Refactor point value object and add observability

server/src/Service/PointProximityValidator.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\ValueObject\Point;
+use App\Exception\PointTooFarException;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+
+final class PointProximityValidator
+{
+    public function __construct(
+        #[Autowire('%app.max_signal_distance_km%')]
+        private readonly float $maximumDistanceKm,
+        #[Autowire(service: 'monolog.logger.signals')]
+        private readonly LoggerInterface $logger,
+    ) {
+    }
+
+    public function assertWithinRange(Point $userLocation, Point $signalLocation): void
+    {
+        $distance = $this->distanceInKm($userLocation, $signalLocation);
+
+        $this->logger->debug('Calculated proximity between user and signal.', [
+            'distance_km' => $distance,
+            'max_distance_km' => $this->maximumDistanceKm,
+        ]);
+
+        if ($distance > $this->maximumDistanceKm) {
+            $this->logger->warning('Rejected signal because it is beyond the allowed proximity.', [
+                'distance_km' => $distance,
+                'max_distance_km' => $this->maximumDistanceKm,
+            ]);
+            throw new PointTooFarException($this->maximumDistanceKm);
+        }
+    }
+
+    private function distanceInKm(Point $a, Point $b): float
+    {
+        $lat1 = deg2rad($a->getLat());
+        $lat2 = deg2rad($b->getLat());
+        $deltaLat = deg2rad($b->getLat() - $a->getLat());
+        $deltaLng = deg2rad($b->getLng() - $a->getLng());
+
+        $haversine = sin($deltaLat / 2) ** 2 + cos($lat1) * cos($lat2) * sin($deltaLng / 2) ** 2;
+        $c = 2 * atan2(sqrt($haversine), sqrt(1 - $haversine));
+
+        return 6371 * $c;
+    }
+}