feat: notify configured recipients when something is booked

src/Service/BookingNotifier.php

@@ -0,0 +1,121 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\Entity\Booking;
+use App\Enum\ResourceType;
+use App\Model\SeriesResult;
+use App\Repository\ResourceTypeSettingsRepository;
+use Psr\Log\LoggerInterface;
+use Symfony\Bridge\Twig\Mime\TemplatedEmail;
+use Symfony\Component\Mailer\MailerInterface;
+use Symfony\Component\Mime\Address;
+
+/**
+ * Tells whoever an administrator named that something was booked.
+ *
+ * Recipients are configured per ResourceType rather than per resource or per group, because that
+ * is the level the admin screen groups by and the only one every resource is guaranteed to have:
+ * a resource's group is optional, and a kind that is not split into groups -- rooms, cars --
+ * would otherwise never notify anybody.
+ *
+ * **Nothing here may break a booking.** It runs after the transaction has committed, so a
+ * failure cannot roll anything back, and a transport that is down is logged rather than thrown:
+ * the booking is made, and the person who made it should not be shown an error about somebody
+ * else's mail server.
+ *
+ * Every recipient gets their own mail, addressed only to them. Nobody sees who else is on the
+ * list, and a single bad address loses its own mail rather than everybody's.
+ *
+ * Each mail is multipart: the MyE&P layout for clients that render HTML, and a hand-written text
+ * part for those that do not. The text part is written rather than generated because there is no
+ * html-to-markdown converter installed, and three facts and a name read better as plain lines
+ * than as a flattened table anyway.
+ */
+final readonly class BookingNotifier
+{
+    public function __construct(
+        private MailerInterface $mailer,
+        private ResourceTypeSettingsRepository $settings,
+        private LoggerInterface $logger,
+        private string $sender,
+    ) {
+    }
+
+    public function bookingCreated(Booking $booking): void
+    {
+        $resource = $booking->getResource();
+
+        $this->send(
+            $resource->getType(),
+            \sprintf('Neue Buchung: %s am %s', $resource->getLabel(), $booking->getDate()->format('d.m.Y')),
+            'email/booking_created',
+            ['booking' => $booking],
+        );
+    }
+
+    /**
+     * One mail for a whole series, not one per occurrence.
+     *
+     * A year of weekly bookings is the same act and would otherwise arrive as fifty-two mails in
+     * one second -- the same reason AuditLogger records a series once rather than per day.
+     */
+    public function seriesCreated(SeriesResult $result): void
+    {
+        if ($result->isCompletelyBlocked()) {
+            return;
+        }
+
+        $series = $result->series;
+        $resource = $series->getResource();
+
+        $this->send(
+            $resource->getType(),
+            \sprintf('Neue Serienbuchung: %s ab %s', $resource->getLabel(), $series->getStartDate()->format('d.m.Y')),
+            'email/series_created',
+            ['result' => $result, 'series' => $series],
+        );
+    }
+
+    /**
+     * @param string               $template the template pair's basename; both .html.twig and
+     *                                       .txt.twig of it are rendered
+     * @param array<string, mixed> $context
+     */
+    private function send(ResourceType $type, string $subject, string $template, array $context): void
+    {
+        $recipients = $this->settings->recipientsFor($type);
+
+        if ([] === $recipients) {
+            return;
+        }
+
+        foreach ($recipients as $recipient) {
+            // A fresh message per recipient: ->to() on a reused one appends rather than replaces,
+            // which would put the whole list back on everybody's copy.
+            $email = (new TemplatedEmail())
+                ->from(new Address($this->sender, 'E&P Platz'))
+                ->to($recipient)
+                ->subject($subject)
+                ->htmlTemplate($template.'.html.twig')
+                ->textTemplate($template.'.txt.twig')
+                ->context($context);
+
+            try {
+                $this->mailer->send($email);
+            } catch (\Throwable $e) {
+                // Caught per recipient, so one unreachable address does not cost the others theirs.
+                // \Throwable rather than TransportExceptionInterface because the templates are
+                // rendered inside send(): a typo in one of them would otherwise surface as a failed
+                // booking, which is exactly what this class promises never to do.
+                $this->logger->error('Booking notification could not be sent.', [
+                    'subject' => $subject,
+                    'recipient' => $recipient,
+                    'exception' => $e,
+                ]);
+            }
+        }
+    }
+}