Proyectos de Subversion Moodle

<?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/>.

/**

 * Chat external API

 *

 * @package    mod_chat

 * @category   external

 * @copyright  2015 Juan Leyva <juan@moodle.com>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 * @since      Moodle 3.0

 */

defined('MOODLE_INTERNAL') || die;

require_once($CFG->dirroot . '/mod/chat/lib.php');

use core_course\external\helper_for_get_mods_by_courses;

use core_external\external_api;

use core_external\external_function_parameters;

use core_external\external_multiple_structure;

use core_external\external_single_structure;

use core_external\external_value;

use core_external\external_warnings;

use core_external\util;

use mod_chat\external\chat_message_exporter;

/**

 * Chat external functions

 *

 * @package    mod_chat

 * @category   external

 * @copyright  2015 Juan Leyva <juan@moodle.com>

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 * @since      Moodle 3.0

 */

class mod_chat_external extends external_api {

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function login_user_parameters() {

        return new external_function_parameters(

            array(

                'chatid' => new external_value(PARAM_INT, 'chat instance id'),

                'groupid' => new external_value(PARAM_INT, 'group id, 0 means that the function will determine the user group',

                                                VALUE_DEFAULT, 0),

            )

        );

    }

    /**

     * Log the current user into a chat room in the given chat.

     *

     * @param int $chatid the chat instance id

     * @param int $groupid the user group id

     * @return array of warnings and the chat unique session id

     * @since Moodle 3.0

     * @throws moodle_exception

     */

    public static function login_user($chatid, $groupid = 0) {

        global $DB;

        $params = self::validate_parameters(self::login_user_parameters(),

                                            array(

                                                'chatid' => $chatid,

                                                'groupid' => $groupid

                                            ));

        $warnings = array();

        // Request and permission validation.

        $chat = $DB->get_record('chat', array('id' => $params['chatid']), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        require_capability('mod/chat:chat', $context);

        if (!empty($params['groupid'])) {

            $groupid = $params['groupid'];

            // Determine is the group is visible to user.

            if (!groups_group_visible($groupid, $course, $cm)) {

                throw new moodle_exception('notingroup');

            }

        } else {

            // Check to see if groups are being used here.

            if ($groupmode = groups_get_activity_groupmode($cm)) {

                $groupid = groups_get_activity_group($cm);

                // Determine is the group is visible to user (this is particullary for the group 0).

                if (!groups_group_visible($groupid, $course, $cm)) {

                    throw new moodle_exception('notingroup');

                }

            } else {

                $groupid = 0;

            }

        }

        // Get the unique chat session id.

        // Since we are going to use the chat via Web Service requests we set the ajax version (since it's the most similar).

        if (!$chatsid = chat_login_user($chat->id, 'ajax', $groupid, $course)) {

            throw new moodle_exception('cantlogin', 'chat');

        }

        $result = array();

        $result['chatsid'] = $chatsid;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.0

     */

    public static function login_user_returns() {

        return new external_single_structure(

            array(

                'chatsid' => new external_value(PARAM_ALPHANUM, 'unique chat session id'),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function get_chat_users_parameters() {

        return new external_function_parameters(

            array(

                'chatsid' => new external_value(PARAM_ALPHANUM, 'chat session id (obtained via mod_chat_login_user)')

            )

        );

    }

    /**

     * Get the list of users in the given chat session.

     *

     * @param int $chatsid the chat session id

     * @return array of warnings and the user lists

     * @since Moodle 3.0

     * @throws moodle_exception

     */

    public static function get_chat_users($chatsid) {

        global $DB, $PAGE;

        $params = self::validate_parameters(self::get_chat_users_parameters(),

                                            array(

                                                'chatsid' => $chatsid

                                            ));

        $warnings = array();

        // Request and permission validation.

        if (!$chatuser = $DB->get_record('chat_users', array('sid' => $params['chatsid']))) {

            throw new moodle_exception('notlogged', 'chat');

        }

        $chat = $DB->get_record('chat', array('id' => $chatuser->chatid), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        require_capability('mod/chat:chat', $context);

        // First, delete old users from the chats.

        chat_delete_old_users();

        $users = chat_get_users($chatuser->chatid, $chatuser->groupid, $cm->groupingid);

        $returnedusers = array();

        foreach ($users as $user) {

            $userpicture = new user_picture($user);

            $userpicture->size = 1; // Size f1.

