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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   * Node (base class) used to construct a tree of availability conditions.
  19   *
  20   * @package core_availability
  21   * @copyright 2014 The Open University
  22   * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23   */
  24  
  25  namespace core_availability;
  26  
  27  defined('MOODLE_INTERNAL') || die();
  28  
  29  /**
  30   * Node (base class) used to construct a tree of availability conditions.
  31   *
  32   * @package core_availability
  33   * @copyright 2014 The Open University
  34   * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  35   */
  36  abstract class tree_node {
  37      /**
  38       * Determines whether this particular item is currently available
  39       * according to the availability criteria.
  40       *
  41       * - This does not include the 'visible' setting (i.e. this might return
  42       *   true even if visible is false); visible is handled independently.
  43       * - This does not take account of the viewhiddenactivities capability.
  44       *   That should apply later.
  45       *
  46       * The $not option is potentially confusing. This option always indicates
  47       * the 'real' value of NOT. For example, a condition inside a 'NOT AND'
  48       * group will get this called with $not = true, but if you put another
  49       * 'NOT OR' group inside the first group, then a condition inside that will
  50       * be called with $not = false. We need to use the real values, rather than
  51       * the more natural use of the current value at this point inside the tree,
  52       * so that the information displayed to users makes sense.
  53       *
  54       * @param bool $not Set true if we are inverting the condition
  55       * @param \core_availability\info $info Item we're checking
  56       * @param bool $grabthelot Performance hint: if true, caches information
  57       *   required for all course-modules, to make the front page and similar
  58       *   pages work more quickly (works only for current user)
  59       * @param int $userid User ID to check availability for
  60       * @return result Availability check result
  61       */
  62      public abstract function check_available($not,
  63              \core_availability\info $info, $grabthelot, $userid);
  64  
  65      /**
  66       * Checks whether this condition is actually going to be available for
  67       * all users under normal circumstances.
  68       *
  69       * Normally, if there are any conditions, then it may be hidden. However
  70       * in the case of date conditions there are some conditions which will
  71       * definitely not result in it being hidden for anyone.
  72       *
  73       * @param bool $not Set true if we are inverting the condition
  74       * @return bool True if condition will return available for everyone
  75       */
  76      public abstract function is_available_for_all($not = false);
  77  
  78      /**
  79       * Saves tree data back to a structure object.
  80       *
  81       * @return \stdClass Structure object (ready to be made into JSON format)
  82       */
  83      public abstract function save();
  84  
  85      /**
  86       * Updates this node after restore, returning true if anything changed.
  87       * The default behaviour is simply to return false. If there is a problem
  88       * with the update, $logger can be used to output a warning.
  89       *
  90       * Note: If you need information about the date offset, call
  91       * \core_availability\info::get_restore_date_offset($restoreid).
  92       *
  93       * @param string $restoreid Restore ID
  94       * @param int $courseid ID of target course
  95       * @param \base_logger $logger Logger for any warnings
  96       * @param string $name Name of this item (for use in warning messages)
  97       * @return bool True if there was any change
  98       */
  99      public function update_after_restore($restoreid, $courseid, \base_logger $logger, $name) {
 100          return false;
 101      }
 102  
 103      /**
 104       * Updates this node if it contains any references (dependencies) to the
 105       * given table and id.
 106       *
 107       * @param string $table Table name e.g. 'course_modules'
 108       * @param int $oldid Previous ID
 109       * @param int $newid New ID
 110       * @return bool True if it changed, otherwise false
 111       */
 112      public abstract function update_dependency_id($table, $oldid, $newid);
 113  
 114      /**
 115       * Checks whether this condition applies to user lists. The default is
 116       * false (the condition is used to control access, but does not prevent
 117       * the student from appearing in lists).
 118       *
 119       * For example, group conditions apply to user lists: we do not want to
 120       * include a student in a list of users if they are prohibited from
 121       * accessing the activity because they don't belong to a relevant group.
 122       * However, date conditions do not apply - we still want to show users
 123       * in a list of people who might have submitted an assignment, even if they
 124       * are no longer able to access the assignment in question because there is
 125       * a date restriction.
