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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   * This defines the core classes of the Moodle question engine.
  19   *
  20   * @package    moodlecore
  21   * @subpackage questionengine
  22   * @copyright  2009 The Open University
  23   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24   */
  25  
  26  
  27  defined('MOODLE_INTERNAL') || die();
  28  
  29  require_once($CFG->libdir . '/filelib.php');
  30  require_once (__DIR__ . '/questionusage.php');
  31  require_once (__DIR__ . '/questionattempt.php');
  32  require_once (__DIR__ . '/questionattemptstep.php');
  33  require_once (__DIR__ . '/states.php');
  34  require_once (__DIR__ . '/datalib.php');
  35  require_once (__DIR__ . '/renderer.php');
  36  require_once (__DIR__ . '/bank.php');
  37  require_once (__DIR__ . '/../type/questiontypebase.php');
  38  require_once (__DIR__ . '/../type/questionbase.php');
  39  require_once (__DIR__ . '/../type/rendererbase.php');
  40  require_once (__DIR__ . '/../behaviour/behaviourtypebase.php');
  41  require_once (__DIR__ . '/../behaviour/behaviourbase.php');
  42  require_once (__DIR__ . '/../behaviour/rendererbase.php');
  43  require_once($CFG->libdir . '/questionlib.php');
  44  
  45  
  46  /**
  47   * This static class provides access to the other question engine classes.
  48   *
  49   * It provides functions for managing question behaviours), and for
  50   * creating, loading, saving and deleting {@link question_usage_by_activity}s,
  51   * which is the main class that is used by other code that wants to use questions.
  52   *
  53   * @copyright  2009 The Open University
  54   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  55   */
  56  abstract class question_engine {
  57      /** @var array behaviour name => 1. Records which behaviours have been loaded. */
  58      private static $loadedbehaviours = array();
  59  
  60      /** @var array behaviour name => question_behaviour_type for this behaviour. */
  61      private static $behaviourtypes = array();
  62  
  63      /**
  64       * Create a new {@link question_usage_by_activity}. The usage is
  65       * created in memory. If you want it to persist, you will need to call
  66       * {@link save_questions_usage_by_activity()}.
  67       *
  68       * @param string $component the plugin creating this attempt. For example mod_quiz.
  69       * @param object $context the context this usage belongs to.
  70       * @return question_usage_by_activity the newly created object.
  71       */
  72      public static function make_questions_usage_by_activity($component, $context) {
  73          return new question_usage_by_activity($component, $context);
  74      }
  75  
  76      /**
  77       * Load a {@link question_usage_by_activity} from the database, based on its id.
  78       * @param int $qubaid the id of the usage to load.
  79       * @param moodle_database $db a database connectoin. Defaults to global $DB.
  80       * @return question_usage_by_activity loaded from the database.
  81       */
  82      public static function load_questions_usage_by_activity($qubaid, moodle_database $db = null) {
  83          $dm = new question_engine_data_mapper($db);
  84          return $dm->load_questions_usage_by_activity($qubaid);
  85      }
  86  
  87      /**
  88       * Save a {@link question_usage_by_activity} to the database. This works either
  89       * if the usage was newly created by {@link make_questions_usage_by_activity()}
  90       * or loaded from the database using {@link load_questions_usage_by_activity()}
  91       * @param question_usage_by_activity the usage to save.
  92       * @param moodle_database $db a database connectoin. Defaults to global $DB.
  93       */
  94      public static function save_questions_usage_by_activity(question_usage_by_activity $quba, moodle_database $db = null) {
  95          $dm = new question_engine_data_mapper($db);
  96          $observer = $quba->get_observer();
  97          if ($observer instanceof question_engine_unit_of_work) {
  98              $observer->save($dm);
  99          } else {
 100              $dm->insert_questions_usage_by_activity($quba);
 101          }
 102      }
 103  
 104      /**
 105       * Delete a {@link question_usage_by_activity} from the database, based on its id.
 106       * @param int $qubaid the id of the usage to delete.
 107       */
 108      public static function delete_questions_usage_by_activity($qubaid) {
 109          self::delete_questions_usage_by_activities(new qubaid_list(array($qubaid)));
 110      }
 111  
 112      /**
 113       * Delete {@link question_usage_by_activity}s from the database.
 114       * @param qubaid_condition $qubaids identifies which questions usages to delete.
 115       */
 116      public static function delete_questions_usage_by_activities(qubaid_condition $qubaids) {
 117          $dm = new question_engine_data_mapper();
 118          $dm->delete_questions_usage_by_activities($qubaids);
 119      }
 120  
 121      /**
 122       * Change the maxmark for the question_attempt with number in usage $slot
 123       * for all the specified question_attempts.
