class ConfigImporter

class ConfigImporter {
    use StringTranslationTrait;
    use DependencySerializationTrait;
    
    /**
     * The name used to identify the lock.
     */
    const LOCK_NAME = 'config_importer';
    
    /**
     * The storage comparer used to discover configuration changes.
     *
     * @var \Drupal\Core\Config\StorageComparerInterface
     */
    protected $storageComparer;
    
    /**
     * The event dispatcher used to notify subscribers.
     *
     * @var \Symfony\Contracts\EventDispatcher\EventDispatcherInterface
     */
    protected $eventDispatcher;
    
    /**
     * The configuration manager.
     *
     * @var \Drupal\Core\Config\ConfigManagerInterface
     */
    protected $configManager;
    
    /**
     * The used lock backend instance.
     *
     * @var \Drupal\Core\Lock\LockBackendInterface
     */
    protected $lock;
    
    /**
     * The typed config manager.
     *
     * @var \Drupal\Core\Config\TypedConfigManagerInterface
     */
    protected $typedConfigManager;
    
    /**
     * List of configuration file changes processed by the import().
     *
     * @var array
     */
    protected $processedConfiguration;
    
    /**
     * List of extension changes processed by the import().
     *
     * @var array
     */
    protected $processedExtensions;
    
    /**
     * List of extension changes to be processed by the import().
     *
     * @var array
     */
    protected $extensionChangelist;
    
    /**
     * Indicates changes to import have been validated.
     *
     * @var bool
     */
    protected $validated;
    
    /**
     * The module handler.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The theme handler.
     *
     * @var \Drupal\Core\Extension\ThemeHandlerInterface
     */
    protected $themeHandler;
    
    /**
     * Flag set to import system.theme during processing theme install and uninstalls.
     *
     * @var bool
     */
    protected $processedSystemTheme = FALSE;
    
    /**
     * A log of any errors encountered.
     *
     * If errors are logged during the validation event the configuration
     * synchronization will not occur. If errors occur during an import then best
     * efforts are made to complete the synchronization.
     *
     * @var array
     */
    protected $errors = [];
    
    /**
     * The total number of extensions to process.
     *
     * @var int
     */
    protected $totalExtensionsToProcess = 0;
    
    /**
     * The total number of configuration objects to process.
     *
     * @var int
     */
    protected $totalConfigurationToProcess = 0;
    
    /**
     * The module installer.
     *
     * @var \Drupal\Core\Extension\ModuleInstallerInterface
     */
    protected $moduleInstaller;
    
    /**
     * The module extension list.
     *
     * @var \Drupal\Core\Extension\ModuleExtensionList
     */
    protected $moduleExtensionList;
    
    /**
     * The theme extension list.
     *
     * @var \Drupal\Core\Extension\ThemeExtensionList
     */
    protected $themeExtensionList;
    
    /**
     * Constructs a configuration import object.
     *
     * @param \Drupal\Core\Config\StorageComparerInterface $storage_comparer
     *   A storage comparer object used to determine configuration changes and
     *   access the source and target storage objects.
     * @param \Symfony\Contracts\EventDispatcher\EventDispatcherInterface $event_dispatcher
     *   The event dispatcher used to notify subscribers of config import events.
     * @param \Drupal\Core\Config\ConfigManagerInterface $config_manager
     *   The configuration manager.
     * @param \Drupal\Core\Lock\LockBackendInterface $lock
     *   The lock backend to ensure multiple imports do not occur at the same time.
     * @param \Drupal\Core\Config\TypedConfigManagerInterface $typed_config
     *   The typed configuration manager.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler
     * @param \Drupal\Core\Extension\ModuleInstallerInterface $module_installer
     *   The module installer.
     * @param \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler
     *   The theme handler
     * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
     *   The string translation service.
     * @param \Drupal\Core\Extension\ModuleExtensionList $extension_list_module
     *   The module extension list.
     * @param \Drupal\Core\Extension\ThemeExtensionList $extension_list_theme
     *   The theme extension list.
     */
    public function __construct(StorageComparerInterface $storage_comparer, EventDispatcherInterface $event_dispatcher, ConfigManagerInterface $config_manager, LockBackendInterface $lock, TypedConfigManagerInterface $typed_config, ModuleHandlerInterface $module_handler, ModuleInstallerInterface $module_installer, ThemeHandlerInterface $theme_handler, TranslationInterface $string_translation, ModuleExtensionList $extension_list_module, ?ThemeExtensionList $extension_list_theme = NULL) {
        $this->moduleExtensionList = $extension_list_module;
        $this->storageComparer = $storage_comparer;
        $this->eventDispatcher = $event_dispatcher;
        $this->configManager = $config_manager;
        $this->lock = $lock;
        $this->typedConfigManager = $typed_config;
        $this->moduleHandler = $module_handler;
        $this->moduleInstaller = $module_installer;
        $this->themeHandler = $theme_handler;
        $this->stringTranslation = $string_translation;
        if ($extension_list_theme === NULL) {
            @trigger_error('Calling ' . __METHOD__ . ' without the $extension_list_theme argument is deprecated in drupal:10.1.0 and will be required in drupal:11.0.0. See https://www.drupal.org/node/3284397', E_USER_DEPRECATED);
            $extension_list_theme = \Drupal::service('extension.list.theme');
        }
        $this->themeExtensionList = $extension_list_theme;
        foreach ($this->storageComparer
            ->getAllCollectionNames() as $collection) {
            $this->processedConfiguration[$collection] = $this->storageComparer
                ->getEmptyChangelist();
        }
        $this->processedExtensions = $this->getEmptyExtensionsProcessedList();
    }
    
