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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  namespace core_question\local\bank;
  18  
  19  use core\output\datafilter;
  20  
  21  /**
  22   * An abstract class for filtering/searching questions.
  23   *
  24   * @package    core_question
  25   * @copyright  2013 Ray Morris
  26   * @author     Safat Shahin <safatshahin@catalyst-au.net>
  27   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  28   */
  29  abstract class condition {
  30  
  31      /** @var int The default filter type */
  32      const JOINTYPE_DEFAULT = datafilter::JOINTYPE_ANY;
  33  
  34      /** @var ?array Filter properties for this condition. */
  35      public ?array $filter;
  36  
  37      /** @var string SQL fragment to add to the where clause. */
  38      protected string $where = '';
  39  
  40      /** @var array query param used in where. */
  41      protected array $params = [];
  42  
  43      /**
  44       * Return title of the condition
  45       *
  46       * @return string title of the condition
  47       */
  48      abstract public function get_title();
  49  
  50      /**
  51       * Return filter class associated with this condition
  52       *
  53       * @return string filter class
  54       */
  55      abstract public function get_filter_class();
  56  
  57      /**
  58       * Extract the required filter from the provided question bank view.
  59       *
  60       * This will look for the filter matching {@see get_condition_key()}
  61       *
  62       * @param view|null $qbank
  63       */
  64      public function __construct(view $qbank = null) {
  65          if (is_null($qbank)) {
  66              return;
  67          }
  68          $this->filter = static::get_filter_from_list($qbank->get_pagevars('filter'));
  69          // Build where and params.
  70          [$this->where, $this->params] = $this->filter ? static::build_query_from_filter($this->filter) : ['', []];
  71      }
  72  
  73      /**
  74       * Whether customisation is allowed.
  75       *
  76       * @return bool
  77       */
  78      public function allow_custom() {
  79          return true;
  80      }
  81  
  82      /**
  83       * Whether multiple values are allowed .
  84       *
  85       * @return bool
  86       */
  87      public function allow_multiple() {
  88          return true;
  89      }
  90  
  91      /**
  92       * Initial values of the condition
  93       *
  94       * @return array
  95       */
  96      public function get_initial_values() {
  97          return [];
  98      }
  99  
 100      /**
 101       * Extra data specific to this condition.
 102       *
 103       * @return \stdClass
 104       */
 105      public function get_filteroptions(): \stdClass {
 106          return (object)[];
 107      }
 108  
 109      /**
 110       * Whether empty value is allowed
 111       *
 112       * @return bool
 113       */
 114      public function allow_empty() {
 115          return true;
 116      }
 117  
 118      /**
 119       * Whether this filter is required - if so it cannot be removed from the list of filters.
 120       *
 121       * @return bool
 122       */
 123      public function is_required(): bool {
 124          return false;
 125      }
 126  
 127      /**
 128       * Return this condition class
 129       *
 130       * @return string
 131       */
 132      public function get_condition_class() {
 133          return get_class($this);
 134      }
 135  
 136      /**
 137       * Each condition will need a unique key to be identified and sequenced by the api.
 138       * Use a unique string for the condition identifier, use string directly, dont need to use language pack.
 139       * Using language pack might break the filter object for multilingual support.
 140       *
 141       * @return string
 142       */
 143      public static function get_condition_key() {
 144          return '';
 145      }
 146  
 147      /**
 148       * Return an SQL fragment to be ANDed into the WHERE clause to filter which questions are shown.
 149       *
 150       * @return string SQL fragment. Must use named parameters.
 151       */
 152      public function where() {
 153          return $this->where;
 154      }
 155  
 156      /**
 157       * Return parameters to be bound to the above WHERE clause fragment.
 158       * @return array parameter name => value.
 159       */
 160      public function params() {
 161          return $this->params;
 162      }
 163  
 164      /**
 165       * Display GUI for selecting criteria for this condition. Displayed when Show More is open.
 166       *
 167       * Compare display_options(), which displays always, whether Show More is open or not.
 168       * @return bool|string HTML form fragment
 169       * @deprecated since Moodle 4.0 MDL-72321 - please do not use this function any more.
 170       * @todo Final deprecation on Moodle 4.1 MDL-72572
 171       */
 172      public function display_options_adv() {
 173          debugging('Function display_options_adv() is deprecated, please use filtering objects', DEBUG_DEVELOPER);
 174          return false;
 175      }
 176  
 177      /**
 178       * Display GUI for selecting criteria for this condition. Displayed always, whether Show More is open or not.
 179       *
 180       * Compare display_options_adv(), which displays when Show More is open.
 181       * @return bool|string HTML form fragment
 182       * @deprecated since Moodle 4.0 MDL-72321 - please do not use this function any more.
 183       * @todo Final deprecation on Moodle 4.1 MDL-72572
 184       */
 185      public function display_options() {
 186          debugging('Function display_options() is deprecated, please use filtering objects', DEBUG_DEVELOPER);
 187          return false;
 188      }
 189  
 190      /**
 191       * Get the list of available joins for the filter.
 192       *
 193       * @return array
 194       */
 195      public function get_join_list(): array {
 196          return [
 197              datafilter::JOINTYPE_NONE,
 198              datafilter::JOINTYPE_ANY,
 199              datafilter::JOINTYPE_ALL,
 200          ];
 201      }
 202  
 203      /**
 204       * Given an array of filters, pick the entry that matches the condition key and return it.
 205       *
 206       * @param array $filters Array of filters, keyed by condition.
 207       * @return ?array The filter that matches this condition
 208       */
 209      public static function get_filter_from_list(array $filters): ?array {
 210          return $filters[static::get_condition_key()] ?? null;
 211      }
 212  
 213      /**
 214       * Build query from filter value
 215       *
 216       * @param array $filter filter properties
 217       * @return array where sql and params
 218       */
 219      public static function build_query_from_filter(array $filter): array {
 220          return ['', []];
 221      }
 222  }