trait ContextAwarePluginTrait

trait ContextAwarePluginTrait {
    
    /**
     * The data objects representing the context of this plugin.
     *
     * @var \Drupal\Core\Plugin\Context\ContextInterface[]
     */
    protected $context = [];
    
    /**
     * {@inheritdoc}
     */
    public function getContexts() {
        // Make sure all context objects are initialized.
        foreach ($this->getContextDefinitions() as $name => $definition) {
            $this->getContext($name);
        }
        return $this->context;
    }
    
    /**
     * {@inheritdoc}
     *
     * @return \Drupal\Core\Plugin\Context\ContextInterface
     *   The context object.
     */
    public function getContext($name) {
        // Check for a valid context value.
        if (!isset($this->context[$name])) {
            $this->context[$name] = new Context($this->getContextDefinition($name));
        }
        return $this->context[$name];
    }
    
    /**
     * {@inheritdoc}
     */
    public function setContext($name, ComponentContextInterface $context) {
        // Check that the context passed is an instance of our extended interface.
        if (!$context instanceof ContextInterface) {
            throw new ContextException("Passed {$name} context must be an instance of \\Drupal\\Core\\Plugin\\Context\\ContextInterface");
        }
        $this->context[$name] = $context;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContextValues() {
        $values = [];
        foreach ($this->getContextDefinitions() as $name => $definition) {
            $values[$name] = isset($this->context[$name]) ? $this->context[$name]
                ->getContextValue() : NULL;
        }
        return $values;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContextValue($name) {
        return $this->getContext($name)
            ->getContextValue();
    }
    
    /**
     * {@inheritdoc}
     */
    public function setContextValue($name, $value) {
        $this->setContext($name, Context::createFromContext($this->getContext($name), $value));
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContextMapping() {
        $configuration = $this instanceof ConfigurableInterface ? $this->getConfiguration() : $this->configuration;
        return $configuration['context_mapping'] ?? [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function setContextMapping(array $context_mapping) {
        if ($this instanceof ConfigurableInterface) {
            $configuration = $this->getConfiguration();
            $configuration['context_mapping'] = array_filter($context_mapping);
            $this->setConfiguration($configuration);
        }
        else {
            $this->configuration['context_mapping'] = $context_mapping;
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public abstract function getPluginDefinition();
    
    /**
     * {@inheritdoc}
     *
     * @return \Drupal\Core\Plugin\Context\ContextDefinitionInterface[]
     */
    public function getContextDefinitions() {
        $definition = $this->getPluginDefinition();
        if ($definition instanceof ContextAwarePluginDefinitionInterface) {
            return $definition->getContextDefinitions();
        }
        return !empty($definition['context_definitions']) ? $definition['context_definitions'] : [];
    }
    
    /**
     * {@inheritdoc}
     *
     * @return \Drupal\Core\Plugin\Context\ContextDefinitionInterface
     */
    public function getContextDefinition($name) {
        $definition = $this->getPluginDefinition();
        if ($definition instanceof ContextAwarePluginDefinitionInterface) {
            if ($definition->hasContextDefinition($name)) {
                return $definition->getContextDefinition($name);
            }
        }
        elseif (!empty($definition['context_definitions'][$name])) {
            return $definition['context_definitions'][$name];
        }
        throw new ContextException(sprintf("The %s context is not a valid context.", $name));
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateContexts() {
        $violations = new ConstraintViolationList();
        // @todo Implement the Symfony Validator component to let the validator
        //   traverse and set property paths accordingly.
        //   See https://www.drupal.org/project/drupal/issues/3153847.
        foreach ($this->getContexts() as $context) {
            $violations->addAll($context->validate());
        }
        return $violations;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheContexts() {
        $cache_contexts = [];
        // Applied contexts can affect the cache contexts when this plugin is
        // involved in caching, collect and return them.
        foreach ($this->getContexts() as $context) {
            
            /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
            if ($context instanceof CacheableDependencyInterface) {
                $cache_contexts = Cache::mergeContexts($cache_contexts, $context->getCacheContexts());
            }
        }
        return $cache_contexts;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheTags() {
        $tags = [];
        // Applied contexts can affect the cache tags when this plugin is
        // involved in caching, collect and return them.
        foreach ($this->getContexts() as $context) {
            
            /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
            if ($context instanceof CacheableDependencyInterface) {
                $tags = Cache::mergeTags($tags, $context->getCacheTags());
            }
        }
        return $tags;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheMaxAge() {
        $max_age = Cache::PERMANENT;
        // Applied contexts can affect the cache max age when this plugin is
        // involved in caching, collect and return them.
        foreach ($this->getContexts() as $context) {
            
            /** @var \Drupal\Core\Cache\CacheableDependencyInterface $context */
            if ($context instanceof CacheableDependencyInterface) {
                $max_age = Cache::mergeMaxAges($max_age, $context->getCacheMaxAge());
            }
        }
        return $max_age;
    }

}