feat: all-season assignments

src/Validator/Constraints/SeasonAssignmentValidator.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace App\Validator\Constraints;
+
+use App\Config\SeasonCalendar;
+use App\Repository\SeasonAssignmentRepository;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * One season assignment per teamer per season.
+ *
+ * "Once a year" was a stated fact rather than an enforced one; this is what enforces it, on
+ * create and on edit alike, so the teamer's season view can rely on resolving a single
+ * assignment.
+ */
+class SeasonAssignmentValidator extends ConstraintValidator
+{
+    public function __construct(
+        private readonly SeasonAssignmentRepository $seasonAssignmentRepository,
+        private readonly SeasonCalendar $seasonCalendar,
+    ) {
+    }
+
+    public function validate(mixed $value, Constraint $constraint): void
+    {
+        /** @var \App\Entity\SeasonAssignment $seasonAssignment */
+        $seasonAssignment = $value;
+
+        // An assignment the office has laid out but not staffed yet is a normal working state,
+        // and a missing start date is the create form's own problem to report.
+        if (null === $teamer = $seasonAssignment->getTeamer()) {
+            return;
+        }
+
+        if (null === $dateFrom = $seasonAssignment->getDateFrom()) {
+            return;
+        }
+
+        // A placement starting outside any season window belongs to no season, so there is
+        // nothing to be the second of.
+        if (null === $seasonYear = $this->seasonCalendar->seasonYearFor($dateFrom)) {
+            return;
+        }
+
+        [$windowStart, $windowEnd] = $this->seasonCalendar->windowFor($seasonYear);
+
+        $existing = $this->seasonAssignmentRepository->countInSeasonWindow(
+            $teamer,
+            $windowStart->toDateTimeImmutable(),
+            $windowEnd->toDateTimeImmutable(),
+            $seasonAssignment->getId()
+        );
+
+        if (0 < $existing) {
+            $this
+                ->context
+                ->buildViolation($constraint->message)
+                ->addViolation()
+            ;
+        }
+    }
+}