class TypedDataResolver

class TypedDataResolver {
    
    /**
     * The typed data manager.
     *
     * @var \Drupal\Core\TypedData\TypedDataManagerInterface
     */
    protected $manager;
    
    /**
     * The string translation service.
     *
     * @var \Drupal\Core\StringTranslation\TranslationInterface
     */
    protected $translation;
    
    /**
     * Typed Data Resolver Service constructor.
     *
     * @param \Drupal\Core\TypedData\TypedDataManagerInterface $manager
     *   The typed data manager.
     * @param \Drupal\Core\StringTranslation\TranslationInterface $translation
     *   The string translation service.
     */
    public function __construct(TypedDataManagerInterface $manager, TranslationInterface $translation) {
        $this->manager = $manager;
        $this->translation = $translation;
    }
    
    /**
     * Convert a property to a context.
     *
     * This method will respect the value of contexts as well, so if a context
     * object is pass that contains a value, the appropriate value will be
     * extracted and injected into the resulting context object if available.
     *
     * @param string $property_path
     *   The name of the property.
     * @param \Drupal\Core\Plugin\Context\ContextInterface $context
     *   The context from which we will extract values if available.
     *
     * @return \Drupal\Core\Plugin\Context\Context
     *   A context object that represents the definition & value of the property.
     *
     * @throws \Exception
     */
    public function getContextFromProperty(string $property_path, ContextInterface $context) {
        $value = NULL;
        $data_definition = NULL;
        if ($context->hasContextValue()) {
            
            /** @var \Drupal\Core\TypedData\ComplexDataInterface $data */
            $data = $context->getContextData();
            foreach (explode(':', $property_path) as $name) {
                if ($data instanceof ListInterface) {
                    if (!is_numeric($name)) {
                        // Implicitly default to delta 0 for lists when not specified.
                        $data = $data->first();
                    }
                    else {
                        // If we have a delta, fetch it and continue with the next part.
                        $data = $data->get($name);
                        continue;
                    }
                }
                // Forward to the target value if this is a data reference.
                if ($data instanceof DataReferenceInterface) {
                    $data = $data->getTarget();
                }
                if (!$data->getDataDefinition()
                    ->getPropertyDefinition($name)) {
                    throw new \Exception("Unknown property {$name} in property path {$property_path}");
                }
                $data = $data->get($name);
            }
            $value = $data->getValue();
            $data_definition = $data instanceof DataReferenceInterface ? $data->getDataDefinition()
                ->getTargetDefinition() : $data->getDataDefinition();
        }
        else {
            
            /** @var \Drupal\Core\TypedData\ComplexDataDefinitionInterface $data_definition */
            $data_definition = $context->getContextDefinition()
                ->getDataDefinition();
            foreach (explode(':', $property_path) as $name) {
                if ($data_definition instanceof ListDataDefinitionInterface) {
                    $data_definition = $data_definition->getItemDefinition();
                    // If the delta was specified explicitly, continue with the next part.
                    if (is_numeric($name)) {
                        continue;
                    }
                }
                // Forward to the target definition if this is a data reference
                // definition.
                if ($data_definition instanceof DataReferenceDefinitionInterface) {
                    $data_definition = $data_definition->getTargetDefinition();
                }
                if (!$data_definition->getPropertyDefinition($name)) {
                    throw new \Exception("Unknown property {$name} in property path {$property_path}");
                }
                $data_definition = $data_definition->getPropertyDefinition($name);
            }
            // Forward to the target definition if this is a data reference
            // definition.
            if ($data_definition instanceof DataReferenceDefinitionInterface) {
                $data_definition = $data_definition->getTargetDefinition();
            }
        }
        if (strpos($data_definition->getDataType(), 'entity:') === 0) {
            $context_definition = new EntityContextDefinition($data_definition->getDataType(), $data_definition->getLabel(), $data_definition->isRequired(), FALSE, $data_definition->getDescription());
        }
        else {
            $context_definition = new ContextDefinition($data_definition->getDataType(), $data_definition->getLabel(), $data_definition->isRequired(), FALSE, $data_definition->getDescription());
        }
        return new Context($context_definition, $value);
    }
    
