<?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/>.

/**
 * This is the external API for this tool.
 *
 * @package    tool_mobile
 * @copyright  2016 Juan Leyva
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace tool_mobile;
defined('MOODLE_INTERNAL') || die();

require_once("$CFG->libdir/externallib.php");
require_once("$CFG->dirroot/webservice/lib.php");

use external_api;
use external_files;
use external_function_parameters;
use external_value;
use external_single_structure;
use external_multiple_structure;
use external_warnings;
use context_system;
use moodle_exception;
use moodle_url;
use core_text;
use core_user;
use coding_exception;

/**
 * This is the external API for this tool.
 *
 * @copyright  2016 Juan Leyva
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class external extends external_api {

    /**
     * Returns description of get_plugins_supporting_mobile() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.1
     */
    public static function get_plugins_supporting_mobile_parameters() {
        return new external_function_parameters(array());
    }

    /**
     * Returns a list of Moodle plugins supporting the mobile app.
     *
     * @return array an array of warnings and objects containing the plugin information
     * @since  Moodle 3.1
     */
    public static function get_plugins_supporting_mobile() {
        return array(
            'plugins' => api::get_plugins_supporting_mobile(),
            'warnings' => array(),
        );
    }

    /**
     * Returns description of get_plugins_supporting_mobile() result value.
     *
     * @return external_description
     * @since  Moodle 3.1
     */
    public static function get_plugins_supporting_mobile_returns() {
        return new external_single_structure(
            array(
                'plugins' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'component' => new external_value(PARAM_COMPONENT, 'The plugin component name.'),
                            'version' => new external_value(PARAM_NOTAGS, 'The plugin version number.'),
                            'addon' => new external_value(PARAM_COMPONENT, 'The Mobile addon (package) name.'),
                            'dependencies' => new external_multiple_structure(
                                                new external_value(PARAM_COMPONENT, 'Mobile addon name.'),
                                                'The list of Mobile addons this addon depends on.'
                                               ),
                            'fileurl' => new external_value(PARAM_URL, 'The addon package url for download
                                                            or empty if it doesn\'t exist.'),
                            'filehash' => new external_value(PARAM_RAW, 'The addon package hash or empty if it doesn\'t exist.'),
                            'filesize' => new external_value(PARAM_INT, 'The addon package size or empty if it doesn\'t exist.'),
                            'handlers' => new external_value(PARAM_RAW, 'Handlers definition (JSON)', VALUE_OPTIONAL),
                            'lang' => new external_value(PARAM_RAW, 'Language strings used by the handlers (JSON)', VALUE_OPTIONAL),
                        )
                    )
                ),
                'warnings' => new external_warnings(),
            )
        );
    }

    /**
     * Returns description of get_public_config() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.2
     */
    public static function get_public_config_parameters() {
        return new external_function_parameters(array());
    }

    /**
     * Returns a list of the site public settings, those not requiring authentication.
     *
     * @return array with the settings and warnings
     * @since  Moodle 3.2
     */
    public static function get_public_config() {
        $result = api::get_public_config();
        $result['warnings'] = array();
        return $result;
    }

