<?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/>.

/**
 * Manual enrolment plugin main library file.
 *
 * @package    enrol_manual
 * @copyright  2010 Petr Skoda {@link http://skodak.org}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

class enrol_manual_plugin extends enrol_plugin {

    protected $lasternoller = null;
    protected $lasternollerinstanceid = 0;

    public function roles_protected() {
        // Users may tweak the roles later.
        return false;
    }

    public function allow_enrol(stdClass $instance) {
        // Users with enrol cap may unenrol other users manually manually.
        return true;
    }

    public function allow_unenrol(stdClass $instance) {
        // Users with unenrol cap may unenrol other users manually manually.
        return true;
    }

    public function allow_manage(stdClass $instance) {
        // Users with manage cap may tweak period and status.
        return true;
    }

    /**
     * Returns link to manual enrol UI if exists.
     * Does the access control tests automatically.
     *
     * @param stdClass $instance
     * @return moodle_url
     */
    public function get_manual_enrol_link($instance) {
        $name = $this->get_name();
        if ($instance->enrol !== $name) {
            throw new coding_exception('invalid enrol instance!');
        }

        if (!enrol_is_enabled($name)) {
            return NULL;
        }

        $context = context_course::instance($instance->courseid, MUST_EXIST);

        if (!has_capability('enrol/manual:enrol', $context)) {
            // Note: manage capability not used here because it is used for editing
            // of existing enrolments which is not possible here.
            return NULL;
        }

        return new moodle_url('/enrol/manual/manage.php', array('enrolid'=>$instance->id, 'id'=>$instance->courseid));
    }

    /**
     * Return true if we can add a new instance to this course.
     *
     * @param int $courseid
     * @return boolean
     */
    public function can_add_instance($courseid) {
        global $DB;

        $context = context_course::instance($courseid, MUST_EXIST);
        if (!has_capability('moodle/course:enrolconfig', $context) or !has_capability('enrol/manual:config', $context)) {
            return false;
        }

        if ($DB->record_exists('enrol', array('courseid'=>$courseid, 'enrol'=>'manual'))) {
            // Multiple instances not supported.
            return false;
        }

        return true;
    }

    /**
     * Returns edit icons for the page with list of instances.
     * @param stdClass $instance
     * @return array
     */
    public function get_action_icons(stdClass $instance) {
        global $OUTPUT;

        $context = context_course::instance($instance->courseid);

        $icons = array();
        if (has_capability('enrol/manual:enrol', $context) or has_capability('enrol/manual:unenrol', $context)) {
            $managelink = new moodle_url("/enrol/manual/manage.php", array('enrolid'=>$instance->id));
            $icons[] = $OUTPUT->action_icon($managelink, new pix_icon('t/enrolusers', get_string('enrolusers', 'enrol_manual'), 'core', array('class'=>'iconsmall')));
        }

        if (has_any_capability(['enrol/manual:config', 'moodle/course:editcoursewelcomemessage'], $context)) {
            $linkparams = [
                'courseid' => $instance->courseid,
                'id' => $instance->id,
                'type' => $instance->enrol,
            ];
            $editlink = new moodle_url('/enrol/editinstance.php', $linkparams);
            $icon = new pix_icon('t/edit', get_string('edit'), 'core', ['class' => 'iconsmall']);
            $icons[] = $OUTPUT->action_icon($editlink, $icon);
        }

        return $icons;
    }

    /**
     * Add new instance of enrol plugin with default settings.
     * @param stdClass $course
     * @return int id of new instance, null if can not be created
     */
    public function add_default_instance($course) {
        $expirynotify = $this->get_config('expirynotify', 0);

        $fields = array(
            'status'          => $this->get_config('status'),
            'roleid'          => $this->get_config('roleid', 0),
            'enrolperiod'     => $this->get_config('enrolperiod', 0),
            'expirynotify'    => $expirynotify,
            'notifyall'       => $expirynotify == 2 ? 1 : 0,
            'expirythreshold' => $this->get_config('expirythreshold', 86400),
            'customint1' => $this->get_config('sendcoursewelcomemessage'),
        );
        return $this->add_instance($course, $fields);
    }

