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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   * More object oriented wrappers around parts of the Moodle question bank.
  19   *
  20   * In due course, I expect that the question bank will be converted to a
  21   * fully object oriented structure, at which point this file can be a
  22   * starting point.
  23   *
  24   * @package    moodlecore
  25   * @subpackage questionbank
  26   * @copyright  2009 The Open University
  27   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  28   */
  29  
  30  
  31  defined('MOODLE_INTERNAL') || die();
  32  
  33  require_once (__DIR__ . '/../type/questiontypebase.php');
  34  
  35  
  36  /**
  37   * This static class provides access to the other question bank.
  38   *
  39   * It provides functions for managing question types and question definitions.
  40   *
  41   * @copyright  2009 The Open University
  42   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  43   */
  44  abstract class question_bank {
  45      // TODO: This limit can be deleted if someday we move all TEXTS to BIG ones. MDL-19603
  46      const MAX_SUMMARY_LENGTH = 32000;
  47  
  48      /** @var array question type name => question_type subclass. */
  49      private static $questiontypes = array();
  50  
  51      /** @var array question type name => 1. Records which question definitions have been loaded. */
  52      private static $loadedqdefs = array();
  53  
  54      /** @var boolean nasty hack to allow unit tests to call {@link load_question()}. */
  55      private static $testmode = false;
  56      private static $testdata = array();
  57  
  58      private static $questionconfig = null;
  59  
  60      /**
  61       * @var array string => string The standard set of grade options (fractions)
  62       * to use when editing questions, in the range 0 to 1 inclusive. Array keys
  63       * are string becuase: a) we want grades to exactly 7 d.p., and b. you can't
  64       * have float array keys in PHP.
  65       * Initialised by {@link ensure_grade_options_initialised()}.
  66       */
  67      private static $fractionoptions = null;
  68      /** @var array string => string The full standard set of (fractions) -1 to 1 inclusive. */
  69      private static $fractionoptionsfull = null;
  70  
  71      /**
  72       * @param string $qtypename a question type name, e.g. 'multichoice'.
  73       * @return bool whether that question type is installed in this Moodle.
  74       */
  75      public static function is_qtype_installed($qtypename) {
  76          $plugindir = core_component::get_plugin_directory('qtype', $qtypename);
  77          return $plugindir && is_readable($plugindir . '/questiontype.php');
  78      }
  79  
  80      /**
  81       * Get the question type class for a particular question type.
  82       * @param string $qtypename the question type name. For example 'multichoice' or 'shortanswer'.
  83       * @param bool $mustexist if false, the missing question type is returned when
  84       *      the requested question type is not installed.
  85       * @return question_type the corresponding question type class.
  86       */
  87      public static function get_qtype($qtypename, $mustexist = true) {
  88          global $CFG;
  89          if (isset(self::$questiontypes[$qtypename])) {
  90              return self::$questiontypes[$qtypename];
  91          }
  92          $file = core_component::get_plugin_directory('qtype', $qtypename) . '/questiontype.php';
  93          if (!is_readable($file)) {
  94              if ($mustexist || $qtypename == 'missingtype') {
  95                  throw new coding_exception('Unknown question type ' . $qtypename);
  96              } else {
  97                  return self::get_qtype('missingtype');
  98              }
  99          }
 100          include_once($file);
 101          $class = 'qtype_' . $qtypename;
 102          if (!class_exists($class)) {
 103              throw new coding_exception("Class {$class} must be defined in {$file}.");
 104          }
 105          self::$questiontypes[$qtypename] = new $class();
 106          return self::$questiontypes[$qtypename];
 107      }
 108  
 109      /**
 110       * Load the question configuration data from config_plugins.
 111       * @return object get_config('question') with caching.
 112       */
 113      public static function get_config() {
 114          if (is_null(self::$questionconfig)) {
 115              self::$questionconfig = get_config('question');
 116          }
 117          return self::$questionconfig;
 118      }
 119  
 120      /**
 121       * @param string $qtypename the internal name of a question type. For example multichoice.
 122       * @return bool whether users are allowed to create questions of this type.