 124       * @param qubaid_condition $qubaids Selects which usages are updated.
 125       * @param int $slot the number is usage to affect.
 126       * @param number $newmaxmark the new max mark to set.
 127       */
 128      public static function set_max_mark_in_attempts(qubaid_condition $qubaids,
 129              $slot, $newmaxmark) {
 130          $dm = new question_engine_data_mapper();
 131          $dm->set_max_mark_in_attempts($qubaids, $slot, $newmaxmark);
 132      }
 133  
 134      /**
 135       * Validate that the manual grade submitted for a particular question is in range.
 136       * @param int $qubaid the question_usage id.
 137       * @param int $slot the slot number within the usage.
 138       * @return bool whether the submitted data is in range.
 139       */
 140      public static function is_manual_grade_in_range($qubaid, $slot) {
 141          $prefix = 'q' . $qubaid . ':' . $slot . '_';
 142          $mark = question_utils::optional_param_mark($prefix . '-mark');
 143          $maxmark = optional_param($prefix . '-maxmark', null, PARAM_FLOAT);
 144          $minfraction = optional_param($prefix . ':minfraction', null, PARAM_FLOAT);
 145          $maxfraction = optional_param($prefix . ':maxfraction', null, PARAM_FLOAT);
 146          return $mark === '' ||
 147                  ($mark !== null && $mark >= $minfraction * $maxmark && $mark <= $maxfraction * $maxmark) ||
 148                  ($mark === null && $maxmark === null);
 149      }
 150  
 151      /**
 152       * @param array $questionids of question ids.
 153       * @param qubaid_condition $qubaids ids of the usages to consider.
 154       * @return boolean whether any of these questions are being used by any of
 155       *      those usages.
 156       */
 157      public static function questions_in_use(array $questionids, qubaid_condition $qubaids = null) {
 158          if (is_null($qubaids)) {
 159              return false;
 160          }
 161          $dm = new question_engine_data_mapper();
 162          return $dm->questions_in_use($questionids, $qubaids);
 163      }
 164  
 165      /**
 166       * Get the number of times each variant has been used for each question in a list
 167       * in a set of usages.
 168       * @param array $questionids of question ids.
 169       * @param qubaid_condition $qubaids ids of the usages to consider.
 170       * @return array questionid => variant number => num uses.
 171       */
 172      public static function load_used_variants(array $questionids, qubaid_condition $qubaids) {
 173          $dm = new question_engine_data_mapper();
 174          return $dm->load_used_variants($questionids, $qubaids);
 175      }
 176  
 177      /**
 178       * Create an archetypal behaviour for a particular question attempt.
 179       * Used by {@link question_definition::make_behaviour()}.
 180       *
 181       * @param string $preferredbehaviour the type of model required.
 182       * @param question_attempt $qa the question attempt the model will process.
 183       * @return question_behaviour an instance of appropriate behaviour class.
 184       */
 185      public static function make_archetypal_behaviour($preferredbehaviour, question_attempt $qa) {
 186          if (!self::is_behaviour_archetypal($preferredbehaviour)) {
 187              throw new coding_exception('The requested behaviour is not actually ' .
 188                      'an archetypal one.');
 189          }
 190  
 191          self::load_behaviour_class($preferredbehaviour);
 192          $class = 'qbehaviour_' . $preferredbehaviour;
 193          return new $class($qa, $preferredbehaviour);
 194      }
 195  
 196      /**
 197       * @param string $behaviour the name of a behaviour.
 198       * @return array of {@link question_display_options} field names, that are
 199       * not relevant to this behaviour before a 'finish' action.
 200       */
 201      public static function get_behaviour_unused_display_options($behaviour) {
 202          return self::get_behaviour_type($behaviour)->get_unused_display_options();
 203      }
 204  
 205      /**
 206       * With this behaviour, is it possible that a question might finish as the student
 207       * interacts with it, without a call to the {@link question_attempt::finish()} method?
 208       * @param string $behaviour the name of a behaviour. E.g. 'deferredfeedback'.
 209       * @return bool whether with this behaviour, questions may finish naturally.
 210       */
 211      public static function can_questions_finish_during_the_attempt($behaviour) {
 212          return self::get_behaviour_type($behaviour)->can_questions_finish_during_the_attempt();
 213      }
 214  
 215      /**
 216       * Create a behaviour for a particular type. If that type cannot be
 217       * found, return an instance of qbehaviour_missing.
