // assumes that _skin is called before getRequires is called on
                    // the module.
                    if (m.skinnable) {
                        var req=this.required, l=req.length;
                        for (var j=0; j<l; j=j+1) {
                            // YAHOO.log('checking ' + r[j]);
                            if (req[j].indexOf(r[j]) > -1) {
                                // YAHOO.log('adding ' + r[j]);
                                d.push(req[j]);
                            }
                        }
                    }
                }

                if (o && this.loadOptional) {
                    for (i=0; i<o.length; i=i+1) {
                        d.push(o[i]);
                        YUI.ArrayUtil.appendArray(d, this.getRequires(info[o[i]]));
                    }
                }

                mod.expanded = YUI.ArrayUtil.uniq(d);

                return mod.expanded;
            },

            /**
             * Returns an object literal of the modules the supplied module satisfies
             * @method getProvides
             * @param mod The module definition from moduleInfo
             * @return what this module provides
             */
            getProvides: function(name) {
                var mod = this.moduleInfo[name];

                var o = {};
                o[name] = true;

                var s = mod && mod.supersedes;

                YUI.ObjectUtil.appendArray(o, s);

                // YAHOO.log(this.sorted + ", " + name + " provides " + YUI.ObjectUtil.keys(o));

                return o;
            },

            /**
             * Calculates the dependency tree, the result is stored in the sorted
             * property
             * @method calculate
             * @param o optional options object
             */
            calculate: function(o) {
                if (this.dirty) {
                    this._config(o);
                    this._setup();
                    this._explode();
                    this._skin();
                    if (this.allowRollup) {
                        this._rollup();
                    }
                    this._reduce();
                    this._sort();

                    // Y.log("after calculate: " + lang.dump(this.required));

                    this.dirty = false;
                }
            },

            /**
             * Investigates the current YUI configuration on the page.  By default,
             * modules already detected will not be loaded again unless a force
             * option is encountered.  Called by calculate()
             * @method _setup
             * @private
             */
            _setup: function() {

                this.loaded = lang.merge(this.inserted); // shallow clone

                if (!this._sandbox) {
                    this.loaded = lang.merge(this.loaded, env.modules);
                }

                // Y.log("already loaded stuff: " + lang.dump(this.loaded, 0));

                // add the ignore list to the list of loaded packages
                if (this.ignore) {
                    YUI.ObjectUtil.appendArray(this.loaded, this.ignore);
                }

                // remove modules on the force list from the loaded list
                if (this.force) {
                    for (var i=0; i<this.force.length; i=i+1) {
                        if (this.force[i] in this.loaded) {
                            delete this.loaded[this.force[i]];
                        }
                    }
                }
            },

            /**
             * Inspects the required modules list looking for additional
             * dependencies.  Expands the required list to include all
             * required modules.  Called by calculate()
             * @method _explode
             * @private
             */
            _explode: function() {

                var r=this.required, i, mod;

                for (i in r) {
                    mod = this.moduleInfo[i];
                    if (mod) {

                        var req = this.getRequires(mod);

                        if (req) {
                            YUI.ObjectUtil.appendArray(r, req);
                        }
                    }
                }
            },

            /**
             * Sets up the requirements for the skin assets if any of the
             * requested modules are skinnable
             * @method _skin
             * @private
             */
            _skin: function() {

                var r=this.required, i, mod;

                for (i in r) {
                    mod = this.moduleInfo[i];
                    if (mod && mod.skinnable) {
                        var o=this.skin.overrides, j;
                        if (o && o[i]) {
                            for (j=0; j<o[i].length; j=j+1) {
                                this.require(this.formatSkin(o[i][j], i));
                            }
                        } else {
                            this.require(this.formatSkin(this.skin.defaultSkin, i));
                        }
                    }
                }
            },

