class StorageComparer

class StorageComparer implements StorageComparerInterface {
    use DependencySerializationTrait;
    
    /**
     * The source storage used to discover configuration changes.
     *
     * @var \Drupal\Core\Config\StorageInterface
     */
    protected $sourceStorage;
    
    /**
     * The source storages keyed by collection.
     *
     * @var \Drupal\Core\Config\StorageInterface[]
     */
    protected $sourceStorages;
    
    /**
     * The target storage used to write configuration changes.
     *
     * @var \Drupal\Core\Config\StorageInterface
     */
    protected $targetStorage;
    
    /**
     * The target storages keyed by collection.
     *
     * @var \Drupal\Core\Config\StorageInterface[]
     */
    protected $targetStorages;
    
    /**
     * List of changes to between the source storage and the target storage.
     *
     * The list is keyed by storage collection name.
     *
     * @var array
     */
    protected $changelist;
    
    /**
     * Sorted list of all the configuration object names in the source storage.
     *
     * The list is keyed by storage collection name.
     *
     * @var array
     */
    protected $sourceNames = [];
    
    /**
     * Sorted list of all the configuration object names in the target storage.
     *
     * The list is keyed by storage collection name.
     *
     * @var array
     */
    protected $targetNames = [];
    
    /**
     * A memory cache backend to statically cache source configuration data.
     *
     * @var \Drupal\Core\Cache\MemoryBackend
     */
    protected $sourceCacheStorage;
    
    /**
     * A memory cache backend to statically cache target configuration data.
     *
     * @var \Drupal\Core\Cache\MemoryBackend
     */
    protected $targetCacheStorage;
    
    /**
     * Constructs the Configuration storage comparer.
     *
     * @param \Drupal\Core\Config\StorageInterface $source_storage
     *   Storage object used to read configuration.
     * @param \Drupal\Core\Config\StorageInterface $target_storage
     *   Storage object used to write configuration.
     */
    public function __construct(StorageInterface $source_storage, StorageInterface $target_storage) {
        if ($source_storage->getCollectionName() !== StorageInterface::DEFAULT_COLLECTION) {
            $source_storage = $source_storage->createCollection(StorageInterface::DEFAULT_COLLECTION);
        }
        if ($target_storage->getCollectionName() !== StorageInterface::DEFAULT_COLLECTION) {
            $target_storage = $target_storage->createCollection(StorageInterface::DEFAULT_COLLECTION);
        }
        // Wrap the storages in a static cache so that multiple reads of the same
        // raw configuration object are not costly.
        $this->sourceCacheStorage = new MemoryBackend();
        $this->sourceStorage = new CachedStorage($source_storage, $this->sourceCacheStorage);
        $this->targetCacheStorage = new MemoryBackend();
        $this->targetStorage = new CachedStorage($target_storage, $this->targetCacheStorage);
        $this->changelist[StorageInterface::DEFAULT_COLLECTION] = $this->getEmptyChangelist();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSourceStorage($collection = StorageInterface::DEFAULT_COLLECTION) {
        if (!isset($this->sourceStorages[$collection])) {
            if ($collection == StorageInterface::DEFAULT_COLLECTION) {
                $this->sourceStorages[$collection] = $this->sourceStorage;
            }
            else {
                $this->sourceStorages[$collection] = $this->sourceStorage
                    ->createCollection($collection);
            }
        }
        return $this->sourceStorages[$collection];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getTargetStorage($collection = StorageInterface::DEFAULT_COLLECTION) {
        if (!isset($this->targetStorages[$collection])) {
            if ($collection == StorageInterface::DEFAULT_COLLECTION) {
                $this->targetStorages[$collection] = $this->targetStorage;
            }
            else {
                $this->targetStorages[$collection] = $this->targetStorage
                    ->createCollection($collection);
            }
        }
        return $this->targetStorages[$collection];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getEmptyChangelist() {
        return [
            'create' => [],
            'update' => [],
            'delete' => [],
            'rename' => [],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getChangelist($op = NULL, $collection = StorageInterface::DEFAULT_COLLECTION) {
        if ($op) {
            return $this->changelist[$collection][$op];
        }
        return $this->changelist[$collection];
    }
    
