Add validator for tag descriptions

src/NodaValidationHelper.php

@@ -11,7 +11,59 @@ declare(strict_types = 1);
  */
 final class NodaValidationHelper {
 
-    const ACTOR_DESCRIPTION_REQUIRED_DISTINCT_CHARS = 2;
+    const ACTOR_DESCRIPTION_REQUIRED_DISTINCT_CHARS = 3;
+
+    /**
+     * Validates an actor description for completeness. Of course, only an informed
+     * guess based on the length and character composition of the description can be
+     * made.
+     *
+     * @param string $description Input descrition.
+     * @param string $name       Names of the actor. Optional. Setting this enables
+     *                           checks e.g. to prevent duplicating the actor name
+     *                           as a description.
+     *
+     * @return void
+     */
+    public static function validateTagDescription(string $description, string $name = ""):void {
+
+        // For nodac, empty tag descriptions are to be allowed. Thus, a
+        // dedicated check for fully empty ones with a dedicated exception
+        // is needed.
+        if (empty($description)) {
+            throw new MDInvalidEmptyInputException("No tag name is provided");
+        }
+
+        // Throw error on descriptions that are too short
+        if (\mb_strlen($description) < 10) {
+            throw new MDgenericInvalidInputsException("Tag description is too short");
+        }
+
+        // Validate tag description based on character composition.
+
+        // Ensure more than 3 distinct characters are used.
+        $chars = \str_split($description);
+
+        $uniqueChars = array_unique($chars);
+        if (count($uniqueChars) <= self::ACTOR_DESCRIPTION_REQUIRED_DISTINCT_CHARS) {
+            throw new MDgenericInvalidInputsException("There need to be more than " . self::ACTOR_DESCRIPTION_REQUIRED_DISTINCT_CHARS . " distinct characters.");
+        }
+
+        // Ensure more than the actor name is used.
+        $clearedChars = ['  ' => ' ', ',' => ' ', ';' => ' ', '.' => ' '];
+
+        $uniqueNames = array_unique(array_diff(explode(' ', strtr($name, $clearedChars)), ['']));
+        sort($uniqueNames);
+
+        $descCleared = strtr($description, $clearedChars);
+        $descWords = array_unique(array_diff(explode(' ', $descCleared), ['']));
+        sort($descWords);
+
+        if ($uniqueNames === $descWords) {
+            throw new MDgenericInvalidInputsException("The tag name was simply repeated in the description. This is not enough.");
+        }
+
+    }
 
     /**
      * Validates an actor description for completeness. Of course, only an informed