            /**
             * Returns the skin module name for the specified skin name.  If a
             * module name is supplied, the returned skin module name is
             * specific to the module passed in.
             * @method formatSkin
             * @param skin {string} the name of the skin
             * @param mod {string} optional: the name of a module to skin
             * @return {string} the full skin module name
             */
            formatSkin: function(skin, mod) {
                var s = this.SKIN_PREFIX + skin;
                if (mod) {
                    s = s + "-" + mod;
                }

                return s;
            },

            /**
             * Reverses <code>formatSkin</code>, providing the skin name and
             * module name if the string matches the pattern for skins.
             * @method parseSkin
             * @param mod {string} the module name to parse
             * @return {skin: string, module: string} the parsed skin name
             * and module name, or null if the supplied string does not match
             * the skin pattern
             */
            parseSkin: function(mod) {

                if (mod.indexOf(this.SKIN_PREFIX) === 0) {
                    var a = mod.split("-");
                    return {skin: a[1], module: a[2]};
                }

                return null;
            },

            /**
             * Look for rollup packages to determine if all of the modules a
             * rollup supersedes are required.  If so, include the rollup to
             * help reduce the total number of connections required.  Called
             * by calculate()
             * @method _rollup
             * @private
             */
            _rollup: function() {
                var i, j, m, s, rollups={}, r=this.required, roll;

                // find and cache rollup modules
                if (this.dirty || !this.rollups) {
                    for (i in this.moduleInfo) {
                        m = this.moduleInfo[i];
                        //if (m && m.rollup && m.supersedes) {
                        if (m && m.rollup) {
                            rollups[i] = m;
                        }
                    }

                    this.rollups = rollups;
                }

                // make as many passes as needed to pick up rollup rollups
                for (;;) {
                    var rolled = false;

                    // go through the rollup candidates
                    for (i in rollups) {

                        // there can be only one
                        if (!r[i] && !this.loaded[i]) {
                            m =this.moduleInfo[i]; s = m.supersedes; roll=false;

                            if (!m.rollup) {
                                continue;
                            }

                            var skin = this.parseSkin(i), c = 0;
                            if (skin) {

                                for (j in r) {
                                    if (i !== j && this.parseSkin(j)) {
                                        c++;
                                        roll = (c >= m.rollup);
                                        if (roll) {
                                            // Y.log("skin rollup " + lang.dump(r));
                                            break;
                                        }
                                    }
                                }

                            } else {

                                // check the threshold
                                for (j=0;j<s.length;j=j+1) {

                                    // if the superseded module is loaded, we can't load the rollup
                                    if (this.loaded[s[j]] && (!YUI.dupsAllowed[s[j]])) {
                                        roll = false;
                                        break;
                                    // increment the counter if this module is required.  if we are
                                    // beyond the rollup threshold, we will use the rollup module
                                    } else if (r[s[j]]) {
                                        c++;
                                        roll = (c >= m.rollup);
                                        if (roll) {
                                            // Y.log("over thresh " + c + ", " + lang.dump(r));
                                            break;
                                        }
                                    }
                                }
                            }

                            if (roll) {
                                // Y.log("rollup: " +  i + ", " + lang.dump(this, 1));
                                // add the rollup
                                r[i] = true;
                                rolled = true;

                                // expand the rollup's dependencies
                                this.getRequires(m);
                            }
                        }
                    }

                    // if we made it here w/o rolling up something, we are done
                    if (!rolled) {
                        break;
                    }
                }
            },

            /**
             * Remove superceded modules and loaded modules.  Called by
             * calculate() after we have the mega list of all dependencies
             * @method _reduce
             * @private
             */
            _reduce: function() {

                var i, j, s, m, r=this.required;
                for (i in r) {

                    // remove if already loaded
                    if (i in this.loaded) {
                        delete r[i];

                    // remove anything this module supersedes
                    } else {

                        var skinDef = this.parseSkin(i);

                        if (skinDef) {
                            //YAHOO.log("skin found in reduce: " + skinDef.skin + ", " + skinDef.module);
                            // the skin rollup will not have a module name
                            if (!skinDef.module) {
                                var skin_pre = this.SKIN_PREFIX + skinDef.skin;
                                //YAHOO.log("skin_pre: " + skin_pre);
                                for (j in r) {
                                    if (j !== i && j.indexOf(skin_pre) > -1) {
                                        //YAHOO.log ("removing component skin: " + j);
                                        delete r[j];
                                    }
                                }
                            }
                        } else {