    /**
     * Add new instance of enrol plugin.
     * @param stdClass $course
     * @param array instance fields
     * @return int id of new instance, null if can not be created
     */
    public function add_instance($course, ?array $fields = NULL) {
        global $DB;

        if ($DB->record_exists('enrol', array('courseid'=>$course->id, 'enrol'=>'manual'))) {
            // only one instance allowed, sorry
            return NULL;
        }

        return parent::add_instance($course, $fields);
    }

    /**
     * Update instance of enrol plugin.
     * @param stdClass $instance
     * @param stdClass $data modified instance fields
     * @return boolean
     */
    public function update_instance($instance, $data) {
        global $DB;

        // Delete all other instances, leaving only one.
        if ($instances = $DB->get_records('enrol', array('courseid' => $instance->courseid, 'enrol' => 'manual'), 'id ASC')) {
            foreach ($instances as $anotherinstance) {
                if ($anotherinstance->id != $instance->id) {
                    $this->delete_instance($anotherinstance);
                }
            }
        }

        // This method is used when configuring the enrolment method, and when only updating the welcome message.
        // The 'expirynotify' property won't be set when updating the welcome message.
        if (isset($data->expirynotify)) {
            $data->notifyall = $data->expirynotify == 2 ? 1 : 0;
        }

        return parent::update_instance($instance, $data);
    }

    /**
     * Returns a button to manually enrol users through the manual enrolment plugin.
     *
     * By default the first manual enrolment plugin instance available in the course is used.
     * If no manual enrolment instances exist within the course then false is returned.
     *
     * This function also adds a quickenrolment JS ui to the page so that users can be enrolled
     * via AJAX.
     *
     * @param course_enrolment_manager $manager
     * @return enrol_user_button
     */
    public function get_manual_enrol_button(course_enrolment_manager $manager) {
        global $CFG, $PAGE;
        require_once($CFG->dirroot.'/cohort/lib.php');

        static $called = false;

        $instance = null;
        foreach ($manager->get_enrolment_instances() as $tempinstance) {
            if ($tempinstance->enrol == 'manual') {
                if ($instance === null) {
                    $instance = $tempinstance;
                }
            }
        }
        if (empty($instance)) {
            return false;
        }

        $link = $this->get_manual_enrol_link($instance);
        if (!$link) {
            return false;
        }

        $button = new enrol_user_button($link, get_string('enrolusers', 'enrol_manual'), 'get');
        $button->class .= ' enrol_manual_plugin';
        $button->type = single_button::BUTTON_PRIMARY;

        $context = context_course::instance($instance->courseid);
        $arguments = array('contextid' => $context->id);

        if (!$called) {
            $called = true;
            // Calling the following more than once will cause unexpected results.
            $PAGE->requires->js_call_amd('enrol_manual/quickenrolment', 'init', array($arguments));
        }

        return $button;
    }

    /**
     * Sync all meta course links.
     *
     * @param progress_trace $trace
     * @param int $courseid one course, empty mean all
     * @return int 0 means ok, 1 means error, 2 means plugin disabled
     */
    public function sync(progress_trace $trace, $courseid = null) {
        global $DB;

        if (!enrol_is_enabled('manual')) {
            $trace->finished();
            return 2;
        }

        // Unfortunately this may take a long time, execution can be interrupted safely here.
        core_php_time_limit::raise();
        raise_memory_limit(MEMORY_HUGE);

        $trace->output('Verifying manual enrolment expiration...');

        $params = array('now'=>time(), 'useractive'=>ENROL_USER_ACTIVE, 'courselevel'=>CONTEXT_COURSE);
        $coursesql = "";
        if ($courseid) {
            $coursesql = "AND e.courseid = :courseid";
            $params['courseid'] = $courseid;
        }

        // Deal with expired accounts.
        $action = $this->get_config('expiredaction', ENROL_EXT_REMOVED_KEEP);

        if ($action == ENROL_EXT_REMOVED_UNENROL) {
            $instances = array();
            $sql = "SELECT ue.*, e.courseid, c.id AS contextid
                      FROM {user_enrolments} ue
                      JOIN {enrol} e ON (e.id = ue.enrolid AND e.enrol = 'manual')
                      JOIN {context} c ON (c.instanceid = e.courseid AND c.contextlevel = :courselevel)
                     WHERE ue.timeend > 0 AND ue.timeend < :now
                           $coursesql";
            $rs = $DB->get_recordset_sql($sql, $params);
            foreach ($rs as $ue) {
                if (empty($instances[$ue->enrolid])) {
                    $instances[$ue->enrolid] = $DB->get_record('enrol', array('id'=>$ue->enrolid));
                }
                $instance = $instances[$ue->enrolid];
                // Always remove all manually assigned roles here, this may break enrol_self roles but we do not want hardcoded hacks here.
                role_unassign_all(array('userid'=>$ue->userid, 'contextid'=>$ue->contextid, 'component'=>'', 'itemid'=>0), true);
                $this->unenrol_user($instance, $ue->userid);
                $trace->output("unenrolling expired user $ue->userid from course $instance->courseid", 1);
            }
            $rs->close();
            unset($instances);