 218       *
 219       * Normally you should use {@link make_archetypal_behaviour()}, or
 220       * call the constructor of a particular model class directly. This method
 221       * is only intended for use by {@link question_attempt::load_from_records()}.
 222       *
 223       * @param string $behaviour the type of model to create.
 224       * @param question_attempt $qa the question attempt the model will process.
 225       * @param string $preferredbehaviour the preferred behaviour for the containing usage.
 226       * @return question_behaviour an instance of appropriate behaviour class.
 227       */
 228      public static function make_behaviour($behaviour, question_attempt $qa, $preferredbehaviour) {
 229          try {
 230              self::load_behaviour_class($behaviour);
 231          } catch (Exception $e) {
 232              self::load_behaviour_class('missing');
 233              return new qbehaviour_missing($qa, $preferredbehaviour);
 234          }
 235          $class = 'qbehaviour_' . $behaviour;
 236          return new $class($qa, $preferredbehaviour);
 237      }
 238  
 239      /**
 240       * Load the behaviour class(es) belonging to a particular model. That is,
 241       * include_once('/question/behaviour/' . $behaviour . '/behaviour.php'), with a bit
 242       * of checking.
 243       * @param string $qtypename the question type name. For example 'multichoice' or 'shortanswer'.
 244       */
 245      public static function load_behaviour_class($behaviour) {
 246          global $CFG;
 247          if (isset(self::$loadedbehaviours[$behaviour])) {
 248              return;
 249          }
 250          $file = $CFG->dirroot . '/question/behaviour/' . $behaviour . '/behaviour.php';
 251          if (!is_readable($file)) {
 252              throw new coding_exception('Unknown question behaviour ' . $behaviour);
 253          }
 254          include_once($file);
 255  
 256          $class = 'qbehaviour_' . $behaviour;
 257          if (!class_exists($class)) {
 258              throw new coding_exception('Question behaviour ' . $behaviour .
 259                      ' does not define the required class ' . $class . '.');
 260          }
 261  
 262          self::$loadedbehaviours[$behaviour] = 1;
 263      }
 264  
 265      /**
 266       * Create a behaviour for a particular type. If that type cannot be
 267       * found, return an instance of qbehaviour_missing.
 268       *
 269       * Normally you should use {@link make_archetypal_behaviour()}, or
 270       * call the constructor of a particular model class directly. This method
 271       * is only intended for use by {@link question_attempt::load_from_records()}.
 272       *
 273       * @param string $behaviour the type of model to create.
 274       * @param question_attempt $qa the question attempt the model will process.
 275       * @param string $preferredbehaviour the preferred behaviour for the containing usage.
 276       * @return question_behaviour_type an instance of appropriate behaviour class.
 277       */
 278      public static function get_behaviour_type($behaviour) {
 279  
 280          if (array_key_exists($behaviour, self::$behaviourtypes)) {
 281              return self::$behaviourtypes[$behaviour];
 282          }
 283  
 284          self::load_behaviour_type_class($behaviour);
 285  
 286          $class = 'qbehaviour_' . $behaviour . '_type';
 287          if (class_exists($class)) {
 288              self::$behaviourtypes[$behaviour] = new $class();
 289          } else {
 290              debugging('Question behaviour ' . $behaviour .
 291                      ' does not define the required class ' . $class . '.', DEBUG_DEVELOPER);
 292              self::$behaviourtypes[$behaviour] = new question_behaviour_type_fallback($behaviour);
 293          }
 294  
 295          return self::$behaviourtypes[$behaviour];
 296      }
 297  
 298      /**
 299       * Load the behaviour type class for a particular behaviour. That is,
 300       * include_once('/question/behaviour/' . $behaviour . '/behaviourtype.php').
 301       * @param string $behaviour the behaviour name. For example 'interactive' or 'deferredfeedback'.
 302       */
 303      protected static function load_behaviour_type_class($behaviour) {
 304          global $CFG;
 305          if (isset(self::$behaviourtypes[$behaviour])) {
 306              return;
 307          }
 308          $file = $CFG->dirroot . '/question/behaviour/' . $behaviour . '/behaviourtype.php';
 309          if (!is_readable($file)) {
 310              debugging('Question behaviour ' . $behaviour .
 311                      ' is missing the behaviourtype.php file.', DEBUG_DEVELOPER);
 312          }
 313          include_once($file);
 314      }
 315  
 316      /**
 317       * Return an array where the keys are the internal names of the archetypal
 318       * behaviours, and the values are a human-readable name. An
 319       * archetypal behaviour is one that is suitable to pass the name of to
 320       * {@link question_usage_by_activity::set_preferred_behaviour()}.