    /**
     * Logs an error message.
     *
     * @param string $message
     *   The message to log.
     */
    public function logError($message) {
        $this->errors[] = $message;
    }
    
    /**
     * Returns error messages created while running the import.
     *
     * @return array
     *   List of messages.
     */
    public function getErrors() {
        return $this->errors;
    }
    
    /**
     * Gets the configuration storage comparer.
     *
     * @return \Drupal\Core\Config\StorageComparerInterface
     *   Storage comparer object used to calculate configuration changes.
     */
    public function getStorageComparer() {
        return $this->storageComparer;
    }
    
    /**
     * Resets the storage comparer and processed list.
     *
     * @return $this
     *   The ConfigImporter instance.
     */
    public function reset() {
        $this->storageComparer
            ->reset();
        // Empty all the lists.
        foreach ($this->storageComparer
            ->getAllCollectionNames() as $collection) {
            $this->processedConfiguration[$collection] = $this->storageComparer
                ->getEmptyChangelist();
        }
        $this->extensionChangelist = $this->processedExtensions = $this->getEmptyExtensionsProcessedList();
        $this->validated = FALSE;
        $this->processedSystemTheme = FALSE;
        return $this;
    }
    
    /**
     * Gets an empty list of extensions to process.
     *
     * @return array
     *   An empty list of extensions to process.
     */
    protected function getEmptyExtensionsProcessedList() {
        return [
            'module' => [
                'install' => [],
                'uninstall' => [],
            ],
            'theme' => [
                'install' => [],
                'uninstall' => [],
            ],
        ];
    }
    
    /**
     * Checks if there are any unprocessed configuration changes.
     *
     * @return bool
     *   TRUE if there are changes to process and FALSE if not.
     */
    public function hasUnprocessedConfigurationChanges() {
        foreach ($this->storageComparer
            ->getAllCollectionNames() as $collection) {
            foreach ([
                'delete',
                'create',
                'rename',
                'update',
            ] as $op) {
                if (count($this->getUnprocessedConfiguration($op, $collection))) {
                    return TRUE;
                }
            }
        }
        return FALSE;
    }
    
    /**
     * Gets list of processed changes.
     *
     * @param string $collection
     *   (optional) The configuration collection to get processed changes for.
     *   Defaults to the default collection.
     *
     * @return array
     *   An array containing a list of processed changes.
     */
    public function getProcessedConfiguration($collection = StorageInterface::DEFAULT_COLLECTION) {
        return $this->processedConfiguration[$collection];
    }
    
    /**
     * Sets a change as processed.
     *
     * @param string $collection
     *   The configuration collection to set a change as processed for.
     * @param string $op
     *   The change operation performed, either delete, create, rename, or update.
     * @param string $name
     *   The name of the configuration processed.
     */
    protected function setProcessedConfiguration($collection, $op, $name) {
        $this->processedConfiguration[$collection][$op][] = $name;
    }
    
    /**
     * Gets a list of unprocessed changes for a given operation.
     *
     * @param string $op
     *   The change operation to get the unprocessed list for, either delete,
     *   create, rename, or update.
     * @param string $collection
     *   (optional) The configuration collection to get unprocessed changes for.
     *   Defaults to the default collection.
     *
     * @return array
     *   An array of configuration names.
     */
    public function getUnprocessedConfiguration($op, $collection = StorageInterface::DEFAULT_COLLECTION) {
        return array_diff($this->storageComparer
            ->getChangelist($op, $collection), $this->processedConfiguration[$collection][$op]);
    }
    
    /**
     * Gets list of processed extension changes.
     *
     * @return array
     *   An array containing a list of processed extension changes.
     */
    public function getProcessedExtensions() {
        return $this->processedExtensions;
    }
    
    /**
     * Sets an extension change as processed.
     *
     * @param string $type
     *   The type of extension, either 'theme' or 'module'.
     * @param string $op
     *   The change operation performed, either install or uninstall.
     * @param string $name
     *   The name of the extension processed.
     */
    protected function setProcessedExtension($type, $op, $name) {
        $this->processedExtensions[$type][$op][] = $name;
    }
    
