class AssetOptimizer

abstract class AssetOptimizer {
    
    /**
     * Checks for and if found fixes incorrectly set asset types.
     *
     * @param array $asset
     *   A core single asset definition array.
     */
    protected abstract function fixType(array &$asset);
    
    /**
     * Asset type (css or js).
     *
     * @var string
     */
    protected $extension;
    
    /**
     * A config object for the advagg configuration.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $config;
    
    /**
     * Event Dispatcher service.
     *
     * @var \Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher
     */
    protected $eventDispatcher;
    
    /**
     * The AdvAgg cache.
     *
     * @var \Drupal\Core\Cache\CacheBackendInterface
     */
    protected $cache;
    
    /**
     * Config level of caching of assets.
     *
     * @var int
     */
    protected $cacheLevel;
    
    /**
     * The cache time.
     *
     * @var int
     */
    protected $cacheTime;
    
    /**
     * Config to control fixing the asset type (file, external).
     *
     * @var bool
     */
    protected $fixType;
    
    /**
     * Whether or not to gzip assets.
     *
     * @var bool
     */
    protected $gZip;
    
    /**
     * Whether or not to brotli compress assets.
     *
     * @var bool
     */
    protected $brotli;
    
    /**
     * Array of domains to prefetch. Copied to $GLOBALS for later use.
     *
     * @var array
     */
    protected $dnsPrefetch;
    
    /**
     * Constructs the Optimizer object.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   A config factory for retrieving required config objects.
     * @param \Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher $event_dispatcher
     *   The event dispatcher.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache
     *   The AdvAgg cache.
     */
    public function __construct(ConfigFactoryInterface $config_factory, ContainerAwareEventDispatcher $event_dispatcher, CacheBackendInterface $cache) {
        $this->config = $config_factory->get('advagg.settings');
        $this->eventDispatcher = $event_dispatcher;
        $this->cache = $cache;
        $this->dnsPrefetch = [];
        $this->cacheLevel = $this->config
            ->get('cache_level');
        $this->fixType = $this->config
            ->get("{$this->extension}.fix_type");
        if ($this->fixType) {
            $this->basePath = substr($GLOBALS['base_root'] . $GLOBALS['base_path'], strpos($GLOBALS['base_root'] . $GLOBALS['base_path'], '//') + 2);
            $this->basePathLen = strlen($this->basePath);
        }
        $this->gZip = $this->shouldGZip();
        $this->brotli = $this->shouldBrotli();
    }
    
    /**
     * Process a core asset array.
     *
     * @param array $assets
     *   The core asset array (css or js) to process.
     */
    public function processAssetArray(array &$assets) {
        $protocol_relative = $this->config
            ->get('path.convert.absolute_to_protocol_relative');
        $force_https = $this->config
            ->get('path.convert.force_https');
        foreach ($assets as &$asset) {
            if (!is_string($asset['data'])) {
                continue;
            }
            // Fix type if it was incorrectly set.
            if ($this->fixType) {
                $this->fixType($asset);
            }
            if ($asset['type'] === 'file' && $asset['preprocess']) {
                if (!is_readable($asset['data'])) {
                    continue;
                }
                $this->scanFile($asset);
            }
            elseif ($asset['type'] === 'external') {
                if ($force_https) {
                    $asset['data'] = $this->convertPathForceHttps($asset['data']);
                }
                elseif ($protocol_relative) {
                    $asset['data'] = $this->convertPathProtocolRelative($asset['data']);
                }
                $scheme = parse_url($asset['data'], PHP_URL_SCHEME);
                $host = parse_url($asset['data'], PHP_URL_HOST);
                $asset_url = isset($scheme) ? "{$scheme}://{$host}" : "//{$host}";
                $this->dnsPrefetch[] = $asset_url;
            }
        }
        if (!isset($GLOBALS['_advagg_prefetch'])) {
            $GLOBALS['_advagg_prefetch'] = [];
        }
        $GLOBALS['_advagg_prefetch'] += $this->dnsPrefetch;
    }
    