    /**
     * Adds changes to the changelist.
     *
     * @param string $collection
     *   The storage collection to add changes for.
     * @param string $op
     *   The change operation performed. Either delete, create, rename, or update.
     * @param array $changes
     *   Array of changes to add to the changelist.
     * @param array $sort_order
     *   Array to sort that can be used to sort the changelist. This array must
     *   contain all the items that are in the change list.
     */
    protected function addChangeList($collection, $op, array $changes, array $sort_order = NULL) {
        // Only add changes that aren't already listed.
        $changes = array_diff($changes, $this->changelist[$collection][$op]);
        $this->changelist[$collection][$op] = array_merge($this->changelist[$collection][$op], $changes);
        if (isset($sort_order)) {
            $count = count($this->changelist[$collection][$op]);
            // Sort the changelist in the same order as the $sort_order array and
            // ensure the array is keyed from 0.
            $this->changelist[$collection][$op] = array_values(array_intersect($sort_order, $this->changelist[$collection][$op]));
            if ($count != count($this->changelist[$collection][$op])) {
                throw new \InvalidArgumentException("Sorting the {$op} changelist should not change its length.");
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function createChangelist() {
        foreach ($this->getAllCollectionNames() as $collection) {
            $this->changelist[$collection] = $this->getEmptyChangelist();
            $this->getAndSortConfigData($collection);
            $this->addChangelistCreate($collection);
            $this->addChangelistUpdate($collection);
            $this->addChangelistDelete($collection);
            // Only collections that support configuration entities can have renames.
            if ($collection == StorageInterface::DEFAULT_COLLECTION) {
                $this->addChangelistRename($collection);
            }
        }
        return $this;
    }
    
    /**
     * Creates the delete changelist.
     *
     * The list of deletes is sorted so that dependencies are deleted after
     * configuration entities that depend on them. For example, fields should be
     * deleted after field storages.
     *
     * @param string $collection
     *   The storage collection to operate on.
     */
    protected function addChangelistDelete($collection) {
        $deletes = array_diff(array_reverse($this->targetNames[$collection]), $this->sourceNames[$collection]);
        $this->addChangeList($collection, 'delete', $deletes);
    }
    
    /**
     * Creates the create changelist.
     *
     * The list of creates is sorted so that dependencies are created before
     * configuration entities that depend on them. For example, field storages
     * should be created before fields.
     *
     * @param string $collection
     *   The storage collection to operate on.
     */
    protected function addChangelistCreate($collection) {
        $creates = array_diff($this->sourceNames[$collection], $this->targetNames[$collection]);
        $this->addChangeList($collection, 'create', $creates);
    }
    
    /**
     * Creates the update changelist.
     *
     * The list of updates is sorted so that dependencies are created before
     * configuration entities that depend on them. For example, field storages
     * should be updated before fields.
     *
     * @param string $collection
     *   The storage collection to operate on.
     */
    protected function addChangelistUpdate($collection) {
        $recreates = [];
        foreach (array_intersect($this->sourceNames[$collection], $this->targetNames[$collection]) as $name) {
            $source_data = $this->getSourceStorage($collection)
                ->read($name);
            $target_data = $this->getTargetStorage($collection)
                ->read($name);
            if ($source_data !== $target_data) {
                if (isset($source_data['uuid']) && $source_data['uuid'] !== $target_data['uuid']) {
                    // The entity has the same file as an existing entity but the UUIDs do
                    // not match. This means that the entity has been recreated so config
                    // synchronization should do the same.
                    $recreates[] = $name;
                }
                else {
                    $this->addChangeList($collection, 'update', [
                        $name,
                    ]);
                }
            }
        }
        if (!empty($recreates)) {
            // Recreates should become deletes and creates. Deletes should be ordered
            // so that dependencies are deleted first.
            $this->addChangeList($collection, 'create', $recreates, $this->sourceNames[$collection]);
            $this->addChangeList($collection, 'delete', $recreates, array_reverse($this->targetNames[$collection]));
        }
    }
    
    /**
     * Creates the rename changelist.
     *
     * The list of renames is created from the different source and target names
     * with same UUID. These changes will be removed from the create and delete
     * lists.
     *
     * @param string $collection
     *   The storage collection to operate on.
     */
    protected function addChangelistRename($collection) {
        // Renames will be present in both the create and delete lists.
        $create_list = $this->getChangelist('create', $collection);
        $delete_list = $this->getChangelist('delete', $collection);
        if (empty($create_list) || empty($delete_list)) {
            return;
        }
        $create_uuids = [];
        foreach ($this->sourceNames[$collection] as $name) {
            $data = $this->getSourceStorage($collection)
                ->read($name);
            if (isset($data['uuid']) && in_array($name, $create_list)) {
                $create_uuids[$data['uuid']] = $name;
            }
        }
        if (empty($create_uuids)) {
            return;
        }
        $renames = [];
        // Renames should be ordered so that dependencies are renamed last. This
        // ensures that if there is logic in the configuration entity class to keep
        // names in sync it will still work. $this->targetNames is in the desired
        // order due to the use of configuration dependencies in
        // \Drupal\Core\Config\StorageComparer::getAndSortConfigData().
        // Node type is a good example of a configuration entity that renames other
        // configuration when it is renamed.
        // @see \Drupal\node\Entity\NodeType::postSave()
        foreach ($this->targetNames[$collection] as $name) {
            $data = $this->getTargetStorage($collection)
                ->read($name);
            if (isset($data['uuid']) && isset($create_uuids[$data['uuid']])) {
                // Remove the item from the create list.
                $this->removeFromChangelist($collection, 'create', $create_uuids[$data['uuid']]);
                // Remove the item from the delete list.
                $this->removeFromChangelist($collection, 'delete', $name);
                // Create the rename name.
                $renames[] = $this->createRenameName($name, $create_uuids[$data['uuid']]);
            }
        }
        $this->addChangeList($collection, 'rename', $renames);
    }
    
