import {EventBus} from './EventBus'
import {Collection} from '../util'
import {Bus, Dispatchable} from './types'

/**
 * A non-queued bus implementation that executes subscribers immediately in the main thread.
 * This bus also supports "propagating" events along to any other connected buses.
 * Such behavior is useful, e.g., if we want to have a semi-isolated request-
 * level bus whose events still reach the global EventBus instance.
 */
export class PropagatingEventBus extends EventBus {
    protected recipients: Collection<Bus> = new Collection<Bus>()

    async dispatch(event: Dispatchable): Promise<void> {
        await super.dispatch(event)
        await this.recipients.promiseMap(bus => bus.dispatch(event))
    }

    /**
     * Register the given bus to receive events fired on this bus.
     * @param recipient
     */
    connect(recipient: Bus): void {
        if ( !this.recipients.includes(recipient) ) {
            this.recipients.push(recipient)
        }
    }
}