1<?php
2// This file is part of Moodle - http://moodle.org/
3//
4// Moodle is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// Moodle is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13//
14// You should have received a copy of the GNU General Public License
15// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
16
17/**
18 * Exception handler for LTI services
19 *
20 * @package   mod_lti
21 * @copyright Copyright (c) 2015 Moodlerooms Inc. (http://www.moodlerooms.com)
22 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
23 */
24
25namespace mod_lti;
26
27defined('MOODLE_INTERNAL') || die();
28
29require_once(__DIR__.'/../locallib.php');
30require_once(__DIR__.'/../servicelib.php');
31
32/**
33 * Handles exceptions when handling incoming LTI messages.
34 *
35 * Ensures that LTI always returns a XML message that can be consumed by the caller.
36 *
37 * @package   mod_lti
38 * @copyright Copyright (c) 2015 Moodlerooms Inc. (http://www.moodlerooms.com)
39 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
40 */
41class service_exception_handler {
42    /**
43     * Enable error response logging.
44     *
45     * @var bool
46     */
47    protected $log = false;
48
49    /**
50     * The LTI service message ID, if known.
51     *
52     * @var string
53     */
54    protected $id = '';
55
56    /**
57     * The LTI service message type, if known.
58     *
59     * @var string
60     */
61    protected $type = 'unknownRequest';
62
63    /**
64     * Constructor.
65     *
66     * @param boolean $log Enable error response logging.
67     */
68    public function __construct($log) {
69        $this->log = $log;
70    }
71
72    /**
73     * Set the LTI message ID being handled.
74     *
75     * @param string $id
76     */
77    public function set_message_id($id) {
78        if (!empty($id)) {
79            $this->id = $id;
80        }
81    }
82
83    /**
84     * Set the LTI message type being handled.
85     *
86     * @param string $type
87     */
88    public function set_message_type($type) {
89        if (!empty($type)) {
90            $this->type = $type;
91        }
92    }
93
94    /**
95     * Echo an exception message encapsulated in XML.
96     *
97     * @param \Exception|\Throwable $exception The exception that was thrown
98     */
99    public function handle($exception) {
100        $message = $exception->getMessage();
101
102        // Add the exception backtrace for developers.
103        if (debugging('', DEBUG_DEVELOPER)) {
104            $message .= "\n".format_backtrace(get_exception_info($exception)->backtrace, true);
105        }
106
107        // Switch to response.
108        $type = str_replace('Request', 'Response', $this->type);
109
110        // Build the appropriate xml.
111        $response = lti_get_response_xml('failure', $message, $this->id, $type);
112
113        $xml = $response->asXML();
114
115        // Log the request if necessary.
116        if ($this->log) {
117            lti_log_response($xml, $exception);
118        }
119
120        echo $xml;
121    }
122}
123