    /**
     * Populates the extension change list.
     */
    protected function createExtensionChangelist() {
        // Create an empty changelist.
        $this->extensionChangelist = $this->getEmptyExtensionsProcessedList();
        // Read the extensions information to determine changes.
        $current_extensions = $this->storageComparer
            ->getTargetStorage()
            ->read('core.extension');
        $new_extensions = $this->storageComparer
            ->getSourceStorage()
            ->read('core.extension');
        // If there is no extension information in sync then exit. This is probably
        // due to an empty sync directory.
        if (!$new_extensions) {
            return;
        }
        // Reset the module list in case a stale cache item has been set by another
        // process during deployment.
        $this->moduleExtensionList
            ->reset();
        // Get a list of modules with dependency weights as values.
        $module_data = $this->moduleExtensionList
            ->getList();
        // Use the actual module weights.
        $module_list = array_combine(array_keys($module_data), array_keys($module_data));
        $module_list = array_map(function ($module) use ($module_data) {
            return $module_data[$module]->sort;
        }, $module_list);
        // Determine which modules to uninstall.
        $uninstall = array_keys(array_diff_key($current_extensions['module'], $new_extensions['module']));
        // Sort the list of newly uninstalled extensions by their weights, so that
        // dependencies are uninstalled last. Extensions of the same weight are
        // sorted in reverse alphabetical order, to ensure the order is exactly
        // opposite from installation. For example, this module list:
        // @code
        // array(
        //   'actions' => 0,
        //   'ban' => 0,
        //   'options' => -2,
        //   'text' => -1,
        // );
        // @endcode
        // Will result in the following sort order:
        // 1. -2   options
        // 2. -1   text
        // 3.  0 0 ban
        // 4.  0 1 actions
        // @todo Move this sorting functionality to the extension system.
        array_multisort(array_values($module_list), SORT_ASC, array_keys($module_list), SORT_DESC, $module_list);
        $this->extensionChangelist['module']['uninstall'] = array_intersect(array_keys($module_list), $uninstall);
        // Determine which modules to install.
        $install = array_keys(array_diff_key($new_extensions['module'], $current_extensions['module']));
        // Always install required modules first. Respect the dependencies between
        // the modules.
        $install_required = [];
        $install_non_required = [];
        foreach ($install as $module) {
            if (!isset($module_data[$module])) {
                // The module doesn't exist. This is handled in
                // \Drupal\Core\EventSubscriber\ConfigImportSubscriber::validateModules().
                continue;
            }
            if (!empty($module_data[$module]->info['required'])) {
                $install_required[$module] = $module_data[$module]->sort;
            }
            else {
                $install_non_required[$module] = $module_data[$module]->sort;
            }
        }
        // Ensure that installed modules are sorted in exactly the reverse order
        // (with dependencies installed first, and modules of the same weight sorted
        // in alphabetical order).
        arsort($install_required);
        arsort($install_non_required);
        $this->extensionChangelist['module']['install'] = array_keys($install_required + $install_non_required);
        // If we're installing the install profile ensure it comes last in the
        // list of modules to be installed. This will occur when installing a site
        // from configuration.
        if (isset($new_extensions['profile'])) {
            $install_profile_key = array_search($new_extensions['profile'], $this->extensionChangelist['module']['install'], TRUE);
            // If the profile is not in the list of modules to be installed this will
            // generate a validation error. See
            // \Drupal\Core\EventSubscriber\ConfigImportSubscriber::validateModules().
            if ($install_profile_key !== FALSE) {
                unset($this->extensionChangelist['module']['install'][$install_profile_key]);
                $this->extensionChangelist['module']['install'][] = $new_extensions['profile'];
            }
        }
        // Get a list of themes with dependency weights as values.
        $theme_data = $this->themeExtensionList
            ->getList();
        // Use the actual theme weights.
        $theme_list = array_combine(array_keys($theme_data), array_keys($theme_data));
        $theme_list = array_map(function ($theme) use ($theme_data) {
            return $theme_data[$theme]->sort;
        }, $theme_list);
        array_multisort(array_values($theme_list), SORT_ASC, array_keys($theme_list), SORT_DESC, $theme_list);
        // Work out what themes to install and to uninstall.
        $uninstall = array_keys(array_diff_key($current_extensions['theme'], $new_extensions['theme']));
        $this->extensionChangelist['theme']['uninstall'] = array_intersect(array_keys($theme_list), $uninstall);
        // Ensure that installed themes are sorted in exactly the reverse order
        // (with dependencies installed first, and themes of the same weight sorted
        // in alphabetical order).
        $install = array_keys(array_diff_key($new_extensions['theme'], $current_extensions['theme']));
        $theme_list = array_reverse($theme_list);
        $this->extensionChangelist['theme']['install'] = array_intersect(array_keys($theme_list), $install);
    }
    
