source: Dev/trunk/src/client/dijit/tree/TreeStoreModel.js

define([
        "dojo/_base/array", // array.filter array.forEach array.indexOf array.some
        "dojo/aspect", // aspect.after
        "dojo/_base/declare", // declare
        "dojo/_base/lang" // lang.hitch
], function(array, aspect, declare, lang){

        // module:
        //              dijit/tree/TreeStoreModel

        return declare("dijit.tree.TreeStoreModel", null, {
                // summary:
                //              Implements dijit/Tree/model connecting to a dojo.data store with a single
                //              root item.  Any methods passed into the constructor will override
                //              the ones defined here.

                // store: dojo/data/api/Read
                //              Underlying store
                store: null,

                // childrenAttrs: String[]
                //              One or more attribute names (attributes in the dojo.data item) that specify that item's children
                childrenAttrs: ["children"],

                // newItemIdAttr: String
                //              Name of attribute in the Object passed to newItem() that specifies the id.
                //
                //              If newItemIdAttr is set then it's used when newItem() is called to see if an
                //              item with the same id already exists, and if so just links to the old item
                //              (so that the old item ends up with two parents).
                //
                //              Setting this to null or "" will make every drop create a new item.
                newItemIdAttr: "id",

                // labelAttr: String
                //              If specified, get label for tree node from this attribute, rather
                //              than by calling store.getLabel()
                labelAttr: "",

                // root: [readonly] dojo/data/Item
                //              Pointer to the root item (read only, not a parameter)
                root: null,

                // query: anything
                //              Specifies datastore query to return the root item for the tree.
                //              Must only return a single item.   Alternately can just pass in pointer
                //              to root item.
                // example:
                //      |       {id:'ROOT'}
                query: null,

                // deferItemLoadingUntilExpand: Boolean
                //              Setting this to true will cause the TreeStoreModel to defer calling loadItem on nodes
                //              until they are expanded. This allows for lazying loading where only one
                //              loadItem (and generally one network call, consequently) per expansion
                //              (rather than one for each child).
                //              This relies on partial loading of the children items; each children item of a
                //              fully loaded item should contain the label and info about having children.
                deferItemLoadingUntilExpand: false,

                constructor: function(/* Object */ args){
                        // summary:
                        //              Passed the arguments listed above (store, etc)
                        // tags:
                        //              private

                        lang.mixin(this, args);

                        this.connects = [];

                        var store = this.store;
                        if(!store.getFeatures()['dojo.data.api.Identity']){
                                throw new Error("dijit.tree.TreeStoreModel: store must support dojo.data.Identity");
                        }

                        // if the store supports Notification, subscribe to the notification events
                        if(store.getFeatures()['dojo.data.api.Notification']){
                                this.connects = this.connects.concat([
                                        aspect.after(store, "onNew", lang.hitch(this, "onNewItem"), true),
                                        aspect.after(store, "onDelete", lang.hitch(this, "onDeleteItem"), true),
                                        aspect.after(store, "onSet", lang.hitch(this, "onSetItem"), true)
                                ]);
                        }
                },

                destroy: function(){
                        var h;
                        while(h = this.connects.pop()){ h.remove(); }
                        // TODO: should cancel any in-progress processing of getRoot(), getChildren()
                },

                // =======================================================================
                // Methods for traversing hierarchy

                getRoot: function(onItem, onError){
                        // summary:
                        //              Calls onItem with the root item for the tree, possibly a fabricated item.
                        //              Calls onError on error.
                        if(this.root){
                                onItem(this.root);
                        }else{
                                this.store.fetch({
                                        query: this.query,
                                        onComplete: lang.hitch(this, function(items){
                                                if(items.length != 1){
                                                        throw new Error("dijit.tree.TreeStoreModel: root query returned " + items.length +
                                                                " items, but must return exactly one");
                                                }
                                                this.root = items[0];
                                                onItem(this.root);
                                        }),
                                        onError: onError
                                });
                        }
                },

                mayHaveChildren: function(/*dojo/data/Item*/ item){
                        // summary:
                        //              Tells if an item has or may have children.  Implementing logic here
                        //              avoids showing +/- expando icon for nodes that we know don't have children.
                        //              (For efficiency reasons we may not want to check if an element actually
                        //              has children until user clicks the expando node)
                        return array.some(this.childrenAttrs, function(attr){
                                return this.store.hasAttribute(item, attr);
                        }, this);
                },

                getChildren: function(/*dojo/data/Item*/ parentItem, /*function(items)*/ onComplete, /*function*/ onError){
                        // summary:
                        //              Calls onComplete() with array of child items of given parent item, all loaded.