                             m = this.moduleInfo[i];
                             s = m && m.supersedes;
                             if (s) {
                                 for (j=0;j<s.length;j=j+1) {
                                     if (s[j] in r) {
                                         delete r[s[j]];
                                     }
                                 }
                             }
                        }
                    }
                }
            },

            /**
             * Sorts the dependency tree.  The last step of calculate()
             * @method _sort
             * @private
             */
            _sort: function() {
                // create an indexed list
                var s=[], info=this.moduleInfo, loaded=this.loaded;

                // returns true if b is not loaded, and is required
                // directly or by means of modules it supersedes.
                var requires = function(aa, bb) {
                    if (loaded[bb]) {
                        return false;
                    }

                    var ii, mm=info[aa], rr=mm && mm.expanded;

                    if (rr && YUI.ArrayUtil.indexOf(rr, bb) > -1) {
                        return true;
                    }

                    var ss=info[bb] && info[bb].supersedes;
                    if (ss) {
                        for (ii=0; ii<ss.length; ii=ii+1) {
                            if (requires(aa, ss[ii])) {
                                return true;
                            }
                        }
                    }

                    return false;
                };

                // get the required items out of the obj into an array so we
                // can sort
                for (var i in this.required) {
                    s.push(i);
                }

                // pointer to the first unsorted item
                var p=0;

                // keep going until we make a pass without moving anything
                for (;;) {

                    var l=s.length, a, b, j, k, moved=false;

                    // start the loop after items that are already sorted
                    for (j=p; j<l; j=j+1) {

                        // check the next module on the list to see if its
                        // dependencies have been met
                        a = s[j];

                        // check everything below current item and move if we
                        // find a requirement for the current item
                        for (k=j+1; k<l; k=k+1) {
                            if (requires(a, s[k])) {

                                // extract the dependency so we can move it up
                                b = s.splice(k, 1);

                                // insert the dependency above the item that
                                // requires it
                                s.splice(j, 0, b[0]);

                                moved = true;
                                break;
                            }
                        }

                        // jump out of loop if we moved something
                        if (moved) {
                            break;
                        // this item is sorted, move our pointer and keep going
                        } else {
                            p = p + 1;
                        }
                    }

                    // when we make it here and moved is false, we are
                    // finished sorting
                    if (!moved) {
                        break;
                    }

                }

                this.sorted = s;
            },

            toString: function() {
                var o = {
                    type: "YUILoader",
                    base: this.base,
                    filter: this.filter,
                    required: this.required,
                    loaded: this.loaded,
                    inserted: this.inserted
                };

                lang.dump(o, 1);
            },

            /**
             * inserts the requested modules and their dependencies.
             * <code>type</code> can be "js" or "css".  Both script and
             * css are inserted if type is not provided.
             * @method insert
             * @param o optional options object
             * @param type {string} the type of dependency to insert
             */
            insert: function(o, type) {
                // if (o) {
                //     Y.log("insert: " + lang.dump(o, 1) + ", " + type);
                // } else {
                //     Y.log("insert: " + this.toString() + ", " + type);
                // }

                // build the dependency list
                this.calculate(o);

                if (!type) {
                    // Y.log("trying to load css first");
                    var self = this;
                    this._internalCallback = function() {
                                self._internalCallback = null;
                                self.insert(null, "js");
                            };
                    this.insert(null, "css");
                    return;
                }

                // set a flag to indicate the load has started
                this._loading = true;

                // keep the loadType (js, css or undefined) cached
                this.loadType = type;

                // start the load
                this.loadNext();

