/**
 * Save page content
 * @param object $wikipage
 * @param string $newcontent
 * @param int $userid
 */
function wiki_save_page($wikipage, $newcontent, $userid)
{
    global $DB;
    $wiki = wiki_get_wiki_from_pageid($wikipage->id);
    $cm = get_coursemodule_from_instance('wiki', $wiki->id);
    $context = get_context_instance(CONTEXT_MODULE, $cm->id);
    if (has_capability('mod/wiki:editpage', $context)) {
        $version = wiki_get_current_version($wikipage->id);
        $version->content = $newcontent;
        $version->userid = $userid;
        $version->version++;
        $version->timecreated = time();
        $versionid = $DB->insert_record('wiki_versions', $version);
        $wikipage->timemodified = $version->timecreated;
        $wikipage->userid = $userid;
        $return = wiki_refresh_cachedcontent($wikipage, $newcontent);
        return $return;
    } else {
        return false;
    }
}

/**
 * Validate comment parameter before perform other comments actions
 *
 * @param stdClass $comment_param {
 *              context  => context the context object
 *              courseid => int course id
 *              cm       => stdClass course module object
 *              commentarea => string comment area
 *              itemid      => int itemid
 * }
 *
 * @package  mod_wiki
 * @category comment
 *
 * @return boolean
 */
function wiki_comment_validate($comment_param)
{
    global $DB, $CFG;
    require_once $CFG->dirroot . '/mod/wiki/locallib.php';
    // validate comment area
    if ($comment_param->commentarea != 'wiki_page') {
        throw new comment_exception('invalidcommentarea');
    }
    // validate itemid
    if (!($record = $DB->get_record('wiki_pages', array('id' => $comment_param->itemid)))) {
        throw new comment_exception('invalidcommentitemid');
    }
    if (!($subwiki = wiki_get_subwiki($record->subwikiid))) {
        throw new comment_exception('invalidsubwikiid');
    }
    if (!($wiki = wiki_get_wiki_from_pageid($comment_param->itemid))) {
        throw new comment_exception('invalidid', 'data');
    }
    if (!($course = $DB->get_record('course', array('id' => $wiki->course)))) {
        throw new comment_exception('coursemisconf');
    }
    if (!($cm = get_coursemodule_from_instance('wiki', $wiki->id, $course->id))) {
        throw new comment_exception('invalidcoursemodule');
    }
    $context = context_module::instance($cm->id);
    // group access
    if ($subwiki->groupid) {
        $groupmode = groups_get_activity_groupmode($cm, $course);
        if ($groupmode == SEPARATEGROUPS and !has_capability('moodle/site:accessallgroups', $context)) {
            if (!groups_is_member($subwiki->groupid)) {
                throw new comment_exception('notmemberofgroup');
            }
        }
    }
    // validate context id
    if ($context->id != $comment_param->context->id) {
        throw new comment_exception('invalidcontext');
    }
    // validation for comment deletion
    if (!empty($comment_param->commentid)) {
        if ($comment = $DB->get_record('comments', array('id' => $comment_param->commentid))) {
            if ($comment->commentarea != 'wiki_page') {
                throw new comment_exception('invalidcommentarea');
            }
            if ($comment->contextid != $context->id) {
                throw new comment_exception('invalidcontext');
            }
            if ($comment->itemid != $comment_param->itemid) {
                throw new comment_exception('invalidcommentitemid');
            }
        } else {
            throw new comment_exception('invalidcommentid');
        }
    }
    return true;
}

/**
 * Delete specificed versions of a page or versions created by users
 * if version is 0 then it will remove all versions of the page
 *
 * @param array $deleteversions delete versions for a page
 * @param context_module $context module context
 */
function wiki_delete_page_versions($deleteversions, $context = null)
{
    global $DB;
    /// delete page-versions
    foreach ($deleteversions as $id => $versions) {
        $params = array('pageid' => $id);
        if (is_null($context)) {
            $wiki = wiki_get_wiki_from_pageid($id);
            $cm = get_coursemodule_from_instance('wiki', $wiki->id);
            $context = context_module::instance($cm->id);
        }
        // Delete all versions, if version specified is 0.
        if (in_array(0, $versions)) {
            $oldversions = $DB->get_records('wiki_versions', $params);
            $DB->delete_records('wiki_versions', $params, IGNORE_MISSING);
        } else {
            list($insql, $param) = $DB->get_in_or_equal($versions);
            $insql .= ' AND pageid = ?';
            array_push($param, $params['pageid']);
            $oldversions = $DB->get_recordset_select('wiki_versions', 'version ' . $insql, $param);
            $DB->delete_records_select('wiki_versions', 'version ' . $insql, $param);
        }
        foreach ($oldversions as $version) {
            // Trigger page version deleted event.
            $event = \mod_wiki\event\page_version_deleted::create(array('context' => $context, 'objectid' => $version->id, 'other' => array('pageid' => $id)));
            $event->add_record_snapshot('wiki_versions', $version);
            $event->trigger();
        }
    }
}

