ldc-mesbr-app/app/Http/Resources/CouponsResource.php

<?php

namespace App\Http\Resources;

use Illuminate\Http\Resources\Json\JsonResource;

class CouponsResource extends JsonResource
{
    /**
     * Transform the resource collection into an array.
     *
     * @param  \Illuminate\Http\Request $request
     * @return array
     */
    public function toArray($request)
    {
        $coupon = [
            'code' => $this->coupon_code,
            'name' => $this->coupon_name,
            'value' => $this->coupon_value,
            'used' => isset($this->isUsed) ? $this->isUsed : false,
            'desktop_image_available' => $this->returnUrl($this->coupon_thumbnail1),
            'desktop_image_unavailable' => $this->returnUrl($this->coupon_thumbnail2),
            'mobile_image_available' => $this->returnUrl($this->coupon_thumbnail3),
            'mobile_image_unavailable' => $this->returnUrl($this->coupon_thumbnail4),
            'validity_text' => $this->coupon_validity_text
        ];

        if (isset($this->isUsed)){
            return array_merge($coupon, [
                'used' => $this->isUsed,
            ]);
        }
        return $coupon;
    }

    private function returnUrl($assets)
    {
        return !empty($assets) ? config('app.url') . "/$assets" : null;
    }
}