Feature: Updating Listreners, Separating Logic from listeners, Queuing Policies

src/Catalog/Services/StockService.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Modules\Core\Catalog\Services;
+
+use Illuminate\Support\Facades\DB;
+use Lunar\Models\Order;
+use Lunar\Models\Product;
+use Lunar\Models\ProductVariant;
+
+/**
+ * The one place ProductVariant::stock is written as a result of an order —
+ * previously this lived entirely inside Modules\Core\Order\Listeners\
+ * DecrementStockOnOrderPlaced, a listener with no Service behind it at
+ * all, even though stock (the column, its invariants — "never negative",
+ * "only in_stock variants") is fundamentally a Catalog concern, not an
+ * Order one. That listener is now a thin caller of this class, matching
+ * how every other module's event reaction delegates its actual write to
+ * a Service (e.g. Modules\Core\Order\Listeners\RecordPaymentTransaction
+ * -> Modules\Core\Order\Services\TransactionRecorder).
+ *
+ * Only decrements for `purchasable === 'in_stock'` variants — 'always' and
+ * 'backorder' variants are deliberately allowed to sell past (or without
+ * regard to) their stock count already (see ProductVariant::
+ * canBeFulfilledAtQuantity()), so decrementing their stock would just make
+ * that column an inaccurate, decreasingly-negative number with no purchasing
+ * consequence. Only `OrderLine::type === 'physical'` lines are considered —
+ * a digital line has no stock to decrement (ProductVariant::getType()).
+ *
+ * A single UPDATE per variant (`DB::table(...)->update()` with a raw
+ * expression), not a read-then-write on the Eloquent model — avoids a
+ * lost-update race between two orders decrementing the same variant
+ * concurrently, and skips Modules\Core\Catalog\Services\ProductIndexer::
+ * stock's staleness gap for the DB value itself even though the search
+ * index still only refreshes on the next reindex event/nightly job (see
+ * that class's own docblock).
+ *
+ * Never lets stock go negative (`GREATEST(stock - qty, 0)` via a raw
+ * expression) — an order can still be placed against a variant whose stock
+ * was already fully consumed by another concurrent order (Lunar has no
+ * stock-reservation step at cart/checkout time), so this is a best-effort
+ * count, not a hard inventory guarantee.
+ */
+class StockService
+{
+    public function decrementForOrder(Order $order): void
+    {
+        $lines = $order->lines()
+            ->where('type', 'physical')
+            ->where('purchasable_type', ProductVariant::morphName())
+            ->get(['purchasable_id', 'quantity']);
+
+        if ($lines->isEmpty()) {
+            return;
+        }
+
+        foreach ($lines as $line) {
+            DB::table((new ProductVariant())->getTable())
+                ->where('id', $line->purchasable_id)
+                ->where('purchasable', 'in_stock')
+                ->update([
+                    'stock' => DB::raw('GREATEST(stock - '.(int) $line->quantity.', 0)'),
+                ]);
+        }
+
+        $productIds = ProductVariant::whereIn('id', $lines->pluck('purchasable_id'))
+            ->pluck('product_id')
+            ->unique();
+
+        Product::whereIn('id', $productIds)->get()->each->searchable();
+    }
+}