portal-api/app/Services/Coupon/CouponService.php

<?php

namespace App\Services\Coupon;

use App\Models\Coupon;
use App\Models\CouponRedemption;
use App\Models\Customer;
use App\Models\Order;
use App\Models\Product;
use Illuminate\Validation\ValidationException;

class CouponService
{
    public const MIN_PAYABLE = 1000;

    /**
     * @return array{coupon: Coupon, discount: int}
     */
    public function preview(string $code, Customer $customer, Product $product, string $billingCycle, int $subTotal, string $context = Coupon::APPLIES_NEW): array
    {
        $coupon = Coupon::where('code', Coupon::normalizeCode($code))->first();

        return $this->evaluate($coupon, $customer, $product, $billingCycle, $subTotal, $context);
    }

    /**
     * @return array{coupon: Coupon, discount: int}
     */
    public function lockAndApply(string $code, Customer $customer, Product $product, string $billingCycle, int $subTotal, string $context = Coupon::APPLIES_NEW): array
    {
        $coupon = Coupon::where('code', Coupon::normalizeCode($code))->lockForUpdate()->first();

        return $this->evaluate($coupon, $customer, $product, $billingCycle, $subTotal, $context);
    }

    public function record(Coupon $coupon, Order $order, int $discount): CouponRedemption
    {
        return CouponRedemption::create([
            'coupon_id' => $coupon->id,
            'customer_id' => $order->customer_id,
            'order_id' => $order->id,
            'amount' => $discount,
        ]);
    }

    public function setReleased(Order $order, bool $released): void
    {
        CouponRedemption::where('order_id', $order->id)
            ->update(['released_at' => $released ? now() : null]);
    }

    /**
     * @return array{coupon: Coupon, discount: int}
     */
    private function evaluate(?Coupon $coupon, Customer $customer, Product $product, string $billingCycle, int $subTotal, string $context): array
    {
        if (! $coupon || ! $coupon->is_active) {
            $this->fail('Mã giảm giá không hợp lệ.');
        }

        if ($coupon->starts_at?->isFuture()) {
            $this->fail('Mã giảm giá chưa đến thời gian áp dụng.');
        }

        if ($coupon->ends_at?->isPast()) {
            $this->fail('Mã giảm giá đã hết hạn.');
        }

        if (! in_array($coupon->applies_to, [$context, Coupon::APPLIES_ALL], true)) {
            $this->fail($context === Coupon::APPLIES_NEW
                ? 'Mã giảm giá này không áp dụng cho đơn mới.'
                : 'Mã giảm giá này chỉ áp dụng cho đơn mới.');
        }

        if (! $this->inScope($coupon, $product, $billingCycle)) {
            $this->fail('Mã giảm giá không áp dụng cho sản phẩm hoặc chu kỳ thanh toán này.');
        }

        if ($subTotal < $coupon->min_order) {
            $this->fail(sprintf('Đơn hàng tối thiểu %s VNĐ để áp dụng mã này.', number_format($coupon->min_order)));
        }

        $this->assertUsageLeft($coupon, $customer);

        $discount = $this->amountFor($coupon, $subTotal);
        if ($discount <= 0) {
            $this->fail('Đơn hàng không đủ điều kiện áp dụng mã giảm giá.');
        }

        return ['coupon' => $coupon, 'discount' => $discount];
    }

    private function inScope(Coupon $coupon, Product $product, string $billingCycle): bool
    {
        return $this->matches($coupon->product_types, $product->product_type)
            && $this->matches($coupon->product_ids, $product->id)
            && $this->matches($coupon->billing_cycles, $billingCycle);
    }

    private function matches(?array $allowed, string|int|null $value): bool
    {
        return empty($allowed) || in_array($value, $allowed, false);
    }

    private function assertUsageLeft(Coupon $coupon, Customer $customer): void
    {
        $redemptions = $coupon->activeRedemptions();

        if ($coupon->usage_limit !== null && (clone $redemptions)->count() >= $coupon->usage_limit) {
            $this->fail('Mã giảm giá đã hết lượt sử dụng.');
        }

        if ($coupon->per_customer_limit !== null
            && (clone $redemptions)->where('customer_id', $customer->id)->count() >= $coupon->per_customer_limit) {
            $this->fail('Bạn đã dùng hết số lần cho phép của mã giảm giá này.');
        }
    }

    private function amountFor(Coupon $coupon, int $subTotal): int
    {
        $discount = $coupon->type === Coupon::TYPE_PERCENT
            ? intdiv($subTotal * $coupon->value, 100)
            : $coupon->value;

        if ($coupon->max_discount !== null) {
            $discount = min($discount, $coupon->max_discount);
        }

        return min($discount, $subTotal - self::MIN_PAYABLE);
    }

    private function fail(string $message): never
    {
        throw ValidationException::withMessages(['coupon_code' => $message]);
    }
}