                        var store = this.store;
                        if(!store.isItemLoaded(parentItem)){
                                // The parent is not loaded yet, we must be in deferItemLoadingUntilExpand
                                // mode, so we will load it and just return the children (without loading each
                                // child item)
                                var getChildren = lang.hitch(this, arguments.callee);
                                store.loadItem({
                                        item: parentItem,
                                        onItem: function(parentItem){
                                                getChildren(parentItem, onComplete, onError);
                                        },
                                        onError: onError
                                });
                                return;
                        }
                        // get children of specified item
                        var childItems = [];
                        for(var i=0; i<this.childrenAttrs.length; i++){
                                var vals = store.getValues(parentItem, this.childrenAttrs[i]);
                                childItems = childItems.concat(vals);
                        }

                        // count how many items need to be loaded
                        var _waitCount = 0;
                        if(!this.deferItemLoadingUntilExpand){
                                array.forEach(childItems, function(item){ if(!store.isItemLoaded(item)){ _waitCount++; } });
                        }

                        if(_waitCount == 0){
                                // all items are already loaded (or we aren't loading them).  proceed...
                                onComplete(childItems);
                        }else{
                                // still waiting for some or all of the items to load
                                array.forEach(childItems, function(item, idx){
                                        if(!store.isItemLoaded(item)){
                                                store.loadItem({
                                                        item: item,
                                                        onItem: function(item){
                                                                childItems[idx] = item;
                                                                if(--_waitCount == 0){
                                                                        // all nodes have been loaded, send them to the tree
                                                                        onComplete(childItems);
                                                                }
                                                        },
                                                        onError: onError
                                                });
                                        }
                                });
                        }
                },

                // =======================================================================
                // Inspecting items

                isItem: function(/* anything */ something){
                        return this.store.isItem(something);    // Boolean
                },

                fetchItemByIdentity: function(/* object */ keywordArgs){
                        // summary:
                        //              Given the identity of an item, this method returns the item that has
                        //              that identity through the onItem callback.  Conforming implementations
                        //              should return null if there is no item with the given identity.
                        //              Implementations of fetchItemByIdentity() may sometimes return an item
                        //              from a local cache and may sometimes fetch an item from a remote server.
                        // tags:
                        //              extension
                        this.store.fetchItemByIdentity(keywordArgs);
                },

                getIdentity: function(/* item */ item){
                        return this.store.getIdentity(item);    // Object
                },

                getLabel: function(/*dojo/data/Item*/ item){
                        // summary:
                        //              Get the label for an item
                        if(this.labelAttr){
                                return this.store.getValue(item,this.labelAttr);        // String
                        }else{
                                return this.store.getLabel(item);       // String
                        }
                },

                // =======================================================================
                // Write interface

                newItem: function(/* dijit/tree/dndSource.__Item */ args, /*dojo/data/api/Item*/ parent, /*int?*/ insertIndex){
                        // summary:
                        //              Creates a new item.   See `dojo/data/api/Write` for details on args.
                        //              Used in drag & drop when item from external source dropped onto tree.
                        // description:
                        //              Developers will need to override this method if new items get added
                        //              to parents with multiple children attributes, in order to define which
                        //              children attribute points to the new item.

                        var pInfo = {parent: parent, attribute: this.childrenAttrs[0]}, LnewItem;

                        if(this.newItemIdAttr && args[this.newItemIdAttr]){
                                // Maybe there's already a corresponding item in the store; if so, reuse it.
                                this.fetchItemByIdentity({identity: args[this.newItemIdAttr], scope: this, onItem: function(item){
                                        if(item){
                                                // There's already a matching item in store, use it
                                                this.pasteItem(item, null, parent, true, insertIndex);
                                        }else{
                                                // Create new item in the tree, based on the drag source.
                                                LnewItem=this.store.newItem(args, pInfo);
                                                if(LnewItem && (insertIndex!=undefined)){
                                                        // Move new item to desired position
                                                        this.pasteItem(LnewItem, parent, parent, false, insertIndex);
                                                }
                                        }
                                }});
                        }else{
                                // [as far as we know] there is no id so we must assume this is a new item
                                LnewItem=this.store.newItem(args, pInfo);
                                if(LnewItem && (insertIndex!=undefined)){
                                        // Move new item to desired position
                                        this.pasteItem(LnewItem, parent, parent, false, insertIndex);
                                }
                        }
                },

                pasteItem: function(/*Item*/ childItem, /*Item*/ oldParentItem, /*Item*/ newParentItem, /*Boolean*/ bCopy, /*int?*/ insertIndex){
                        // summary:
                        //              Move or copy an item from one parent item to another.
                        //              Used in drag & drop
                        var store = this.store,
                                parentAttr = this.childrenAttrs[0];     // name of "children" attr in parent item

