invoiceninja/app/Utils/Traits/Invoice/ActionsInvoice.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com)
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2020. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://opensource.org/licenses/AAL
 */

namespace App\Utils\Traits\Invoice;

use App\Models\Invoice;

trait ActionsInvoice
{
    public function invoiceDeletable($invoice) :bool
    {
        if ($invoice->status_id <= Invoice::STATUS_SENT && 
            $invoice->is_deleted == false && 
            $invoice->deleted_at == null && 
            $invoice->balance == 0) {
            return true;
        }

        return false;
    }

    public function invoiceCancellable($invoice) :bool
    {
        if (($invoice->status_id == Invoice::STATUS_SENT || 
             $invoice->status_id == Invoice::STATUS_PARTIAL) && 
             $invoice->is_deleted == false && 
             $invoice->deleted_at == null) {
            return true;
        }

        return false;
    }

    public function invoiceReversable($invoice) :bool
    {
        if (($invoice->status_id == Invoice::STATUS_SENT || 
             $invoice->status_id == Invoice::STATUS_PARTIAL || 
             $invoice->status_id == Invoice::STATUS_CANCELLED || 
             $invoice->status_id == Invoice::STATUS_PAID) && 
             $invoice->is_deleted == false && 
             $invoice->deleted_at == null) {
            return true;
        }

        return false;
    }
}