    /**
     * Returns description of get_public_config() result value.
     *
     * @return external_description
     * @since  Moodle 3.2
     */
    public static function get_public_config_returns() {
        return new external_single_structure(
            array(
                'wwwroot' => new external_value(PARAM_RAW, 'Site URL.'),
                'httpswwwroot' => new external_value(PARAM_RAW, 'Site https URL (if httpslogin is enabled).'),
                'sitename' => new external_value(PARAM_RAW, 'Site name.'),
                'guestlogin' => new external_value(PARAM_INT, 'Whether guest login is enabled.'),
                'rememberusername' => new external_value(PARAM_INT, 'Values: 0 for No, 1 for Yes, 2 for optional.'),
                'authloginviaemail' => new external_value(PARAM_INT, 'Whether log in via email is enabled.'),
                'registerauth' => new external_value(PARAM_PLUGIN, 'Authentication method for user registration.'),
                'forgottenpasswordurl' => new external_value(PARAM_URL, 'Forgotten password URL.'),
                'authinstructions' => new external_value(PARAM_RAW, 'Authentication instructions.'),
                'authnoneenabled' => new external_value(PARAM_INT, 'Whether auth none is enabled.'),
                'enablewebservices' => new external_value(PARAM_INT, 'Whether Web Services are enabled.'),
                'enablemobilewebservice' => new external_value(PARAM_INT, 'Whether the Mobile service is enabled.'),
                'maintenanceenabled' => new external_value(PARAM_INT, 'Whether site maintenance is enabled.'),
                'maintenancemessage' => new external_value(PARAM_RAW, 'Maintenance message.'),
                'logourl' => new external_value(PARAM_URL, 'The site logo URL', VALUE_OPTIONAL),
                'compactlogourl' => new external_value(PARAM_URL, 'The site compact logo URL', VALUE_OPTIONAL),
                'typeoflogin' => new external_value(PARAM_INT, 'The type of login. 1 for app, 2 for browser, 3 for embedded.'),
                'launchurl' => new external_value(PARAM_URL, 'SSO login launch URL.', VALUE_OPTIONAL),
                'mobilecssurl' => new external_value(PARAM_URL, 'Mobile custom CSS theme', VALUE_OPTIONAL),
                'tool_mobile_disabledfeatures' => new external_value(PARAM_RAW, 'Disabled features in the app', VALUE_OPTIONAL),
                'identityproviders' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'name' => new external_value(PARAM_TEXT, 'The identity provider name.'),
                            'iconurl' => new external_value(PARAM_URL, 'The icon URL for the provider.'),
                            'url' => new external_value(PARAM_URL, 'The URL of the provider.'),
                        )
                    ),
                    'Identity providers', VALUE_OPTIONAL
                ),
                'country' => new external_value(PARAM_NOTAGS, 'Default site country', VALUE_OPTIONAL),
                'agedigitalconsentverification' => new external_value(PARAM_BOOL, 'Whether age digital consent verification
                    is enabled.', VALUE_OPTIONAL),
                'supportname' => new external_value(PARAM_NOTAGS, 'Site support contact name
                    (only if age verification is enabled).', VALUE_OPTIONAL),
                'supportemail' => new external_value(PARAM_EMAIL, 'Site support contact email
                    (only if age verification is enabled).', VALUE_OPTIONAL),
                'supportpage' => new external_value(PARAM_URL, 'Site support page link.', VALUE_OPTIONAL),

>                 'supportavailability' => new external_value(PARAM_INT, 'Determines who has access to contact site support.',
                'autolang' => new external_value(PARAM_INT, 'Whether to detect default language
>                     VALUE_OPTIONAL),


                    from browser setting.', VALUE_OPTIONAL),
                'lang' => new external_value(PARAM_LANG, 'Default language for the site.', VALUE_OPTIONAL),
                'langmenu' => new external_value(PARAM_INT, 'Whether the language menu should be displayed.', VALUE_OPTIONAL),
                'langlist' => new external_value(PARAM_RAW, 'Languages on language menu.', VALUE_OPTIONAL),
                'locale' => new external_value(PARAM_RAW, 'Sitewide locale.', VALUE_OPTIONAL),
                'tool_mobile_minimumversion' => new external_value(PARAM_NOTAGS, 'Minimum required version to access.',
                    VALUE_OPTIONAL),
                'tool_mobile_iosappid' => new external_value(PARAM_ALPHANUM, 'iOS app\'s unique identifier.',
                    VALUE_OPTIONAL),
                'tool_mobile_androidappid' => new external_value(PARAM_NOTAGS, 'Android app\'s unique identifier.',
                    VALUE_OPTIONAL),
                'tool_mobile_setuplink' => new external_value(PARAM_URL, 'App download page.', VALUE_OPTIONAL),
                'tool_mobile_qrcodetype' => new external_value(PARAM_INT, 'QR login configuration.', VALUE_OPTIONAL),
                'warnings' => new external_warnings(),
            )
        );
    }

    /**
     * Returns description of get_config() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.2
     */
    public static function get_config_parameters() {
        return new external_function_parameters(
            array(
                'section' => new external_value(PARAM_ALPHANUMEXT, 'Settings section name.', VALUE_DEFAULT, ''),
            )
        );
    }

    /**
     * Returns a list of site settings, filtering by section.
     *
     * @param string $section settings section name
     * @return array with the settings and warnings
     * @since  Moodle 3.2
     */
    public static function get_config($section = '') {

        $params = self::validate_parameters(self::get_config_parameters(), array('section' => $section));

        $settings = api::get_config($params['section']);
        $result['settings'] = array();
        foreach ($settings as $name => $value) {
            $result['settings'][] = array(
                'name' => $name,
                'value' => $value,
            );
        }