    /**
     * Gets a list changes for extensions.
     *
     * @param string $type
     *   The type of extension, either 'theme' or 'module'.
     * @param string $op
     *   The change operation to get the unprocessed list for, either install
     *   or uninstall.
     *
     * @return array
     *   An array of extension names.
     */
    public function getExtensionChangelist($type, $op = NULL) {
        if ($op) {
            return $this->extensionChangelist[$type][$op];
        }
        return $this->extensionChangelist[$type];
    }
    
    /**
     * Gets a list of unprocessed changes for extensions.
     *
     * @param string $type
     *   The type of extension, either 'theme' or 'module'.
     *
     * @return array
     *   An array of extension names.
     */
    protected function getUnprocessedExtensions($type) {
        $changelist = $this->getExtensionChangelist($type);
        return [
            'install' => array_diff($changelist['install'], $this->processedExtensions[$type]['install']),
            'uninstall' => array_diff($changelist['uninstall'], $this->processedExtensions[$type]['uninstall']),
        ];
    }
    
    /**
     * Imports the changelist to the target storage.
     *
     * @return $this
     *   The ConfigImporter instance.
     *
     * @throws \Drupal\Core\Config\ConfigException
     */
    public function import() {
        if ($this->hasUnprocessedConfigurationChanges()) {
            $sync_steps = $this->initialize();
            foreach ($sync_steps as $step) {
                $context = [];
                do {
                    $this->doSyncStep($step, $context);
                } while ($context['finished'] < 1);
            }
        }
        return $this;
    }
    
    /**
     * Calls a config import step.
     *
     * @param string|callable $sync_step
     *   The step to do. Either a method on the ConfigImporter class or a
     *   callable.
     * @param array $context
     *   A batch context array. If the config importer is not running in a batch
     *   the only array key that is used is $context['finished']. A process needs
     *   to set $context['finished'] = 1 when it is done.
     *
     * @throws \InvalidArgumentException
     *   Exception thrown if the $sync_step can not be called.
     */
    public function doSyncStep($sync_step, &$context) {
        if ($this->validated) {
            $this->storageComparer
                ->writeMode();
        }
        if (is_string($sync_step) && method_exists($this, $sync_step)) {
            \Drupal::service('config.installer')->setSyncing(TRUE);
            $this->{$sync_step}($context);
        }
        elseif (is_callable($sync_step)) {
            \Drupal::service('config.installer')->setSyncing(TRUE);
            $sync_step($context, $this);
        }
        else {
            throw new \InvalidArgumentException('Invalid configuration synchronization step');
        }
        \Drupal::service('config.installer')->setSyncing(FALSE);
    }
    
    /**
     * Initializes the config importer in preparation for processing a batch.
     *
     * @return array
     *   An array of \Drupal\Core\Config\ConfigImporter method names and callables
     *   that are invoked to complete the import. If there are modules or themes
     *   to process then an extra step is added.
     *
     * @throws \Drupal\Core\Config\ConfigImporterException
     *   If the configuration is already importing.
     */
    public function initialize() {
        // Ensure that the changes have been validated.
        $this->validate();
        if (!$this->lock
            ->acquire(static::LOCK_NAME)) {
            // Another process is synchronizing configuration.
            throw new ConfigImporterException(sprintf('%s is already importing', static::LOCK_NAME));
        }
        $sync_steps = [];
        $modules = $this->getUnprocessedExtensions('module');
        foreach ([
            'install',
            'uninstall',
        ] as $op) {
            $this->totalExtensionsToProcess += count($modules[$op]);
        }
        $themes = $this->getUnprocessedExtensions('theme');
        foreach ([
            'install',
            'uninstall',
        ] as $op) {
            $this->totalExtensionsToProcess += count($themes[$op]);
        }
        // We have extensions to process.
        if ($this->totalExtensionsToProcess > 0) {
            $sync_steps[] = 'processExtensions';
        }
        $sync_steps[] = 'processConfigurations';
        $sync_steps[] = 'processMissingContent';
        // Allow modules to add new steps to configuration synchronization.
        $this->moduleHandler
            ->alter('config_import_steps', $sync_steps, $this);
        $sync_steps[] = 'finish';
        return $sync_steps;
    }
    
    /**
     * Processes extensions as a batch operation.
     *
     * @param array|\ArrayAccess $context
     *   The batch context.
     */
    protected function processExtensions(&$context) {
        $operation = $this->getNextExtensionOperation();
        if (!empty($operation)) {
            $this->processExtension($operation['type'], $operation['op'], $operation['name']);
            $context['message'] = t('Synchronizing extensions: @op @name.', [
                '@op' => $operation['op'],
                '@name' => $operation['name'],
            ]);
            $processed_count = count($this->processedExtensions['module']['install']) + count($this->processedExtensions['module']['uninstall']);
            $processed_count += count($this->processedExtensions['theme']['uninstall']) + count($this->processedExtensions['theme']['install']);
            $context['finished'] = $processed_count / $this->totalExtensionsToProcess;
        }
        else {
            $context['finished'] = 1;
        }
    }
    