            $profileimageurl = $userpicture->get_url($PAGE)->out(false);

            $returnedusers[] = array(

                'id' => $user->id,

                'fullname' => fullname($user),

                'profileimageurl' => $profileimageurl

            );

        }

        $result = array();

        $result['users'] = $returnedusers;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.0

     */

    public static function get_chat_users_returns() {

        return new external_single_structure(

            array(

                'users' => new external_multiple_structure(

                    new external_single_structure(

                        array(

                            'id' => new external_value(PARAM_INT, 'user id'),

                            'fullname' => new external_value(PARAM_NOTAGS, 'user full name'),

                            'profileimageurl' => new external_value(PARAM_URL, 'user picture URL'),

                        )

                    ),

                    'list of users'

                ),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function send_chat_message_parameters() {

        return new external_function_parameters(

            array(

                'chatsid' => new external_value(PARAM_ALPHANUM, 'chat session id (obtained via mod_chat_login_user)'),

                'messagetext' => new external_value(PARAM_RAW, 'the message text'),

                'beepid' => new external_value(PARAM_RAW, 'the beep id', VALUE_DEFAULT, ''),

            )

        );

    }

    /**

     * Send a message on the given chat session.

     *

     * @param int $chatsid the chat session id

     * @param string $messagetext the message text

     * @param string $beepid the beep message id

     * @return array of warnings and the new message id (0 if the message was empty)

     * @since Moodle 3.0

     * @throws moodle_exception

     */

    public static function send_chat_message($chatsid, $messagetext, $beepid = '') {

        global $DB;

        $params = self::validate_parameters(self::send_chat_message_parameters(),

                                            array(

                                                'chatsid' => $chatsid,

                                                'messagetext' => $messagetext,

                                                'beepid' => $beepid

                                            ));

        $warnings = array();

        // Request and permission validation.

        if (!$chatuser = $DB->get_record('chat_users', array('sid' => $params['chatsid']))) {

            throw new moodle_exception('notlogged', 'chat');

        }

        $chat = $DB->get_record('chat', array('id' => $chatuser->chatid), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        require_capability('mod/chat:chat', $context);

        $chatmessage = clean_text($params['messagetext'], FORMAT_MOODLE);

        if (!empty($params['beepid'])) {

            $chatmessage = 'beep ' . $params['beepid'];

        }

        if (!empty($chatmessage)) {

            // Send the message.

            $messageid = chat_send_chatmessage($chatuser, $chatmessage, 0, $cm);

            // Update ping time.

            $chatuser->lastmessageping = time() - 2;

            $DB->update_record('chat_users', $chatuser);

        } else {

            $messageid = 0;

        }

        $result = array();

        $result['messageid'] = $messageid;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.0

     */

    public static function send_chat_message_returns() {

        return new external_single_structure(

            array(

                'messageid' => new external_value(PARAM_INT, 'message sent id'),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function get_chat_latest_messages_parameters() {

        return new external_function_parameters(

            array(

                'chatsid' => new external_value(PARAM_ALPHANUM, 'chat session id (obtained via mod_chat_login_user)'),

                'chatlasttime' => new external_value(PARAM_INT, 'last time messages were retrieved (epoch time)', VALUE_DEFAULT, 0)

            )

        );

    }

    /**

     * Get the latest messages from the given chat session.

     *

     * @param int $chatsid the chat session id

     * @param int $chatlasttime last time messages were retrieved (epoch time)

     * @return array of warnings and the new message id (0 if the message was empty)

     * @since Moodle 3.0

     * @throws moodle_exception

     */

    public static function get_chat_latest_messages($chatsid, $chatlasttime = 0) {

        global $DB, $CFG;

        $params = self::validate_parameters(self::get_chat_latest_messages_parameters(),

                                            array(

                                                'chatsid' => $chatsid,

                                                'chatlasttime' => $chatlasttime

                                            ));

        $warnings = array();

        // Request and permission validation.

        if (!$chatuser = $DB->get_record('chat_users', array('sid' => $params['chatsid']))) {

            throw new moodle_exception('notlogged', 'chat');

        }

        $chat = $DB->get_record('chat', array('id' => $chatuser->chatid), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        require_capability('mod/chat:chat', $context);

        $chatlasttime = $params['chatlasttime'];

        if ((time() - $chatlasttime) > $CFG->chat_old_ping) {

            chat_delete_old_users();

        }

        // Set default chat last time (to not retrieve all the conversations).

        if ($chatlasttime == 0) {

            $chatlasttime = time() - $CFG->chat_old_ping;

        }

        if ($latestmessage = chat_get_latest_message($chatuser->chatid, $chatuser->groupid)) {

            $chatnewlasttime = $latestmessage->timestamp;

        } else {

            $chatnewlasttime = 0;

        }

        $messages = chat_get_latest_messages($chatuser, $chatlasttime);

        $returnedmessages = array();

        foreach ($messages as $message) {

            // FORMAT_MOODLE is mandatory in the chat plugin.

