invoiceninja/app/Services/Invoice/ApplyPayment.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com).
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2023. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://www.elastic.co/licensing/elastic-license
 */

namespace App\Services\Invoice;

use App\Models\Invoice;
use App\Models\Payment;
use App\Services\AbstractService;

class ApplyPayment extends AbstractService
{
    public function __construct(private Invoice $invoice, private Payment $payment, private float $payment_amount)
    {
    }

    /* Apply payment to a single invoice */
    public function run()
    {
        $this->invoice->fresh('client');

        $amount_paid = 0;

        if ($this->invoice->hasPartial()) {
            if ($this->invoice->partial == $this->payment_amount) {
                //is partial and amount is exactly the partial amount

                $amount_paid = $this->payment_amount * -1;

                $this->invoice->service()->clearPartial()->setDueDate()->setStatus(Invoice::STATUS_PARTIAL)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            } elseif ($this->invoice->partial > 0 && $this->invoice->partial > $this->payment_amount) {
                //partial amount exists, but the amount is less than the partial amount

                $amount_paid = $this->payment_amount * -1;

                $this->invoice->service()->updatePartial($amount_paid)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            } elseif ($this->invoice->partial > 0 && $this->invoice->partial < $this->payment_amount) {
                //partial exists and the amount paid is GREATER than the partial amount

                $amount_paid = $this->payment_amount * -1;

                $this->invoice->service()->clearPartial()->setDueDate()->setStatus(Invoice::STATUS_PARTIAL)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            }

            $this->invoice->service()->checkReminderStatus()->save();

        } else {
            if ($this->payment_amount == $this->invoice->balance) {
                $amount_paid = $this->payment_amount * -1;

                $this->invoice->service()->clearPartial()->setStatus(Invoice::STATUS_PAID)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            } elseif ($this->payment_amount < $this->invoice->balance) {
                //partial invoice payment made

                $amount_paid = $this->payment_amount * -1;

                $this->invoice->service()->clearPartial()->setStatus(Invoice::STATUS_PARTIAL)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            } elseif ($this->payment_amount > $this->invoice->balance) {
                //partial invoice payment made

                $amount_paid = $this->invoice->balance * -1;

                $this->invoice->service()->clearPartial()->setStatus(Invoice::STATUS_PAID)->updateBalance($amount_paid)->updatePaidToDate($amount_paid * -1)->save();
            }
        }

        $this->payment
             ->ledger()
             ->updatePaymentBalance($amount_paid);

        $this->invoice
             ->client
             ->service()
             ->updateBalance($amount_paid)
             ->save();

        $this->invoice
             ->service()
             ->applyNumber()
             ->workFlow()
             ->save();

        return $this->invoice;
    }
}