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.deploy/artwork-evolution-release/app/Observers/ArtworkFavouriteObserver.php

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+<?php
+
+declare(strict_types=1);
+
+namespace App\Observers;
+
+use App\Jobs\RecComputeSimilarByBehaviorJob;
+use App\Jobs\RecComputeSimilarHybridJob;
+use App\Models\ArtworkFavourite;
+use App\Services\UserStatsService;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * Updates the artwork creator's favorites_received_count and last_active_at
+ * whenever a favourite is added or removed.
+ */
+class ArtworkFavouriteObserver
+{
+    public function __construct(
+        private readonly UserStatsService $userStats,
+    ) {}
+
+    public function created(ArtworkFavourite $favourite): void
+    {
+        $creatorId = $this->creatorId($favourite->artwork_id);
+        if ($creatorId) {
+            $this->userStats->incrementFavoritesReceived($creatorId);
+        }
+
+        // §7.5 On-demand: recompute behavior similarity when artwork reaches threshold
+        $this->maybeRecomputeBehavior($favourite->artwork_id);
+    }
+
+    public function deleted(ArtworkFavourite $favourite): void
+    {
+        $creatorId = $this->creatorId($favourite->artwork_id);
+        if ($creatorId) {
+            $this->userStats->decrementFavoritesReceived($creatorId);
+        }
+    }
+
+    private function creatorId(int $artworkId): ?int
+    {
+        $id = DB::table('artworks')
+            ->where('id', $artworkId)
+            ->value('user_id');
+
+        return $id !== null ? (int) $id : null;
+    }
+
+    /**
+     * Dispatch on-demand behavior recomputation when an artwork crosses a
+     * favourites threshold (5, 10, 25, 50 …).
+     */
+    private function maybeRecomputeBehavior(int $artworkId): void
+    {
+        $count = (int) DB::table('artwork_favourites')
+            ->where('artwork_id', $artworkId)
+            ->count();
+
+        $thresholds = [5, 10, 25, 50, 100];
+
+        if (in_array($count, $thresholds, true)) {
+            RecComputeSimilarByBehaviorJob::dispatch($artworkId)->delay(now()->addSeconds(30));
+            RecComputeSimilarHybridJob::dispatch($artworkId)->delay(now()->addMinute());
+        }
+    }
+}