            [$messageformatted] = \core_external\util::format_text(

                $message->message,

                FORMAT_MOODLE,

                $context->id,

                'mod_chat',

                '',

            );

            $returnedmessages[] = array(

                'id' => $message->id,

                'userid' => $message->userid,

                'system' => (bool) $message->issystem,

                'message' => $messageformatted,

                'timestamp' => $message->timestamp,

            );

        }

        // Update our status since we are active in the chat.

        $DB->set_field('chat_users', 'lastping', time(), array('id' => $chatuser->id));

        $result = array();

        $result['messages'] = $returnedmessages;

        $result['chatnewlasttime'] = $chatnewlasttime;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.0

     */

    public static function get_chat_latest_messages_returns() {

        return new external_single_structure(

            array(

                'messages' => new external_multiple_structure(

                    new external_single_structure(

                        array(

                            'id' => new external_value(PARAM_INT, 'message id'),

                            'userid' => new external_value(PARAM_INT, 'user id'),

                            'system' => new external_value(PARAM_BOOL, 'true if is a system message (like user joined)'),

                            'message' => new external_value(PARAM_RAW, 'message text'),

                            'timestamp' => new external_value(PARAM_INT, 'timestamp for the message'),

                        )

                    ),

                    'list of users'

                ),

                'chatnewlasttime' => new external_value(PARAM_INT, 'new last time'),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function view_chat_parameters() {

        return new external_function_parameters(

            array(

                'chatid' => new external_value(PARAM_INT, 'chat instance id')

            )

        );

    }

    /**

     * Trigger the course module viewed event and update the module completion status.

     *

     * @param int $chatid the chat instance id

     * @return array of warnings and status result

     * @since Moodle 3.0

     * @throws moodle_exception

     */

    public static function view_chat($chatid) {

        global $DB, $CFG;

        $params = self::validate_parameters(self::view_chat_parameters(),

                                            array(

                                                'chatid' => $chatid

                                            ));

        $warnings = array();

        // Request and permission validation.

        $chat = $DB->get_record('chat', array('id' => $params['chatid']), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        require_capability('mod/chat:chat', $context);

        // Call the url/lib API.

        chat_view($chat, $course, $cm, $context);

        $result = array();

        $result['status'] = true;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.0

     */

    public static function view_chat_returns() {

        return new external_single_structure(

            array(

                'status' => new external_value(PARAM_BOOL, 'status: true if success'),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Describes the parameters for get_chats_by_courses.

     *

     * @return external_function_parameters

     * @since Moodle 3.0

     */

    public static function get_chats_by_courses_parameters() {

        return new external_function_parameters (

            array(

                'courseids' => new external_multiple_structure(

                    new external_value(PARAM_INT, 'course id'), 'Array of course ids', VALUE_DEFAULT, array()

                ),

            )

        );

    }

    /**

     * Returns a list of chats in a provided list of courses,

     * if no list is provided all chats that the user can view will be returned.

     *

     * @param array $courseids the course ids

     * @return array of chats details

     * @since Moodle 3.0

     */

    public static function get_chats_by_courses($courseids = array()) {

        global $CFG;

        $returnedchats = array();

        $warnings = array();

        $params = self::validate_parameters(self::get_chats_by_courses_parameters(), array('courseids' => $courseids));

        $courses = array();

        if (empty($params['courseids'])) {

            $courses = enrol_get_my_courses();

            $params['courseids'] = array_keys($courses);

        }

        // Ensure there are courseids to loop through.

        if (!empty($params['courseids'])) {

            list($courses, $warnings) = util::validate_courses($params['courseids'], $courses);

            // Get the chats in this course, this function checks users visibility permissions.

            // We can avoid then additional validate_context calls.

