af83/chouette-core

import { Subject } from 'rxjs'
import { filter, map } from 'rxjs/operators'

import { get, set } from 'lodash'

const subject = Symbol('subject')

export default class EventEmitter {
  constructor() {
    set(this, subject, new Subject())
  }

  emit(event, ...args) {
    if (!Boolean(event)) {
      throw new Error(`Cannot emit event: falsey or empty event name`)
    }
    get(this, subject).next([event, args])
  }

  on(event, callback) {
    if (!Boolean(event)) {
      throw new Error(`Cannot add event listener: falsey or empty event name`)
    }

    return get(this, subject).pipe(
      filter(([emitEvent, _]) => event === emitEvent),
      map(([_, args]) => args)
    ).subscribe(args => {
      callback(...args)
    })
  }
}