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   1  <?php
   2  // This file is part of Moodle - http://moodle.org/
   3  //
   4  // Moodle is free software: you can redistribute it and/or modify
   5  // it under the terms of the GNU General Public License as published by
   6  // the Free Software Foundation, either version 3 of the License, or
   7  // (at your option) any later version.
   8  //
   9  // Moodle is distributed in the hope that it will be useful,
  10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  // GNU General Public License for more details.
  13  //
  14  // You should have received a copy of the GNU General Public License
  15  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16  
  17  /**
  18   * Group visibility methods
  19   *
  20   * @package   core_group
  21   * @copyright 2022 onwards Catalyst IT EU {@link https://catalyst-eu.net}
  22   * @author    Mark Johnson <mark.johnson@catalyst-eu.net>
  23   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24   */
  25  
  26  namespace core_group;
  27  
  28  /**
  29   * Group visibility methods.
  30   */
  31  class visibility {
  32  
  33      /**
  34       * Store the number groups with visibility other than ALL on the course.
  35       *
  36       * @param int $courseid Course ID to update the cache for.
  37       * @param \cache|null $cache Existing cache instance. If null, once will be created.
  38       * @return void
  39       * @throws \dml_exception
  40       */
  41      public static function update_hiddengroups_cache(int $courseid, ?\cache $cache = null): void {
  42          global $DB;
  43          if (!$cache) {
  44              $cache = \cache::make('core', 'coursehiddengroups');
  45          }
  46          $hiddengroups = $DB->count_records_select('groups', 'courseid = ? AND visibility != ?',
  47                  [$courseid, GROUPS_VISIBILITY_ALL]);
  48          $cache->set($courseid, $hiddengroups);
  49      }
  50  
  51      /**
  52       * Return whether a course currently had hidden groups.
  53       *
  54       * This can be used as a shortcut to decide whether visibility restrictions need to be applied. If this returns false,
  55       * we may be able to use cached data, or do a much simpler query.
  56       *
  57       * @param int $courseid
  58       * @return bool
  59       * @throws \coding_exception
  60       * @throws \dml_exception
  61       */
  62      public static function course_has_hidden_groups(int $courseid): bool {
  63          $cache = \cache::make('core', 'coursehiddengroups');
  64          $hiddengroups = $cache->get($courseid);
  65          if ($hiddengroups === false) {
  66              self::update_hiddengroups_cache($courseid, $cache);
  67              $cache->get($courseid);
  68          }
  69          return $hiddengroups > 0;
  70      }
  71  
  72      /**
  73       * Can the current user view all the groups on the course?
  74       *
  75       * Returns true if there are no groups on the course with visibility != ALL,
  76       * or if the user has viewhiddengroups.
  77       *
  78       * This is useful for deciding whether we need to perform additional visibility checkes
  79       * such as the sql_* methods of this class.
  80       *
  81       * @param int $courseid
  82       * @return bool
  83       */
  84      public static function can_view_all_groups(int $courseid): bool {
  85          $viewhidden = has_capability('moodle/course:viewhiddengroups', \context_course::instance($courseid));
  86          $hashidden = self::course_has_hidden_groups($courseid);
  87          return $viewhidden || !$hashidden;
  88      }
  89  
  90      /**
  91       * Return SQL conditions for determining whether a user can see a group and its memberships.
  92       *
  93       * @param int $userid
  94       * @param string $groupsalias The SQL alias being used for the groups table.
  95       * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
  96       * @return array [$where, $params]
  97       */
  98      public static function sql_group_visibility_where(int $userid,
  99              string $groupsalias = 'g', string $groupsmembersalias = 'gm'): array {
 100          global $USER;
 101          // Apply visibility restrictions.
 102          // Everyone can see who is in groups with ALL visibility.
 103          $where = "({$groupsalias}.visibility = :all";
 104          $params['all'] = GROUPS_VISIBILITY_ALL;
 105          if ($userid == $USER->id) {
 106              // If the user is looking at their own groups, they can see those with MEMBERS or OWN visibility.
 107              $where .= " OR {$groupsalias}.visibility IN (:members, :own)";
 108              $params['members'] = GROUPS_VISIBILITY_MEMBERS;
 109              $params['own'] = GROUPS_VISIBILITY_OWN;
 110          } else {
 111              list($memberssql, $membersparams) = self::sql_members_visibility_condition($groupsalias, $groupsmembersalias);
 112              // If someone else's groups, they can see those with MEMBERS visibilty, only if they are a member too.
 113              $where .= " OR ($memberssql)";
 114              $params = array_merge($params, $membersparams);
 115          }
 116          $where .= ")";
 117          return [$where, $params];
 118      }
 119  
 120      /**
 121       * Return SQL conditions for determining whether a user can see a group's members.
 122       *
 123       * @param string $groupsalias The SQL alias being used for the groups table.
 124       * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
 125       * @param string $useralias The SQL alias being used for the user table.
 126       * @param string $paramprefix Prefix for the parameter names.
 127       * @return array [$where, $params]
 128       */
 129      public static function sql_member_visibility_where(
 130          string $groupsalias = 'g',
 131          string $groupsmembersalias = 'gm',
 132          string $useralias = 'u',
 133          string $paramprefix = '',
 134      ): array {
 135          global $USER;
 136  
 137          list($memberssql, $membersparams) = self::sql_members_visibility_condition($groupsalias, $groupsmembersalias, $paramprefix);
 138  
 139          $where = "(
 140              {$groupsalias}.visibility = :{$paramprefix}all
 141              OR ($memberssql)
 142              OR ({$groupsalias}.visibility = :{$paramprefix}own AND {$useralias}.id = :{$paramprefix}currentuser2)
 143          )";
 144          $params = [
 145              "{$paramprefix}all" => GROUPS_VISIBILITY_ALL,
 146              "{$paramprefix}own" => GROUPS_VISIBILITY_OWN,
 147              "{$paramprefix}currentuser2" => $USER->id,
 148          ];
 149          $params = array_merge($params, $membersparams);
 150          return [$where, $params];
 151      }
 152  
 153      /**
 154       * Return a condition to check if a user can view a group because it has MEMBERS visibility and they are a member.
 155       *
 156       * @param string $groupsalias The SQL alias being used for the groups table.
 157       * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
 158       * @param string $paramprefix Prefix for the parameter names.
 159       * @return array [$sql, $params]
 160       */
 161      protected static function sql_members_visibility_condition(
 162          string $groupsalias = 'g',
 163          string $groupsmembersalias = 'gm',
 164          string $paramprefix = '',
 165      ): array {
 166          global $USER;
 167          $sql = "{$groupsalias}.visibility = :{$paramprefix}members
 168                      AND (
 169                          SELECT gm2.id
 170                            FROM {groups_members} gm2
 171                           WHERE gm2.groupid = {$groupsmembersalias}.groupid
 172                                 AND gm2.userid = :{$paramprefix}currentuser
 173                      ) IS NOT NULL";
 174          $params = [
 175              "{$paramprefix}members" => GROUPS_VISIBILITY_MEMBERS,
 176              "{$paramprefix}currentuser" => $USER->id
 177          ];
 178  
 179          return [$sql, $params];
 180      }
 181  }