    /**
     * Removes the entry from the given operation changelist for the given name.
     *
     * @param string $collection
     *   The storage collection to operate on.
     * @param string $op
     *   The changelist to act on. Either delete, create, rename or update.
     * @param string $name
     *   The name of the configuration to remove.
     */
    protected function removeFromChangelist($collection, $op, $name) {
        $key = array_search($name, $this->changelist[$collection][$op]);
        if ($key !== FALSE) {
            unset($this->changelist[$collection][$op][$key]);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function moveRenameToUpdate($rename, $collection = StorageInterface::DEFAULT_COLLECTION) {
        $names = $this->extractRenameNames($rename);
        $this->removeFromChangelist($collection, 'rename', $rename);
        $this->addChangeList($collection, 'update', [
            $names['new_name'],
        ], $this->sourceNames[$collection]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function reset() {
        $this->changelist = [
            StorageInterface::DEFAULT_COLLECTION => $this->getEmptyChangelist(),
        ];
        $this->sourceNames = $this->targetNames = [];
        // Reset the static configuration data caches.
        $this->sourceCacheStorage
            ->deleteAll();
        $this->targetCacheStorage
            ->deleteAll();
        return $this->createChangelist();
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasChanges() {
        foreach ($this->getAllCollectionNames() as $collection) {
            foreach ([
                'delete',
                'create',
                'update',
                'rename',
            ] as $op) {
                if (!empty($this->changelist[$collection][$op])) {
                    return TRUE;
                }
            }
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateSiteUuid() {
        $source = $this->sourceStorage
            ->read('system.site');
        $target = $this->targetStorage
            ->read('system.site');
        // It is possible that the storage does not contain system.site
        // configuration. In such cases the site UUID cannot be valid.
        return $source && $target && $source['uuid'] === $target['uuid'];
    }
    
    /**
     * Gets and sorts configuration data from the source and target storages.
     */
    protected function getAndSortConfigData($collection) {
        $source_storage = $this->getSourceStorage($collection);
        $target_storage = $this->getTargetStorage($collection);
        $target_names = $target_storage->listAll();
        $source_names = $source_storage->listAll();
        // Prime the static caches by reading all the configuration in the source
        // and target storages.
        $target_data = $target_storage->readMultiple($target_names);
        $source_data = $source_storage->readMultiple($source_names);
        // If the collection only supports simple configuration do not use
        // configuration dependencies.
        if ($collection == StorageInterface::DEFAULT_COLLECTION) {
            $dependency_manager = new ConfigDependencyManager();
            $this->targetNames[$collection] = $dependency_manager->setData($target_data)
                ->sortAll();
            $this->sourceNames[$collection] = $dependency_manager->setData($source_data)
                ->sortAll();
        }
        else {
            $this->targetNames[$collection] = $target_names;
            $this->sourceNames[$collection] = $source_names;
        }
    }
    
    /**
     * Creates a rename name from the old and new names for the object.
     *
     * @param string $old_name
     *   The old configuration object name.
     * @param string $new_name
     *   The new configuration object name.
     *
     * @return string
     *   The configuration change name that encodes both the old and the new name.
     *
     * @see \Drupal\Core\Config\StorageComparerInterface::extractRenameNames()
     */
    protected function createRenameName($old_name, $new_name) {
        return $old_name . '::' . $new_name;
    }
    
    /**
     * {@inheritdoc}
     */
    public function extractRenameNames($name) {
        $names = explode('::', $name, 2);
        return [
            'old_name' => $names[0],
            'new_name' => $names[1],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAllCollectionNames($include_default = TRUE) {
        $collections = array_unique(array_merge($this->sourceStorage
            ->getAllCollectionNames(), $this->targetStorage
            ->getAllCollectionNames()));
        if ($include_default) {
            array_unshift($collections, StorageInterface::DEFAULT_COLLECTION);
        }
        return $collections;
    }

}