        $result['warnings'] = array();
        return $result;
    }

    /**
     * Returns description of get_config() result value.
     *
     * @return external_description
     * @since  Moodle 3.2
     */
    public static function get_config_returns() {
        return new external_single_structure(
            array(
                'settings' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'name' => new external_value(PARAM_RAW, 'The name of the setting'),
                            'value' => new external_value(PARAM_RAW, 'The value of the setting'),
                        )
                    ),
                    'Settings'
                ),
                'warnings' => new external_warnings(),
            )
        );
    }

    /**
     * Returns description of get_autologin_key() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.2
     */
    public static function get_autologin_key_parameters() {
        return new external_function_parameters (
            array(
                'privatetoken' => new external_value(PARAM_ALPHANUM, 'Private token, usually generated by login/token.php'),
            )
        );
    }

    /**
     * Creates an auto-login key for the current user. Is created only in https sites and is restricted by time and ip address.
     *
     * Please note that it only works if the request comes from the Moodle mobile or desktop app.
     *
     * @param string $privatetoken the user private token for validating the request
     * @return array with the settings and warnings
     * @since  Moodle 3.2
     */
    public static function get_autologin_key($privatetoken) {
        global $CFG, $DB, $USER;

        $params = self::validate_parameters(self::get_autologin_key_parameters(), array('privatetoken' => $privatetoken));
        $privatetoken = $params['privatetoken'];

        $context = context_system::instance();

        // We must toletare these two exceptions: forcepasswordchangenotice and usernotfullysetup.
        try {
            self::validate_context($context);
        } catch (moodle_exception $e) {
            if ($e->errorcode != 'usernotfullysetup' && $e->errorcode != 'forcepasswordchangenotice') {
                // In case we receive a different exception, throw it.
                throw $e;
            }
        }

        // Only requests from the Moodle mobile or desktop app. This enhances security to avoid any type of XSS attack.
        // This code goes intentionally here and not inside the check_autologin_prerequisites() function because it
        // is used by other PHP scripts that can be opened in any browser.
        if (!\core_useragent::is_moodle_app()) {
            throw new moodle_exception('apprequired', 'tool_mobile');
        }
        api::check_autologin_prerequisites($USER->id);

        if (isset($_GET['privatetoken']) or empty($privatetoken)) {
            throw new moodle_exception('invalidprivatetoken', 'tool_mobile');
        }

        // Check the request counter, we must limit the number of times the privatetoken is sent.
        // Between each request 6 minutes are required.
        $last = get_user_preferences('tool_mobile_autologin_request_last', 0, $USER);
        // Check if we must reset the count.
        $mintimereq = get_config('tool_mobile', 'autologinmintimebetweenreq');
        $mintimereq = empty($mintimereq) ? 6 * MINSECS : $mintimereq;
        $timenow = time();
        if ($timenow - $last < $mintimereq) {
            $minutes = $mintimereq / MINSECS;

<             throw new moodle_exception('autologinkeygenerationlockout', 'tool_mobile', $minutes);



>             throw new moodle_exception('autologinkeygenerationlockout', 'tool_mobile', '', $minutes);


        }
        set_user_preference('tool_mobile_autologin_request_last', $timenow, $USER);

        // We are expecting a privatetoken linked to the current token being used.
        // This WS is only valid when using mobile services via REST (this is intended).
        $currenttoken = required_param('wstoken', PARAM_ALPHANUM);
        $conditions = array(
            'userid' => $USER->id,
            'token' => $currenttoken,
            'privatetoken' => $privatetoken,
        );
        if (!$token = $DB->get_record('external_tokens', $conditions)) {
            throw new moodle_exception('invalidprivatetoken', 'tool_mobile');
        }

        $result = array();
        $result['key'] = api::get_autologin_key();
        $autologinurl = new moodle_url("/$CFG->admin/tool/mobile/autologin.php");
        $result['autologinurl'] = $autologinurl->out(false);
        $result['warnings'] = array();
        return $result;
    }

    /**
     * Returns description of get_autologin_key() result value.
     *
     * @return external_description
     * @since  Moodle 3.2
     */
    public static function get_autologin_key_returns() {
        return new external_single_structure(
            array(
                'key' => new external_value(PARAM_ALPHANUMEXT, 'Auto-login key for a single usage with time expiration.'),
                'autologinurl' => new external_value(PARAM_URL, 'Auto-login URL.'),
                'warnings' => new external_warnings(),
            )
        );
    }

