akaunting/app/Imports/Purchases/Sheets/BillTotals.php

<?php

namespace App\Imports\Purchases\Sheets;

use App\Abstracts\Import;
use App\Http\Requests\Purchase\BillTotal as Request;
use App\Models\Purchase\Bill;
use App\Models\Purchase\BillTotal as Model;

class BillTotals extends Import
{
    public function model(array $row)
    {
        return new Model($row);
    }

    public function map($row): array
    {
        if ($this->isEmpty($row, 'bill_number')) {
            return [];
        }

        $row = parent::map($row);

        $row['bill_id'] = (int) Bill::number($row['bill_number'])->pluck('id')->first();

        return $row;
    }

    public function rules(): array
    {
        $rules = (new Request())->rules();

        $rules['bill_number'] = 'required|string';
        unset($rules['bill_id']);

        return $rules;
    }
}