            },

            /*
             * Interns the script for the requested modules.  The callback is
             * provided a reference to the sandboxed YAHOO object.  This only
             * applies to the script: css can not be sandboxed; css will be
             * loaded into the page normally if specified.
             * @method sandbox
             * @param callback {Function} the callback to exectued when the load is
             *        complete.
             */
            sandbox: function(o, type) {
                if (o) {
                    // YAHOO.log("sandbox: " + lang.dump(o, 1) + ", " + type);
                } else {
                    // YAHOO.log("sandbox: " + this.toString() + ", " + type);
                }

                this._config(o);

                if (!this.onSuccess) {
    throw new Error("You must supply an onSuccess handler for your sandbox");
                }

                this._sandbox = true;

                var self = this;

                // take care of any css first (this can't be sandboxed)
                if (!type || type !== "js") {
                    this._internalCallback = function() {
                                self._internalCallback = null;
                                self.sandbox(null, "js");
                            };
                    this.insert(null, "css");
                    return;
                }

                // get the connection manager if not on the page
                if (!util.Connect) {
                    // get a new loader instance to load connection.
                    var ld = new YAHOO.util.YUILoader();
                    ld.insert({
                        base: this.base,
                        filter: this.filter,
                        require: "connection",
                        onSuccess: function() {
                            this.sandbox(null, "js");
                        },
                        scope: this
                    }, "js");
                    return;
                }

                this._scriptText = [];
                this._loadCount = 0;
                this._stopCount = this.sorted.length;
                this._xhr = [];

                this.calculate();

                var s=this.sorted, l=s.length, i, m, url;

                for (i=0; i<l; i=i+1) {
                    m = this.moduleInfo[s[i]];

                    // undefined modules cause a failure
                    if (!m) {
                        this.onFailure.call(this.scope, {
                                msg: "undefined module " + m,
                                data: this.data
                            });
                        for (var j=0;j<this._xhr.length;j=j+1) {
                            this._xhr[j].abort();
                        }
                        return;
                    }

                    // css files should be done
                    if (m.type !== "js") {
                        this._loadCount++;
                        continue;
                    }

                    url = m.fullpath || this._url(m.path);

                    // YAHOO.log("xhr request: " + url + ", " + i);

                    var xhrData = {

                        success: function(o) {

                            var idx=o.argument[0], name=o.argument[2];

                            // store the response in the position it was requested
                            this._scriptText[idx] = o.responseText;

                            // YAHOO.log("received: " + o.responseText.substr(0, 100) + ", " + idx);

                            if (this.onProgress) {
                                this.onProgress.call(this.scope, {
                                            name: name,
                                            scriptText: o.responseText,
                                            xhrResponse: o,
                                            data: this.data
                                        });
                            }

                            // only generate the sandbox once everything is loaded
                            this._loadCount++;

                            if (this._loadCount >= this._stopCount) {

                                // the variable to find
                                var v = this.varName || "YAHOO";

                                // wrap the contents of the requested modules in an anonymous function
                                var t = "(function() {\n";

                                // return the locally scoped reference.
                                var b = "\nreturn " + v + ";\n})();";

                                var ref = eval(t + this._scriptText.join("\n") + b);

                                this._pushEvents(ref);

                                if (ref) {
                                    this.onSuccess.call(this.scope, {
                                            reference: ref,
                                            data: this.data
                                        });
                                } else {
                                    this.onFailure.call(this.scope, {
                                            msg: this.varName + " reference failure",
                                            data: this.data
                                        });
                                }
                            }
                        },

                        failure: function(o) {
                            this.onFailure.call(this.scope, {
                                    msg: "XHR failure",
                                    xhrResponse: o,
                                    data: this.data
                                });
                        },

                        scope: this,

                        // module index, module name, sandbox name
                        argument: [i, url, s[i]]

                    };

                    this._xhr.push(util.Connect.asyncRequest('GET', url, xhrData));
                }
            },

            /**
             * Executed every time a module is loaded, and if we are in a load
             * cycle, we attempt to load the next script.  Public so that it
             * is possible to call this if using a method other than
             * YAHOO.register to determine when scripts are fully loaded
             * @method loadNext
             * @param mname {string} optional the name of the module that has
             * been loaded (which is usually why it is time to load the next
             * one)
             */
            loadNext: function(mname) {

