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app/Services/CouponService.php

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+<?php
+
+namespace App\Services;
+
+use App\Models\Coupon;
+use Illuminate\Database\UniqueConstraintViolationException;
+use Illuminate\Support\Str;
+
+class CouponService
+{
+    public function findOrCreateForPhone(string $phone): Coupon
+    {
+        $existing = Coupon::query()->where('phone', $phone)->first();
+
+        if ($existing) {
+            return $existing;
+        }
+
+        return $this->createWithUniqueCode($phone);
+    }
+
+    private function createWithUniqueCode(string $phone): Coupon
+    {
+        for ($attempt = 0; $attempt < 10; $attempt++) {
+            try {
+                return Coupon::query()->create([
+                    'phone' => $phone,
+                    'code' => $this->generateCouponCode(),
+                ]);
+            } catch (UniqueConstraintViolationException) {
+                continue;
+            }
+        }
+
+        throw new \RuntimeException('Unable to generate a unique coupon code.');
+    }
+
+    private function generateCouponCode(): string
+    {
+        $x = random_int(1, 9);
+        $yyyy = Str::upper(Str::random(4));
+
+        return "{$x}_{$yyyy}";
+    }
+}