    /**
     * Extracts a context from an array of contexts by a tokenized pattern.
     *
     * This is more than simple isset/empty checks on the contexts array. The
     * pattern could be node:uid:name which will iterate over all provided
     * contexts in the array for one named 'node', it will then load the data
     * definition of 'node' and check for a property named 'uid'. This will then
     * set a new (temporary) context on the array and recursively call itself to
     * navigate through related properties all the way down until the request
     * property is located. At that point the property is passed to a
     * TypedDataResolver which will convert it to an appropriate ContextInterface
     * object.
     *
     * @param string $token
     *   A ":" delimited set of tokens representing
     * @param \Drupal\Core\Plugin\Context\ContextInterface[] $contexts
     *   The array of available contexts.
     *
     * @return \Drupal\Core\Plugin\Context\ContextInterface
     *   The requested token as a full Context object.
     *
     * @throws \Drupal\ctools\ContextNotFoundException
     */
    public function convertTokenToContext(string $token, array $contexts) {
        // If the requested token is already a context, just return it.
        if (isset($contexts[$token])) {
            return $contexts[$token];
        }
        else {
            [
                $base,
                $property_path,
            ] = explode(':', $token, 2);
            // A base must always be set. This method recursively calls itself
            // setting bases for this reason.
            if (!empty($contexts[$base])) {
                return $this->getContextFromProperty($property_path, $contexts[$base]);
            }
            // @todo improve this exception message.
            throw new ContextNotFoundException("The requested context was not found in the supplied array of contexts.");
        }
    }
    
    /**
     * Provides an administrative label for a tokenized relationship.
     *
     * @param string $token
     *   The token related to a context in the contexts array.
     * @param \Drupal\Core\Plugin\Context\ContextInterface[] $contexts
     *   An array of contexts from which to extract our token's label.
     *
     * @return \Drupal\Core\StringTranslation\TranslatableMarkup
     *   The administrative label of $token.
     */
    public function getLabelByToken(string $token, array $contexts) {
        // @todo Optimize this by allowing to limit the desired token?
        $tokens = $this->getTokensForContexts($contexts);
        if (isset($tokens[$token])) {
            return $tokens[$token];
        }
    }
    
    /**
     * Extracts an array of tokens and labels.
     *
     * @param \Drupal\Core\Plugin\Context\ContextInterface[] $contexts
     *   The array of contexts with which we are currently dealing.
     *
     * @return array
     *   An array of token keys and corresponding labels.
     */
    public function getTokensForContexts(array $contexts) {
        $tokens = [];
        foreach ($contexts as $context_id => $context) {
            $data_definition = $context->getContextDefinition()
                ->getDataDefinition();
            if ($data_definition instanceof ComplexDataDefinitionInterface) {
                foreach ($this->getTokensFromComplexData($data_definition) as $token => $label) {
                    $tokens["{$context_id}:{$token}"] = $data_definition->getLabel() . ': ' . $label;
                }
            }
        }
        return $tokens;
    }
    
    /**
     * Returns tokens for a complex data definition.
     *
     * @param \Drupal\Core\TypedData\ComplexDataDefinitionInterface $complex_data_definition
     *   Complex Data Definition.
     *
     * @return array
     *   An array of token keys and corresponding labels.
     */
    protected function getTokensFromComplexData(ComplexDataDefinitionInterface $complex_data_definition) {
        $tokens = [];
        // Loop over all properties.
        foreach ($complex_data_definition->getPropertyDefinitions() as $property_name => $property_definition) {
            // Item definitions do not always have a label. Use the list definition
            // label if the item does not have one.
            $property_label = $property_definition->getLabel();
            if ($property_definition instanceof ListDataDefinitionInterface) {
                $property_definition = $property_definition->getItemDefinition();
                $property_label = $property_definition->getLabel() ?: $property_label;
            }
            // If the property is complex too, recurse to find child properties.
            if ($property_definition instanceof ComplexDataDefinitionInterface) {
                $property_tokens = $this->getTokensFromComplexData($property_definition);
                foreach ($property_tokens as $token => $label) {
                    $tokens[$property_name . ':' . $token] = count($property_tokens) > 1 ? $property_label . ': ' . $label : $property_label;
                }
            }
            // Only expose references as tokens.
            // @todo Consider to expose primitive and non-reference typed data
            //   definitions too, like strings, integers and dates. The current UI
            //   will not scale to that.
            if ($property_definition instanceof DataReferenceDefinitionInterface) {
                $tokens[$property_name] = $property_definition->getLabel();
            }
        }
        return $tokens;
    }

}