print_error('invalidcourseid');
}
if (!($context = get_context_instance(CONTEXT_COURSE, $course->id))) {
    print_error('invalidcontext');
}
require_login($course->id);
if ($course->metacourse) {
    print_error('cantunenrollfrommetacourse', '', $CFG->wwwroot . '/course/view.php?id=' . $course->id);
}
if ($userid) {
    // Unenrolling someone else
    require_capability('moodle/role:assign', $context, NULL, false);
    $roles = get_user_roles($context, $userid, false);
    // verify user may unassign all roles at course context
    foreach ($roles as $role) {
        if (!user_can_assign($context, $role->roleid)) {
            print_error('cannotunassignrolefrom', '', '', $role->roleid);
        }
    }
} else {
    // Unenrol yourself
    require_capability('moodle/role:unassignself', $context, NULL, false);
}
if (!empty($USER->access['rsw'][$context->path])) {
    print_error('cantunenrollinthisrole', '', $CFG->wwwroot . '/course/view.php?id=' . $course->id);
}
if ($confirm and confirm_sesskey()) {
    if ($userid) {
        if (!role_unassign(0, $userid, 0, $context->id)) {
            print_error("unenrolerror");
        }

}
if ($roleid > 0) {
    $a = new stdClass();
    $a->number = $totalcount;
    $a->role = $rolenames[$roleid];
    $heading = format_string(get_string('xuserswiththerole', 'role', $a));
    if ($currentgroup and $group) {
        $a->group = $group->name;
        $heading .= ' ' . format_string(get_string('ingroup', 'role', $a));
    }
    if ($accesssince) {
        $a->timeperiod = $timeoptions[$accesssince];
        $heading .= ' ' . format_string(get_string('inactiveformorethan', 'role', $a));
    }
    $heading .= ": {$a->number}";
    if (user_can_assign($context, $roleid)) {
        $headingurl = new moodle_url($CFG->wwwroot . '/' . $CFG->admin . '/roles/assign.php', array('roleid' => $roleid, 'contextid' => $context->id));
        $heading .= $OUTPUT->action_icon($headingurl, new pix_icon('t/edit', get_string('edit')));
    }
    echo $OUTPUT->heading($heading, 3);
} else {
    if ($course->id != SITEID && has_capability('moodle/course:enrolreview', $context)) {
        $editlink = $OUTPUT->action_icon(new moodle_url('/enrol/users.php', array('id' => $course->id)), new pix_icon('t/edit', get_string('edit')));
    } else {
        $editlink = '';
    }
    if ($course->id == SITEID and $roleid < 0) {
        $strallparticipants = get_string('allsiteusers', 'role');
    } else {
        $strallparticipants = get_string('allparticipants');
    }

 /**
  * Test returning of assignable roles in context.
  */
 public function test_get_assignable_roles()
 {
     global $DB;
     $this->resetAfterTest();
     $course = $this->getDataGenerator()->create_course();
     $coursecontext = context_course::instance($course->id);
     $teacherrole = $DB->get_record('role', array('shortname' => 'editingteacher'), '*', MUST_EXIST);
     $teacher = $this->getDataGenerator()->create_user();
     role_assign($teacherrole->id, $teacher->id, $coursecontext);
     $teacherename = (object) array('roleid' => $teacherrole->id, 'name' => 'Učitel', 'contextid' => $coursecontext->id);
     $DB->insert_record('role_names', $teacherename);
     $studentrole = $DB->get_record('role', array('shortname' => 'student'), '*', MUST_EXIST);
     $student = $this->getDataGenerator()->create_user();
     role_assign($studentrole->id, $student->id, $coursecontext);
     $contexts = $DB->get_records('context');
     $users = $DB->get_records('user');
     $allroles = $DB->get_records('role');
     // Evaluate all results for all users in all contexts.
     foreach ($users as $user) {
         $this->setUser($user);
         foreach ($contexts as $contextid => $unused) {
             $context = context_helper::instance_by_id($contextid);
             $roles = get_assignable_roles($context, ROLENAME_SHORT);
             foreach ($allroles as $roleid => $role) {
                 if (isset($roles[$roleid])) {
                     if (is_siteadmin()) {
                         $this->assertTrue($DB->record_exists('role_context_levels', array('contextlevel' => $context->contextlevel, 'roleid' => $roleid)));
                     } else {
                         $this->assertTrue(user_can_assign($context, $roleid), "u:{$user->id} r:{$roleid}");
                     }
                     $this->assertEquals($role->shortname, $roles[$roleid]);
                 } else {
                     $allowed = $DB->record_exists('role_context_levels', array('contextlevel' => $context->contextlevel, 'roleid' => $roleid));
                     if (is_siteadmin()) {
                         $this->assertFalse($allowed);
                     } else {
                         $this->assertFalse($allowed and user_can_assign($context, $roleid), "u:{$user->id}, r:{$allroles[$roleid]->name}, c:{$context->contextlevel}");
                     }
                 }
             }
         }
     }
     // Not-logged-in user.
     $this->setUser(0);
     foreach ($contexts as $contextid => $unused) {
         $context = context_helper::instance_by_id($contextid);
         $roles = get_assignable_roles($context, ROLENAME_SHORT);
         $this->assertSame(array(), $roles);
     }
     // Test current user.
     $this->setUser(0);
     $admin = $DB->get_record('user', array('username' => 'admin'), '*', MUST_EXIST);
     $roles1 = get_assignable_roles($coursecontext, ROLENAME_SHORT, false, $admin);
     $roles2 = get_assignable_roles($coursecontext, ROLENAME_SHORT, false, $admin->id);
     $this->setAdminUser();
     $roles3 = get_assignable_roles($coursecontext, ROLENAME_SHORT);
     $this->assertSame($roles1, $roles3);
     $this->assertSame($roles2, $roles3);
     // Test parameter defaults.
     $this->setAdminUser();
     $roles1 = get_assignable_roles($coursecontext);
     $roles2 = get_assignable_roles($coursecontext, ROLENAME_ALIAS, false, $admin);
     $this->assertEquals($roles2, $roles1);
     // Verify returned names - let's allow all roles everywhere to simplify this a bit.
     $alllevels = context_helper::get_all_levels();
     $alllevels = array_keys($alllevels);
     foreach ($allroles as $roleid => $role) {
         set_role_contextlevels($roleid, $alllevels);
     }
     $alltypes = array(ROLENAME_ALIAS, ROLENAME_ALIAS_RAW, ROLENAME_BOTH, ROLENAME_ORIGINAL, ROLENAME_ORIGINALANDSHORT, ROLENAME_SHORT);
     foreach ($alltypes as $type) {
         $rolenames = role_fix_names($allroles, $coursecontext, $type);
         $roles = get_assignable_roles($coursecontext, $type, false, $admin);
         foreach ($roles as $roleid => $rolename) {
             $this->assertSame($rolenames[$roleid]->localname, $rolename);
         }
     }
     // Verify counts.
     $alltypes = array(ROLENAME_ALIAS, ROLENAME_ALIAS_RAW, ROLENAME_BOTH, ROLENAME_ORIGINAL, ROLENAME_ORIGINALANDSHORT, ROLENAME_SHORT);
     foreach ($alltypes as $type) {
         $roles = get_assignable_roles($coursecontext, $type, false, $admin);
         list($rolenames, $rolecounts, $nameswithcounts) = get_assignable_roles($coursecontext, $type, true, $admin);
         $this->assertEquals($roles, $rolenames);
         foreach ($rolenames as $roleid => $name) {
             if ($roleid == $teacherrole->id or $roleid == $studentrole->id) {
                 $this->assertEquals(1, $rolecounts[$roleid]);
             } else {
                 $this->assertEquals(0, $rolecounts[$roleid]);
             }
             $this->assertSame("{$name} ({$rolecounts[$roleid]})", $nameswithcounts[$roleid]);
         }
     }
 }

