Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\Utility;
Chris@0: 
Chris@0: use Drupal\Core\Cache\Cache;
Chris@0: use Drupal\Core\Cache\CacheBackendInterface;
Chris@0: use Drupal\Core\Cache\CacheCollector;
Chris@0: use Drupal\Core\DestructableInterface;
Chris@0: use Drupal\Core\Lock\LockBackendInterface;
Chris@0: 
Chris@0: /**
Chris@0:  * Builds the run-time theme registry.
Chris@0:  *
Chris@0:  * A cache collector to allow the theme registry to be accessed as a
Chris@0:  * complete registry, while internally caching only the parts of the registry
Chris@0:  * that are actually in use on the site. On cache misses the complete
Chris@0:  * theme registry is loaded and used to update the run-time cache.
Chris@0:  */
Chris@0: class ThemeRegistry extends CacheCollector implements DestructableInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * Whether the partial registry can be persisted to the cache.
Chris@0:    *
Chris@0:    * This is only allowed if all modules and the request method is GET. _theme()
Chris@0:    * should be very rarely called on POST requests and this avoids polluting
Chris@0:    * the runtime cache.
Chris@0:    */
Chris@0:   protected $persistable;
Chris@0: 
Chris@0:   /**
Chris@0:    * The complete theme registry array.
Chris@0:    */
Chris@0:   protected $completeRegistry;
Chris@0: 
Chris@0:   /**
Chris@0:    * Constructs a ThemeRegistry object.
Chris@0:    *
Chris@0:    * @param string $cid
Chris@0:    *   The cid for the array being cached.
Chris@0:    * @param \Drupal\Core\Cache\CacheBackendInterface $cache
Chris@0:    *   The cache backend.
Chris@0:    * @param \Drupal\Core\Lock\LockBackendInterface $lock
Chris@0:    *   The lock backend.
Chris@0:    * @param array $tags
Chris@0:    *   (optional) The tags to specify for the cache item.
Chris@0:    * @param bool $modules_loaded
Chris@0:    *   Whether all modules have already been loaded.
Chris@0:    */
Chris@0:   public function __construct($cid, CacheBackendInterface $cache, LockBackendInterface $lock, $tags = [], $modules_loaded = FALSE) {
Chris@0:     $this->cid = $cid;
Chris@0:     $this->cache = $cache;
Chris@0:     $this->lock = $lock;
Chris@0:     $this->tags = $tags;
Chris@0:     $this->persistable = $modules_loaded && \Drupal::hasRequest() && \Drupal::request()->isMethod('GET');
Chris@0: 
Chris@0:     // @todo: Implement lazyload.
Chris@0:     $this->cacheLoaded = TRUE;
Chris@0: 
Chris@0:     if ($this->persistable && $cached = $this->cache->get($this->cid)) {
Chris@0:       $this->storage = $cached->data;
Chris@0:     }
Chris@0:     else {
Chris@0:       // If there is no runtime cache stored, fetch the full theme registry,
Chris@0:       // but then initialize each value to NULL. This allows offsetExists()
Chris@0:       // to function correctly on non-registered theme hooks without triggering
Chris@0:       // a call to resolveCacheMiss().
Chris@0:       $this->storage = $this->initializeRegistry();
Chris@0:       foreach (array_keys($this->storage) as $key) {
Chris@0:         $this->persist($key);
Chris@0:       }
Chris@0:       // RegistryTest::testRaceCondition() ensures that the cache entry is
Chris@0:       // written on the initial construction of the theme registry.
Chris@0:       $this->updateCache();
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Initializes the full theme registry.
Chris@0:    *
Chris@0:    * @return
Chris@0:    *   An array with the keys of the full theme registry, but the values
Chris@0:    *   initialized to NULL.
Chris@0:    */
Chris@0:   public function initializeRegistry() {
Chris@0:     // @todo DIC this.
Chris@0:     $this->completeRegistry = \Drupal::service('theme.registry')->get();
Chris@0: 
Chris@0:     return array_fill_keys(array_keys($this->completeRegistry), NULL);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function has($key) {
Chris@0:     // Since the theme registry allows for theme hooks to be requested that
Chris@0:     // are not registered, just check the existence of the key in the registry.
Chris@0:     // Use array_key_exists() here since a NULL value indicates that the theme
Chris@0:     // hook exists but has not yet been requested.
Chris@14:     return isset($this->storage[$key]) || array_key_exists($key, $this->storage);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function get($key) {
Chris@0:     // If the offset is set but empty, it is a registered theme hook that has
Chris@0:     // not yet been requested. Offsets that do not exist at all were not
Chris@0:     // registered in hook_theme().
Chris@0:     if (isset($this->storage[$key])) {
Chris@0:       return $this->storage[$key];
Chris@0:     }
Chris@0:     elseif (array_key_exists($key, $this->storage)) {
Chris@0:       return $this->resolveCacheMiss($key);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function resolveCacheMiss($key) {
Chris@0:     if (!isset($this->completeRegistry)) {
Chris@0:       $this->completeRegistry = \Drupal::service('theme.registry')->get();
Chris@0:     }
Chris@0:     $this->storage[$key] = $this->completeRegistry[$key];
Chris@0:     if ($this->persistable) {
Chris@0:       $this->persist($key);
Chris@0:     }
Chris@0:     return $this->storage[$key];
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   protected function updateCache($lock = TRUE) {
Chris@0:     if (!$this->persistable) {
Chris@0:       return;
Chris@0:     }
Chris@0:     // @todo: Is the custom implementation necessary?
Chris@0:     $data = [];
Chris@0:     foreach ($this->keysToPersist as $offset => $persist) {
Chris@0:       if ($persist) {
Chris@0:         $data[$offset] = $this->storage[$offset];
Chris@0:       }
Chris@0:     }
Chris@0:     if (empty($data)) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     $lock_name = $this->cid . ':' . __CLASS__;
Chris@0:     if (!$lock || $this->lock->acquire($lock_name)) {
Chris@0:       if ($cached = $this->cache->get($this->cid)) {
Chris@0:         // Use array merge instead of union so that filled in values in $data
Chris@0:         // overwrite empty values in the current cache.
Chris@0:         $data = array_merge($cached->data, $data);
Chris@0:       }
Chris@0:       else {
Chris@0:         $registry = $this->initializeRegistry();
Chris@0:         $data = array_merge($registry, $data);
Chris@0:       }
Chris@0:       $this->cache->set($this->cid, $data, Cache::PERMANENT, $this->tags);
Chris@0:       if ($lock) {
Chris@0:         $this->lock->release($lock_name);
Chris@0:       }
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0: }