Rename the files

tns-core-modules/data/virtual-array/package.json

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+{
+	"name" : "virtual-array",
+	"main" : "virtual-array.js"
+}

tns-core-modules/data/virtual-array/virtual-array.d.ts

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+/**
+ * Contains the VirtualArray class, which is an advanced array like class that helps loading items on demand.
+ */
+declare module "data/virtual-array" {
+    import observable = require("data/observable");
+    import observableArray = require("data/observable-array");
+
+    /**
+     * Provides event args for "changed" event.
+     */
+    export interface ChangedData<T> extends observableArray.ChangedData<T> {
+        //
+    }
+
+    /**
+     * Change types (Add, Delete, Update, Splice).
+     */
+    export class ChangeType extends observableArray.ChangeType {
+        //
+    }
+
+    /**
+     * Advanced array like class that helps loading items on demand.
+     */
+    export class VirtualArray<T> extends observable.Observable {
+        /**
+         * String value used when hooking to change event.
+         */
+        public static changeEvent: string;
+
+        /**
+         * String value used when hooking to itemsLoading event.
+         */
+        public static itemsLoadingEvent: string;
+
+        constructor(arrayLength?: number);
+
+        /**
+         * Gets or sets length for the virtual array.
+         */
+        length: number;
+
+        /**
+         * Gets or sets load size for the virtual array.
+         */
+        loadSize: number;
+
+        /**
+         * Returns item at specified index.
+         */
+        getItem(index: number): T;
+
+        /**
+         * Sets item at specified index.
+         */
+        setItem(index: number, value: T): void;
+
+        /**
+         * Loads items from an array starting at index.
+         */
+        load(index: number, items: T[]): void;
+
+        /**
+         * A basic method signature to hook an event listener (shortcut alias to the addEventListener method).
+         * @param eventNames - String corresponding to events (e.g. "propertyChange"). Optionally could be used more events separated by `,` (e.g. "propertyChange", "change"). 
+         * @param callback - Callback function which will be executed when event is raised.
+         * @param thisArg - An optional parameter which will be used as `this` context for callback execution.
+         */
+        on(eventNames: string, callback: (data: observable.EventData) => void, thisArg?: any);
+
+        /**
+         * Raised when still not loaded items are requested.
+         */
+        on(event: "itemsLoading", callback: (args: ItemsLoading) => void, thisArg?: any);
+
+        /**
+         * Raised when a change occurs.
+         */
+        on(event: "change", callback: (args: ChangedData<T>) => void, thisArg?: any);
+    }
+
+    /**
+     * Event args for "itemsLoading" event.
+     */
+    export interface ItemsLoading extends observable.EventData {
+        /**
+         * Start index.
+         */
+        index: number;
+
+        /**
+         * Number of items to load.
+         */
+        count: number;
+    }
+}

tns-core-modules/data/virtual-array/virtual-array.ts

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+import observable = require("data/observable");
+import types = require("utils/types");
+import virtualArrayDef = require("data/virtual-array");
+
+var CHANGE = "change", UPDATE = "update", DELETE = "delete", ADD = "add";
+
+export class ChangeType implements virtualArrayDef.ChangeType {
+    static Add = "add";
+    static Delete = "delete";
+    static Update = "update";
+    static Splice = "splice";
+}
+
+export class VirtualArray<T> extends observable.Observable {
+    public static changeEvent = CHANGE;
+    public static itemsLoadingEvent = "itemsLoading";
+
+    private _requestedIndexes: Array<number>;
+    private _loadedIndexes: Array<number>;
+    private _length: number;
+    private _cache: {};
+
+    constructor(length = 0) {
+        super();
+
+        this._length = length;
+        this._cache = {};
+
+        this._requestedIndexes = [];
+        this._loadedIndexes = [];
+    }
+
+    get length(): number {
+        return this._length;
+    }
+    set length(value: number) {
+        if (this._length !== value) {
+
+            var index = this._length;
+            var count = value - this._length;
+
+            this._length = value;
+
+            this.notify({
+                eventName: CHANGE, object: this,
+                action: count > 0 ? ADD : DELETE,
+                index: index,
+                removed: new Array(count < 0 ? Math.abs(count) : 0),
+                addedCount: count > 0 ? count : 0
+            });
+        }
+    }
+
+    private _loadSize: number;
+    get loadSize(): number {
+        return this._loadSize;
+    }
+    set loadSize(value: number) {
+        this._loadSize = value;
+    }
+
+    getItem(index: number): T {
+        var item = this._cache[index];
+
+        if (types.isUndefined(item)) {
+            if (index >= 0 && index < this.length && this._requestedIndexes.indexOf(index) < 0 && this._loadedIndexes.indexOf(index) < 0) {
+                this.requestItems(index);
+            }
+        }
+
+        return item;
+    }
+
+    setItem(index: number, value: T) {
+        if (this._cache[index] !== value) {
+            this.load(index, [value]);
+        }
+    }
+
+    load(index: number, items: T[]): void {
+        var i: number;
+        for (i = 0; i < items.length; i++) {
+
+            var itemIndex = index + i;
+
+            this._cache[itemIndex] = items[i];
+
+            this._requestedIndexes.splice(this._requestedIndexes.indexOf(itemIndex), 1);
+
+            if (this._loadedIndexes.indexOf(itemIndex) < 0) {
+                this._loadedIndexes.push(itemIndex);
+            }
+        }
+
+        // Remove requested but never loaded indexes.
+        if (this._requestedIndexes.length > 0) {
+            for (i = 0; i < this.loadSize - items.length; i++) {
+                this._requestedIndexes.splice(this._requestedIndexes.indexOf(index + i), 1);
+            }
+        }
+
+        this.notify({
+            eventName: CHANGE, object: this,
+            action: UPDATE,
+            index: index,
+            removed: new Array(items.length),
+            addedCount: items.length
+        });
+    }
+
+    private requestItems(index: number): void {
+        var indexesToLoad = [];
+
+        var pageIndex = this._loadSize > 0 ? this._loadSize * Math.floor(index / this._loadSize) : index;
+        var count = 0;
+        var start = -1;
+
+        for (var i = 0; i < this.loadSize; i++) {
+            var itemIndex = pageIndex + i;
+
+            if (itemIndex >= this._length) {
+                break;
+            }
+
+            if (this._loadedIndexes.indexOf(itemIndex) < 0) {
+                if (start < 0) {
+                    start = itemIndex;
+                }
+
+                indexesToLoad.push(itemIndex);
+
+                if (this._requestedIndexes.indexOf(itemIndex) < 0) {
+                    this._requestedIndexes.push(itemIndex);
+                }
+
+                count++;
+            } else {
+                if (count > 0) {
+                    this.notify({
+                        eventName: VirtualArray.itemsLoadingEvent, object: this,
+                        index: start,
+                        count: count
+                    });
+                }
+
+                start = -1;
+                count = 0;
+            }
+        }
+
+        if (start >= 0 && count > 0) {
+            this.notify({
+                eventName: VirtualArray.itemsLoadingEvent, object: this,
+                index: start,
+                count: count
+            });
+        }
+    }
+}