feathersjs/feathers

import { EventEmitter } from 'events'
import { NextFunction } from '@feathersjs/hooks'
import { HookContext, FeathersService } from './declarations'
import { getServiceOptions, defaultEventMap } from './service'

export function eventHook(context: HookContext, next: NextFunction) {
  const { events } = getServiceOptions((context as any).self)
  const defaultEvent = (defaultEventMap as any)[context.method] || null

  context.event = defaultEvent

  return next().then(() => {
    // Send the event only if the service does not do so already (indicated in the `events` option)
    // This is used for custom events and for client services receiving event from the server
    if (typeof context.event === 'string' && !events.includes(context.event)) {
      const results = Array.isArray(context.result) ? context.result : [context.result]

      results.forEach((element) => (context as any).self.emit(context.event, element, context))
    }
  })
}

export function eventMixin<A>(service: FeathersService<A>) {
  const isEmitter = typeof service.on === 'function' && typeof service.emit === 'function'

  if (!isEmitter) {
    Object.assign(service, EventEmitter.prototype)
  }

  return service
}