wip: email uniqueness validation

src/Form/Model/ParticipantEditDto.php

@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form\Model;
+
+use Symfony\Component\Validator\Constraints as Assert;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
+
+/**
+ * Wrapper DTO for editing a participant within a booking context.
+ *
+ * This wrapper enables clean validation of participant email uniqueness
+ * without requiring back-references or form coupling. It contains both
+ * the participant being edited and the full booking context needed for
+ * cross-participant validation.
+ */
+class ParticipantEditDto
+{
+    public function __construct(
+        #[Assert\Valid]
+        public readonly ParticipantDto $participant,
+        public readonly BookingDto $bookingContext,
+    ) {
+    }
+
+    /**
+     * Validates that adult participants have unique email addresses.
+     *
+     * Children (under 16) are exempt from this validation and can share
+     * email addresses with adults. Email comparison is case-insensitive
+     * and whitespace is normalized.
+     */
+    #[Assert\Callback(groups: ['booking_create', 'booking_edit'])]
+    public function validateEmailUniqueness(ExecutionContextInterface $context): void
+    {
+        // Skip validation for children (under 16)
+        if (true === $this->participant->isChild()) {
+            return;
+        }
+
+        // Skip if email is null or empty (handled by @Email and @NotBlank constraints)
+        if (null === $this->participant->email || '' === trim($this->participant->email)) {
+            return;
+        }
+
+        // Normalize current participant's email for comparison
+        $normalizedEmail = strtolower(trim($this->participant->email));
+
+        // Check against all adult participants in booking context
+        foreach ($this->bookingContext->participants as $index => $otherParticipant) {
+            // Skip self-comparison (same participant index)
+            if ($index === $this->participant->index) {
+                continue;
+            }
+
+            // Skip children (they can share email addresses)
+            if (true === $otherParticipant->isChild()) {
+                continue;
+            }
+
+            // Skip null or empty emails
+            if (null === $otherParticipant->email || '' === trim($otherParticipant->email)) {
+                continue;
+            }
+
+            // Compare normalized emails
+            $otherNormalizedEmail = strtolower(trim($otherParticipant->email));
+
+            if ($normalizedEmail === $otherNormalizedEmail) {
+                // Add violation to participant.email path
+                $context->buildViolation('Diese E-Mail Adresse wird bereits von einem anderen Teilnehmer verwendet')
+                    ->atPath('participant.email')
+                    ->addViolation();
+
+                // Stop after first duplicate found (no need to report multiple times)
+                return;
+            }
+        }
+    }
+}