/**
* EventBus
*
* Implementation of the event bus pattern for domain events.
* Provides publish-subscribe functionality for loose coupling between components.
*/
export class EventBus {
private static instance: EventBus;
private handlers: Map<string, Function[]> = new Map();
private constructor() {}
/**
* Gets the singleton instance of EventBus.
* @returns EventBus instance
*/
public static getInstance(): EventBus {
if (!EventBus.instance) {
EventBus.instance = new EventBus();
}
return EventBus.instance;
}
/**
* Registers an event handler for a specific event type.
* @param eventType The event type to subscribe to
* @param handler The handler function to be called when the event occurs
*/
public subscribe(eventType: string, handler: Function): void {
if (!this.handlers.has(eventType)) {
this.handlers.set(eventType, []);
}
const eventHandlers = this.handlers.get(eventType)!;
if (!eventHandlers.includes(handler)) {
eventHandlers.push(handler);
}
}
/**
* Unregisters an event handler for a specific event type.
* @param eventType The event type to unsubscribe from
* @param handler The handler function to be removed
*/
public unsubscribe(eventType: string, handler: Function): void {
if (!this.handlers.has(eventType)) {
return;
}
const eventHandlers = this.handlers.get(eventType)!;
const index = eventHandlers.indexOf(handler);
if (index !== -1) {
eventHandlers.splice(index, 1);
}
// Remove the event type if there are no more handlers
if (eventHandlers.length === 0) {
this.handlers.delete(eventType);
}
}
/**
* Publishes an event to all registered handlers.
* @param eventType The type of event to publish
* @param event The event data
*/
public publish(eventType: string, event: any): void {
if (!this.handlers.has(eventType)) {
return;
}
const eventHandlers = this.handlers.get(eventType)!;
for (const handler of eventHandlers) {
try {
handler(event);
} catch (error) {
console.error(`Error in event handler for ${eventType}:`, error);
}
}
}
/**
* Clears all event handlers.
*/
public clear(): void {
this.handlers.clear();
}
}
