buuh/packages/core/lib/bus.js

// Ported from nanobus 4.5.0 (MIT) — https://github.com/choojs/nanobus
// Event emitter with a '*' wildcard channel and nanotiming instrumentation.

import nanotiming from './timing.js'
import { ok, equal } from './assert.js'

function assertEventName (eventName, method) {
  ok(
    typeof eventName === 'string' || typeof eventName === 'symbol',
    `nanobus.${method}: eventName should be type string or symbol`
  )
}

export default class Nanobus {
  constructor (name) {
    this._name = name || 'nanobus'
    this._starListeners = []
    this._listeners = {}
  }

  emit (eventName, ...data) {
    assertEventName(eventName, 'emit')

    const emitTiming = nanotiming(this._name + "('" + eventName.toString() + "')")
    const listeners = this._listeners[eventName]
    if (listeners && listeners.length > 0) {
      this._emit(this._listeners[eventName], data)
    }

    if (this._starListeners.length > 0) {
      this._emit(this._starListeners, eventName, data, emitTiming.uuid)
    }
    emitTiming()

    return this
  }

  on (eventName, listener) {
    assertEventName(eventName, 'on')
    equal(typeof listener, 'function', 'nanobus.on: listener should be type function')

    if (eventName === '*') {
      this._starListeners.push(listener)
    } else {
      if (!this._listeners[eventName]) this._listeners[eventName] = []
      this._listeners[eventName].push(listener)
    }
    return this
  }

  addListener (eventName, listener) {
    return this.on(eventName, listener)
  }

  prependListener (eventName, listener) {
    assertEventName(eventName, 'prependListener')
    equal(typeof listener, 'function', 'nanobus.prependListener: listener should be type function')

    if (eventName === '*') {
      this._starListeners.unshift(listener)
    } else {
      if (!this._listeners[eventName]) this._listeners[eventName] = []
      this._listeners[eventName].unshift(listener)
    }
    return this
  }

  once (eventName, listener) {
    assertEventName(eventName, 'once')
    equal(typeof listener, 'function', 'nanobus.once: listener should be type function')

    const self = this
    this.on(eventName, function once (...args) {
      listener.apply(self, args)
      self.removeListener(eventName, once)
    })
    return this
  }

  prependOnceListener (eventName, listener) {
    assertEventName(eventName, 'prependOnceListener')
    equal(typeof listener, 'function', 'nanobus.prependOnceListener: listener should be type function')

    const self = this
    this.prependListener(eventName, function once (...args) {
      listener.apply(self, args)
      self.removeListener(eventName, once)
    })
    return this
  }

  removeListener (eventName, listener) {
    assertEventName(eventName, 'removeListener')
    equal(typeof listener, 'function', 'nanobus.removeListener: listener should be type function')

    if (eventName === '*') {
      this._starListeners = this._starListeners.slice()
      return remove(this._starListeners, listener)
    } else {
      if (typeof this._listeners[eventName] !== 'undefined') {
        this._listeners[eventName] = this._listeners[eventName].slice()
      }
      return remove(this._listeners[eventName], listener)
    }

    function remove (arr, listener) {
      if (!arr) return
      const index = arr.indexOf(listener)
      if (index !== -1) {
        arr.splice(index, 1)
        return true
      }
    }
  }

  removeAllListeners (eventName) {
    if (eventName) {
      if (eventName === '*') {
        this._starListeners = []
      } else {
        this._listeners[eventName] = []
      }
    } else {
      this._starListeners = []
      this._listeners = {}
    }
    return this
  }

  listeners (eventName) {
    const listeners = eventName !== '*'
      ? this._listeners[eventName]
      : this._starListeners

    return listeners ? listeners.slice() : []
  }

  _emit (arr, eventName, data, uuid) {
    if (typeof arr === 'undefined') return
    if (arr.length === 0) return
    if (data === undefined) {
      data = eventName
      eventName = null
    }

    if (eventName) {
      if (uuid !== undefined) {
        data = [eventName].concat(data, uuid)
      } else {
        data = [eventName].concat(data)
      }
    }

    // Take a copy in case a listener mutates the array while we iterate.
    const listeners = arr.slice()
    for (let i = 0; i < listeners.length; i++) {
      const listener = listeners[i]
      listener.apply(listener, data)
    }
  }
}