/**
 * @global object
 * @param object $forum
 * @param object $currentgroup
 * @param int $unused
 * @param object $cm
 * @param object $context
 * @return bool
 */
function forum_user_can_post_discussion($forum, $currentgroup=null, $unused=-1, $cm=NULL, $context=NULL) {
// $forum is an object
    global $USER;

    // shortcut - guest and not-logged-in users can not post
    if (isguestuser() or !isloggedin()) {
        return false;
    }

    if (!$cm) {
        debugging('missing cm', DEBUG_DEVELOPER);
        if (!$cm = get_coursemodule_from_instance('forum', $forum->id, $forum->course)) {
            print_error('invalidcoursemodule');
        }
    }

    if (!$context) {
        $context = context_module::instance($cm->id);
    }

    if ($currentgroup === null) {
        $currentgroup = groups_get_activity_group($cm);
    }

    $groupmode = groups_get_activity_groupmode($cm);

    if ($forum->type == 'news') {
        $capname = 'mod/forum:addnews';
    } else if ($forum->type == 'qanda') {
        $capname = 'mod/forum:addquestion';
    } else {
        $capname = 'mod/forum:startdiscussion';
    }

    if (!has_capability($capname, $context)) {
        return false;
    }

    if ($forum->type == 'single') {
        return false;
    }

    if ($forum->type == 'eachuser') {
        if (forum_user_has_posted_discussion($forum->id, $USER->id)) {
            return false;
        }
    }

    if (!$groupmode or has_capability('moodle/site:accessallgroups', $context)) {
        return true;
    }

    if ($currentgroup) {
        return groups_is_member($currentgroup);
    } else {
        // no group membership and no accessallgroups means no new discussions
        // reverted to 1.7 behaviour in 1.9+,  buggy in 1.8.0-1.9.0
        return false;
    }
}

 /**
  * Test forum_user_has_posted_discussion with multiple groups.
  */
 public function test_forum_user_has_posted_discussion_multiple_groups()
 {
     global $CFG;
     $this->resetAfterTest(true);
     $course = self::getDataGenerator()->create_course();
     $author = self::getDataGenerator()->create_user();
     $this->getDataGenerator()->enrol_user($author->id, $course->id);
     $group1 = $this->getDataGenerator()->create_group(array('courseid' => $course->id));
     $group2 = $this->getDataGenerator()->create_group(array('courseid' => $course->id));
     groups_add_member($group1->id, $author->id);
     groups_add_member($group2->id, $author->id);
     $forum = self::getDataGenerator()->create_module('forum', (object) ['course' => $course->id], ['groupmode' => SEPARATEGROUPS]);
     self::setUser($author);
     // The user has not posted in either group.
     $this->assertFalse(forum_user_has_posted_discussion($forum->id, $author->id));
     $this->assertFalse(forum_user_has_posted_discussion($forum->id, $author->id, $group1->id));
     $this->assertFalse(forum_user_has_posted_discussion($forum->id, $author->id, $group2->id));
     // Post in one group.
     $record = new stdClass();
     $record->course = $course->id;
     $record->userid = $author->id;
     $record->forum = $forum->id;
     $record->groupid = $group1->id;
     $discussion = self::getDataGenerator()->get_plugin_generator('mod_forum')->create_discussion($record);
     // The author has now posted in one group, but the other user has not.
     $this->assertTrue(forum_user_has_posted_discussion($forum->id, $author->id));
     $this->assertTrue(forum_user_has_posted_discussion($forum->id, $author->id, $group1->id));
     $this->assertFalse(forum_user_has_posted_discussion($forum->id, $author->id, $group2->id));
     // Post in the other group.
     $record = new stdClass();
     $record->course = $course->id;
     $record->userid = $author->id;
     $record->forum = $forum->id;
     $record->groupid = $group2->id;
     $discussion = self::getDataGenerator()->get_plugin_generator('mod_forum')->create_discussion($record);
     // The author has now posted in one group, but the other user has not.
     $this->assertTrue(forum_user_has_posted_discussion($forum->id, $author->id));
     $this->assertTrue(forum_user_has_posted_discussion($forum->id, $author->id, $group1->id));
     $this->assertTrue(forum_user_has_posted_discussion($forum->id, $author->id, $group2->id));
 }