 321       *
 322       * @return array model name => lang string for this behaviour name.
 323       */
 324      public static function get_archetypal_behaviours() {
 325          $archetypes = array();
 326          $behaviours = core_component::get_plugin_list('qbehaviour');
 327          foreach ($behaviours as $behaviour => $notused) {
 328              if (self::is_behaviour_archetypal($behaviour)) {
 329                  $archetypes[$behaviour] = self::get_behaviour_name($behaviour);
 330              }
 331          }
 332          asort($archetypes, SORT_LOCALE_STRING);
 333          return $archetypes;
 334      }
 335  
 336      /**
 337       * @param string $behaviour the name of a behaviour. E.g. 'deferredfeedback'.
 338       * @return bool whether this is an archetypal behaviour.
 339       */
 340      public static function is_behaviour_archetypal($behaviour) {
 341          return self::get_behaviour_type($behaviour)->is_archetypal();
 342      }
 343  
 344      /**
 345       * Return an array where the keys are the internal names of the behaviours
 346       * in preferred order and the values are a human-readable name.
 347       *
 348       * @param array $archetypes, array of behaviours
 349       * @param string $orderlist, a comma separated list of behaviour names
 350       * @param string $disabledlist, a comma separated list of behaviour names
 351       * @param string $current, current behaviour name
 352       * @return array model name => lang string for this behaviour name.
 353       */
 354      public static function sort_behaviours($archetypes, $orderlist, $disabledlist, $current=null) {
 355  
 356          // Get disabled behaviours
 357          if ($disabledlist) {
 358              $disabled = explode(',', $disabledlist);
 359          } else {
 360              $disabled = array();
 361          }
 362  
 363          if ($orderlist) {
 364              $order = explode(',', $orderlist);
 365          } else {
 366              $order = array();
 367          }
 368  
 369          foreach ($disabled as $behaviour) {
 370              if (array_key_exists($behaviour, $archetypes) && $behaviour != $current) {
 371                  unset($archetypes[$behaviour]);
 372              }
 373          }
 374  
 375          // Get behaviours in preferred order
 376          $behaviourorder = array();
 377          foreach ($order as $behaviour) {
 378              if (array_key_exists($behaviour, $archetypes)) {
 379                  $behaviourorder[$behaviour] = $archetypes[$behaviour];
 380              }
 381          }
 382          // Get the rest of behaviours and sort them alphabetically
 383          $leftover = array_diff_key($archetypes, $behaviourorder);
 384          asort($leftover, SORT_LOCALE_STRING);
 385  
 386          // Set up the final order to be displayed
 387          return $behaviourorder + $leftover;
 388      }
 389  
 390      /**
 391       * Return an array where the keys are the internal names of the behaviours
 392       * in preferred order and the values are a human-readable name.
 393       *
 394       * @param string $currentbehaviour
 395       * @return array model name => lang string for this behaviour name.
 396       */
 397      public static function get_behaviour_options($currentbehaviour) {
 398          $config = question_bank::get_config();
 399          $archetypes = self::get_archetypal_behaviours();
 400  
 401          // If no admin setting return all behavious
 402          if (empty($config->disabledbehaviours) && empty($config->behavioursortorder)) {
 403              return $archetypes;
 404          }
 405  
 406          if (empty($config->behavioursortorder)) {
 407              $order = '';
 408          } else {
 409              $order = $config->behavioursortorder;
 410          }
 411          if (empty($config->disabledbehaviours)) {
 412              $disabled = '';
 413          } else {
 414              $disabled = $config->disabledbehaviours;
 415          }
 416  
 417          return self::sort_behaviours($archetypes, $order, $disabled, $currentbehaviour);
 418      }
 419  
 420      /**
 421       * Get the translated name of a behaviour, for display in the UI.
 422       * @param string $behaviour the internal name of the model.
 423       * @return string name from the current language pack.
 424       */
 425      public static function get_behaviour_name($behaviour) {
 426          return get_string('pluginname', 'qbehaviour_' . $behaviour);
 427      }
 428  
 429      /**
 430       * @return array all the file area names that may contain response files.
 431       */
 432      public static function get_all_response_file_areas() {
 433          $variables = array();
 434          foreach (question_bank::get_all_qtypes() as $qtype) {
 435              $variables += $qtype->response_file_areas();
 436          }
 437  
 438          $areas = array();
 439          foreach (array_unique($variables) as $variable) {
 440              $areas[] = 'response_' . $variable;
 441          }
 442          return $areas;
 443      }
 444  
 445      /**
 446       * Returns the valid choices for the number of decimal places for showing
 447       * question marks. For use in the user interface.