    /**
     * Processes configuration as a batch operation.
     *
     * @param array|\ArrayAccess $context
     *   The batch context.
     */
    protected function processConfigurations(&$context) {
        // The first time this is called we need to calculate the total to process.
        // This involves recalculating the changelist which will ensure that if
        // extensions have been processed any configuration affected will be taken
        // into account.
        if ($this->totalConfigurationToProcess == 0) {
            $this->storageComparer
                ->reset();
            foreach ($this->storageComparer
                ->getAllCollectionNames() as $collection) {
                foreach ([
                    'delete',
                    'create',
                    'rename',
                    'update',
                ] as $op) {
                    $this->totalConfigurationToProcess += count($this->getUnprocessedConfiguration($op, $collection));
                }
            }
            // Adjust the totals for system.theme.
            // @see \Drupal\Core\Config\ConfigImporter::processExtension
            if ($this->processedSystemTheme) {
                $this->totalConfigurationToProcess++;
            }
        }
        $operation = $this->getNextConfigurationOperation();
        if (!empty($operation)) {
            if ($this->checkOp($operation['collection'], $operation['op'], $operation['name'])) {
                $this->processConfiguration($operation['collection'], $operation['op'], $operation['name']);
            }
            if ($operation['collection'] == StorageInterface::DEFAULT_COLLECTION) {
                $context['message'] = $this->t('Synchronizing configuration: @op @name.', [
                    '@op' => $operation['op'],
                    '@name' => $operation['name'],
                ]);
            }
            else {
                $context['message'] = $this->t('Synchronizing configuration: @op @name in @collection.', [
                    '@op' => $operation['op'],
                    '@name' => $operation['name'],
                    '@collection' => $operation['collection'],
                ]);
            }
            $processed_count = 0;
            foreach ($this->storageComparer
                ->getAllCollectionNames() as $collection) {
                foreach ([
                    'delete',
                    'create',
                    'rename',
                    'update',
                ] as $op) {
                    $processed_count += count($this->processedConfiguration[$collection][$op]);
                }
            }
            $context['finished'] = $processed_count / $this->totalConfigurationToProcess;
        }
        else {
            $context['finished'] = 1;
        }
    }
    
    /**
     * Handles processing of missing content.
     *
     * @param array|\ArrayAccess $context
     *   Standard batch context.
     */
    protected function processMissingContent(&$context) {
        $sandbox =& $context['sandbox']['config'];
        if (!isset($sandbox['missing_content'])) {
            $missing_content = $this->configManager
                ->findMissingContentDependencies();
            $sandbox['missing_content']['data'] = $missing_content;
            $sandbox['missing_content']['total'] = count($missing_content);
        }
        else {
            $missing_content = $sandbox['missing_content']['data'];
        }
        if (!empty($missing_content)) {
            $event = new MissingContentEvent($missing_content);
            // Fire an event to allow listeners to create the missing content.
            $this->eventDispatcher
                ->dispatch($event, ConfigEvents::IMPORT_MISSING_CONTENT);
            $sandbox['missing_content']['data'] = $event->getMissingContent();
        }
        $current_count = count($sandbox['missing_content']['data']);
        if ($current_count) {
            $context['message'] = $this->t('Resolving missing content');
            $context['finished'] = ($sandbox['missing_content']['total'] - $current_count) / $sandbox['missing_content']['total'];
        }
        else {
            $context['finished'] = 1;
        }
    }
    
    /**
     * Finishes the batch.
     *
     * @param array|\ArrayAccess $context
     *   The batch context.
     */
    protected function finish(&$context) {
        $this->eventDispatcher
            ->dispatch(new ConfigImporterEvent($this), ConfigEvents::IMPORT);
        // The import is now complete.
        $this->lock
            ->release(static::LOCK_NAME);
        $this->reset();
        $context['message'] = t('Finalizing configuration synchronization.');
        $context['finished'] = 1;
    }
    
    /**
     * Gets the next extension operation to perform.
     *
     * Uninstalls are processed first with themes coming before modules. Then
     * installs are processed with modules coming before themes. This order is
     * necessary because themes can depend on modules.
     *
     * @return array|bool
     *   An array containing the next operation and extension name to perform it
     *   on. If there is nothing left to do returns FALSE;
     */
    protected function getNextExtensionOperation() {
        foreach ([
            'uninstall',
            'install',
        ] as $op) {
            $types = $op === 'uninstall' ? [
                'theme',
                'module',
            ] : [
                'module',
                'theme',
            ];
            foreach ($types as $type) {
                $unprocessed = $this->getUnprocessedExtensions($type);
                if (!empty($unprocessed[$op])) {
                    return [
                        'op' => $op,
                        'type' => $type,
                        'name' => array_shift($unprocessed[$op]),
                    ];
                }
            }
        }
        return FALSE;
    }
    