    /**
     * Returns description of get_content() parameters
     *
     * @return external_function_parameters
     * @since Moodle 3.5
     */
    public static function get_content_parameters() {
        return new external_function_parameters(
            array(
                'component' => new external_value(PARAM_COMPONENT, 'Component where the class is e.g. mod_assign.'),
                'method' => new external_value(PARAM_ALPHANUMEXT, 'Method to execute in class \$component\output\mobile.'),
                'args' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'name' => new external_value(PARAM_ALPHANUMEXT, 'Param name.'),
                            'value' => new external_value(PARAM_RAW, 'Param value.')
                        )
                    ), 'Args for the method are optional.', VALUE_OPTIONAL
                )
            )
        );
    }

    /**
     * Returns a piece of content to be displayed in the Mobile app, it usually returns a template, javascript and
     * other structured data that will be used to render a view in the Mobile app.
     *
     * Callbacks (placed in \$component\output\mobile) that are called by this web service are responsible for doing the
     * appropriate security checks to access the information to be returned.
     *
     * @param string $component name of the component.
     * @param string $method function method name in class \$component\output\mobile.
     * @param array $args optional arguments for the method.
     * @return array HTML, JavaScript and other required data and information to create a view in the app.
     * @since Moodle 3.5
     * @throws coding_exception
     */
    public static function get_content($component, $method, $args = array()) {
        global $OUTPUT, $PAGE, $USER;

        $params = self::validate_parameters(self::get_content_parameters(),
            array(
                'component' => $component,
                'method' => $method,
                'args' => $args
            )
        );

        // Reformat arguments into something less unwieldy.
        $arguments = array();
        foreach ($params['args'] as $paramargument) {
            $arguments[$paramargument['name']] = $paramargument['value'];
        }

        // The component was validated via the PARAM_COMPONENT parameter type.
        $classname = '\\' . $params['component'] .'\output\mobile';
        if (!method_exists($classname, $params['method'])) {
            throw new coding_exception("Missing method in $classname");
        }
        $result = call_user_func_array(array($classname, $params['method']), array($arguments));

        // Populate otherdata.
        $otherdata = array();
        if (!empty($result['otherdata'])) {
            $result['otherdata'] = (array) $result['otherdata'];
            foreach ($result['otherdata'] as $name => $value) {
                $otherdata[] = array(
                    'name' => $name,
                    'value' => $value
                );
            }
        }

        return array(
            'templates'  => !empty($result['templates']) ? $result['templates'] : array(),
            'javascript' => !empty($result['javascript']) ? $result['javascript'] : '',
            'otherdata'  => $otherdata,
            'files'      => !empty($result['files']) ? $result['files'] : array(),
            'restrict'   => !empty($result['restrict']) ? $result['restrict'] : array(),
            'disabled'   => !empty($result['disabled']) ? true : false,
        );
    }

    /**
     * Returns description of get_content() result value
     *
     * @return array
     * @since Moodle 3.5
     */
    public static function get_content_returns() {
        return new external_single_structure(
            array(
                'templates' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'id' => new external_value(PARAM_TEXT, 'ID of the template.'),
                            'html' => new external_value(PARAM_RAW, 'HTML code.'),
                        )
                    ),
                    'Templates required by the generated content.'
                ),
                'javascript' => new external_value(PARAM_RAW, 'JavaScript code.'),
                'otherdata' => new external_multiple_structure(
                    new external_single_structure(
                        array(
                            'name' => new external_value(PARAM_RAW, 'Field name.'),
                            'value' => new external_value(PARAM_RAW, 'Field value.')
                        )
                    ),
                    'Other data that can be used or manipulated by the template via 2-way data-binding.'
                ),
                'files' => new external_files('Files in the content.'),
                'restrict' => new external_single_structure(
                    array(
                        'users' => new external_multiple_structure(
                            new external_value(PARAM_INT, 'user id'), 'List of allowed users.', VALUE_OPTIONAL
                        ),
                        'courses' => new external_multiple_structure(
                            new external_value(PARAM_INT, 'course id'), 'List of allowed courses.', VALUE_OPTIONAL
                        ),
                    ),
                    'Restrict this content to certain users or courses.'
                ),
                'disabled' => new external_value(PARAM_BOOL, 'Whether we consider this disabled or not.', VALUE_OPTIONAL),
            )
        );
    }