 448       * @return array suitable for passing to {@link html_writer::select()} or similar.
 449       */
 450      public static function get_dp_options() {
 451          return question_display_options::get_dp_options();
 452      }
 453  
 454      /**
 455       * Initialise the JavaScript required on pages where questions will be displayed.
 456       */
 457      public static function initialise_js() {
 458          return question_flags::initialise_js();
 459      }
 460  }
 461  
 462  
 463  /**
 464   * This class contains all the options that controls how a question is displayed.
 465   *
 466   * Normally, what will happen is that the calling code will set up some display
 467   * options to indicate what sort of question display it wants, and then before the
 468   * question is rendered, the behaviour will be given a chance to modify the
 469   * display options, so that, for example, A question that is finished will only
 470   * be shown read-only, and a question that has not been submitted will not have
 471   * any sort of feedback displayed.
 472   *
 473   * @copyright  2009 The Open University
 474   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 475   */
 476  class question_display_options {
 477      /**#@+ @var integer named constants for the values that most of the options take. */
 478      const HIDDEN = 0;
 479      const VISIBLE = 1;
 480      const EDITABLE = 2;
 481      /**#@-*/
 482  
 483      /**#@+ @var integer named constants for the {@link $marks} option. */
 484      const MAX_ONLY = 1;
 485      const MARK_AND_MAX = 2;
 486      /**#@-*/
 487  
 488      /**
 489       * @var integer maximum value for the {@link $markpd} option. This is
 490       * effectively set by the database structure, which uses NUMBER(12,7) columns
 491       * for question marks/fractions.
 492       */
 493      const MAX_DP = 7;
 494  
 495      /**
 496       * @var boolean whether the question should be displayed as a read-only review,
 497       * or in an active state where you can change the answer.
 498       */
 499      public $readonly = false;
 500  
 501      /**
 502       * @var boolean whether the question type should output hidden form fields
 503       * to reset any incorrect parts of the resonse to blank.
 504       */
 505      public $clearwrong = false;
 506  
 507      /**
 508       * Should the student have what they got right and wrong clearly indicated.
 509       * This includes the green/red hilighting of the bits of their response,
 510       * whether the one-line summary of the current state of the question says
 511       * correct/incorrect or just answered.
 512       * @var integer {@link question_display_options::HIDDEN} or
 513       * {@link question_display_options::VISIBLE}
 514       */
 515      public $correctness = self::VISIBLE;
 516  
 517      /**
 518       * The the mark and/or the maximum available mark for this question be visible?
 519       * @var integer {@link question_display_options::HIDDEN},
 520       * {@link question_display_options::MAX_ONLY} or {@link question_display_options::MARK_AND_MAX}
 521       */
 522      public $marks = self::MARK_AND_MAX;
 523  
 524      /** @var number of decimal places to use when formatting marks for output. */
 525      public $markdp = 2;
 526  
 527      /**
 528       * Should the flag this question UI element be visible, and if so, should the
 529       * flag state be changable?
 530       * @var integer {@link question_display_options::HIDDEN},
 531       * {@link question_display_options::VISIBLE} or {@link question_display_options::EDITABLE}
 532       */
 533      public $flags = self::VISIBLE;
 534  
 535      /**
 536       * Should the specific feedback be visible.
 537       * @var integer {@link question_display_options::HIDDEN} or
 538       * {@link question_display_options::VISIBLE}
 539       */
 540      public $feedback = self::VISIBLE;
 541  
 542      /**
 543       * For questions with a number of sub-parts (like matching, or
 544       * multiple-choice, multiple-reponse) display the number of sub-parts that
 545       * were correct.
 546       * @var integer {@link question_display_options::HIDDEN} or
 547       * {@link question_display_options::VISIBLE}
 548       */
 549      public $numpartscorrect = self::VISIBLE;
 550  
 551      /**
 552       * Should the general feedback be visible?
 553       * @var integer {@link question_display_options::HIDDEN} or
 554       * {@link question_display_options::VISIBLE}
 555       */
 556      public $generalfeedback = self::VISIBLE;
 557  
 558      /**
 559       * Should the automatically generated display of what the correct answer is
 560       * be visible?