            $chats = get_all_instances_in_courses("chat", $courses);

            foreach ($chats as $chat) {

                $chatcontext = context_module::instance($chat->coursemodule);

                $chatdetails = helper_for_get_mods_by_courses::standard_coursemodule_element_values($chat, 'mod_chat');

                if (has_capability('mod/chat:chat', $chatcontext)) {

                    $chatdetails['chatmethod']    = $CFG->chat_method;

                    $chatdetails['keepdays']      = $chat->keepdays;

                    $chatdetails['studentlogs']   = $chat->studentlogs;

                    $chatdetails['chattime']      = $chat->chattime;

                    $chatdetails['schedule']      = $chat->schedule;

                }

                if (has_capability('moodle/course:manageactivities', $chatcontext)) {

                    $chatdetails['timemodified']  = $chat->timemodified;

                }

                $returnedchats[] = $chatdetails;

            }

        }

        $result = array();

        $result['chats'] = $returnedchats;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Describes the get_chats_by_courses return value.

     *

     * @return external_single_structure

     * @since Moodle 3.0

     */

    public static function get_chats_by_courses_returns() {

        return new external_single_structure(

            array(

                'chats' => new external_multiple_structure(

                    new external_single_structure(array_merge(

                        helper_for_get_mods_by_courses::standard_coursemodule_elements_returns(),

                        [

                            'chatmethod' => new external_value(PARAM_PLUGIN, 'chat method (sockets, ajax, header_js)',

                                VALUE_OPTIONAL),

                            'keepdays' => new external_value(PARAM_INT, 'keep days', VALUE_OPTIONAL),

                            'studentlogs' => new external_value(PARAM_INT, 'student logs visible to everyone', VALUE_OPTIONAL),

                            'chattime' => new external_value(PARAM_INT, 'chat time', VALUE_OPTIONAL),

                            'schedule' => new external_value(PARAM_INT, 'schedule type', VALUE_OPTIONAL),

                            'timemodified' => new external_value(PARAM_INT, 'time of last modification', VALUE_OPTIONAL),

                        ]

                    ), 'Chats')

                ),

                'warnings' => new external_warnings(),

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.4

     */

    public static function get_sessions_parameters() {

        return new external_function_parameters(

            array(

                'chatid' => new external_value(PARAM_INT, 'Chat instance id.'),

                'groupid' => new external_value(PARAM_INT, 'Get messages from users in this group.

                'showall' => new external_value(PARAM_BOOL, 'Whether to show completed sessions or not.', VALUE_DEFAULT, false),

            )

        );

    }

    /**

     * Retrieves chat sessions for a given chat.

     *

     * @param int $chatid the chat instance id

     * @param int $groupid filter messages by this group. 0 to determine the group.

     * @param bool $showall whether to include incomplete sessions or not

     * @return array of warnings and the sessions

     * @since Moodle 3.4

     * @throws moodle_exception

     */

    public static function get_sessions($chatid, $groupid = 0, $showall = false) {

        global $DB;

        $params = self::validate_parameters(self::get_sessions_parameters(),

                                            array(

                                                'chatid' => $chatid,

                                                'groupid' => $groupid,

                                                'showall' => $showall,

                                            ));

        $sessions = $warnings = array();

        // Request and permission validation.

        $chat = $DB->get_record('chat', array('id' => $params['chatid']), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        if (empty($chat->studentlogs) && !has_capability('mod/chat:readlog', $context)) {

            throw new moodle_exception('nopermissiontoseethechatlog', 'chat');

        }

        if (!empty($params['groupid'])) {

            $groupid = $params['groupid'];

            // Determine is the group is visible to user.

            if (!groups_group_visible($groupid, $course, $cm)) {

                throw new moodle_exception('notingroup');

            }

        } else {

            // Check to see if groups are being used here.

            if ($groupmode = groups_get_activity_groupmode($cm)) {

                $groupid = groups_get_activity_group($cm);

                // Determine is the group is visible to user (this is particullary for the group 0).

                if (!groups_group_visible($groupid, $course, $cm)) {

                    throw new moodle_exception('notingroup');

                }

            } else {

                $groupid = 0;

            }

        }

        $messages = chat_get_session_messages($chat->id, $groupid, 0, 0, 'timestamp DESC');

        if ($messages) {

            $chatsessions = chat_get_sessions($messages, $params['showall']);

            // Format sessions for external.

            foreach ($chatsessions as $session) {

                $sessionusers = array();

                foreach ($session->sessionusers as $sessionuser => $usermessagecount) {

                    $sessionusers[] = array(

                        'userid' => $sessionuser,

                        'messagecount' => $usermessagecount

                    );