    /**
     * Returns description of method parameters
     *
     * @return external_function_parameters
     * @since Moodle 3.7
     */
    public static function call_external_functions_parameters() {
        return new external_function_parameters([
            'requests' => new external_multiple_structure(
                new external_single_structure([
                    'function' => new external_value(PARAM_ALPHANUMEXT, 'Function name'),
                    'arguments' => new external_value(PARAM_RAW, 'JSON-encoded object with named arguments', VALUE_DEFAULT, '{}'),
                    'settingraw' => new external_value(PARAM_BOOL, 'Return raw text', VALUE_DEFAULT, false),
                    'settingfilter' => new external_value(PARAM_BOOL, 'Filter text', VALUE_DEFAULT, false),
                    'settingfileurl' => new external_value(PARAM_BOOL, 'Rewrite plugin file URLs', VALUE_DEFAULT, true),
                    'settinglang' => new external_value(PARAM_LANG, 'Session language', VALUE_DEFAULT, ''),
                ])
            )
        ]);
    }

    /**
     * Call multiple external functions and return all responses.
     *
     * @param array $requests List of requests.
     * @return array Responses.
     * @since Moodle 3.7
     */
    public static function call_external_functions($requests) {
        global $SESSION;

        $params = self::validate_parameters(self::call_external_functions_parameters(), ['requests' => $requests]);

        // We need to check if the functions being called are included in the service of the current token.
        // This function only works when using mobile services via REST (this is intended).
        $webservicemanager = new \webservice;
        $token = $webservicemanager->get_user_ws_token(required_param('wstoken', PARAM_ALPHANUM));

        $settings = \external_settings::get_instance();
        $defaultlang = current_language();
        $responses = [];

        foreach ($params['requests'] as $request) {
            // Some external functions modify _GET or $_POST data, we need to restore the original data after each call.
            $originalget = fullclone($_GET);
            $originalpost = fullclone($_POST);

            // Set external settings and language.
            $settings->set_raw($request['settingraw']);
            $settings->set_filter($request['settingfilter']);
            $settings->set_fileurl($request['settingfileurl']);
            $settings->set_lang($request['settinglang']);
            $SESSION->lang = $request['settinglang'] ?: $defaultlang;

            // Parse arguments to an array, validation is done in external_api::call_external_function.
            $args = @json_decode($request['arguments'], true);
            if (!is_array($args)) {
                $args = [];
            }

            if ($webservicemanager->service_function_exists($request['function'], $token->externalserviceid)) {
                $response = external_api::call_external_function($request['function'], $args, false);
            } else {
                // Function not included in the service, return an access exception.
                $response = [
                    'error' => true,
                    'exception' => [
                        'errorcode' => 'accessexception',
                        'module' => 'webservice'
                    ]
                ];
                if (debugging('', DEBUG_DEVELOPER)) {
                    $response['exception']['debuginfo'] = 'Access to the function is not allowed.';
                }
            }

            if (isset($response['data'])) {
                $response['data'] = json_encode($response['data']);
            }
            if (isset($response['exception'])) {
                $response['exception'] = json_encode($response['exception']);
            }
            $responses[] = $response;

            // Restore original $_GET and $_POST.
            $_GET = $originalget;
            $_POST = $originalpost;

            if ($response['error']) {
                // Do not process the remaining requests.
                break;
            }
        }

        return ['responses' => $responses];
    }

    /**
     * Returns description of method result value
     *
     * @return external_single_structure
     * @since Moodle 3.7
     */
    public static function call_external_functions_returns() {
        return new external_function_parameters([
            'responses' => new external_multiple_structure(
                new external_single_structure([
                    'error' => new external_value(PARAM_BOOL, 'Whether an exception was thrown.'),
                    'data' => new external_value(PARAM_RAW, 'JSON-encoded response data', VALUE_OPTIONAL),
                    'exception' => new external_value(PARAM_RAW, 'JSON-encoed exception info', VALUE_OPTIONAL),
                ])
             )
        ]);
    }

    /**
     * Returns description of get_tokens_for_qr_login() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.9
     */
    public static function get_tokens_for_qr_login_parameters() {
        return new external_function_parameters (
            [
                'qrloginkey' => new external_value(PARAM_ALPHANUMEXT, 'The user key for validating the request.'),
                'userid' => new external_value(PARAM_INT, 'The user the key belongs to.'),
            ]
        );
    }

    /**
     * Returns a WebService token (and private token) for QR login
     *
     * @param string $qrloginkey the user key generated and embedded into the QR code for validating the request
     * @param int $userid the user the key belongs to
     * @return array with the tokens and warnings
     * @since  Moodle 3.9
     */
    public static function get_tokens_for_qr_login($qrloginkey, $userid) {
        global $PAGE, $DB;

