class ReactionRuleConfig

class ReactionRuleConfig extends ConfigEntityBase implements RulesUiComponentProviderInterface, RulesTriggerableInterface {
    
    /**
     * The unique ID of the Reaction Rule.
     *
     * @var string
     */
    public $id = NULL;
    
    /**
     * The label of the Reaction rule.
     *
     * @var string
     */
    protected $label;
    
    /**
     * The description of the rule, which is used only in the user interface.
     *
     * @var string
     */
    protected $description = '';
    
    /**
     * The "tags" of a Reaction rule.
     *
     * @var string[]
     */
    protected $tags = [];
    
    /**
     * The version the Reaction rule was created for.
     *
     * @var int
     */
    protected $config_version = Rules::CONFIG_VERSION;
    
    /**
     * The expression plugin specific configuration as nested array.
     *
     * @var array
     */
    protected $expression = [
        'id' => 'rules_rule',
    ];
    
    /**
     * Stores a reference to the executable expression version of this component.
     *
     * @var \Drupal\rules\Engine\ExpressionInterface
     */
    protected $expressionObject;
    
    /**
     * The events this reaction rule is reacting on.
     *
     * Events array. The array is numerically indexed and contains arrays with the
     * following structure:
     * - event_name: String with the event machine name.
     * - configuration: An array containing the event configuration.
     *
     * @var array
     */
    protected $events = [];
    
    /**
     * Sets a Rules expression instance for this Reaction rule.
     *
     * @param \Drupal\rules\Engine\ExpressionInterface $expression
     *   The expression to set.
     *
     * @return $this
     */
    public function setExpression(ExpressionInterface $expression) {
        $this->expressionObject = $expression;
        $this->expression = $expression->getConfiguration();
        return $this;
    }
    
    /**
     * Gets a Rules expression instance for this Reaction rule.
     *
     * @return \Drupal\rules\Engine\ExpressionInterface
     *   A Rules expression instance.
     */
    public function getExpression() {
        // Ensure that an executable Rules expression is available.
        if (!isset($this->expressionObject)) {
            $this->expressionObject = $this->getExpressionManager()
                ->createInstance($this->expression['id'], $this->expression);
        }
        return $this->expressionObject;
    }
    
    /**
     * {@inheritdoc}
     *
     * Gets the Rules component that is invoked when the events are dispatched.
     * The returned component has the definitions of the available event context
     * set.
     */
    public function getComponent() {
        $component = RulesComponent::create($this->getExpression());
        $component->addContextDefinitionsForEvents($this->getEventNames());
        return $component;
    }
    
    /**
     * {@inheritdoc}
     */
    public function updateFromComponent(RulesComponent $component) {
        // Note that the available context definitions stem from the configured
        // events, which are handled separately.
        $this->setExpression($component->getExpression());
        return $this;
    }
    
    /**
     * Returns the Rules expression manager.
     *
     * @todo Actually we should use dependency injection here, but is that even
     *   possible with config entities? How?
     *
     * @return \Drupal\rules\Engine\ExpressionManager
     *   The Rules expression manager.
     */
    protected function getExpressionManager() {
        return \Drupal::service('plugin.manager.rules_expression');
    }
    
    /**
     * {@inheritdoc}
     */
    public function createDuplicate() {
        $duplicate = parent::createDuplicate();
        unset($duplicate->expressionObject);
        return $duplicate;
    }
    
    /**
     * Overrides \Drupal\Core\Entity\Entity::label().
     *
     * When a certain component does not have a label return the ID.
     */
    public function label() {
        if (!($label = $this->get('label'))) {
            $label = $this->id();
        }
        return $label;
    }
    
    /**
     * Returns the description.
     */
    public function getDescription() {
        return $this->description;
    }
    
    /**
     * Checks if there are tags associated with this config.
     *
     * @return bool
     *   TRUE if the config has tags.
     */
    public function hasTags() {
        return !empty($this->tags);
    }
    
    /**
     * Returns the tags associated with this config.
     *
     * @return string[]
     *   The numerically indexed array of tag names.
     */
    public function getTags() {
        return $this->tags;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getEvents() {
        return $this->events;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getEventNames() {
        return array_column($this->events, 'event_name');
    }
    
    /**
     * {@inheritdoc}
     */
    public function addEvent(string $event_name, array $configuration = []) {
        if (!$this->hasEvent($event_name)) {
            $event = [
                'event_name' => $event_name,
            ];
            // Only set configuration key if there is configuration.
            // @todo Is this really necessary, as the method parameter has an array
            // type and defaults to the empty array. So $configuration should always
            // be a valid value.
            if (!empty($configuration)) {
                $event['configuration'] = $configuration;
            }
            $this->events[] = $event;
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function hasEvent(string $event_name) {
        return in_array($event_name, $this->getEventNames());
    }
    
    /**
     * {@inheritdoc}
     */
    public function removeEvent(string $event_name) {
        $indexed_event_names = array_combine(array_keys($this->events), array_column($this->events, 'event_name'));
        if (($id = array_search($event_name, $indexed_event_names)) !== FALSE) {
            unset($this->events[$id]);
        }
        // Use array_values() to re-index $this->events to ensure that this data
        // structure always has numerical keys that are ordered sequentially,
        // starting with 0. Removing an event might have left a gap in this
        // sequence, which would affect how the configuration was stored.
        $this->events = array_values($this->events);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        parent::calculateDependencies();
        $this->addDependencies($this->getComponent()
            ->calculateDependencies());
        return $this->dependencies;
    }
    
    /**
     * Magic clone method.
     */
    public function __clone() {
        // Remove the reference to the expression object in the clone so that the
        // expression object tree is created from scratch.
        unset($this->expressionObject);
    }

}