 561       * @var integer {@link question_display_options::HIDDEN} or
 562       * {@link question_display_options::VISIBLE}
 563       */
 564      public $rightanswer = self::VISIBLE;
 565  
 566      /**
 567       * Should the manually added marker's comment be visible. Should the link for
 568       * adding/editing the comment be there.
 569       * @var integer {@link question_display_options::HIDDEN},
 570       * {@link question_display_options::VISIBLE}, or {@link question_display_options::EDITABLE}.
 571       * Editable means that form fields are displayed inline.
 572       */
 573      public $manualcomment = self::VISIBLE;
 574  
 575      /**
 576       * Should we show a 'Make comment or override grade' link?
 577       * @var string base URL for the edit comment script, which will be shown if
 578       * $manualcomment = self::VISIBLE.
 579       */
 580      public $manualcommentlink = null;
 581  
 582      /**
 583       * Used in places like the question history table, to show a link to review
 584       * this question in a certain state. If blank, a link is not shown.
 585       * @var string base URL for a review question script.
 586       */
 587      public $questionreviewlink = null;
 588  
 589      /**
 590       * Should the history of previous question states table be visible?
 591       * @var integer {@link question_display_options::HIDDEN} or
 592       * {@link question_display_options::VISIBLE}
 593       */
 594      public $history = self::HIDDEN;
 595  
 596      /**
 597       * @since 2.9
 598       * @var string extra HTML to include at the end of the outcome (feedback) box
 599       * of the question display.
 600       *
 601       * This field is now badly named. The place it included is was changed
 602       * (for the better) but the name was left unchanged for backwards compatibility.
 603       */
 604      public $extrainfocontent = '';
 605  
 606      /**
 607       * @since 2.9
 608       * @var string extra HTML to include in the history box of the question display,
 609       * if it is shown.
 610       */
 611      public $extrahistorycontent = '';
 612  
 613      /**
 614       * If not empty, then a link to edit the question will be included in
 615       * the info box for the question.
 616       *
 617       * If used, this array must contain an element courseid or cmid.
 618       *
 619       * It shoudl also contain a parameter returnurl => moodle_url giving a
 620       * sensible URL to go back to when the editing form is submitted or cancelled.
 621       *
 622       * @var array url parameter for the edit link. id => questiosnid will be
 623       * added automatically.
 624       */
 625      public $editquestionparams = array();
 626  
 627      /**
 628       * @var int the context the attempt being output belongs to.
 629       */
 630      public $context;
 631  
 632      /**
 633       * Set all the feedback-related fields {@link $feedback}, {@link generalfeedback},
 634       * {@link rightanswer} and {@link manualcomment} to
 635       * {@link question_display_options::HIDDEN}.
 636       */
 637      public function hide_all_feedback() {
 638          $this->feedback = self::HIDDEN;
 639          $this->numpartscorrect = self::HIDDEN;
 640          $this->generalfeedback = self::HIDDEN;
 641          $this->rightanswer = self::HIDDEN;
 642          $this->manualcomment = self::HIDDEN;
 643          $this->correctness = self::HIDDEN;
 644      }
 645  
 646      /**
 647       * Returns the valid choices for the number of decimal places for showing
 648       * question marks. For use in the user interface.
 649       *
 650       * Calling code should probably use {@link question_engine::get_dp_options()}
 651       * rather than calling this method directly.
 652       *
 653       * @return array suitable for passing to {@link html_writer::select()} or similar.
 654       */
 655      public static function get_dp_options() {
 656          $options = array();
 657          for ($i = 0; $i <= self::MAX_DP; $i += 1) {
 658              $options[$i] = $i;
 659          }
 660          return $options;
 661      }
 662  }
 663  
 664  
 665  /**
 666   * Contains the logic for handling question flags.
 667   *
 668   * @copyright  2010 The Open University
 669   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 670   */
 671  abstract class question_flags {
 672      /**
 673       * Get the checksum that validates that a toggle request is valid.
 674       * @param int $qubaid the question usage id.
 675       * @param int $questionid the question id.
 676       * @param int $sessionid the question_attempt id.
 677       * @param object $user the user. If null, defaults to $USER.
 678       * @return string that needs to be sent to question/toggleflag.php for it to work.
 679       */
 680      protected static function get_toggle_checksum($qubaid, $questionid,
 681              $qaid, $slot, $user = null) {
 682          if (is_null($user)) {
 683              global $USER;
 684              $user = $USER;
 685          }
 686          return md5($qubaid . "_" . $user->secret . "_" . $questionid . "_" . $qaid . "_" . $slot);
 687      }
 688  
 689      /**
 690       * Get the postdata that needs to be sent to question/toggleflag.php to change the flag state.