 123       */
 124      public static function qtype_enabled($qtypename) {
 125          $config = self::get_config();
 126          $enabledvar = $qtypename . '_disabled';
 127          return self::qtype_exists($qtypename) && empty($config->$enabledvar) &&
 128                  self::get_qtype($qtypename)->menu_name() != '';
 129      }
 130  
 131      /**
 132       * @param string $qtypename the internal name of a question type. For example multichoice.
 133       * @return bool whether this question type exists.
 134       */
 135      public static function qtype_exists($qtypename) {
 136          return array_key_exists($qtypename, core_component::get_plugin_list('qtype'));
 137      }
 138  
 139      /**
 140       * @param $qtypename the internal name of a question type, for example multichoice.
 141       * @return string the human_readable name of this question type, from the language pack.
 142       */
 143      public static function get_qtype_name($qtypename) {
 144          return self::get_qtype($qtypename)->local_name();
 145      }
 146  
 147      /**
 148       * @return array all the installed question types.
 149       */
 150      public static function get_all_qtypes() {
 151          $qtypes = array();
 152          foreach (core_component::get_plugin_list('qtype') as $plugin => $notused) {
 153              try {
 154                  $qtypes[$plugin] = self::get_qtype($plugin);
 155              } catch (coding_exception $e) {
 156                  // Catching coding_exceptions here means that incompatible
 157                  // question types do not cause the rest of Moodle to break.
 158              }
 159          }
 160          return $qtypes;
 161      }
 162  
 163      /**
 164       * Sort an array of question types according to the order the admin set up,
 165       * and then alphabetically for the rest.
 166       * @param array qtype->name() => qtype->local_name().
 167       * @return array sorted array.
 168       */
 169      public static function sort_qtype_array($qtypes, $config = null) {
 170          if (is_null($config)) {
 171              $config = self::get_config();
 172          }
 173  
 174          $sortorder = array();
 175          $otherqtypes = array();
 176          foreach ($qtypes as $name => $localname) {
 177              $sortvar = $name . '_sortorder';
 178              if (isset($config->$sortvar)) {
 179                  $sortorder[$config->$sortvar] = $name;
 180              } else {
 181                  $otherqtypes[$name] = $localname;
 182              }
 183          }
 184  
 185          ksort($sortorder);
 186          core_collator::asort($otherqtypes);
 187  
 188          $sortedqtypes = array();
 189          foreach ($sortorder as $name) {
 190              $sortedqtypes[$name] = $qtypes[$name];
 191          }
 192          foreach ($otherqtypes as $name => $notused) {
 193              $sortedqtypes[$name] = $qtypes[$name];
 194          }
 195          return $sortedqtypes;
 196      }
 197  
 198      /**
 199       * @return array all the question types that users are allowed to create,
 200       *      sorted into the preferred order set on the admin screen.
 201       */
 202      public static function get_creatable_qtypes() {
 203          $config = self::get_config();
 204          $allqtypes = self::get_all_qtypes();
 205  
 206          $qtypenames = array();
 207          foreach ($allqtypes as $name => $qtype) {
 208              if (self::qtype_enabled($name)) {
 209                  $qtypenames[$name] = $qtype->local_name();
 210              }
 211          }
 212  
 213          $qtypenames = self::sort_qtype_array($qtypenames);
 214  
 215          $creatableqtypes = array();
 216          foreach ($qtypenames as $name => $notused) {
 217              $creatableqtypes[$name] = $allqtypes[$name];
 218          }
 219          return $creatableqtypes;
 220      }
 221  
 222      /**
 223       * Load the question definition class(es) belonging to a question type. That is,
 224       * include_once('/question/type/' . $qtypename . '/question.php'), with a bit
 225       * of checking.
 226       * @param string $qtypename the question type name. For example 'multichoice' or 'shortanswer'.
 227       */
 228      public static function load_question_definition_classes($qtypename) {
 229          global $CFG;
 230          if (isset(self::$loadedqdefs[$qtypename])) {
 231              return;
 232          }
 233          $file = $CFG->dirroot . '/question/type/' . $qtypename . '/question.php';
 234          if (!is_readable($file)) {
 235              throw new coding_exception('Unknown question type (no definition) ' . $qtypename);
 236          }
 237          include_once($file);
 238          self::$loadedqdefs[$qtypename] = 1;
 239      }
 240  
 241      /**
 242       * This method needs to be called whenever a question is edited.