        } else if ($action == ENROL_EXT_REMOVED_SUSPENDNOROLES or $action == ENROL_EXT_REMOVED_SUSPEND) {
            $instances = array();
            $sql = "SELECT ue.*, e.courseid, c.id AS contextid
                      FROM {user_enrolments} ue
                      JOIN {enrol} e ON (e.id = ue.enrolid AND e.enrol = 'manual')
                      JOIN {context} c ON (c.instanceid = e.courseid AND c.contextlevel = :courselevel)
                     WHERE ue.timeend > 0 AND ue.timeend < :now
                           AND ue.status = :useractive
                           $coursesql";
            $rs = $DB->get_recordset_sql($sql, $params);
            foreach ($rs as $ue) {
                if (empty($instances[$ue->enrolid])) {
                    $instances[$ue->enrolid] = $DB->get_record('enrol', array('id'=>$ue->enrolid));
                }
                $instance = $instances[$ue->enrolid];
                if ($action == ENROL_EXT_REMOVED_SUSPENDNOROLES) {
                    // Remove all manually assigned roles here, this may break enrol_self roles but we do not want hardcoded hacks here.
                    role_unassign_all(array('userid'=>$ue->userid, 'contextid'=>$ue->contextid, 'component'=>'', 'itemid'=>0), true);
                    $this->update_user_enrol($instance, $ue->userid, ENROL_USER_SUSPENDED);
                    $trace->output("suspending expired user $ue->userid in course $instance->courseid, roles unassigned", 1);
                } else {
                    $this->update_user_enrol($instance, $ue->userid, ENROL_USER_SUSPENDED);
                    $trace->output("suspending expired user $ue->userid in course $instance->courseid, roles kept", 1);
                }
            }
            $rs->close();
            unset($instances);

        } else {
            // ENROL_EXT_REMOVED_KEEP means no changes.
        }

        $trace->output('...manual enrolment updates finished.');
        $trace->finished();

        return 0;
    }

    /**
     * Returns the user who is responsible for manual enrolments in given instance.
     *
     * Usually it is the first editing teacher - the person with "highest authority"
     * as defined by sort_by_roleassignment_authority() having 'enrol/manual:manage'
     * capability.
     *
     * @param int $instanceid enrolment instance id
     * @return stdClass user record
     */
    protected function get_enroller($instanceid) {
        global $DB;

        if ($this->lasternollerinstanceid == $instanceid and $this->lasternoller) {
            return $this->lasternoller;
        }

        $instance = $DB->get_record('enrol', array('id'=>$instanceid, 'enrol'=>$this->get_name()), '*', MUST_EXIST);
        $context = context_course::instance($instance->courseid);

        if ($users = get_enrolled_users($context, 'enrol/manual:manage')) {
            $users = sort_by_roleassignment_authority($users, $context);
            $this->lasternoller = reset($users);
            unset($users);
        } else {
            $this->lasternoller = parent::get_enroller($instanceid);
        }

        $this->lasternollerinstanceid = $instanceid;

        return $this->lasternoller;
    }

    /**
     * The manual plugin has several bulk operations that can be performed.
     * @param course_enrolment_manager $manager
     * @return array
     */
    public function get_bulk_operations(course_enrolment_manager $manager) {
        global $CFG;
        require_once($CFG->dirroot.'/enrol/manual/locallib.php');
        $context = $manager->get_context();
        $bulkoperations = array();
        if (has_capability("enrol/manual:manage", $context)) {
            $bulkoperations['editselectedusers'] = new enrol_manual_editselectedusers_operation($manager, $this);
        }
        if (has_capability("enrol/manual:unenrol", $context)) {
            $bulkoperations['deleteselectedusers'] = new enrol_manual_deleteselectedusers_operation($manager, $this);
        }
        return $bulkoperations;
    }