 691       * You need to append &newstate=0/1 to this.
 692       * @return the post data to send.
 693       */
 694      public static function get_postdata(question_attempt $qa) {
 695          $qaid = $qa->get_database_id();
 696          $qubaid = $qa->get_usage_id();
 697          $qid = $qa->get_question()->id;
 698          $slot = $qa->get_slot();
 699          $checksum = self::get_toggle_checksum($qubaid, $qid, $qaid, $slot);
 700          return "qaid={$qaid}&qubaid={$qubaid}&qid={$qid}&slot={$slot}&checksum={$checksum}&sesskey=" .
 701                  sesskey() . '&newstate=';
 702      }
 703  
 704      /**
 705       * If the request seems valid, update the flag state of a question attempt.
 706       * Throws exceptions if this is not a valid update request.
 707       * @param int $qubaid the question usage id.
 708       * @param int $questionid the question id.
 709       * @param int $sessionid the question_attempt id.
 710       * @param string $checksum checksum, as computed by {@link get_toggle_checksum()}
 711       *      corresponding to the last three arguments.
 712       * @param bool $newstate the new state of the flag. true = flagged.
 713       */
 714      public static function update_flag($qubaid, $questionid, $qaid, $slot, $checksum, $newstate) {
 715          // Check the checksum - it is very hard to know who a question session belongs
 716          // to, so we require that checksum parameter is matches an md5 hash of the
 717          // three ids and the users username. Since we are only updating a flag, that
 718          // probably makes it sufficiently difficult for malicious users to toggle
 719          // other users flags.
 720          if ($checksum != self::get_toggle_checksum($qubaid, $questionid, $qaid, $slot)) {
 721              throw new moodle_exception('errorsavingflags', 'question');
 722          }
 723  
 724          $dm = new question_engine_data_mapper();
 725          $dm->update_question_attempt_flag($qubaid, $questionid, $qaid, $slot, $newstate);
 726      }
 727  
 728      public static function initialise_js() {
 729          global $CFG, $PAGE, $OUTPUT;
 730          static $done = false;
 731          if ($done) {
 732              return;
 733          }
 734          $module = array(
 735              'name' => 'core_question_flags',
 736              'fullpath' => '/question/flags.js',
 737              'requires' => array('base', 'dom', 'event-delegate', 'io-base'),
 738          );
 739          $actionurl = $CFG->wwwroot . '/question/toggleflag.php';
 740          $flagtext = array(
 741              0 => get_string('clickflag', 'question'),
 742              1 => get_string('clickunflag', 'question')
 743          );
 744          $flagattributes = array(
 745              0 => array(
 746                  'src' => $OUTPUT->pix_url('i/unflagged') . '',
 747                  'title' => get_string('clicktoflag', 'question'),
 748                  'alt' => get_string('notflagged', 'question'),
 749                //  'text' => get_string('clickflag', 'question'),
 750              ),
 751              1 => array(
 752                  'src' => $OUTPUT->pix_url('i/flagged') . '',
 753                  'title' => get_string('clicktounflag', 'question'),
 754                  'alt' => get_string('flagged', 'question'),
 755                 // 'text' => get_string('clickunflag', 'question'),
 756              ),
 757          );
 758          $PAGE->requires->js_init_call('M.core_question_flags.init',
 759                  array($actionurl, $flagattributes, $flagtext), false, $module);
 760          $done = true;
 761      }
 762  }
 763  
 764  
 765  /**
 766   * Exception thrown when the system detects that a student has done something
 767   * out-of-order to a question. This can happen, for example, if they click
 768   * the browser's back button in a quiz, then try to submit a different response.
 769   *
 770   * @copyright  2010 The Open University
 771   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 772   */
 773  class question_out_of_sequence_exception extends moodle_exception {
 774      public function __construct($qubaid, $slot, $postdata) {
 775          if ($postdata == null) {
 776              $postdata = data_submitted();
 777          }
 778          parent::__construct('submissionoutofsequence', 'question', '', null,
 779                  "QUBAid: {$qubaid}, slot: {$slot}, post data: " . print_r($postdata, true));
 780      }
 781  }
 782  
 783  
 784  /**
 785   * Useful functions for writing question types and behaviours.
 786   *
 787   * @copyright 2010 The Open University
 788   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 789   */
 790  abstract class question_utils {
 791      /**
 792       * Tests to see whether two arrays have the same keys, with the same values
 793       * (as compared by ===) for each key. However, the order of the arrays does
 794       * not have to be the same.
