feat: warn about overlapping bookings instead of refusing them

src/Controller/Booking/CreateController.php

@@ -7,10 +7,10 @@ namespace App\Controller\Booking;
 use App\Config\BookingHorizon;
 use App\Controller\Traits\BoardResponseTrait;
 use App\Controller\Traits\CurrentUserTrait;
+use App\Controller\Traits\OverlapWarningTrait;
 use App\Entity\BookingSeries;
 use App\Entity\Resource;
 use App\Enum\RecurrenceRule;
-use App\Exception\AlreadyHoldingResourceException;
 use App\Exception\ResourceAlreadyBookedException;
 use App\Form\BookingRequest;
 use App\Form\BookingType;
@@ -34,6 +34,7 @@ final class CreateController extends AbstractController
     use BoardResponseTrait;
     use CurrentUserTrait;
     use HxTrait;
+    use OverlapWarningTrait;
 
     public function __construct(
         private readonly BoardContextFactory $boardContext,
@@ -91,12 +92,14 @@ final class CreateController extends AbstractController
                     : null;
 
                 if (null === $result) {
-                    $this->manager->book($this->currentUser(), $resource, $data->date, $data->timeRange());
+                    $booking = $this->manager->book($this->currentUser(), $resource, $data->date, $data->timeRange());
                     $this->addFlash('success', \sprintf('%s gebucht (%s).', $resource->getLabel(), $data->timeRange()));
+                    $this->warnAboutOverlaps($booking);
                 } else {
                     $this->flashSeriesResult($result, $resource);
+                    $this->warnAboutSeriesOverlaps($result);
                 }
-            } catch (AlreadyHoldingResourceException|ResourceAlreadyBookedException $e) {
+            } catch (ResourceAlreadyBookedException $e) {
                 return $this->invalidModal($form, $resource, $e->getMessage());
             }
 

src/Controller/Booking/EditController.php

@@ -6,12 +6,13 @@ namespace App\Controller\Booking;
 
 use App\Controller\Traits\BoardResponseTrait;
 use App\Controller\Traits\CurrentUserTrait;
+use App\Controller\Traits\OverlapWarningTrait;
 use App\Entity\Booking;
-use App\Exception\AlreadyHoldingResourceException;
 use App\Exception\ResourceAlreadyBookedException;
 use App\Form\BookingRequest;
 use App\Form\BookingType;
 use App\Htmx\HxTrait;
+use App\Repository\BookingRepository;
 use App\Service\BoardContextFactory;
 use App\Service\BookingManager;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
@@ -26,10 +27,12 @@ final class EditController extends AbstractController
     use BoardResponseTrait;
     use CurrentUserTrait;
     use HxTrait;
+    use OverlapWarningTrait;
 
     public function __construct(
         private readonly BoardContextFactory $boardContext,
         private readonly BookingManager $manager,
+        private readonly BookingRepository $bookings,
     ) {
     }
 
@@ -58,11 +61,13 @@ final class EditController extends AbstractController
         if ($form->isSubmitted() && $form->isValid()) {
             try {
                 $this->manager->reschedule($booking, $data->timeRange());
-            } catch (AlreadyHoldingResourceException|ResourceAlreadyBookedException $e) {
+            } catch (ResourceAlreadyBookedException $e) {
                 return $this->invalidModal($form, $booking, $e->getMessage());
             }
 
             $this->addFlash('success', \sprintf('%s geändert (%s).', $booking->getResource()->getLabel(), $booking->getTimeRange()));
+            // Moving a booking can create an overlap that was not there when it was made.
+            $this->warnAboutOverlaps($booking);
 
             return $this->boardResponse($booking->getResource()->getType(), $booking->getDate(), $boardTime);
         }