    /**
     * Gets the next configuration operation to perform.
     *
     * @return array|bool
     *   An array containing the next operation and configuration name to perform
     *   it on. If there is nothing left to do returns FALSE;
     */
    protected function getNextConfigurationOperation() {
        // The order configuration operations is processed is important. Deletes
        // have to come first so that recreates can work.
        foreach ($this->storageComparer
            ->getAllCollectionNames() as $collection) {
            foreach ([
                'delete',
                'create',
                'rename',
                'update',
            ] as $op) {
                $config_names = $this->getUnprocessedConfiguration($op, $collection);
                if (!empty($config_names)) {
                    return [
                        'op' => $op,
                        'name' => array_shift($config_names),
                        'collection' => $collection,
                    ];
                }
            }
        }
        return FALSE;
    }
    
    /**
     * Dispatches validate event for a ConfigImporter object.
     *
     * Events should throw a \Drupal\Core\Config\ConfigImporterException to
     * prevent an import from occurring.
     *
     * @throws \Drupal\Core\Config\ConfigImporterException
     *   Exception thrown if the validate event logged any errors.
     */
    public function validate() {
        if (!$this->validated) {
            $this->errors = [];
            // Create the list of installs and uninstalls.
            $this->createExtensionChangelist();
            // Validate renames.
            foreach ($this->getUnprocessedConfiguration('rename') as $name) {
                $names = $this->storageComparer
                    ->extractRenameNames($name);
                $old_entity_type_id = $this->configManager
                    ->getEntityTypeIdByName($names['old_name']);
                $new_entity_type_id = $this->configManager
                    ->getEntityTypeIdByName($names['new_name']);
                if ($old_entity_type_id != $new_entity_type_id) {
                    $this->logError($this->t('Entity type mismatch on rename. @old_type not equal to @new_type for existing configuration @old_name and staged configuration @new_name.', [
                        '@old_type' => $old_entity_type_id,
                        '@new_type' => $new_entity_type_id,
                        '@old_name' => $names['old_name'],
                        '@new_name' => $names['new_name'],
                    ]));
                }
                // Has to be a configuration entity.
                if (!$old_entity_type_id) {
                    $this->logError($this->t('Rename operation for simple configuration. Existing configuration @old_name and staged configuration @new_name.', [
                        '@old_name' => $names['old_name'],
                        '@new_name' => $names['new_name'],
                    ]));
                }
            }
            $this->eventDispatcher
                ->dispatch(new ConfigImporterEvent($this), ConfigEvents::IMPORT_VALIDATE);
            if (count($this->getErrors())) {
                $errors = array_merge([
                    'There were errors validating the config synchronization.',
                ], $this->getErrors());
                throw new ConfigImporterException(implode(PHP_EOL, $errors));
            }
            else {
                $this->validated = TRUE;
            }
        }
        return $this;
    }
    
    /**
     * Processes a configuration change.
     *
     * @param string $collection
     *   The configuration collection to process changes for.
     * @param string $op
     *   The change operation.
     * @param string $name
     *   The name of the configuration to process.
     *
     * @throws \Exception
     *   Thrown when the import process fails, only thrown when no importer log is
     *   set, otherwise the exception message is logged and the configuration
     *   is skipped.
     */
    protected function processConfiguration($collection, $op, $name) {
        try {
            $processed = FALSE;
            if ($collection == StorageInterface::DEFAULT_COLLECTION) {
                $processed = $this->importInvokeOwner($collection, $op, $name);
            }
            if (!$processed) {
                $this->importConfig($collection, $op, $name);
            }
        } catch (\Exception $e) {
            $this->logError($this->t('Unexpected error during import with operation @op for @name: @message', [
                '@op' => $op,
                '@name' => $name,
                '@message' => $e->getMessage(),
            ]));
            // Error for that operation was logged, mark it as processed so that
            // the import can continue.
            $this->setProcessedConfiguration($collection, $op, $name);
        }
    }
    
    /**
     * Processes an extension change.
     *
     * @param string $type
     *   The type of extension, either 'module' or 'theme'.
     * @param string $op
     *   The change operation.
     * @param string $name
     *   The name of the extension to process.
     */
    protected function processExtension($type, $op, $name) {
        // Set the config installer to use the sync directory instead of the
        // extensions own default config directories.
        \Drupal::service('config.installer')->setSourceStorage($this->storageComparer
            ->getSourceStorage());
        if ($type == 'module') {
            $this->moduleInstaller
                ->{$op}([
                $name,
            ], FALSE);
            // Installing a module can cause a kernel boot therefore inject all the
            // services again.
            $this->reInjectMe();
            // During a module install or uninstall the container is rebuilt and the
            // module handler is called. This causes the container's instance of the
            // module handler not to have loaded all the enabled modules.
            $this->moduleHandler
                ->loadAll();
        }
        if ($type == 'theme') {
            // Theme uninstalls possible remove default or admin themes therefore we
            // need to import this before doing any. If there are no uninstalls and
            // the default or admin theme is changing this will be picked up whilst
            // processing configuration.
            if ($op == 'uninstall' && $this->processedSystemTheme === FALSE) {
                $this->importConfig(StorageInterface::DEFAULT_COLLECTION, 'update', 'system.theme');
                $this->configManager
                    ->getConfigFactory()
                    ->reset('system.theme');
                $this->processedSystemTheme = TRUE;
            }
            \Drupal::service('theme_installer')->{$op}([
                $name,
            ]);
        }
        $this->setProcessedExtension($type, $op, $name);
    }
    