    /**
     * Restore instance and map settings.
     *
     * @param restore_enrolments_structure_step $step
     * @param stdClass $data
     * @param stdClass $course
     * @param int $oldid
     */
    public function restore_instance(restore_enrolments_structure_step $step, stdClass $data, $course, $oldid) {
        global $DB;
        // There is only I manual enrol instance allowed per course.
        if ($instances = $DB->get_records('enrol', array('courseid'=>$data->courseid, 'enrol'=>'manual'), 'id')) {
            $instance = reset($instances);
            $instanceid = $instance->id;
        } else {
            $instanceid = $this->add_instance($course, (array)$data);
        }
        $step->set_mapping('enrol', $oldid, $instanceid);
    }

    /**
     * Restore user enrolment.
     *
     * @param restore_enrolments_structure_step $step
     * @param stdClass $data
     * @param stdClass $instance
     * @param int $oldinstancestatus
     * @param int $userid
     */
    public function restore_user_enrolment(restore_enrolments_structure_step $step, $data, $instance, $userid, $oldinstancestatus) {
        global $DB;

        // Note: this is a bit tricky because other types may be converted to manual enrolments,
        //       and manual is restricted to one enrolment per user.

        $ue = $DB->get_record('user_enrolments', array('enrolid'=>$instance->id, 'userid'=>$userid));
        $enrol = false;
        if ($ue and $ue->status == ENROL_USER_ACTIVE) {
            // We do not want to restrict current active enrolments, let's kind of merge the times only.
            // This prevents some teacher lockouts too.
            if ($data->status == ENROL_USER_ACTIVE) {
                if ($data->timestart > $ue->timestart) {
                    $data->timestart = $ue->timestart;
                    $enrol = true;
                }

                if ($data->timeend == 0) {
                    if ($ue->timeend != 0) {
                        $enrol = true;
                    }
                } else if ($ue->timeend == 0) {
                    $data->timeend = 0;
                } else if ($data->timeend < $ue->timeend) {
                    $data->timeend = $ue->timeend;
                    $enrol = true;
                }
            }
        } else {
            if ($instance->status == ENROL_INSTANCE_ENABLED and $oldinstancestatus != ENROL_INSTANCE_ENABLED) {
                // Make sure that user enrolments are not activated accidentally,
                // we do it only here because it is not expected that enrolments are migrated to other plugins.
                $data->status = ENROL_USER_SUSPENDED;
            }
            $enrol = true;
        }

        if ($enrol) {
            $this->enrol_user($instance, $userid, null, $data->timestart, $data->timeend, $data->status);
        }
    }

    /**
     * Restore role assignment.
     *
     * @param stdClass $instance
     * @param int $roleid
     * @param int $userid
     * @param int $contextid
     */
    public function restore_role_assignment($instance, $roleid, $userid, $contextid) {
        // This is necessary only because we may migrate other types to this instance,
        // we do not use component in manual or self enrol.
        role_assign($roleid, $userid, $contextid, '', 0);
    }

    /**
     * Restore user group membership.
     * @param stdClass $instance
     * @param int $groupid
     * @param int $userid
     */
    public function restore_group_member($instance, $groupid, $userid) {
        global $CFG;
        require_once("$CFG->dirroot/group/lib.php");

        // This might be called when forcing restore as manual enrolments.

        groups_add_member($groupid, $userid);
    }

    /**
     * Is it possible to delete enrol instance via standard UI?
     *
     * @param object $instance
     * @return bool
     */
    public function can_delete_instance($instance) {
        $context = context_course::instance($instance->courseid);
        return has_capability('enrol/manual:config', $context);
    }

    /**
     * Is it possible to hide/show enrol instance via standard UI?
     *
     * @param stdClass $instance
     * @return bool
     */
    public function can_hide_show_instance($instance) {
        $context = context_course::instance($instance->courseid);
        return has_capability('enrol/manual:config', $context);
    }

    /**
     * Enrol all not enrolled cohort members into course via enrol instance.
     *
     * @param stdClass $instance
     * @param int $cohortid
     * @param int $roleid optional role id
     * @param int $timestart 0 means unknown
     * @param int $timeend 0 means forever
     * @param int $status default to ENROL_USER_ACTIVE for new enrolments, no change by default in updates
     * @param bool $recovergrades restore grade history
     * @return int The number of enrolled cohort users
     */
    public function enrol_cohort(stdClass $instance, $cohortid, $roleid = null, $timestart = 0, $timeend = 0, $status = null, $recovergrades = null) {
        global $DB;
        $context = context_course::instance($instance->courseid);
        list($esql, $params) = get_enrolled_sql($context);
        $sql = "SELECT cm.userid FROM {cohort_members} cm LEFT JOIN ($esql) u ON u.id = cm.userid ".
            "WHERE cm.cohortid = :cohortid AND u.id IS NULL";
        $params['cohortid'] = $cohortid;
        $members = $DB->get_fieldset_sql($sql, $params);
        foreach ($members as $userid) {
            $this->enrol_user($instance, $userid, $roleid, $timestart, $timeend, $status, $recovergrades);
        }
        return count($members);
    }

