'use strict';

const common = require('../common');
const EventEmitter = require('events');
const assert = require('assert');

const myEE = new EventEmitter();
let m = 0;
// This one comes last.
myEE.on('foo', common.mustCall(() => assert.strictEqual(m, 2)));

// This one comes second.
myEE.prependListener('foo', common.mustCall(() => assert.strictEqual(m++, 1)));

// This one comes first.
myEE.prependOnceListener('foo',
                         common.mustCall(() => assert.strictEqual(m++, 0)));

myEE.emit('foo');

// Verify that the listener must be a function
assert.throws(() => {
  const ee = new EventEmitter();

  ee.prependOnceListener('foo', null);
}, /^TypeError: "listener" argument must be a function$/);

// Test fallback if prependListener is undefined.
const stream = require('stream');
const util = require('util');

delete EventEmitter.prototype.prependListener;

function Writable() {
  this.writable = true;
  stream.Stream.call(this);
}
util.inherits(Writable, stream.Stream);

function Readable() {
  this.readable = true;
  stream.Stream.call(this);
}
util.inherits(Readable, stream.Stream);

const w = new Writable();
const r = new Readable();
r.pipe(w);