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File: /var/www/html/aprender.faexito.org/lib/lti1p3/src/LtiDeepLink.php
<?php

namespace Packback\Lti1p3;

use Firebase\JWT\JWT;
use Packback\Lti1p3\Interfaces\ILtiRegistration;

class LtiDeepLink
{
    private $registration;
    private $deployment_id;
    private $deep_link_settings;

    public function __construct(ILtiRegistration $registration, string $deployment_id, array $deep_link_settings)
    {
        $this->registration = $registration;
        $this->deployment_id = $deployment_id;
        $this->deep_link_settings = $deep_link_settings;
    }

    public function getResponseJwt($resources)
    {
        $message_jwt = [
            'iss' => $this->registration->getClientId(),
            'aud' => [$this->registration->getIssuer()],
            'exp' => time() + 600,
            'iat' => time(),
            'nonce' => LtiOidcLogin::secureRandomString('nonce-'),
            LtiConstants::DEPLOYMENT_ID => $this->deployment_id,
            LtiConstants::MESSAGE_TYPE => LtiConstants::MESSAGE_TYPE_DEEPLINK_RESPONSE,
            LtiConstants::VERSION => LtiConstants::V1_3,
            LtiConstants::DL_CONTENT_ITEMS => array_map(function ($resource) {
                return $resource->toArray();
            }, $resources),
        ];

        // https://www.imsglobal.org/spec/lti-dl/v2p0/#deep-linking-request-message
        // 'data' is an optional property which, if it exists, must be returned by the tool
        if (isset($this->deep_link_settings['data'])) {
            $message_jwt[LtiConstants::DL_DATA] = $this->deep_link_settings['data'];
        }

        return JWT::encode($message_jwt, $this->registration->getToolPrivateKey(), 'RS256', $this->registration->getKid());
    }

    /**
     * This method builds an auto-submitting HTML form to post the deep linking response message
     * back to platform, as per LTI-DL 2.0 specification. The resulting HTML is then written to standard output,
     * so calling this method will automatically send an HTTP response to conclude the content selection flow.
     *
     * @param  LtiDeepLinkResource[]  $resources The list of selected resources to be sent to the platform
     *
     * @todo Consider wrapping the content inside a well-formed HTML document,
     * and returning it instead of directly writing to standard output
     */
    public function outputResponseForm($resources)
    {
        $jwt = $this->getResponseJwt($resources);
        $formActionUrl = $this->deep_link_settings['deep_link_return_url'];

        echo <<<HTML
<form id="auto_submit" action="{$formActionUrl}" method="POST">
    <input type="hidden" name="JWT" value="{$jwt}" />
    <input type="submit" name="Go" />
</form>
<script>document.getElementById('auto_submit').submit();</script>
HTML;
    }
}