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144 lines
3.5 KiB
TypeScript
144 lines
3.5 KiB
TypeScript
import { Observable, EventData } from '../../data/observable';
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import { ImageSource } from '../../image-source';
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/**
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* Represents a single download request.
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*/
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export interface DownloadRequest {
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/**
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* The url of the image.
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*/
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url: string;
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/**
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* The key used to cache the image.
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*/
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key: string;
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/**
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* An optional function to be called when the download is complete.
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*/
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completed?: (image: any, key: string) => void;
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/**
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* An optional function to be called if the download errors.
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*/
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error?: (key: string) => void;
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}
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/**
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* Represents a class that stores handles image download requests and caches the already downloaded images.
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*/
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export class Cache extends Observable {
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/**
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* String value used when hooking to downloaded event.
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*/
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public static downloadedEvent: string;
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/**
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* String value used when hooking to download error event.
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*/
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public static downloadErrorEvent: string;
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/**
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* The image to be used to notify for a pending download request - e.g. loading indicator.
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*/
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placeholder: ImageSource;
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/**
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* The maximum number of simultaneous download requests. Defaults to 5.
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*/
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maxRequests: number;
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/**
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* Enables previously suspended download requests.
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*/
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enableDownload(): void;
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/**
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* Temporary disables download requests.
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*/
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disableDownload(): void;
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/**
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* Adds a new download request at the top of the download queue. This will be the next immediate download to start.
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*/
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push(request: DownloadRequest);
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/**
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* Adds a new download request at the end of the download queue. This will be the last download to start.
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*/
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enqueue(request: DownloadRequest);
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/**
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* Gets the image for the specified key. May be undefined if the key is not present in the cache.
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*/
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get(key: string): any;
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/**
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* Sets the image for the specified key.
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*/
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set(key: string, image: any): void;
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/**
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* Removes the cache for the specified key.
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*/
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remove(key: string): void;
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/**
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* Removes all the previously cached images.
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*/
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clear(): void;
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/**
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* A basic method signature to hook an event listener (shortcut alias to the addEventListener method).
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* @param eventNames - String corresponding to events (e.g. "propertyChange"). Optionally could be used more events separated by `,` (e.g. "propertyChange", "change").
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* @param callback - Callback function which will be executed when event is raised.
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* @param thisArg - An optional parameter which will be used as `this` context for callback execution.
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*/
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on(eventNames: string, callback: (args: EventData) => void, thisArg?: any);
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/**
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* Raised when the image has been downloaded.
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*/
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on(event: 'downloaded', callback: (args: DownloadedData) => void, thisArg?: any);
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/**
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* Raised if the image download errors.
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*/
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on(event: 'downloadError', callback: (args: DownloadError) => void, thisArg?: any);
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//@private
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/**
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* @private
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*/
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_downloadCore(request: DownloadRequest);
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/**
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* @private
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*/
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_onDownloadCompleted(key: string, image: any);
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//@endprivate
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/**
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* @private
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*/
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_onDownloadError(key: string, err: Error);
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//@endprivate
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}
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/**
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* Provides data for downloaded event.
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*/
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export interface DownloadedData extends EventData {
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/**
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* A string indentifier of the cached image.
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*/
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key: string;
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/**
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* Gets the cached image.
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*/
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image: ImageSource;
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}
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/**
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* Provides data for download error.
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*/
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export interface DownloadError extends EventData {
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/**
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* A string indentifier of the cached image.
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*/
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key: string;
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/**
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* Gets the error.
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*/
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error: Error;
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}
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