src/Controller/Traits/OverlapWarningTrait.php

@@ -0,0 +1,157 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\Traits;
+
+use App\Entity\Booking;
+use App\Model\SeriesResult;
+
+/**
+ * The hint shown after somebody books a second resource of the same kind for a span they already
+ * hold one for.
+ *
+ * Holding two desks at once is allowed -- one of them is usually for the customer you are
+ * meeting -- so this is not a guard and never refuses anything; BookingManager explains what is
+ * still refused. It only says out loud what just happened, because the alternative is finding
+ * out on the day.
+ *
+ * Only same-kind overlaps are reported. A desk next to a parking space next to a monitor is the
+ * everyday combination, and a toast on every one of those would train everybody to ignore the
+ * toast that matters.
+ *
+ * Expects the using controller to extend AbstractController and to inject
+ * App\Repository\BookingRepository as $bookings.
+ */
+trait OverlapWarningTrait
+{
+    private function warnAboutOverlaps(Booking $booking): void
+    {
+        $clashes = $this->bookings->findOverlappingForUser(
+            $booking->getUser(),
+            $booking->getDate(),
+            $booking->getTimeRange(),
+            $booking->getResource()->getType(),
+            $booking,
+        );
+
+        if ([] === $clashes) {
+            return;
+        }
+
+        $day = $booking->getDate()->format('d.m.Y');
+
+        if (1 === \count($clashes)) {
+            $this->addFlash('warning', \sprintf(
+                'Hinweis: Du hast am %s zur gleichen Zeit bereits %s gebucht (%s).',
+                $day,
+                $clashes[0]->getResource()->getLabel(),
+                $clashes[0]->getTimeRange(),
+            ));
+
+            return;
+        }
+
+        $this->addFlash('warning', \sprintf(
+            'Hinweis: Du hast am %s zur gleichen Zeit bereits %d weitere %s gebucht: %s.',
+            $day,
+            \count($clashes),
+            $booking->getResource()->getType()->plural(),
+            implode(', ', self::labelsOf($clashes)),
+        ));
+    }
+
+    /**
+     * The same hint for a whole series, aggregated into one flash -- a weekly series running to
+     * the horizon must not fire a toast per occurrence.
+     */
+    private function warnAboutSeriesOverlaps(SeriesResult $result): void
+    {
+        if ($result->isCompletelyBlocked()) {
+            return;
+        }
+
+        $series = $result->series;
+        $created = $result->created;
+        $type = $series->getResource()->getType();
+
+        $clashes = $this->bookings->findOverlappingForUserInRange(
+            $series->getUser(),
+            $created[0]->getDate(),
+            $created[array_key_last($created)]->getDate(),
+            $series->getTimeRange(),
+            $type,
+            $series,
+        );
+
+        // One query covers the whole window, so it also returns days between two occurrences --
+        // days this series never landed on. Only the ones it did are news.
+        $days = [];
+        foreach ($clashes as $clash) {
+            $days[$clash->getDate()->format('Y-m-d')][] = $clash;
+        }
+
+        $days = array_intersect_key($days, array_flip(array_map(
+            static fn (Booking $booking): string => $booking->getDate()->format('Y-m-d'),
+            $created,
+        )));
+
+        if ([] === $days) {
+            return;
+        }
+
+        if (1 === \count($days)) {
+            $date = array_key_first($days);
+
+            $this->addFlash('warning', \sprintf(
+                'Hinweis: Am %s hast du zur gleichen Zeit bereits %s gebucht.',
+                (new \DateTimeImmutable($date))->format('j.n.'),
+                implode(', ', self::labelsOf($days[$date])),
+            ));
+
+            return;
+        }
+
+        $this->addFlash('warning', \sprintf(
+            'Hinweis: An %d von %d Terminen hast du zur gleichen Zeit bereits andere %s gebucht (%s).',
+            \count($days),
+            \count($created),
+            $type->plural(),
+            self::shortDates(array_keys($days)),
+        ));
+    }
+
+    /**
+     * @param list<Booking> $bookings
+     *
+     * @return list<string>
+     */
+    private static function labelsOf(array $bookings): array
+    {
+        return array_values(array_unique(array_map(
+            static fn (Booking $booking): string => $booking->getResource()->getLabel(),
+            $bookings,
+        )));
+    }
+
+    /**
+     * Cut off after a handful: a series can clash on two dozen days, and a toast listing them all
+     * would cover the board it is reporting on.
+     *
+     * @param list<string> $dates Y-m-d
+     */
+    private static function shortDates(array $dates): string
+    {
+        $shown = \array_slice($dates, 0, 5);
+        $formatted = array_map(
+            static fn (string $date): string => (new \DateTimeImmutable($date))->format('j.n.'),
+            $shown,
+        );
+
+        if (\count($dates) > \count($shown)) {
+            $formatted[] = '…';
+        }
+
+        return implode(', ', $formatted);
+    }
+}