class LoopExpression

class LoopExpression extends ActionExpressionContainer {
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        return [
            // Default to 'list_item' as variable name for the list item.
'list_item' => 'list_item',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function executeWithState(ExecutionStateInterface $state) {
        $list_data = $state->fetchDataByPropertyPath($this->configuration['list']);
        $list_item_name = $this->configuration['list_item'];
        $this->rulesDebugLogger
            ->info('Looping over the list items of %selector.', [
            '%selector' => $this->configuration['list_item'],
            'element' => $this,
        ]);
        foreach ($list_data as $item) {
            $state->setVariableData($list_item_name, $item);
            // Use the iterator to ensure the conditions are sorted.
            foreach ($this as $action) {
                
                /** @var \Drupal\rules\Engine\ExpressionInterface $action */
                $action->executeWithState($state);
            }
        }
        // After the loop the list item is out of scope and cannot be used by any
        // following actions.
        $state->removeVariable($list_item_name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function checkIntegrity(ExecutionMetadataStateInterface $metadata_state, $apply_assertions = TRUE) {
        $violation_list = new IntegrityViolationList();
        if (empty($this->configuration['list'])) {
            $violation_list->addViolationWithMessage($this->t('List variable is missing.'));
            return $violation_list;
        }
        try {
            $list_definition = $metadata_state->fetchDefinitionByPropertyPath($this->configuration['list']);
        } catch (IntegrityException $e) {
            $violation_list->addViolationWithMessage($this->t('List variable %list does not exist. @message', [
                '%list' => $this->configuration['list'],
                '@message' => $e->getMessage(),
            ]));
            return $violation_list;
        }
        $list_item_name = $this->configuration['list_item'] ?? 'list_item';
        if ($metadata_state->hasDataDefinition($list_item_name)) {
            $violation_list->addViolationWithMessage($this->t('List item name %name conflicts with an existing variable.', [
                '%name' => $list_item_name,
            ]));
            return $violation_list;
        }
        if (!$list_definition instanceof ListDataDefinitionInterface) {
            $violation_list->addViolationWithMessage($this->t('The data type of list variable %list is not a list.', [
                '%list' => $this->configuration['list'],
            ]));
            return $violation_list;
        }
        // So far all ok, so continue with checking integrity in contained actions.
        // The parent implementation will take care of invoking pre/post traversal
        // metadata state preparations.
        $violation_list = parent::checkIntegrity($metadata_state, $apply_assertions);
        return $violation_list;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function allowsMetadataAssertions() {
        // As the list can be empty, we cannot ensure child expressions are
        // executed at all - thus no assertions can be added.
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function prepareExecutionMetadataStateBeforeTraversal(ExecutionMetadataStateInterface $metadata_state) {
        try {
            $list_definition = $metadata_state->fetchDefinitionByPropertyPath($this->configuration['list']);
            $list_item_definition = $list_definition->getItemDefinition();
            $metadata_state->setDataDefinition($this->configuration['list_item'], $list_item_definition);
        } catch (IntegrityException $e) {
            // Silently eat the exception: we just continue without adding the list
            // item definition to the state.
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function prepareExecutionMetadataStateAfterTraversal(ExecutionMetadataStateInterface $metadata_state) {
        // Remove the list item variable after the loop, it is out of scope now.
        $metadata_state->removeDataDefinition($this->configuration['list_item']);
    }

}