refactor: extract a configuration validator

src/Validator/ConfigurationValidator.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OliverDaviesLtd\BuildConfigs\Validator;
+
+use Symfony\Component\Validator\Constraints as Assert;
+use Symfony\Component\Validator\ConstraintViolationListInterface;
+use Symfony\Component\Validator\Validation;
+
+final class ConfigurationValidator implements ValidatorInterface
+{
+    public function validate(array $configurationData): ConstraintViolationListInterface
+    {
+        $validator = Validation::createValidator();
+
+        $groups = new Assert\GroupSequence(['Default', 'custom']);
+
+        $constraint = new Assert\Collection(
+            [
+                'name' => [
+                    new Assert\NotNull(),
+                    new Assert\Type('string'),
+                    new Assert\Length(['min' => 1]),
+                ],
+
+                'language' => [
+                    new Assert\NotNull(),
+                    new Assert\Type('string'),
+                    new Assert\Choice(['php']),
+                ],
+
+                'type' => [
+                    new Assert\NotNull(),
+                    new Assert\Type('string'),
+                    new Assert\Choice(['drupal-project', 'php-library']),
+                ],
+
+                'database' => new Assert\Optional(),
+
+                'drupal' => new Assert\Optional(),
+
+                'docker-compose' => new Assert\Optional(),
+
+                'dockerfile' => new Assert\Optional(),
+
+                // TODO: this should be a boolean if present.
+                'justfile' => new Assert\Optional(),
+
+                'php' => new Assert\Optional(),
+
+                'web' => new Assert\Optional(),
+            ],
+        );
+
+        return $validator->validate($configurationData, $constraint, $groups);
+    }
+}