    /**
     * Checks that the operation is still valid.
     *
     * During a configuration import secondary writes and deletes are possible.
     * This method checks that the operation is still valid before processing a
     * configuration change.
     *
     * @param string $collection
     *   The configuration collection.
     * @param string $op
     *   The change operation.
     * @param string $name
     *   The name of the configuration to process.
     *
     * @return bool
     *   TRUE is to continue processing, FALSE otherwise.
     *
     * @throws \Drupal\Core\Config\ConfigImporterException
     */
    protected function checkOp($collection, $op, $name) {
        if ($op == 'rename') {
            $names = $this->storageComparer
                ->extractRenameNames($name);
            $target_exists = $this->storageComparer
                ->getTargetStorage($collection)
                ->exists($names['new_name']);
            if ($target_exists) {
                // If the target exists, the rename has already occurred as the
                // result of a secondary configuration write. Change the operation
                // into an update. This is the desired behavior since renames often
                // have to occur together. For example, renaming a node type must
                // also result in renaming its fields and entity displays.
                $this->storageComparer
                    ->moveRenameToUpdate($name);
                return FALSE;
            }
            return TRUE;
        }
        $target_exists = $this->storageComparer
            ->getTargetStorage($collection)
            ->exists($name);
        switch ($op) {
            case 'delete':
                if (!$target_exists) {
                    // The configuration has already been deleted. For example, a field
                    // is automatically deleted if all the instances are.
                    $this->setProcessedConfiguration($collection, $op, $name);
                    return FALSE;
                }
                break;
            case 'create':
                if ($target_exists) {
                    // If the target already exists, use the entity storage to delete it
                    // again, if is a simple config, delete it directly.
                    if ($entity_type_id = $this->configManager
                        ->getEntityTypeIdByName($name)) {
                        $entity_storage = $this->configManager
                            ->getEntityTypeManager()
                            ->getStorage($entity_type_id);
                        $entity_type = $this->configManager
                            ->getEntityTypeManager()
                            ->getDefinition($entity_type_id);
                        $entity = $entity_storage->load($entity_storage->getIDFromConfigName($name, $entity_type->getConfigPrefix()));
                        $entity->delete();
                        $this->logError($this->t('Deleted and replaced configuration entity "@name"', [
                            '@name' => $name,
                        ]));
                    }
                    else {
                        $this->storageComparer
                            ->getTargetStorage($collection)
                            ->delete($name);
                        $this->logError($this->t('Deleted and replaced configuration "@name"', [
                            '@name' => $name,
                        ]));
                    }
                    return TRUE;
                }
                break;
            case 'update':
                if (!$target_exists) {
                    $this->logError($this->t('Update target "@name" is missing.', [
                        '@name' => $name,
                    ]));
                    // Mark as processed so that the synchronization continues. Once the
                    // the current synchronization is complete it will show up as a
                    // create.
                    $this->setProcessedConfiguration($collection, $op, $name);
                    return FALSE;
                }
                break;
        }
        return TRUE;
    }
    
    /**
     * Writes a configuration change from the source to the target storage.
     *
     * @param string $collection
     *   The configuration collection.
     * @param string $op
     *   The change operation.
     * @param string $name
     *   The name of the configuration to process.
     */
    protected function importConfig($collection, $op, $name) {
        // Allow config factory overriders to use a custom configuration object if
        // they are responsible for the collection.
        $overrider = $this->configManager
            ->getConfigCollectionInfo()
            ->getOverrideService($collection);
        if ($overrider) {
            $config = $overrider->createConfigObject($name, $collection);
        }
        else {
            $config = new Config($name, $this->storageComparer
                ->getTargetStorage($collection), $this->eventDispatcher, $this->typedConfigManager);
        }
        if ($old_data = $this->storageComparer
            ->getTargetStorage($collection)
            ->read($name)) {
            $config->initWithData($old_data);
        }
        if ($op == 'delete') {
            $config->delete();
        }
        else {
            $data = $this->storageComparer
                ->getSourceStorage($collection)
                ->read($name);
            $config->setData($data ? $data : []);
            $config->save();
        }
        $this->setProcessedConfiguration($collection, $op, $name);
    }
    