                }

                $session->sessionusers = $sessionusers;

                $sessions[] = $session;

            }

        }

        $result = array();

        $result['sessions'] = $sessions;

        $result['warnings'] = $warnings;

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.4

     */

    public static function get_sessions_returns() {

        return new external_single_structure(

            array(

                'sessions' => new external_multiple_structure(

                    new external_single_structure(

                        array(

                            'sessionstart' => new external_value(PARAM_INT, 'Session start time.'),

                            'sessionend' => new external_value(PARAM_INT, 'Session end time.'),

                            'sessionusers' => new external_multiple_structure(

                                new external_single_structure(

                                    array(

                                        'userid' => new external_value(PARAM_INT, 'User id.'),

                                        'messagecount' => new external_value(PARAM_INT, 'Number of messages in the session.'),

                                    )

                                ), 'Session users.'

                            ),

                            'iscomplete' => new external_value(PARAM_BOOL, 'Whether the session is completed or not.'),

                        )

                    ),

                    'list of users'

                ),

                'warnings' => new external_warnings()

            )

        );

    }

    /**

     * Returns description of method parameters

     *

     * @return external_function_parameters

     * @since Moodle 3.4

     */

    public static function get_session_messages_parameters() {

        return new external_function_parameters(

            array(

                'chatid' => new external_value(PARAM_INT, 'Chat instance id.'),

                'sessionstart' => new external_value(PARAM_INT, 'The session start time (timestamp).'),

                'sessionend' => new external_value(PARAM_INT, 'The session end time (timestamp).'),

                'groupid' => new external_value(PARAM_INT, 'Get messages from users in this group.

            )

        );

    }

    /**

     * Retrieves messages of the given chat session.

     *

     * @param int $chatid the chat instance id

     * @param int $sessionstart the session start time (timestamp)

     * @param int $sessionend the session end time (timestamp)

     * @param int $groupid filter messages by this group. 0 to determine the group.

     * @return array of warnings and the messages

     * @since Moodle 3.4

     * @throws moodle_exception

     */

    public static function get_session_messages($chatid, $sessionstart, $sessionend, $groupid = 0) {

        global $DB, $PAGE;

        $params = self::validate_parameters(self::get_session_messages_parameters(),

                                            array(

                                                'chatid' => $chatid,

                                                'sessionstart' => $sessionstart,

                                                'sessionend' => $sessionend,

                                                'groupid' => $groupid,

                                            ));

        $messages = $warnings = array();

        // Request and permission validation.

        $chat = $DB->get_record('chat', array('id' => $params['chatid']), '*', MUST_EXIST);

        list($course, $cm) = get_course_and_cm_from_instance($chat, 'chat');

        $context = context_module::instance($cm->id);

        self::validate_context($context);

        if (empty($chat->studentlogs) && !has_capability('mod/chat:readlog', $context)) {

            throw new moodle_exception('nopermissiontoseethechatlog', 'chat');

        }

        if (!empty($params['groupid'])) {

            $groupid = $params['groupid'];

            // Determine is the group is visible to user.

            if (!groups_group_visible($groupid, $course, $cm)) {

                throw new moodle_exception('notingroup');

            }

        } else {

            // Check to see if groups are being used here.

            if ($groupmode = groups_get_activity_groupmode($cm)) {

                $groupid = groups_get_activity_group($cm);

                // Determine is the group is visible to user (this is particullary for the group 0).

                if (!groups_group_visible($groupid, $course, $cm)) {

                    throw new moodle_exception('notingroup');

                }

            } else {

                $groupid = 0;

            }

        }

        $messages = chat_get_session_messages($chat->id, $groupid, $params['sessionstart'], $params['sessionend'],

            'timestamp ASC');

        if ($messages) {

            foreach ($messages as $message) {

                $exporter = new chat_message_exporter($message, array('context' => $context));

                $returneditems[] = $exporter->export($PAGE->get_renderer('core'));

            }

        }

        $result = array(

            'messages' => $messages,

            'warnings' => $warnings,

        );

        return $result;

    }

    /**

     * Returns description of method result value

     *

     * @return \core_external\external_description

     * @since Moodle 3.4

     */

    public static function get_session_messages_returns() {

        return new external_single_structure(

            array(

                'messages' => new external_multiple_structure(

                    chat_message_exporter::get_read_structure()

                ),

                'warnings' => new external_warnings()

            )

        );

    }

}