LoginObserver.php

<?php
/**
 * MageSpecialist
 *
 * NOTICE OF LICENSE
 *
 * This source file is subject to the Open Software License (OSL 3.0)
 * that is bundled with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://opensource.org/licenses/osl-3.0.php
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to info@magespecialist.it so we can send you a copy immediately.
 *
 * @category   MSP
 * @package    MSP_ReCaptcha
 * @copyright  Copyright (c) 2017 Skeeller srl (http://www.magespecialist.it)
 * @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
 */

namespace MSP\ReCaptcha\Observer\Frontend;

use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
use MSP\ReCaptcha\Api\ValidateInterface;
use Magento\Framework\Message\ManagerInterface;
use Magento\Framework\App\ActionFlag;
use Magento\Framework\Session\SessionManagerInterface;
use Magento\Customer\Model\Url;
use Magento\Framework\App\Action\Action;
use MSP\ReCaptcha\Model\Config;

class LoginObserver implements ObserverInterface
{
    /**
     * @var ValidateInterface
     */
    private $validate;

    /**
     * @var Config
     */
    private $config;

    /**
     * @var ManagerInterface
     */
    private $messageManager;

    /**
     * @var SessionManagerInterface
     */
    private $sessionManager;

    /**
     * @var ActionFlag
     */
    private $actionFlag;

    /**
     * @var Url
     */
    private $customerUrl;

    public function __construct(
        ValidateInterface $validate,
        Config $config,
        ManagerInterface $messageManager,
        SessionManagerInterface $sessionManager,
        ActionFlag $actionFlag,
        Url $customerUrl
    ) {
        $this->validate = $validate;
        $this->config = $config;
        $this->messageManager = $messageManager;
        $this->sessionManager = $sessionManager;
        $this->actionFlag = $actionFlag;
        $this->customerUrl = $customerUrl;
    }

    public function execute(Observer $observer)
    {
        if (!$this->config->isEnabledFrontendLogin()) {
            return;
        }

        $controller = $observer->getControllerAction();

        if (!$this->validate->validate()) {
            $beforeUrl = $this->sessionManager->getBeforeAuthUrl();
            $url = $beforeUrl ?: $this->customerUrl->getLoginUrl();

            $this->messageManager->addErrorMessage($this->config->getErrorDescription());
            $this->actionFlag->set('', Action::FLAG_NO_DISPATCH, true);
            $controller->getResponse()->setRedirect($url, ['_secure' => true]);
        }
    }
}