class PluralFormula

class PluralFormula implements PluralFormulaInterface {
    
    /**
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * The plural formula and count keyed by langcode.
     *
     * For example the structure looks like this:
     * @code
     * [
     *   'de' => [
     *     'plurals' => 2,
     *     'formula' => [
     *       // @todo Provide the formula.
     *     ]
     *   ],
     * ]
     * @endcode
     * @var array
     */
    protected $formulae;
    
    /**
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\State\StateInterface $state
     *   The state.
     */
    public function __construct(LanguageManagerInterface $language_manager, StateInterface $state) {
        $this->languageManager = $language_manager;
        $this->state = $state;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setPluralFormula($langcode, $plural_count, array $formula) {
        // Ensure that the formulae are loaded.
        $this->loadFormulae();
        $this->formulae[$langcode] = [
            'plurals' => $plural_count,
            'formula' => $formula,
        ];
        $this->state
            ->set('locale.translation.formulae', $this->formulae);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getNumberOfPlurals($langcode = NULL) {
        // Ensure that the formulae are loaded.
        $this->loadFormulae();
        // Set the langcode to use.
        $langcode = $langcode ?: $this->languageManager
            ->getCurrentLanguage()
            ->getId();
        // We assume 2 plurals if there is no explicit information yet.
        if (!isset($this->formulae[$langcode]['plurals'])) {
            return 2;
        }
        return $this->formulae[$langcode]['plurals'];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormula($langcode) {
        $this->loadFormulae();
        return $this->formulae[$langcode]['formula'] ?? FALSE;
    }
    
    /**
     * Loads the formulae and stores them on the PluralFormula object if not set.
     */
    protected function loadFormulae() {
        if (!isset($this->formulae)) {
            $this->formulae = $this->state
                ->get('locale.translation.formulae', []);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function reset() {
        $this->formulae = NULL;
        return $this;
    }

}