AssetTwigExtension.php

<?php

namespace CI\Twig;

use Silex\Application;

class AssetTwigExtension extends \Twig_Extension
{

    private $CDN = null;
    private $VERSION = null;

    /**
     * Asset_Twig_Extension Constructor
     *
     * @param String $version The version to use for assets
     * @param String $cdnHost The CDN hostname to use, do not include the protocol.
     */
    public function __construct($version = null, $cdnHost = null)
    {
        if($version) {
            $this->VERSION = $version;
        }

        if($cdnHost) {
            $this->CDN = $cdnHost;
        }
    }

    /**
     * Returns the Twig Extension name
     *
     * @return string
     */
    public function getName()
    {
        return 'asset';
    }

    /**
     * Returns the functions for the Twig Extension
     * @return array
     */
    public function getFunctions()
    {
        return array(
            'asset' => new \Twig_Function_Method($this, 'getAssetURL'),
            'assets_version' => new \Twig_Function_Method($this, 'getAssetsVersion'),
        );
    }

    /**
     * Returns the asset with either the CDN, query string, or both attached
     * @param $asset
     *
     * @return string
     */
    public function getAssetURL($asset, $setCDN = true)
    {

        if(! empty($this->VERSION)) {
            $parts = explode('.', $asset);
            $extension = array_pop($parts);
            $filename = implode('.', $parts);

            // set the cache busting query string
            $asset = "{$filename}.{$this->VERSION}.{$extension}";
        }

        // set the CDN host
        if($setCDN && !empty($this->CDN)) {
            $asset = "//{$this->CDN}{$asset}";
        }

        return $asset;
    }

}

AssetTwigExtension_Test.php

<?php

namespace CI\Tests;

use CI\Twig\AssetTwigExtension as TwigAssetExtension;
use PHPUnit_Framework_TestCase;

class AssetTwigExtension_Test extends PHPUnit_Framework_TestCase
{

    /**
     * Tests that the Version is set correctly when passed into the constructor
     * without a CDN.
     * @group Twig
     */
    public function testConstructorSetVersionOnly()
    {
        $version = 12345;
        $extension = new TwigAssetExtension($version);

        $this->assertAttributeEquals(
            $version,
            'VERSION',
            $extension
        );

        $this->assertAttributeEquals(
            null,
            'CDN',
            $extension
        );
    }

    /**
     * Tests that the CDN is set correctly when passed into the constructor
     * without the version.
     * @group Twig
     */
    public function testConstructorSetCDNOnly()
    {
        $cdn = 'cdn.example.com';
        $extension = new TwigAssetExtension(null, $cdn);

        $this->assertAttributeEquals(
            $cdn,
            'CDN',
            $extension
        );

        $this->assertAttributeEquals(
            null,
            'VERSION',
            $extension
        );
    }

    /**
     * Tests that the constructor sets the Version and CDN when provided.
     * @group Twig
     */
    public function testConstructorSetVersionAndCDN()
    {
        $version = 12345;
        $cdn = 'cdn.example.com';
        $extension = new TwigAssetExtension($version, $cdn);

        $this->assertAttributeEquals(
            $cdn,
            'CDN',
            $extension
        );

        $this->assertAttributeEquals(
            $version,
            'VERSION',
            $extension
        );
    }

    /**
     * Tests if the getAssetUrl method doesn't modify the asset if no CDN or version.
     * @group Twig
     */
    public function testGetAssetURLWithoutVersionOrCDN()
    {
        $extension = new TwigAssetExtension();

        $asset = '/path/to/script.js';
        $this->assertEquals(
            "/path/to/script.js",
            $extension->getAssetUrl($asset)
        );
    }

    /**
     * Tests if the getAssetUrl method adds a version to the asset.
     * @group Twig
     */
    public function testGetAssetURLGeneratesVersion()
    {
        $version = 12345;
        $extension = new TwigAssetExtension($version, null);

        $asset = '/path/to/script.js';
        $this->assertEquals(
            "/path/to/script.{$version}.js",
            $extension->getAssetUrl($asset)
        );
        $asset = '/path/to/jQuery.selectBox.min.js';
        $this->assertEquals(
            "/path/to/jQuery.selectBox.min.{$version}.js",
            $extension->getAssetUrl($asset)
        );

    }

    /**
     * Tests if the getAssetUrl method adds a CDN to the asset.
     * @group Twig
     */
    public function testGetAssetURLGeneratesCDN()
    {
        $cdn = 'cdn.example.com';
        $extension = new TwigAssetExtension(null, $cdn);

        $asset = '/path/to/script.js';
        $this->assertEquals(
            "//{$cdn}/path/to/script.js",
            $extension->getAssetUrl($asset)
        );
    }

    /**
     * Tests if the getAssetUrl method will add a CDN and Version to the asset
     * @group Twig
     */
    public function testGetAssetURLGeneratesVersionAndCDN()
    {
        $version = 12345;
        $cdn = 'cdn.example.com';
        $extension = new TwigAssetExtension($version, $cdn);

        $asset = '/path/to/script.js';
        $this->assertEquals(
            "//{$cdn}/path/to/script.{$version}.js",
            $extension->getAssetUrl($asset)
        );
    }

    /**
     * Tests if the getAssetUrl can disable the use of a CDN.
     * @group Twig
     */
    public function testGetAssetURLCanOmitCDN()
    {
        $version = 12345;
        $cdn = 'cdn.example.com';
        $extension = new TwigAssetExtension($version, $cdn);

        $asset = '/path/to/script.js';
        $this->assertEquals(
            "/path/to/script.{$version}.js",
            $extension->getAssetUrl($asset, false)
        );
    }

}