 126       *
 127       * The general idea is that conditions which are likely to be permanent
 128       * (group membership, user profile) apply to user lists. Conditions which
 129       * are likely to be temporary (date, grade requirement) do not.
 130       *
 131       * Conditions which do apply to user lists must implement the
 132       * filter_user_list function.
 133       *
 134       * @return bool True if this condition applies to user lists
 135       */
 136      public function is_applied_to_user_lists() {
 137          return false;
 138      }
 139  
 140      /**
 141       * Tests this condition against a user list. Users who do not meet the
 142       * condition will be removed from the list.
 143       *
 144       * This function must be implemented if is_applied_to_user_lists returns
 145       * true. Otherwise it will not be called.
 146       *
 147       * The function must operate efficiently, e.g. by using a fixed number of
 148       * database queries regardless of how many users are in the list.
 149       *
 150       * Within this function, if you need to check capabilities, please use
 151       * the provided checker which caches results where possible.
 152       *
 153       * @param array $users Array of userid => object
 154       * @param bool $not True if this condition is applying in negative mode
 155       * @param \core_availability\info $info Item we're checking
 156       * @param capability_checker $checker
 157       * @return array Filtered version of input array
 158       * @throws \coding_exception If called on a condition that doesn't apply to user lists
 159       */
 160      public function filter_user_list(array $users, $not,
 161              \core_availability\info $info, capability_checker $checker) {
 162          throw new \coding_exception('Not implemented (do not call unless '.
 163                  'is_applied_to_user_lists is true)');
 164      }
 165  
 166      /**
 167       * Obtains SQL that returns a list of enrolled users that has been filtered
 168       * by the conditions applied in the availability API, similar to calling
 169       * get_enrolled_users and then filter_user_list. As for filter_user_list,
 170       * this ONLY filteres out users with conditions that are marked as applying
 171       * to user lists. For example, group conditions are included but date
 172       * conditions are not included.
 173       *
 174       * The returned SQL is a query that returns a list of user IDs. It does not
 175       * include brackets, so you neeed to add these to make it into a subquery.
 176       * You would normally use it in an SQL phrase like "WHERE u.id IN ($sql)".
 177       *
 178       * The SQL will be complex and may be slow. It uses named parameters (sorry,
 179       * I know they are annoying, but it was unavoidable here).
 180       *
 181       * If there are no conditions, the returned result is array('', array()).
 182       *
 183       * @param bool $not True if this condition is applying in negative mode
 184       * @param \core_availability\info $info Item we're checking
 185       * @param bool $onlyactive If true, only returns active enrolments
 186       * @return array Array with two elements: SQL subquery and parameters array
 187       * @throws \coding_exception If called on a condition that doesn't apply to user lists
 188       */
 189      public function get_user_list_sql($not, \core_availability\info $info, $onlyactive) {
 190          if (!$this->is_applied_to_user_lists()) {
 191              throw new \coding_exception('Not implemented (do not call unless '.
 192                      'is_applied_to_user_lists is true)');
 193          }
 194  
 195          // Handle situation where plugin does not implement this, by returning a
 196          // default (all enrolled users). This ensures compatibility with 2.7
 197          // plugins and behaviour. Plugins should be updated to support this
 198          // new function (if they return true to is_applied_to_user_lists).
 199          debugging('Availability plugins that return true to is_applied_to_user_lists ' .
 200                  'should also now implement get_user_list_sql: ' . get_class($this),
 201                  DEBUG_DEVELOPER);
 202          return get_enrolled_sql($info->get_context(), '', 0, $onlyactive);
 203      }
 204  
 205      /**
 206       * Utility function for generating SQL parameters (because we can't use ?
 207       * parameters because get_enrolled_sql has infected us with horrible named
 208       * parameters).
 209       *
 210       * @param array $params Params array (value will be added to this array)
 211       * @param string|int $value Value
 212       * @return SQL code for the parameter, e.g. ':pr1234'
 213       */
 214      protected static function unique_sql_parameter(array &$params, $value) {
 215          static $count = 1;
 216          $unique = 'usp' . $count;
 217          $params[$unique] = $value;
 218          $count++;
 219          return ':' . $unique;
 220      }
 221  }