HORIZON PROJECT

/*!

 * ee-first

 * Copyright(c) 2014 Jonathan Ong

 * MIT Licensed

 */

'use strict'

/**

 * Module exports.

 * @public

 */

module.exports = first

/**

 * Get the first event in a set of event emitters and event pairs.

 *

 * @param {array} stuff

 * @param {function} done

 * @public

 */

function first(stuff, done) {

  if (!Array.isArray(stuff))

    throw new TypeError('arg must be an array of [ee, events...] arrays')

  var cleanups = []

  for (var i = 0; i < stuff.length; i++) {

    var arr = stuff[i]

    if (!Array.isArray(arr) || arr.length < 2)

      throw new TypeError('each array member must be [ee, events...]')

    var ee = arr[0]

    for (var j = 1; j < arr.length; j++) {

      var event = arr[j]

      var fn = listener(event, callback)

      // listen to the event

      ee.on(event, fn)

      // push this listener to the list of cleanups

      cleanups.push({

        ee: ee,

        event: event,

        fn: fn,

      })

    }

  }

  function callback() {

    cleanup()

    done.apply(null, arguments)

  }

  function cleanup() {

    var x

    for (var i = 0; i < cleanups.length; i++) {

      x = cleanups[i]

      x.ee.removeListener(x.event, x.fn)

    }

  }

  function thunk(fn) {

    done = fn

  }

  thunk.cancel = cleanup

  return thunk

}

/**

 * Create the event listener.

 * @private

 */

function listener(event, done) {

  return function onevent(arg1) {

    var args = new Array(arguments.length)

    var ee = this

    var err = event === 'error'

      ? arg1

      : null

    // copy args to prevent arguments escaping scope

    for (var i = 0; i < args.length; i++) {

      args[i] = arguments[i]

    }

    done(err, ee, event, args)

  }

}