    /**
     * Given a filename calculate various hashes, gather meta data then optimize.
     *
     * If any file optimizations are applied, updates the asset array.
     * Also if enabled preemptively creates compressed versions.
     *
     * @param array $asset
     *   A core asset array.
     */
    protected function scanFile(array &$asset) {
        // Clear PHP's internal file status cache.
        clearstatcache(TRUE, $asset['data']);
        $cid = Crypt::hashBase64($asset['data'] . $this->config
            ->get('global_counter'));
        $cached = $this->cache
            ->get($cid);
        if ($cached && file_exists($cached->data['file'])) {
            if ($this->config
                ->get('css.combine_media') && isset($asset['media']) && $asset['media'] !== 'all') {
                $asset['media'] = 'all';
            }
            $asset['size'] = $cached->data['filesize'];
            if ($this->cacheLevel === 3) {
                $asset['data'] = $cached->data['file'];
                $this->dnsPrefetch += $cached->data['prefetch'];
                return;
            }
            $data = [
                'filesize' => (int) @filesize($asset['data']),
                'mtime' => @filemtime($asset['data']),
            ];
            if ($this->cacheLevel === 2) {
                if ($cached->data['mtime'] === $data['mtime']) {
                    $asset['data'] = $cached->data['file'];
                    $this->dnsPrefetch += $cached->data['prefetch'];
                    return;
                }
            }
            $data['contents'] = @file_get_contents($asset['data']);
            $data['hash'] = Crypt::hashBase64($data['contents']);
            if ($this->cacheLevel === 1) {
                if ($cached->data['hash'] === $data['hash']) {
                    $asset['data'] = $cached->data['file'];
                    $this->dnsPrefetch += $cached->data['prefetch'];
                    return;
                }
            }
        }
        if (empty($data)) {
            $data = [
                'filesize' => (int) @filesize($asset['data']),
                'mtime' => @filemtime($asset['data']),
                'contents' => @file_get_contents($asset['data']),
            ];
            $data['hash'] = Crypt::hashBase64($data['contents']);
        }
        $data['cid'] = $cid;
        $asset['size'] = $data['filesize'];
        if ($data['file'] = $this->optimizeFile($asset, $data)) {
            $asset['contents'] = $data['contents'];
            $data['prefetch'] = $this->addDnsPrefetch($asset);
            $this->dnsPrefetch += $data['prefetch'];
            $data['original'] = $asset['data'];
            unset($data['contents']);
            unset($data['cid']);
            $this->cache
                ->set($cid, $data, $this->getCacheTime(), [
                'advagg',
            ]);
            $asset['data'] = $data['file'];
        }
    }
    
    /**
     * The filename for the CSS or JS optimized file is the cid.
     *
     * The CID is generated from the hashed original filename.
     *
     * @param string $data
     *   The content to output.
     * @param string $cid
     *   The unique segment of the filename.
     *
     * @return bool|string
     *   FALSE or the saved filename.
     */
    protected function writeFile($data, $cid) {
        // Prefix filename to prevent blocking by firewalls which reject files
        // starting with "ad*".
        // Create the css/ or js/ path within the files folder.
        $path = 'public://' . $this->extension . '/optimized';
        $version = Crypt::hashBase64($data);
        $uri = "{$path}/{$this->extension}_{$cid}.{$version}.{$this->extension}";
        // Create the CSS or JS file.
        file_prepare_directory($path, FILE_CREATE_DIRECTORY);
        if (!file_exists($uri)) {
            if (!file_unmanaged_save_data($data, $uri, FILE_EXISTS_REPLACE)) {
                return FALSE;
            }
        }
        // If CSS/JS gzip compression is enabled and the zlib extension is available
        // then create a gzipped version of this file. This file is served
        // conditionally to browsers that accept gzip using .htaccess rules.
        if ($this->gZip && !file_exists($uri . '.gz')) {
            file_unmanaged_save_data(gzencode($data, 9, FORCE_GZIP), $uri . '.gz', FILE_EXISTS_REPLACE);
        }
        // If brotli compression is enabled and available, create br compressed
        // files and serve conditionally via .htaccess rules.
        if ($this->brotli && !file_exists($uri . '.br')) {
            file_unmanaged_save_data(brotli_compress($data, 11, BROTLI_TEXT), $uri . '.br', FILE_EXISTS_REPLACE);
        }
        return $uri;
    }
    