 243       */
 244      public static function notify_question_edited($questionid) {
 245          question_finder::get_instance()->uncache_question($questionid);
 246      }
 247  
 248      /**
 249       * Load a question definition data from the database. The data will be
 250       * returned as a plain stdClass object.
 251       * @param int $questionid the id of the question to load.
 252       * @return object question definition loaded from the database.
 253       */
 254      public static function load_question_data($questionid) {
 255          return question_finder::get_instance()->load_question_data($questionid);
 256      }
 257  
 258      /**
 259       * Load a question definition from the database. The object returned
 260       * will actually be of an appropriate {@link question_definition} subclass.
 261       * @param int $questionid the id of the question to load.
 262       * @param bool $allowshuffle if false, then any shuffle option on the selected
 263       *      quetsion is disabled.
 264       * @return question_definition loaded from the database.
 265       */
 266      public static function load_question($questionid, $allowshuffle = true) {
 267          global $DB;
 268  
 269          if (self::$testmode) {
 270              // Evil, test code in production, but now way round it.
 271              return self::return_test_question_data($questionid);
 272          }
 273  
 274          $questiondata = self::load_question_data($questionid);
 275  
 276          if (!$allowshuffle) {
 277              $questiondata->options->shuffleanswers = false;
 278          }
 279          return self::make_question($questiondata);
 280      }
 281  
 282      /**
 283       * Convert the question information loaded with {@link get_question_options()}
 284       * to a question_definintion object.
 285       * @param object $questiondata raw data loaded from the database.
 286       * @return question_definition loaded from the database.
 287       */
 288      public static function make_question($questiondata) {
 289          return self::get_qtype($questiondata->qtype, false)->make_question($questiondata, false);
 290      }
 291  
 292      /**
 293       * @return question_finder a question finder.
 294       */
 295      public static function get_finder() {
 296          return question_finder::get_instance();
 297          if (is_null(self::$questionfinder)) {
 298              self::$questionfinder = new question_finder();
 299          }
 300          return self::$questionfinder;
 301      }
 302  
 303      /**
 304       * Only to be called from unit tests. Allows {@link load_test_data()} to be used.
 305       */
 306      public static function start_unit_test() {
 307          self::$testmode = true;
 308      }
 309  
 310      /**
 311       * Only to be called from unit tests. Allows {@link load_test_data()} to be used.
 312       */
 313      public static function end_unit_test() {
 314          self::$testmode = false;
 315          self::$testdata = array();
 316      }
 317  
 318      private static function return_test_question_data($questionid) {
 319          if (!isset(self::$testdata[$questionid])) {
 320              throw new coding_exception('question_bank::return_test_data(' . $questionid .
 321                      ') called, but no matching question has been loaded by load_test_data.');
 322          }
 323          return self::$testdata[$questionid];
 324      }
 325  
 326      /**
 327       * To be used for unit testing only. Will throw an exception if
 328       * {@link start_unit_test()} has not been called first.
 329       * @param object $questiondata a question data object to put in the test data store.
 330       */
 331      public static function load_test_question_data(question_definition $question) {
 332          if (!self::$testmode) {
 333              throw new coding_exception('question_bank::load_test_data called when ' .
 334                      'not in test mode.');
 335          }
 336          self::$testdata[$question->id] = $question;
 337      }
 338  
 339      protected static function ensure_fraction_options_initialised() {
 340          if (!is_null(self::$fractionoptions)) {
 341              return;
 342          }
 343  
 344          // define basic array of grades. This list comprises all fractions of the form:
 345          // a. p/q for q <= 6, 0 <= p <= q
 346          // b. p/10 for 0 <= p <= 10
 347          // c. 1/q for 1 <= q <= 10
 348          // d. 1/20
 349          $rawfractions = array(
 350              0.9000000,
 351              0.8333333,
 352              0.8000000,
 353              0.7500000,
 354              0.7000000,
 355              0.6666667,
 356              0.6000000,
 357              0.5000000,
 358              0.4000000,
 359              0.3333333,
 360              0.3000000,
 361              0.2500000,
 362              0.2000000,
 363              0.1666667,
 364              0.1428571,
 365              0.1250000,
 366              0.1111111,
 367              0.1000000,
 368              0.0500000,
 369          );
 370  
 371          // Put the None option at the top.
