interface TranslatableInterface

interface TranslatableInterface {
    
    /**
     * Returns the translation language.
     *
     * @return \Drupal\Core\Language\LanguageInterface
     *   The language object.
     */
    public function language();
    
    /**
     * Checks whether the translation is the default one.
     *
     * @return bool
     *   TRUE if the translation is the default one, FALSE otherwise.
     */
    public function isDefaultTranslation();
    
    /**
     * Checks whether the translation is new.
     *
     * @return bool
     *   TRUE if the translation is new, FALSE otherwise.
     */
    public function isNewTranslation();
    
    /**
     * Returns the languages the data is translated to.
     *
     * @param bool $include_default
     *   (optional) Whether the default language should be included. Defaults to
     *   TRUE.
     *
     * @return \Drupal\Core\Language\LanguageInterface[]
     *   An associative array of language objects, keyed by language codes.
     */
    public function getTranslationLanguages($include_default = TRUE);
    
    /**
     * Gets a translation of the data.
     *
     * The returned translation has to be of the same type than this typed data
     * object.
     *
     * @param $langcode
     *   The language code of the translation to get or
     *   LanguageInterface::LANGCODE_DEFAULT
     *   to get the data in default language.
     *
     * @return static
     *   A typed data object for the translated data.
     *
     * @throws \InvalidArgumentException
     *   If an invalid or non-existing translation language is specified.
     */
    public function getTranslation($langcode);
    
    /**
     * Returns the translatable object in the language it was created.
     *
     * @return static
     *   The translation object referring to the original language.
     */
    public function getUntranslated();
    
    /**
     * Checks there is a translation for the given language code.
     *
     * @param string $langcode
     *   The language code identifying the translation.
     *
     * @return bool
     *   TRUE if the translation exists, FALSE otherwise.
     */
    public function hasTranslation($langcode);
    
    /**
     * Adds a new translation to the translatable object.
     *
     * To create a translation of an entity prefilled with the original data:
     * @code
     *   $entity->addTranslation($langcode, $entity->toArray())
     * @endcode
     *
     * @param string $langcode
     *   The language code identifying the translation.
     * @param array $values
     *   (optional) An array of initial values to be assigned to the translatable
     *   fields. Defaults to none.
     *
     * @return static
     *   A new entity translation object.
     *
     * @throws \InvalidArgumentException
     *   If an invalid or existing translation language is specified.
     */
    public function addTranslation($langcode, array $values = []);
    
    /**
     * Removes the translation identified by the given language code.
     *
     * @param string $langcode
     *   The language code identifying the translation to be removed.
     */
    public function removeTranslation($langcode);
    
    /**
     * Returns the translation support status.
     *
     * @return bool
     *   TRUE if the object has translation support enabled.
     */
    public function isTranslatable();

}