                        // remove child from source item, and record the attribute that child occurred in
                        if(oldParentItem){
                                array.forEach(this.childrenAttrs, function(attr){
                                        if(store.containsValue(oldParentItem, attr, childItem)){
                                                if(!bCopy){
                                                        var values = array.filter(store.getValues(oldParentItem, attr), function(x){
                                                                return x != childItem;
                                                        });
                                                        store.setValues(oldParentItem, attr, values);
                                                }
                                                parentAttr = attr;
                                        }
                                });
                        }

                        // modify target item's children attribute to include this item
                        if(newParentItem){
                                if(typeof insertIndex == "number"){
                                        // call slice() to avoid modifying the original array, confusing the data store
                                        var childItems = store.getValues(newParentItem, parentAttr).slice();
                                        childItems.splice(insertIndex, 0, childItem);
                                        store.setValues(newParentItem, parentAttr, childItems);
                                }else{
                                        store.setValues(newParentItem, parentAttr,
                                                store.getValues(newParentItem, parentAttr).concat(childItem));
                                }
                        }
                },

                // =======================================================================
                // Callbacks

                onChange: function(/*dojo/data/Item*/ /*===== item =====*/){
                        // summary:
                        //              Callback whenever an item has changed, so that Tree
                        //              can update the label, icon, etc.   Note that changes
                        //              to an item's children or parent(s) will trigger an
                        //              onChildrenChange() so you can ignore those changes here.
                        // tags:
                        //              callback
                },

                onChildrenChange: function(/*===== parent, newChildrenList =====*/){
                        // summary:
                        //              Callback to do notifications about new, updated, or deleted items.
                        // parent: dojo/data/Item
                        // newChildrenList: dojo/data/Item[]
                        // tags:
                        //              callback
                },

                onDelete: function(/*dojo/data/Item*/ /*===== item =====*/){
                        // summary:
                        //              Callback when an item has been deleted.
                        // description:
                        //              Note that there will also be an onChildrenChange() callback for the parent
                        //              of this item.
                        // tags:
                        //              callback
                },

                // =======================================================================
                // Events from data store

                onNewItem: function(/* dojo/data/Item */ item, /* Object */ parentInfo){
                        // summary:
                        //              Handler for when new items appear in the store, either from a drop operation
                        //              or some other way.   Updates the tree view (if necessary).
                        // description:
                        //              If the new item is a child of an existing item,
                        //              calls onChildrenChange() with the new list of children
                        //              for that existing item.
                        //
                        // tags:
                        //              extension

                        // We only care about the new item if it has a parent that corresponds to a TreeNode
                        // we are currently displaying
                        if(!parentInfo){
                                return;
                        }

                        // Call onChildrenChange() on parent (ie, existing) item with new list of children
                        // In the common case, the new list of children is simply parentInfo.newValue or
                        // [ parentInfo.newValue ], although if items in the store has multiple
                        // child attributes (see `childrenAttr`), then it's a superset of parentInfo.newValue,
                        // so call getChildren() to be sure to get right answer.
                        this.getChildren(parentInfo.item, lang.hitch(this, function(children){
                                this.onChildrenChange(parentInfo.item, children);
                        }));
                },

                onDeleteItem: function(/*Object*/ item){
                        // summary:
                        //              Handler for delete notifications from underlying store
                        this.onDelete(item);
                },

                onSetItem: function(item, attribute /*===== , oldValue, newValue =====*/){
                        // summary:
                        //              Updates the tree view according to changes in the data store.
                        // description:
                        //              Handles updates to an item's children by calling onChildrenChange(), and
                        //              other updates to an item by calling onChange().
                        //
                        //              See `onNewItem` for more details on handling updates to an item's children.
                        // item: Item
                        // attribute: attribute-name-string
                        // oldValue: Object|Array
                        // newValue: Object|Array
                        // tags:
                        //              extension

                        if(array.indexOf(this.childrenAttrs, attribute) != -1){
                                // item's children list changed
                                this.getChildren(item, lang.hitch(this, function(children){
                                        // See comments in onNewItem() about calling getChildren()
                                        this.onChildrenChange(item, children);
                                }));
                        }else{
                                // item's label/icon/etc. changed.
                                this.onChange(item);
                        }
                }
        });
});