 372          self::$fractionoptions = array(
 373              '0.0' => get_string('none'),
 374              '1.0' => '100%',
 375          );
 376          self::$fractionoptionsfull = array(
 377              '0.0' => get_string('none'),
 378              '1.0' => '100%',
 379          );
 380  
 381          // The the positive grades in descending order.
 382          foreach ($rawfractions as $fraction) {
 383              $percentage = format_float(100 * $fraction, 5, true, true) . '%';
 384              self::$fractionoptions["{$fraction}"] = $percentage;
 385              self::$fractionoptionsfull["{$fraction}"] = $percentage;
 386          }
 387  
 388          // The the negative grades in descending order.
 389          foreach (array_reverse($rawfractions) as $fraction) {
 390              self::$fractionoptionsfull['' . (-$fraction)] =
 391                      format_float(-100 * $fraction, 5, true, true) . '%';
 392          }
 393  
 394          self::$fractionoptionsfull['-1.0'] = '-100%';
 395      }
 396  
 397      /**
 398       * @return array string => string The standard set of grade options (fractions)
 399       * to use when editing questions, in the range 0 to 1 inclusive. Array keys
 400       * are string becuase: a) we want grades to exactly 7 d.p., and b. you can't
 401       * have float array keys in PHP.
 402       * Initialised by {@link ensure_grade_options_initialised()}.
 403       */
 404      public static function fraction_options() {
 405          self::ensure_fraction_options_initialised();
 406          return self::$fractionoptions;
 407      }
 408  
 409      /** @return array string => string The full standard set of (fractions) -1 to 1 inclusive. */
 410      public static function fraction_options_full() {
 411          self::ensure_fraction_options_initialised();
 412          return self::$fractionoptionsfull;
 413      }
 414  
 415      /**
 416       * Perform scheduled maintenance tasks relating to the question bank.
 417       */
 418      public static function cron() {
 419          global $CFG;
 420  
 421          // Delete any old question preview that got left in the database.
 422          require_once($CFG->dirroot . '/question/previewlib.php');
 423          question_preview_cron();
 424  
 425          // Clear older calculated stats from cache.
 426          require_once($CFG->dirroot . '/question/engine/statisticslib.php');
 427          question_usage_statistics_cron();
 428      }
 429  
 430      /**
 431       * Return a list of the different question types present in the given categories.
 432       *
 433       * @param  array $categories a list of category ids
 434       * @return array the list of question types in the categories
 435       * @since  Moodle 3.1
 436       */
 437      public static function get_all_question_types_in_categories($categories) {
 438          global $DB;
 439  
 440          list($categorysql, $params) = $DB->get_in_or_equal($categories);
 441          $sql = "SELECT DISTINCT q.qtype
 442                  FROM {question} q
 443                  WHERE q.category $categorysql";
 444  
 445          $qtypes = $DB->get_fieldset_sql($sql, $params);
 446          return $qtypes;
 447      }
 448  }
 449  
 450  
 451  /**
 452   * Class for loading questions according to various criteria.
 453   *
 454   * @copyright  2009 The Open University
 455   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 456   */
 457  class question_finder implements cache_data_source {
 458      /** @var question_finder the singleton instance of this class. */
 459      protected static $questionfinder = null;
 460  
 461      /**
 462       * @return question_finder a question finder.
 463       */
 464      public static function get_instance() {
 465          if (is_null(self::$questionfinder)) {
 466              self::$questionfinder = new question_finder();
 467          }
 468          return self::$questionfinder;
 469      }
 470  
 471      /* See cache_data_source::get_instance_for_cache. */
 472      public static function get_instance_for_cache(cache_definition $definition) {
 473          return self::get_instance();
 474      }
 475  
 476      /**
 477       * @return get the question definition cache we are using.
 478       */
 479      protected function get_data_cache() {
 480          // Do not double cache here because it may break cache resetting.
 481          return cache::make('core', 'questiondata');
 482      }
 483  
 484      /**
 485       * This method needs to be called whenever a question is edited.
 486       */
 487      public function uncache_question($questionid) {
 488          $this->get_data_cache()->delete($questionid);
 489      }
 490  
 491      /**
 492       * Load a question definition data from the database. The data will be
 493       * returned as a plain stdClass object.
 494       * @param int $questionid the id of the question to load.
 495       * @return object question definition loaded from the database.
