<?php

namespace App\Rules;

use Closure;
use Illuminate\Contracts\Validation\ValidationRule;

class LuhnValid implements ValidationRule
{
    /**
     * Run the validation rule.
     *
     * @param  string  $attribute
     * @param  mixed  $value
     * @param  \Closure(string): \Illuminate\Translation\PotentiallyTranslatedString  $fail
     */
    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        if (!$this->passes($attribute, $value)) {
            $fail('The :attribute is not a valid credit card number.');
        }
    }

    public function passes($attribute, $value)
    {
        // Remove non-numeric characters
        $cardNumber = preg_replace('/\D/', '', $value);

        $sum = 0;
        $shouldDouble = false;

        // Process the digits from right to left
        for ($i = strlen($cardNumber) - 1; $i >= 0; $i--) {
            $digit = (int)$cardNumber[$i];

            if ($shouldDouble) {
                $digit *= 2;
                if ($digit > 9) {
                    $digit -= 9;
                }
            }

            $sum += $digit;
            $shouldDouble = !$shouldDouble;
        }

        // Return true if the total modulo 10 is 0
        return ($sum % 10 === 0);
    }
}