Created
June 10, 2018 11:49
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Typescript implementation of the latest C# version of the Pipe and Filters approach
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| /** | |
| * Type of the message all pipeline messages must inherit from. | |
| * | |
| */ | |
| export abstract class BaseMessage { | |
| cancellationToken: CancellationToken = new CancellationToken(); | |
| onError = () => {}; | |
| onStart = () => {}; | |
| onComplete = () => {}; | |
| onSuccess = () => {}; | |
| onStep = (s: string) => {}; | |
| } | |
| /** | |
| * Type representing an interface of an executbale step. | |
| * | |
| */ | |
| export interface Filter<T extends BaseMessage> { | |
| execute(msg: T): void; | |
| } | |
| /** | |
| * Type representing an interface of a cross-cutting concern. | |
| * | |
| */ | |
| export interface Aspect<T extends BaseMessage> { | |
| next: Aspect<T>; | |
| execute(msg: T): void; | |
| } | |
| /** | |
| * Type representing the the ability to request a pipeline to stop executing. | |
| * | |
| */ | |
| export class CancellationToken { | |
| stop: Boolean; | |
| } | |
| /** | |
| * Type representing the context that all executable steps are run under. | |
| * | |
| */ | |
| export class PipeLine<T extends BaseMessage> { | |
| _filters: Array<Filter<T>> = []; | |
| _finallyFilters: Array<Filter<T>> = []; | |
| _aspects: Array<Aspect<T>> = []; | |
| constructor() { | |
| this.execute = this.execute.bind(this); | |
| this._aspects.push(new ExecutionContext(this.execute)); | |
| } | |
| addAspect(aspect: Aspect<T>): void { | |
| this._aspects.splice(this._aspects.length - 1, 0, aspect); | |
| this._aspects.reduce((a, b) => a.next = b); | |
| } | |
| register(filter: Filter<T>): void { | |
| this._filters.push(filter); | |
| } | |
| finally(filter: Filter<T>): void { | |
| this._finallyFilters.push(filter); | |
| } | |
| invoke(msg: T): void { | |
| this._aspects[0].execute(msg); | |
| } | |
| private execute(msg: T): void { | |
| if (msg.onStart != null) { msg.onStart(); } | |
| try { | |
| this._filters.forEach(f => { | |
| if (msg.cancellationToken.stop) { return; } | |
| f.execute(msg); | |
| }); | |
| if (msg.onSuccess != null) { msg.onSuccess(); } | |
| } finally { | |
| this._finallyFilters.forEach(f => { | |
| f.execute(msg); | |
| }); | |
| if (msg.onComplete != null) { msg.onComplete(); } | |
| } | |
| } | |
| } | |
| class ExecutionContext<T extends BaseMessage> implements Aspect<T>, Filter<T> { | |
| inner: any; | |
| next: Aspect<T>; | |
| constructor(action: Function) { | |
| this.inner = action; | |
| } | |
| execute(msg: T): void { | |
| this.inner(msg); | |
| } | |
| } |
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