    /**
     * We are a good plugin and don't invent our own UI/validation code path.
     *
     * @return boolean
     */
    public function use_standard_editing_ui() {
        return true;
    }

    /**
     * Return an array of valid options for the status.
     *
     * @return array
     */
    protected function get_status_options() {
        $options = array(ENROL_INSTANCE_ENABLED  => get_string('yes'),
                         ENROL_INSTANCE_DISABLED => get_string('no'));
        return $options;
    }

    /**
     * Return an array of valid options for the roleid.
     *
     * @param stdClass $instance
     * @param context $context
     * @return array
     */
    protected function get_roleid_options($instance, $context) {
        if ($instance->id) {
            $roles = get_default_enrol_roles($context, $instance->roleid);
        } else {
            $roles = get_default_enrol_roles($context, $this->get_config('roleid'));
        }
        return $roles;
    }

    /**
     * Return an array of valid options for the expirynotify.
     *
     * @return array
     */
    protected function get_expirynotify_options() {
        $options = array(
            0 => get_string('no'),
            1 => get_string('expirynotifyenroller', 'core_enrol'),
            2 => get_string('expirynotifyall', 'core_enrol')
        );
        return $options;
    }

    /**
     * Add elements to the edit instance form.
     *
     * @param stdClass $instance
     * @param MoodleQuickForm $mform
     * @param context $context
     * @return bool
     */
    public function edit_instance_form($instance, MoodleQuickForm $mform, $context) {

        // Main fields.
        if (has_capability('enrol/manual:config', $context)) {
            $options = $this->get_status_options();
            $mform->addElement('select', 'status', get_string('status', 'enrol_manual'), $options);
            $mform->addHelpButton('status', 'status', 'enrol_manual');
            $mform->setDefault('status', $this->get_config('status'));

            $roles = $this->get_roleid_options($instance, $context);
            $mform->addElement('select', 'roleid', get_string('defaultrole', 'role'), $roles);
            $mform->setDefault('roleid', $this->get_config('roleid'));

            $options = ['optional' => true, 'defaultunit' => 86400];
            $mform->addElement('duration', 'enrolperiod', get_string('defaultperiod', 'enrol_manual'), $options);
            $mform->setDefault('enrolperiod', $this->get_config('enrolperiod'));
            $mform->addHelpButton('enrolperiod', 'defaultperiod', 'enrol_manual');

            $options = $this->get_expirynotify_options();
            $mform->addElement('select', 'expirynotify', get_string('expirynotify', 'core_enrol'), $options);
            $mform->addHelpButton('expirynotify', 'expirynotify', 'core_enrol');

            $options = ['optional' => false, 'defaultunit' => 86400];
            $mform->addElement('duration', 'expirythreshold', get_string('expirythreshold', 'core_enrol'), $options);
            $mform->addHelpButton('expirythreshold', 'expirythreshold', 'core_enrol');
            $mform->disabledIf('expirythreshold', 'expirynotify', 'eq', 0);
        }

        // Course welcome message.
        if (has_any_capability(['enrol/manual:config', 'moodle/course:editcoursewelcomemessage'], $context)) {
            $mform->addElement(
                'select',
                'customint1',
                get_string(
                    identifier: 'sendcoursewelcomemessage',
                    component: 'core_enrol',
                ),
                enrol_send_welcome_email_options(),
            );
            $mform->addHelpButton(
                elementname: 'customint1',
                identifier: 'sendcoursewelcomemessage',
                component: 'core_enrol',
            );

            $options = [
                'cols' => '60',
                'rows' => '8',
            ];
            $mform->addElement(
                'textarea',
                'customtext1',
                get_string(
                    identifier: 'customwelcomemessage',
                    component: 'core_enrol',
                ),
                $options,
            );
            $mform->setDefault('customtext1', get_string('customwelcomemessageplaceholder', 'core_enrol'));
            $mform->hideIf(
                elementname: 'customtext1',
                dependenton: 'customint1',
                condition: 'eq',
                value: ENROL_DO_NOT_SEND_EMAIL,
            );

