Issue #3496205 by d34dman: Update option list to hint towards applicable...

Issue #3496205 by d34dman: Update option list to hint towards applicable languages during configuration

src/Form/SettingsForm.php

@@ -8,6 +8,7 @@ use Drupal\Core\Config\TypedConfigManagerInterface;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\string_plural_form\StringPluralFormManager;
+use Drupal\string_plural_form\StringPluralFormPluginInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Form\ConfigFormBase;
@@ -57,7 +58,6 @@ final class SettingsForm extends ConfigFormBase {
    * {@inheritdoc}
    */
   public function buildForm(array $form, FormStateInterface $form_state): array {
-
     $languages = $this->languageManager->getLanguages(LanguageInterface::STATE_CONFIGURABLE);
     $rules = $this->stringPluralFormManager->getDefinitions();
     $options = [];
@@ -81,13 +81,69 @@ final class SettingsForm extends ConfigFormBase {
         '#type' => 'select',
         '#title' => sprintf("%s (%s)", $language->getName(), $language->getId()),
         '#default_value' => $rules_map[$language->getId()],
-        '#options' => $options,
+        '#options' => $this->getOptionsForLanguage($language->getId()),
         '#required' => TRUE,
       ];
     }
     return parent::buildForm($form, $form_state);
   }
 
+  /**
+   * Get Plural Form rules categorized by applicable to provided language.
+   *
+   * @param string $langcode
+   *   The language code for which rules list needs to be prepared.
+   *
+   * @return string[]
+   *   <optgroup> comptible option list of rules.
+   */
+  protected function getOptionsForLanguage(string $langcode): array {
+    $rules = $this->stringPluralFormManager->getDefinitions();
+    $recommended_rules = [];
+    $other_rules = [];
+
+    foreach ($rules as $rule) {
+      $plural_form = $this->stringPluralFormManager->createInstance($rule['id']);
+      if ($plural_form instanceof StringPluralFormPluginInterface) {
+        if ($this->isRuleRecommendedForLanguage($plural_form, $langcode)) {
+          $recommended_rules[$rule['id']] = $rule['admin_label'];
+        }
+        else {
+          $other_rules[$rule['id']] = $rule['admin_label'];
+        }
+      }
+    }
+    $options = [
+      (string) $this->t('Recommended Rules') => $recommended_rules,
+      (string) $this->t('Other Rules') => $other_rules,
+    ];
+    return $options;
+  }
+
+  /**
+   * Check if given rule is applicable for the language.
+   *
+   * @param \Drupal\string_plural_form\StringPluralFormPluginInterface $rule
+   *   Instance of Rule.
+   * @param string $langcode
+   *   Language code.
+   *
+   * @return bool
+   *   True if rule is applicable for the given language.
+   */
+  protected function isRuleRecommendedForLanguage(StringPluralFormPluginInterface $rule, string $langcode): bool {
+    // In case "ISO 639-1" langcode is being used, then we split the incoming
+    // language code to match only the language part.
+    $code = explode('-', $langcode);
+    $match = $code[0];
+    foreach ($rule->getAssociatedLanguageCodes() as $code) {
+      if ($match == $code) {
+        return TRUE;
+      }
+    }
+    return FALSE;
+  }
+
   /**
    * {@inheritdoc}
    */

src/Plugin/StringPluralForm/SixFormsArabic.php

@@ -47,7 +47,7 @@ class SixFormsArabic extends StringPluralFormBase {
       0 => 0,
       1 => 1,
       2 => 2,
-      default =>  ($n>10 && $n%100>=3 && $n%100<=10) ? 3 : ($n%100>=11 ? 4 : 5)
+      default =>  ($n > 10 && $n % 100 >= 3 && $n % 100 <= 10) ? 3 : ($n % 100 >= 11 ? 4 : 5)
     };
     return $index;
   }