/**
 * @module "data/virtual-array"
 * 
 * Contains the VirtualArray class, which is an advanced array like class that helps loading items on demand.
 */ /** */

import * as observable from "../observable";
import * as observableArray from "../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;
}