    /**
     * Invokes import* methods on configuration entity storage.
     *
     * Allow modules to take over configuration change operations for higher-level
     * configuration data.
     *
     * @todo Add support for other extension types; e.g., themes etc.
     *
     * @param string $collection
     *   The configuration collection.
     * @param string $op
     *   The change operation to get the unprocessed list for, either delete,
     *   create, rename, or update.
     * @param string $name
     *   The name of the configuration to process.
     *
     * @return bool
     *   TRUE if the configuration was imported as a configuration entity. FALSE
     *   otherwise.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   Thrown if the data is owned by an entity type, but the entity storage
     *   does not support imports.
     */
    protected function importInvokeOwner($collection, $op, $name) {
        // Renames are handled separately.
        if ($op == 'rename') {
            return $this->importInvokeRename($collection, $name);
        }
        // Validate the configuration object name before importing it.
        // Config::validateName($name);
        if ($entity_type = $this->configManager
            ->getEntityTypeIdByName($name)) {
            $old_config = new Config($name, $this->storageComparer
                ->getTargetStorage($collection), $this->eventDispatcher, $this->typedConfigManager);
            if ($old_data = $this->storageComparer
                ->getTargetStorage($collection)
                ->read($name)) {
                $old_config->initWithData($old_data);
            }
            $data = $this->storageComparer
                ->getSourceStorage($collection)
                ->read($name);
            $new_config = new Config($name, $this->storageComparer
                ->getTargetStorage($collection), $this->eventDispatcher, $this->typedConfigManager);
            if ($data !== FALSE) {
                $new_config->setData($data);
            }
            $method = 'import' . ucfirst($op);
            $entity_storage = $this->configManager
                ->getEntityTypeManager()
                ->getStorage($entity_type);
            // Call to the configuration entity's storage to handle the configuration
            // change.
            if (!$entity_storage instanceof ImportableEntityStorageInterface) {
                throw new EntityStorageException(sprintf('The entity storage "%s" for the "%s" entity type does not support imports', get_class($entity_storage), $entity_type));
            }
            $entity_storage->{$method}($name, $new_config, $old_config);
            $this->setProcessedConfiguration($collection, $op, $name);
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * Imports a configuration entity rename.
     *
     * @param string $collection
     *   The configuration collection.
     * @param string $rename_name
     *   The rename configuration name, as provided by
     *   \Drupal\Core\Config\StorageComparer::createRenameName().
     *
     * @return bool
     *   TRUE if the configuration was imported as a configuration entity. FALSE
     *   otherwise.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   Thrown if the data is owned by an entity type, but the entity storage
     *   does not support imports.
     *
     * @see \Drupal\Core\Config\ConfigImporter::createRenameName()
     */
    protected function importInvokeRename($collection, $rename_name) {
        $names = $this->storageComparer
            ->extractRenameNames($rename_name);
        $entity_type_id = $this->configManager
            ->getEntityTypeIdByName($names['old_name']);
        $old_config = new Config($names['old_name'], $this->storageComparer
            ->getTargetStorage($collection), $this->eventDispatcher, $this->typedConfigManager);
        if ($old_data = $this->storageComparer
            ->getTargetStorage($collection)
            ->read($names['old_name'])) {
            $old_config->initWithData($old_data);
        }
        $data = $this->storageComparer
            ->getSourceStorage($collection)
            ->read($names['new_name']);
        $new_config = new Config($names['new_name'], $this->storageComparer
            ->getTargetStorage($collection), $this->eventDispatcher, $this->typedConfigManager);
        if ($data !== FALSE) {
            $new_config->setData($data);
        }
        $entity_storage = $this->configManager
            ->getEntityTypeManager()
            ->getStorage($entity_type_id);
        // Call to the configuration entity's storage to handle the configuration
        // change.
        if (!$entity_storage instanceof ImportableEntityStorageInterface) {
            throw new EntityStorageException(sprintf("The entity storage '%s' for the '%s' entity type does not support imports", get_class($entity_storage), $entity_type_id));
        }
        $entity_storage->importRename($names['old_name'], $new_config, $old_config);
        $this->setProcessedConfiguration($collection, 'rename', $rename_name);
        return TRUE;
    }
    
    /**
     * Determines if an import is already running.
     *
     * @return bool
     *   TRUE if an import is already running, FALSE if not.
     */
    public function alreadyImporting() {
        return !$this->lock
            ->lockMayBeAvailable(static::LOCK_NAME);
    }
    
    /**
     * Gets all the service dependencies from \Drupal.
     *
     * Since the ConfigImporter handles module installation the kernel and the
     * container can be rebuilt and altered during processing. It is necessary to
     * keep the services used by the importer in sync.
     */
    protected function reInjectMe() {
        // When rebuilding the container,
        // \Drupal\Core\DrupalKernel::initializeContainer() saves the hashes of the
        // old container and passes them to the new one. So __sleep() will
        // recognize the old services and then __wakeup() will restore them from
        // the new container.
        $this->__sleep();
        $this->__wakeup();
        $this->storageComparer
            ->__sleep();
        $this->storageComparer
            ->__wakeup();
    }

}