        $params = self::validate_parameters(self::get_tokens_for_qr_login_parameters(),
            ['qrloginkey' => $qrloginkey, 'userid' => $userid]);

        $context = context_system::instance();
        // We need this to make work the format text functions.
        $PAGE->set_context($context);

        $qrcodetype = get_config('tool_mobile', 'qrcodetype');
        if ($qrcodetype != api::QR_CODE_LOGIN) {
            throw new moodle_exception('qrcodedisabled', 'tool_mobile');
        }

        // Only requests from the Moodle mobile or desktop app. This enhances security to avoid any type of XSS attack.
        // This code goes intentionally here and not inside the check_autologin_prerequisites() function because it
        // is used by other PHP scripts that can be opened in any browser.
        if (!\core_useragent::is_moodle_app()) {
            throw new moodle_exception('apprequired', 'tool_mobile');
        }
        api::check_autologin_prerequisites($params['userid']);  // Checks https, avoid site admins using this...

        // Validate and delete the key.
        $key = validate_user_key($params['qrloginkey'], 'tool_mobile', null);
        delete_user_key('tool_mobile', $params['userid']);

        // Double check key belong to user.
        if ($key->userid != $params['userid']) {
            throw new moodle_exception('invalidkey');
        }

        // Key validated, check user.
        $user = core_user::get_user($key->userid, '*', MUST_EXIST);
        core_user::require_active_user($user, true, true);

        // Generate WS tokens.
        \core\session\manager::set_user($user);

        // Check if the service exists and is enabled.
        $service = $DB->get_record('external_services', ['shortname' => MOODLE_OFFICIAL_MOBILE_SERVICE, 'enabled' => 1]);
        if (empty($service)) {
            // will throw exception if no token found
            throw new moodle_exception('servicenotavailable', 'webservice');
        }

        // Get an existing token or create a new one.
        $token = external_generate_token_for_current_user($service);
        $privatetoken = $token->privatetoken; // Save it here, the next function removes it.
        external_log_token_request($token);

        $result = [
            'token' => $token->token,
            'privatetoken' => $privatetoken ?: '',
            'warnings' => [],
        ];
        return $result;
    }

    /**
     * Returns description of get_tokens_for_qr_login() result value.
     *
     * @return external_description
     * @since  Moodle 3.9
     */
    public static function get_tokens_for_qr_login_returns() {
        return new external_single_structure(
            [
                'token' => new external_value(PARAM_ALPHANUM, 'A valid WebService token for the official mobile app service.'),
                'privatetoken' => new external_value(PARAM_ALPHANUM, 'Private token used for auto-login processes.'),
                'warnings' => new external_warnings(),
            ]
        );
    }

    /**
     * Returns description of validate_subscription_key() parameters.
     *
     * @return external_function_parameters
     * @since  Moodle 3.9
     */
    public static function validate_subscription_key_parameters() {
        return new external_function_parameters(
            [
                'key' => new external_value(PARAM_RAW, 'Site subscription temporary key.'),
            ]
        );
    }

    /**
     * Check if the given site subscription key is valid
     *
     * @param string $key subscriptiion temporary key
     * @return array with the settings and warnings
     * @since  Moodle 3.9
     */
    public static function validate_subscription_key(string $key): array {
        global $CFG, $PAGE;

        $params = self::validate_parameters(self::validate_subscription_key_parameters(), ['key' => $key]);

        $context = context_system::instance();
        $PAGE->set_context($context);

        $validated = false;
        $sitesubscriptionkey = get_config('tool_mobile', 'sitesubscriptionkey');
        if (!empty($sitesubscriptionkey) && $CFG->enablemobilewebservice && empty($CFG->disablemobileappsubscription)) {
            $sitesubscriptionkey = json_decode($sitesubscriptionkey);
            $validated = time() < $sitesubscriptionkey->validuntil && $params['key'] === $sitesubscriptionkey->key;
            // Delete existing, even if not validated to enforce security and attacks prevention.
            unset_config('sitesubscriptionkey', 'tool_mobile');
        }

        return [
            'validated' => $validated,
            'warnings' => [],
        ];
    }

    /**
     * Returns description of validate_subscription_key() result value.
     *
     * @return external_description
     * @since  Moodle 3.9
     */
    public static function validate_subscription_key_returns() {
        return new external_single_structure(
            [
                'validated' => new external_value(PARAM_BOOL, 'Whether the key is validated or not.'),
                'warnings' => new external_warnings(),
            ]
        );
    }
}