                // It is possible that this function is executed due to something
                // else one the page loading a YUI module.  Only react when we
                // are actively loading something
                if (!this._loading) {
                    return;
                }

                if (mname) {

                    // if the module that was just loaded isn't what we were expecting,
                    // continue to wait
                    if (mname !== this._loading) {
                        return;
                    }

                    // YAHOO.log("loadNext executing, just loaded " + mname);

                    // The global handler that is called when each module is loaded
                    // will pass that module name to this function.  Storing this
                    // data to avoid loading the same module multiple times
                    this.inserted[mname] = true;

                    if (this.onProgress) {
                        this.onProgress.call(this.scope, {
                                name: mname,
                                data: this.data
                            });
                    }
                    //var o = this.getProvides(mname);
                    //this.inserted = lang.merge(this.inserted, o);
                }

                var s=this.sorted, len=s.length, i, m;

                for (i=0; i<len; i=i+1) {

                    // This.inserted keeps track of what the loader has loaded
                    if (s[i] in this.inserted) {
                        // YAHOO.log(s[i] + " alread loaded ");
                        continue;
                    }

                    // Because rollups will cause multiple load notifications
                    // from YAHOO, loadNext may be called multiple times for
                    // the same module when loading a rollup.  We can safely
                    // skip the subsequent requests
                    if (s[i] === this._loading) {
                        // YAHOO.log("still loading " + s[i] + ", waiting");
                        return;
                    }

                    // log("inserting " + s[i]);
                    m = this.moduleInfo[s[i]];

                    if (!m) {
                        this.onFailure.call(this.scope, {
                                msg: "undefined module " + m,
                                data: this.data
                            });
                        return;
                    }

                    // The load type is stored to offer the possibility to load
                    // the css separately from the script.
                    if (!this.loadType || this.loadType === m.type) {
                        this._loading = s[i];
                        //YAHOO.log("attempting to load " + s[i] + ", " + this.base);

                        var fn=(m.type === "css") ? util.Get.css : util.Get.script,
                            url=m.fullpath || this._url(m.path), self=this,
                            c=function(o) {
                                self.loadNext(o.data);
                            };

                        // safari 2.x or lower, script, and part of YUI
                        if (env.ua.webkit && env.ua.webkit < 420 && m.type === "js" &&
                              !m.varName) {
                              //YUI.info.moduleInfo[s[i]]) {
                              //YAHOO.log("using YAHOO env " + s[i] + ", " + m.varName);
                            c = null;
                            this._useYahooListener = true;
                        }

                        fn(url, {
                            data: s[i],
                            onSuccess: c,
                            varName: m.varName,
                            scope: self
                        });

                        return;
                    }
                }

                // we are finished
                this._loading = null;

                // internal callback for loading css first
                if (this._internalCallback) {
                    var f = this._internalCallback;
                    this._internalCallback = null;
                    f.call(this);
                } else if (this.onSuccess) {
                    this._pushEvents();
                    this.onSuccess.call(this.scope, {
                            data: this.data
                        });
                }

            },

            /**
             * In IE, the onAvailable/onDOMReady events need help when Event is
             * loaded dynamically
             * @method _pushEvents
             * @param {Function} optional function reference
             * @private
             */
            _pushEvents: function(ref) {
                var r = ref || YAHOO;
                if (r.util && r.util.Event) {
                    r.util.Event._load();
                }
            },

            /**
             * Generates the full url for a module
             * method _url
             * @param path {string} the path fragment
             * @return {string} the full url
             * @private
             */
            _url: function(path) {

                var u = this.base || "", f=this.filter;
                u = u + path;

                if (f) {
                    // YAHOO.log("filter: " + f + ", " + f.searchExp +
                    // ", " + f.replaceStr);
                    u = u.replace(new RegExp(f.searchExp), f.replaceStr);
                }

                // YAHOO.log(u);

                return u;
            }

        };

    })();

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