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Copy pathindex.ts
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200 lines (169 loc) · 4.66 KB
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import { Observable, EventData } from '../observable';
import { ChangedData, ChangeType } from '../observable-array';
/**
* Event args for "itemsLoading" event.
*/
export interface ItemsLoading extends EventData {
/**
* Start index.
*/
index: number;
/**
* Number of items to load.
*/
count: number;
}
/**
* Advanced array like class that helps loading items on demand.
*/
export class VirtualArray<T> extends Observable {
/**
* String value used when hooking to change event.
*/
public static changeEvent = ChangeType.Change;
/**
* String value used when hooking to itemsLoading event.
*/
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 = [];
}
/**
* Gets or sets length for the virtual array.
*/
get length(): number {
return this._length;
}
set length(value: number) {
if (this._length !== value) {
const index = this._length;
const count = value - this._length;
this._length = value;
this.notify({
eventName: ChangeType.Change,
object: this,
action: count > 0 ? ChangeType.Add : ChangeType.Delete,
index: index,
removed: new Array(count < 0 ? Math.abs(count) : 0),
addedCount: count > 0 ? count : 0,
});
}
}
/**
* Gets or sets load size for the virtual array.
*/
private _loadSize: number;
get loadSize(): number {
return this._loadSize;
}
set loadSize(value: number) {
this._loadSize = value;
}
getItem(index: number): T {
const item = this._cache[index];
if (item === undefined) {
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]);
}
}
/**
* Loads items from an array starting at index.
*/
load(index: number, items: T[]): void {
for (let i = 0; i < items.length; i++) {
const 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 (let i = 0; i < this.loadSize - items.length; i++) {
this._requestedIndexes.splice(this._requestedIndexes.indexOf(index + i), 1);
}
}
this.notify({
eventName: ChangeType.Change,
object: this,
action: ChangeType.Update,
index: index,
removed: new Array(items.length),
addedCount: items.length,
});
}
private requestItems(index: number): void {
const indexesToLoad = [];
const pageIndex = this._loadSize > 0 ? this._loadSize * Math.floor(index / this._loadSize) : index;
let count = 0;
let start = -1;
for (let i = 0; i < this.loadSize; i++) {
const 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,
});
}
}
}
export interface VirtualArray<T> {
/**
* 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: EventData) => void, thisArg?: any): void;
/**
* Raised when still not loaded items are requested.
*/
on(event: 'itemsLoading', callback: (args: ItemsLoading) => void, thisArg?: any): void;
/**
* Raised when a change occurs.
*/
on(event: 'change', callback: (args: ChangedData<T>) => void, thisArg?: any): void;
}