 496       */
 497      public function load_question_data($questionid) {
 498          return $this->get_data_cache()->get($questionid);
 499      }
 500  
 501      /**
 502       * Get the ids of all the questions in a list of categories.
 503       * @param array $categoryids either a categoryid, or a comma-separated list
 504       *      category ids, or an array of them.
 505       * @param string $extraconditions extra conditions to AND with the rest of
 506       *      the where clause. Must use named parameters.
 507       * @param array $extraparams any parameters used by $extraconditions.
 508       * @return array questionid => questionid.
 509       */
 510      public function get_questions_from_categories($categoryids, $extraconditions,
 511              $extraparams = array()) {
 512          global $DB;
 513  
 514          list($qcsql, $qcparams) = $DB->get_in_or_equal($categoryids, SQL_PARAMS_NAMED, 'qc');
 515  
 516          if ($extraconditions) {
 517              $extraconditions = ' AND (' . $extraconditions . ')';
 518          }
 519  
 520          return $DB->get_records_select_menu('question',
 521                  "category {$qcsql}
 522                   AND parent = 0
 523                   AND hidden = 0
 524                   {$extraconditions}", $qcparams + $extraparams, '', 'id,id AS id2');
 525      }
 526  
 527      /**
 528       * Get the ids of all the questions in a list of categories, with the number
 529       * of times they have already been used in a given set of usages.
 530       *
 531       * The result array is returned in order of increasing (count previous uses).
 532       *
 533       * @param array $categoryids an array question_category ids.
 534       * @param qubaid_condition $qubaids which question_usages to count previous uses from.
 535       * @param string $extraconditions extra conditions to AND with the rest of
 536       *      the where clause. Must use named parameters.
 537       * @param array $extraparams any parameters used by $extraconditions.
 538       * @return array questionid => count of number of previous uses.
 539       */
 540      public function get_questions_from_categories_with_usage_counts($categoryids,
 541              qubaid_condition $qubaids, $extraconditions = '', $extraparams = array()) {
 542          global $DB;
 543  
 544          list($qcsql, $qcparams) = $DB->get_in_or_equal($categoryids, SQL_PARAMS_NAMED, 'qc');
 545  
 546          if ($extraconditions) {
 547              $extraconditions = ' AND (' . $extraconditions . ')';
 548          }
 549  
 550          return $DB->get_records_sql_menu("
 551                      SELECT q.id, (SELECT COUNT(1)
 552                                      FROM " . $qubaids->from_question_attempts('qa') . "
 553                                     WHERE qa.questionid = q.id AND " . $qubaids->where() . "
 554                                   ) AS previous_attempts
 555  
 556                        FROM {question} q
 557  
 558                       WHERE q.category {$qcsql}
 559                         AND q.parent = 0
 560                         AND q.hidden = 0
 561                        {$extraconditions}
 562  
 563                    ORDER BY previous_attempts
 564                  ", $qubaids->from_where_params() + $qcparams + $extraparams);
 565      }
 566  
 567      /* See cache_data_source::load_for_cache. */
 568      public function load_for_cache($questionid) {
 569          global $DB;
 570          $questiondata = $DB->get_record_sql('
 571                                      SELECT q.*, qc.contextid
 572                                      FROM {question} q
 573                                      JOIN {question_categories} qc ON q.category = qc.id
 574                                      WHERE q.id = :id', array('id' => $questionid), MUST_EXIST);
 575          get_question_options($questiondata);
 576          return $questiondata;
 577      }
 578  
 579      /* See cache_data_source::load_many_for_cache. */
 580      public function load_many_for_cache(array $questionids) {
 581          global $DB;
 582          list($idcondition, $params) = $DB->get_in_or_equal($questionids);
 583          $questiondata = $DB->get_records_sql('
 584                                              SELECT q.*, qc.contextid
 585                                              FROM {question} q
 586                                              JOIN {question_categories} qc ON q.category = qc.id
 587                                              WHERE q.id ' . $idcondition, $params);
 588  
 589          foreach ($questionids as $id) {
 590              if (!array_key_exists($id, $questionids)) {
 591                  throw new dml_missing_record_exception('question', '', array('id' => $id));
 592              }
 593              get_question_options($questiondata[$id]);
 594          }
 595          return $questiondata;
 596      }
 597  }