// to extend enrolments current user needs to be able to do role assignments
require_capability('moodle/role:assign', $context);
$today = time();
$today = make_timestamp(date('Y', $today), date('m', $today), date('d', $today), 0, 0, 0);
if (count($users) > 0 and $form = data_submitted() and confirm_sesskey()) {
    if (count($form->userid) != count($form->extendperiod) || count($form->userid) != count($form->extendbase)) {
        print_error('invalidformdata', '', $CFG->wwwroot . '/user/index.php?id=' . $id);
    }
    foreach ($form->userid as $k => $v) {
        // find all roles this student have in this course
        if ($students = $DB->get_records_sql("SELECT ra.id, ra.roleid, ra.timestart, ra.timeend\n                                                FROM {role_assignments} ra\n                                               WHERE userid = ?\n                                                     AND contextid = ?", array($v, $context->id))) {
            // enrol these users again, with time extension
            // not that this is not necessarily a student role
            foreach ($students as $student) {
                // only extend if the user can make role assignments on this role
                if (user_can_assign($context, $student->roleid)) {
                    switch ($form->extendperiod[$k]) {
                        case 0:
                            // No change
                            break;
                        case -1:
                            // unlimited
                            $student->timeend = 0;
                            break;
                        default:
                            // extend
                            switch ($form->extendbase[$k]) {
                                case 0:
                                    // course start date
                                    $student->timeend = $course->startdate + $form->extendperiod[$k];
                                    break;

 protected function process_unassignment($data)
 {
     $context = $this->get_context();
     if (!user_can_assign($context, $data->role)) {
         print_error('nopermissions', 'error');
     }
     foreach ($data->_selection as $user) {
         role_unassign($data->role, cm_get_moodleuserid($user), 0, $context->id);
     }
     $tmppage = $this->get_basepage();
     redirect($tmppage->get_url(), get_string('users_removed_from_role', 'block_curr_admin', count($data->_selection)));
 }

/**
 * Gets a list of roles that this user can assign in this context
 * @param object $context
 * @return array
 */
function get_assignable_roles($context, $field = "name")
{
    $options = array();
    if ($roles = get_all_roles()) {
        foreach ($roles as $role) {
            if (user_can_assign($context, $role->id)) {
                $options[$role->id] = strip_tags(format_string($role->{$field}, true));
            }
        }
    }
    return $options;
}

             notify(get_string('coursegroupunknown', 'error', $addgroup[$i]));
         } else {
             if ($gid = groups_get_group_by_name($course[$i]->id, $addgroup[$i])) {
                 $groupid[$i] = $gid;
             } else {
                 notify(get_string('groupunknown', 'error', $addgroup[$i]));
             }
         }
     }
 }
 for ($i = 0; $i < 5; $i++) {
     /// Enrol into courses if necessary
     if ($course[$i]) {
         if (isset($addrole[$i])) {
             $coursecontext = get_context_instance(CONTEXT_COURSE, $course[$i]->id);
             if (!user_can_assign($coursecontext, $addrole[$i])) {
                 notify('--> Can not assign role in course');
                 //TODO: localize
             }
             $ret = role_assign($addrole[$i], $user->id, 0, $coursecontext->id);
         } else {
             if (isset($addtype[$i])) {
                 switch ($addtype[$i]) {
                     case 2:
                         // teacher
                         $ret = add_teacher($user->id, $course[$i]->id, 1);
                         break;
                     case 3:
                         // non-editing teacher
                         $ret = add_teacher($user->id, $course[$i]->id, 0);
                         break;