            // Static form elements cannot be hidden by hideIf() so we need to add a dummy group.
            // See: https://tracker.moodle.org/browse/MDL-66251.
            $group[] = $mform->createElement(
                'static',
                'customwelcomemessage_extra_help',
                null,
                get_string(
                    identifier: 'customwelcomemessage_help',
                    component: 'core_enrol',
                ),
            );
            $mform->addGroup($group, 'group_customwelcomemessage_extra_help', '', ' ', false);
            $mform->hideIf(
                elementname: 'group_customwelcomemessage_extra_help',
                dependenton: 'customint1',
                condition: 'eq',
                value: ENROL_DO_NOT_SEND_EMAIL,
            );
        }

        // Enrolment changes warning.
        if (has_capability('enrol/manual:config', $context) && enrol_accessing_via_instance($instance)) {
            $warntext = get_string('instanceeditselfwarningtext', 'core_enrol');
            $mform->addElement('static', 'selfwarn', get_string('instanceeditselfwarning', 'core_enrol'), $warntext);
        }
    }

    /**
     * Perform custom validation of the data used to edit the instance.
     *
     * @param array $data array of ("fieldname"=>value) of submitted data
     * @param array $files array of uploaded files "element_name"=>tmp_file_path
     * @param object $instance The instance loaded from the DB
     * @param context $context The context of the instance we are editing
     * @return array of "element_name"=>"error_description" if there are errors,
     *         or an empty array if everything is OK.
     * @return void
     */
    public function edit_instance_validation($data, $files, $instance, $context) {
        $errors = array();

        // This method is used when configuring the enrolment method, and when only updating the welcome message.
        // The 'expirynotify' key won't be set when updating the welcome message.
        if (isset($data['expirynotify']) && $data['expirynotify'] > 0 && $data['expirythreshold'] < DAYSECS) {
            $errors['expirythreshold'] = get_string('errorthresholdlow', 'core_enrol');
        }

        $validstatus = array_keys($this->get_status_options());
        $validroles = array_keys($this->get_roleid_options($instance, $context));
        $validexpirynotify = array_keys($this->get_expirynotify_options());

        $tovalidate = array(
            'status' => $validstatus,
            'roleid' => $validroles,
            'enrolperiod' => PARAM_INT,
            'expirynotify' => $validexpirynotify,
            'expirythreshold' => PARAM_INT
        );

        $typeerrors = $this->validate_param_types($data, $tovalidate);
        $errors = array_merge($errors, $typeerrors);

        return $errors;
    }

    /**
     * Check if enrolment plugin is supported in csv course upload.
     *
     * @return bool
     */
    public function is_csv_upload_supported(): bool {
        return true;
    }

    /**
     * Finds matching instances for a given course.
     *
     * @param array $enrolmentdata enrolment data.
     * @param int $courseid Course ID.
     * @return stdClass|null Matching instance
     */
    public function find_instance(array $enrolmentdata, int $courseid): ?stdClass {

        $instances = enrol_get_instances($courseid, false);
        $instance = null;
        foreach ($instances as $i) {
            if ($i->enrol == 'manual') {
                // There can be only one manual enrol instance so find first available.
                $instance = $i;
                break;
            }
        }
        return $instance;
    }

    /**
     * Fill custom fields data for a given enrolment plugin.
     *
     * @param array $enrolmentdata enrolment data.
     * @param int $courseid Course ID.
     * @return array Updated enrolment data with custom fields info.
     */
    public function fill_enrol_custom_fields(array $enrolmentdata, int $courseid): array {
        return $enrolmentdata + [
            'expirynotify' => 0,
            'expirythreshold' => 0,
        ];
    }

    /**
     * Returns defaults for new instances.
     *
     * @return array
     */
    public function get_instance_defaults(): array {
        $fields['customint1'] = $this->get_config('sendcoursewelcomemessage');
        return $fields;
    }
}

/**
 * Serve the manual enrol users form as a fragment.
 *
 * @param array $args List of named arguments for the fragment loader.
 * @return string
 */
function enrol_manual_output_fragment_enrol_users_form($args) {
    $args = (object) $args;
    $context = $args->context;
    $o = '';

    require_capability('enrol/manual:enrol', $context);
    $mform = new enrol_manual_enrol_users_form(null, $args);

    ob_start();
    $mform->display();
    $o .= ob_get_contents();
    ob_end_clean();

    return $o;
}
