How to add a coding-standard to phpcs via composer hook

composer hook-class.php

<?php

namespace TM;

use Composer\Package\Package;
use Composer\Script\Event;

/**
 * Class MyClass
 *
 * @package TM
 */
class MyClass
{
    /**
     * @var array
     */
    protected static $requiredPackage = array(
        'name'    => 'squizlabs/php_codesniffer',
        'version' => '1.5.4'
    );

    /**
     * @param Event $event
     */
    public static function postUpdate(Event $event)
    {
        static::addStandard($event);
    }

    /**
     * @param Event $event
     */
    public static function postInstall(Event $event)
    {
        static::addStandard($event);
    }

    /**
     * @param Event $event
     */
    protected static function addStandard(Event $event)
    {
        $composer = $event->getComposer();

        /* @var $repositoryManager \Composer\Repository\RepositoryManager */
        $repositoryManager = $composer->getRepositoryManager();
        
        $requiredPackage = $repositoryManager->findPackage(
            self::$requiredPackage['name'], self::$requiredPackage['version']
        );

        if (!$requiredPackage instanceof Package) {
            $event->getIO()->write(sprintf('<error>Required package "%s" does not exist!</error>', self::$requiredPackage['name']));

            return;
        }

        $vendorDir = $composer->getConfig()->get('vendor-dir');
        $path = $vendorDir . '/squizlabs/php_codesniffer/CodeSniffer/Standards/Symfony2';

        if (is_dir($path)) {
            $event->getIO()->write('<info>Symfony2 coding standard installed.</info>');

            return;
        }

        /* @var $downloadManager \Composer\Downloader\DownloadManager */
        $downloadManager = $composer->getDownloadManager();
        /* @var $downloader \Composer\Downloader\ZipDownloader */
        $downloader = $downloadManager->getDownloader('zip');

        $package = new Package('lapistano-Symfony2-coding-standard', '1.0', '1.0');
        $package->setDistUrl('https://github.com/lapistano/Symfony2-coding-standard/archive/master.zip');

        $downloader->download($package, $path);
    }
} 

example composer.json

{
    "require-dev": {
        "squizlabs/php_codesniffer": "1.5.4"
    },
    "scripts": {
        "post-update-cmd": "TM\\MyClass::postUpdate",
        "post-install-cmd": "TM\\MyClass::postInstall"
    },
    ...
}