    /**
     * Determine if settings and available PHP modules allow GZipping assets.
     *
     * @return bool
     *   True if asset type can/should be gzipped.
     */
    protected function shouldGZip() {
        if (extension_loaded('zlib') && \Drupal::config('system.performance')->get($this->extension . '.gzip')) {
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * Determine if settings and available PHP modules allow brotli-ing assets.
     *
     * @return bool
     *   True if asset type can/should be brotli-ed.
     */
    protected function shouldBrotli() {
        if (function_exists('brotli_compress') && $this->config
            ->get($this->extension . '.brotli')) {
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * Get how long to cache an asset. Varies on cache level setting.
     *
     * @return int
     *   The seconds to cache the data for.
     */
    protected function getCacheTime() {
        if ($this->cacheTime) {
            return $this->cacheTime;
        }
        $this->cacheTime = (int) microtime(TRUE);
        // 1 Day.
        if ($this->cacheLevel === 1) {
            $this->cacheTime += 86400;
        }
        elseif ($this->cacheLevel === 2) {
            $this->cacheTime += 604800;
        }
        elseif ($this->cacheLevel === 3) {
            $this->cacheTime += 2419200;
        }
        return $this->cacheTime;
    }
    
    /**
     * Perform any in-place optimization & pass to event for further optimization.
     *
     * @param array $asset
     *   Core single asset definition array.
     * @param array $data
     *   An array of extra file information (hashes, modification time etc).
     *
     * @return bool|string
     *   False if contents unchanged or the new file path if optimized.
     */
    protected abstract function optimizeFile(array &$asset, array $data);
    
    /**
     * Extract any domains to prefetch DNS.
     *
     * @param array $asset
     *   A core asset definition array.
     *
     * @return array
     *   An array of domains to prefetch.
     */
    protected abstract function addDnsPrefetch(array $asset);
    
    /**
     * Converts absolute paths to be protocol relative paths.
     *
     * @param string $path
     *   Path to check.
     *
     * @return string
     *   The converted path or the original path if already protocol relative.
     */
    protected function convertPathProtocolRelative($path) {
        if (strpos($path, 'https://') === 0) {
            $path = substr($path, 6);
        }
        elseif (strpos($path, 'http://') === 0) {
            $path = substr($path, 5);
        }
        return $path;
    }
    
    /**
     * Convert http:// to https://.
     *
     * @param string $path
     *   Path to check.
     *
     * @return string
     *   The modified path or the original if already https or relative.
     */
    protected function convertPathForceHttps($path) {
        if (strpos($path, 'http://') === 0) {
            $path = 'https://' . substr($path, 7);
        }
        return $path;
    }
    
    /**
     * Stable sort for CSS and JS items.
     *
     * Preserves the order of items with equal sort criteria.
     *
     * The function will sort by:
     * - $item['group'],      integer, ascending
     * - $item['weight'],     integer, ascending
     *
     * @param array &$assets
     *   Array of JS or CSS items, as in hook_alter_js() and hook_alter_css().
     *   The array keys can be integers or strings. The items are arrays.
     *
     * @see hook_alter_js()
     * @see hook_alter_css()
     */
    public static function sortStable(array &$assets) {
        $nested = [];
        foreach ($assets as $key => $item) {
            // Weight cast to string to preserve float.
            $weight = (string) $item['weight'];
            $nested[$item['group']][$weight][$key] = $item;
        }
        // First order by group, so that, for example, all items in the CSS_SYSTEM
        // group appear before items in the CSS_DEFAULT group, which appear before
        // all items in the CSS_THEME group. Modules may create additional groups by
        // defining their own constants.
        $sorted = [];
        // Sort group; then iterate over it.
        ksort($nested);
        foreach ($nested as &$group_items) {
            // Order by weight and iterate over it.
            ksort($group_items);
            foreach ($group_items as &$weight_items) {
                foreach ($weight_items as $key => &$item) {
                    $sorted[$key] = $item;
                }
                unset($item);
            }
            unset($weight_items);
        }
        unset($group_items);
        $assets = $sorted;
    }
    
    /**
     * Generate an htaccess file in the optimized asset dirs to improve serving.
     *
     * @param string $extension
     *   The file type to use - either CSS or JS.
     * @param bool $regenerate
     *   Whether to regenerate if the file already exists.
     */
    public static function generateHtaccess($extension, $regenerate = FALSE) {
        $path = "public://{$extension}/optimized";
        $file = $path . '/.htaccess';
        if (!$regenerate && file_exists($file)) {
            return;
        }
        
