PHP Decode

<?php 
// This file is part of Moodle - http://moodle.org/ 
// 
// Moodle is free software: you can redistribute it and/or modify 
// it under the terms of the GNU General Public License as published by 
// the Free Software Foundation, either version 3 of the License, or 
// (at your option) any later version. 
// 
// Moodle is distributed in the hope that it will be useful, 
// but WITHOUT ANY WARRANTY; without even the implied warranty of 
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
// GNU General Public License for more details. 
// 
// You should have received a copy of the GNU General Public License 
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>. 
 
/** 
 * Handles LTI 1.3 resource link launches. 
 * 
 * See enrol/lti/launch_deeplink.php for deep linking launches. 
 * 
 * There are 2 pathways through this page: 
 * 1. When first making a resource linking launch from the platform. The launch data is cached at this point, pending user 
 * authentication, and the page is set such that the post-authentication redirect will return here. 
 * 2. The post-authentication redirect. The launch data is fetched from the session launch cache, and the resource is displayed. 
 * 
 * @package    enrol_lti 
 * @copyright  2021 Jake Dallimore <[email protected]> 
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later 
 */ 
 
use enrol_lti\local\ltiadvantage\lib\http_client; 
use enrol_lti\local\ltiadvantage\lib\issuer_database; 
use enrol_lti\local\ltiadvantage\lib\launch_cache_session; 
use enrol_lti\local\ltiadvantage\repository\application_registration_repository; 
use enrol_lti\local\ltiadvantage\repository\context_repository; 
use enrol_lti\local\ltiadvantage\repository\deployment_repository; 
use enrol_lti\local\ltiadvantage\repository\legacy_consumer_repository; 
use enrol_lti\local\ltiadvantage\repository\resource_link_repository; 
use enrol_lti\local\ltiadvantage\repository\user_repository; 
use enrol_lti\local\ltiadvantage\service\tool_launch_service; 
use enrol_lti\local\ltiadvantage\utility\message_helper; 
use Packback\Lti1p3\ImsStorage\ImsCookie; 
use Packback\Lti1p3\LtiMessageLaunch; 
use Packback\Lti1p3\LtiServiceConnector; 
 
require_once(__DIR__ . '/../../config.php'); 
global $CFG; 
require_once($CFG->libdir . '/filelib.php'); 
 
$idtoken = optional_param('id_token', null, PARAM_RAW); 
$launchid = optional_param('launchid', null, PARAM_RAW); 
 
if (!is_enabled_auth('lti')) { 
    throw new moodle_exception('pluginnotenabled', 'auth', '', get_string('pluginname', 'auth_lti')); 
} 
if (!enrol_is_enabled('lti')) { 
    throw new moodle_exception('enrolisdisabled', 'enrol_lti'); 
} 
if (empty($idtoken) && empty($launchid)) { 
    throw new coding_exception('Error: launch requires id_token'); 
} 
 
// Support caching the launch and retrieving it after the account binding process described in auth::complete_login(). 
$sesscache = new launch_cache_session(); 
$issdb = new issuer_database(new application_registration_repository(), new deployment_repository()); 
$cookie = new ImsCookie(); 
$serviceconnector = new LtiServiceConnector($sesscache, new http_client(new curl())); 
if ($idtoken) { 
    $messagelaunch = LtiMessageLaunch::new($issdb, $sesscache, $cookie, $serviceconnector) 
        ->validate(); 
} 
if ($launchid) { 
    $messagelaunch = LtiMessageLaunch::fromCache($launchid, $issdb, $sesscache, $serviceconnector); 
} 
if (empty($messagelaunch)) { 
    throw new moodle_exception('Bad launch. Message launch data could not be found'); 
} 
 
// Authenticate the platform user, which could be an instructor, an admin or a learner. 
// Auth code needs to be told about consumer secrets for the purposes of migration, since these reside in enrol_lti. 
$launchdata = $messagelaunch->getLaunchData(); 
if (!empty($launchdata['https://purl.imsglobal.org/spec/lti/claim/lti1p1']['oauth_consumer_key'])) { 
    $legacyconsumerrepo = new legacy_consumer_repository(); 
    $legacyconsumersecrets = $legacyconsumerrepo->get_consumer_secrets( 
        $launchdata['https://purl.imsglobal.org/spec/lti/claim/lti1p1']['oauth_consumer_key'] 
    ); 
} 
 
// To authenticate, we need the resource's account provisioning mode for the given LTI role. 
if (empty($launchdata['https://purl.imsglobal.org/spec/lti/claim/custom']['id'])) { 
    throw new \moodle_exception('ltiadvlauncherror:missingid', 'enrol_lti'); 
} 
$resourceuuid = $launchdata['https://purl.imsglobal.org/spec/lti/claim/custom']['id']; 
$resource = array_values(\enrol_lti\helper::get_lti_tools(['uuid' => $resourceuuid])); 
$resource = $resource[0] ?? null; 
if (empty($resource) || $resource->status != ENROL_INSTANCE_ENABLED) { 
    throw new \moodle_exception('ltiadvlauncherror:invalidid', 'enrol_lti', '', $resourceuuid); 
} 
 
$provisioningmode = message_helper::is_instructor_launch($launchdata) ? $resource->provisioningmodeinstructor 
    : $resource->provisioningmodelearner; 
$auth = get_auth_plugin('lti'); 
$auth->complete_login( 
    $messagelaunch->getLaunchData(), 
    new moodle_url('/enrol/lti/launch.php', ['launchid' => $messagelaunch->getLaunchId()]), 
    $provisioningmode, 
    $legacyconsumersecrets ?? [] 
); 
 
require_login(null, false); 
global $USER, $CFG, $PAGE; 
$PAGE->set_context(context_system::instance()); 
$PAGE->set_url(new moodle_url('/enrol/lti/launch.php')); 
$PAGE->set_pagelayout('popup'); // Same layout as the tool.php page in Legacy 1.1/2.0 launches. 
$PAGE->set_title(get_string('opentool', 'enrol_lti')); 
 
$toollaunchservice = new tool_launch_service( 
    new deployment_repository(), 
    new application_registration_repository(), 
    new resource_link_repository(), 
    new user_repository(), 
    new context_repository() 
); 
[$userid, $resource] = $toollaunchservice->user_launches_tool($USER, $messagelaunch); 
 
$context = context::instance_by_id($resource->contextid); 
if ($context->contextlevel == CONTEXT_COURSE) { 
    $courseid = $context->instanceid; 
    $redirecturl = new moodle_url('/course/view.php', ['id' => $courseid]); 
} else if ($context->contextlevel == CONTEXT_MODULE) { 
    $cm = get_coursemodule_from_id(false, $context->instanceid, 0, false, MUST_EXIST); 
    $redirecturl = new moodle_url('/mod/' . $cm->modname . '/view.php', ['id' => $cm->id]); 
} else { 
    throw new moodle_exception('invalidcontext'); 
} 
 
if (empty($CFG->allowframembedding)) { 
    $stropentool = get_string('opentool', 'enrol_lti'); 
    echo html_writer::tag('p', get_string('frameembeddingnotenabled', 'enrol_lti')); 
    echo html_writer::link($redirecturl, $stropentool, ['target' => '_blank']); 
} else { 
    redirect($redirecturl); 
} 
 ?>