 /**
  * Edit a page contents.
  *
  * @param int $pageid The page ID.
  * @param string $content Page contents.
  * @param int $section Section to be edited.
  * @return array of warnings and page data.
  * @since Moodle 3.1
  */
 public static function edit_page($pageid, $content, $section = null)
 {
     global $USER;
     $params = self::validate_parameters(self::edit_page_parameters(), array('pageid' => $pageid, 'content' => $content, 'section' => $section));
     $warnings = array();
     // Get wiki page.
     if (!($page = wiki_get_page($params['pageid']))) {
         throw new moodle_exception('incorrectpageid', 'wiki');
     }
     // Get wiki instance.
     if (!($wiki = wiki_get_wiki_from_pageid($params['pageid']))) {
         throw new moodle_exception('incorrectwikiid', 'wiki');
     }
     // Get subwiki instance.
     if (!($subwiki = wiki_get_subwiki($page->subwikiid))) {
         throw new moodle_exception('incorrectsubwikiid', 'wiki');
     }
     // Permission validation.
     $cm = get_coursemodule_from_instance('wiki', $wiki->id, $wiki->course);
     $context = context_module::instance($cm->id);
     self::validate_context($context);
     if (!wiki_user_can_edit($subwiki)) {
         throw new moodle_exception('cannoteditpage', 'wiki');
     }
     if (wiki_is_page_section_locked($page->id, $USER->id, $params['section'])) {
         throw new moodle_exception('pageislocked', 'wiki');
     }
     // Save content.
     if (!is_null($params['section'])) {
         $version = wiki_get_current_version($page->id);
         $content = wiki_parser_proxy::get_section($version->content, $version->contentformat, $params['section'], false);
         if (!$content) {
             throw new moodle_exception('invalidsection', 'wiki');
         }
         $save = wiki_save_section($page, $params['section'], $params['content'], $USER->id);
     } else {
         $save = wiki_save_page($page, $params['content'], $USER->id);
     }
     wiki_delete_locks($page->id, $USER->id, $params['section']);
     if (!$save) {
         throw new moodle_exception('savingerror', 'wiki');
     }
     $result = array();
     $result['pageid'] = $page->id;
     $result['warnings'] = $warnings;
     return $result;
 }

 /**
  * Trigger the page viewed event and update the module completion status.
  *
  * @param int $pageid The page ID.
  * @return array of warnings and status result.
  * @since Moodle 3.1
  * @throws moodle_exception if page is not valid.
  */
 public static function view_page($pageid)
 {
     $params = self::validate_parameters(self::view_page_parameters(), array('pageid' => $pageid));
     $warnings = array();
     // Get wiki page.
     if (!($page = wiki_get_page($params['pageid']))) {
         throw new moodle_exception('incorrectpageid', 'wiki');
     }
     // Get wiki instance.
     if (!($wiki = wiki_get_wiki_from_pageid($params['pageid']))) {
         throw new moodle_exception('incorrectwikiid', 'wiki');
     }
     // Permission validation.
     list($course, $cm) = get_course_and_cm_from_instance($wiki, 'wiki');
     $context = context_module::instance($cm->id);
     self::validate_context($context);
     // Check if user can view this wiki.
     if (!($subwiki = wiki_get_subwiki($page->subwikiid))) {
         throw new moodle_exception('incorrectsubwikiid', 'wiki');
     }
     if (!wiki_user_can_view($subwiki, $wiki)) {
         throw new moodle_exception('cannotviewpage', 'wiki');
     }
     // Trigger page_viewed event and completion.
     wiki_page_view($wiki, $page, $course, $cm, $context);
     $result = array();
     $result['status'] = true;
     $result['warnings'] = $warnings;
     return $result;
 }

 /**
  * Get a page contents.
  *
  * @param int $pageid The page ID.
  * @return array of warnings and page data.
  * @since Moodle 3.1
  */
 public static function get_page_contents($pageid)
 {
     $params = self::validate_parameters(self::get_page_contents_parameters(), array('pageid' => $pageid));
     $warnings = array();
     // Get wiki page.
     if (!($page = wiki_get_page($params['pageid']))) {
         throw new moodle_exception('incorrectpageid', 'wiki');
     }
     // Get wiki instance.
     if (!($wiki = wiki_get_wiki_from_pageid($params['pageid']))) {
         throw new moodle_exception('incorrectwikiid', 'wiki');
     }
     // Permission validation.
     $cm = get_coursemodule_from_instance('wiki', $wiki->id, $wiki->course);
     $context = context_module::instance($cm->id);
     self::validate_context($context);
     // Check if user can view this wiki.
     if (!($subwiki = wiki_get_subwiki($page->subwikiid))) {
         throw new moodle_exception('incorrectsubwikiid', 'wiki');
     }
     if (!wiki_user_can_view($subwiki, $wiki)) {
         throw new moodle_exception('cannotviewpage', 'wiki');
     }
     $returnedpage = array();
     $returnedpage['id'] = $page->id;
     $returnedpage['wikiid'] = $wiki->id;
     $returnedpage['subwikiid'] = $page->subwikiid;
     $returnedpage['groupid'] = $subwiki->groupid;
     $returnedpage['userid'] = $subwiki->userid;
     $returnedpage['title'] = $page->title;
     // Refresh page cached content if needed.
     if ($page->timerendered + WIKI_REFRESH_CACHE_TIME < time()) {
         if ($content = wiki_refresh_cachedcontent($page)) {
             $page = $content['page'];
         }
     }
     list($returnedpage['cachedcontent'], $returnedpage['contentformat']) = external_format_text($page->cachedcontent, FORMAT_HTML, $context->id, 'mod_wiki', 'attachments', $subwiki->id);
     $returnedpage['caneditpage'] = wiki_user_can_edit($subwiki);
     $result = array();
     $result['page'] = $returnedpage;
     $result['warnings'] = $warnings;
     return $result;
 }