        /** @var \Drupal\Core\Config\Config $config */
        $config = \Drupal::config('advagg.settings');
        if ($extension === 'js') {
            $type = 'application/javascript';
        }
        else {
            $type = 'text/css';
        }
        file_prepare_directory($path, FILE_CREATE_DIRECTORY);
        $immutable = $config->get('immutable') ? ', immutable' : '';
        $options = '';
        if ($config->get('symlinks')) {
            $options = 'Options +FollowSymlinks';
        }
        elseif ($config->get('symlinksifownermatch')) {
            $options = 'Options +SymLinksIfOwnerMatch';
        }
        $htaccess = <<<EOT
      {<span class="php-variable">$options</span>}
      <IfModule mod_rewrite.c>
        RewriteEngine on
        <IfModule mod_headers.c>
          # Serve brotli compressed {<span class="php-variable">$extension</span>} files if they exist and the client accepts br.
          RewriteCond %{HTTP:Accept-encoding} br
          RewriteCond %{REQUEST_FILENAME}\\.br -s
          RewriteRule ^(.*)\\.{<span class="php-variable">$extension</span>} \$1\\.{<span class="php-variable">$extension</span>}\\.br [QSA]
          RewriteRule \\.{<span class="php-variable">$extension</span>}\\.br\$ - [T={<span class="php-variable">$type</span>},E=no-gzip:1]

          <FilesMatch "\\.{<span class="php-variable">$extension</span>}\\.br\$">
            # Serve correct encoding type.
            Header set Content-Encoding br
            # Force proxies to cache br/gzip/non-gzipped assets separately.
            Header append Vary Accept-Encoding
          </FilesMatch>

          # Serve gzip compressed {<span class="php-variable">$extension</span>} files if they exist and the client accepts gzip.
          RewriteCond %{HTTP:Accept-encoding} gzip
          RewriteCond %{REQUEST_FILENAME}\\.gz -s
          RewriteRule ^(.*)\\.{<span class="php-variable">$extension</span>} \$1\\.{<span class="php-variable">$extension</span>}\\.gz [QSA]
          RewriteRule \\.{<span class="php-variable">$extension</span>}\\.gz\$ - [T=application/javascript,E=no-gzip:1]

          <FilesMatch "\\.{<span class="php-variable">$extension</span>}\\.gz\$">
            # Serve correct encoding type.
            Header set Content-Encoding gzip
            # Force proxies to cache br/gzip/non-gzipped assets separately.
            Header append Vary Accept-Encoding
          </FilesMatch>
        </IfModule>
      </IfModule>

      <FilesMatch "{<span class="php-variable">$extension</span>}(\\.gz|\\.br)?">
        # No mod_headers. Apache module headers is not enabled.
        <IfModule !mod_headers.c>
          # No mod_expires. Apache module expires is not enabled.
          <IfModule !mod_expires.c>
            # Use ETags.
            FileETag MTime Size
          </IfModule>
        </IfModule>

        # Use Expires Directive if apache module expires is enabled.
        <IfModule mod_expires.c>
          # Do not use ETags.
          FileETag None
          # Enable expirations.
          ExpiresActive On
          # Cache all aggregated {<span class="php-variable">$extension</span>} files for 52 weeks after access (A).
          ExpiresDefault A31449600
        </IfModule>

        # Use Headers Directive if apache module headers is enabled.
        <IfModule mod_headers.c>
          # Do not use etags for cache validation.
          Header unset ETag
          # Serve correct content type.
          Header set Content-Type {<span class="php-variable">$type</span>}
          <IfModule !mod_expires.c>
            # Set a far future Cache-Control header to 52 weeks.
            Header set Cache-Control "max-age=31449600, no-transform, public{<span class="php-variable">$immutable</span>}"
          </IfModule>
          <IfModule mod_expires.c>
            Header append Cache-Control "no-transform, public{<span class="php-variable">$immutable</span>}"
          </IfModule>
        </IfModule>
        ForceType {<span class="php-variable">$type</span>}
      </FilesMatch>
EOT;
        file_unmanaged_save_data($htaccess, $file, FILE_EXISTS_REPLACE);
    }

}