 795       * @param array $array1 the first array.
 796       * @param array $array2 the second array.
 797       * @return bool whether the two arrays have the same keys with the same
 798       *      corresponding values.
 799       */
 800      public static function arrays_have_same_keys_and_values(array $array1, array $array2) {
 801          if (count($array1) != count($array2)) {
 802              return false;
 803          }
 804          foreach ($array1 as $key => $value1) {
 805              if (!array_key_exists($key, $array2)) {
 806                  return false;
 807              }
 808              if (((string) $value1) !== ((string) $array2[$key])) {
 809                  return false;
 810              }
 811          }
 812          return true;
 813      }
 814  
 815      /**
 816       * Tests to see whether two arrays have the same value at a particular key.
 817       * This method will return true if:
 818       * 1. Neither array contains the key; or
 819       * 2. Both arrays contain the key, and the corresponding values compare
 820       *      identical when cast to strings and compared with ===.
 821       * @param array $array1 the first array.
 822       * @param array $array2 the second array.
 823       * @param string $key an array key.
 824       * @return bool whether the two arrays have the same value (or lack of
 825       *      one) for a given key.
 826       */
 827      public static function arrays_same_at_key(array $array1, array $array2, $key) {
 828          if (array_key_exists($key, $array1) && array_key_exists($key, $array2)) {
 829              return ((string) $array1[$key]) === ((string) $array2[$key]);
 830          }
 831          if (!array_key_exists($key, $array1) && !array_key_exists($key, $array2)) {
 832              return true;
 833          }
 834          return false;
 835      }
 836  
 837      /**
 838       * Tests to see whether two arrays have the same value at a particular key.
 839       * Missing values are replaced by '', and then the values are cast to
 840       * strings and compared with ===.
 841       * @param array $array1 the first array.
 842       * @param array $array2 the second array.
 843       * @param string $key an array key.
 844       * @return bool whether the two arrays have the same value (or lack of
 845       *      one) for a given key.
 846       */
 847      public static function arrays_same_at_key_missing_is_blank(
 848              array $array1, array $array2, $key) {
 849          if (array_key_exists($key, $array1)) {
 850              $value1 = $array1[$key];
 851          } else {
 852              $value1 = '';
 853          }
 854          if (array_key_exists($key, $array2)) {
 855              $value2 = $array2[$key];
 856          } else {
 857              $value2 = '';
 858          }
 859          return ((string) $value1) === ((string) $value2);
 860      }
 861  
 862      /**
 863       * Tests to see whether two arrays have the same value at a particular key.
 864       * Missing values are replaced by 0, and then the values are cast to
 865       * integers and compared with ===.
 866       * @param array $array1 the first array.
 867       * @param array $array2 the second array.
 868       * @param string $key an array key.
 869       * @return bool whether the two arrays have the same value (or lack of
 870       *      one) for a given key.
 871       */
 872      public static function arrays_same_at_key_integer(
 873              array $array1, array $array2, $key) {
 874          if (array_key_exists($key, $array1)) {
 875              $value1 = (int) $array1[$key];
 876          } else {
 877              $value1 = 0;
 878          }
 879          if (array_key_exists($key, $array2)) {
 880              $value2 = (int) $array2[$key];
 881          } else {
 882              $value2 = 0;
 883          }
 884          return $value1 === $value2;
 885      }
 886  
 887      private static $units     = array('', 'i', 'ii', 'iii', 'iv', 'v', 'vi', 'vii', 'viii', 'ix');
 888      private static $tens      = array('', 'x', 'xx', 'xxx', 'xl', 'l', 'lx', 'lxx', 'lxxx', 'xc');
 889      private static $hundreds  = array('', 'c', 'cc', 'ccc', 'cd', 'd', 'dc', 'dcc', 'dccc', 'cm');
 890      private static $thousands = array('', 'm', 'mm', 'mmm');
 891  
 892      /**
 893       * Convert an integer to roman numerals.
 894       * @param int $number an integer between 1 and 3999 inclusive. Anything else
 895       *      will throw an exception.
 896       * @return string the number converted to lower case roman numerals.
 897       */
 898      public static function int_to_roman($number) {
 899          if (!is_integer($number) || $number < 1 || $number > 3999) {
 900              throw new coding_exception('Only integers between 0 and 3999 can be ' .
 901                      'converted to roman numerals.', $number);
 902          }
 903  
 904          return self::$thousands[$number / 1000 % 10] . self::$hundreds[$number / 100 % 10] .
 905                  self::$tens[$number / 10 % 10] . self::$units[$number % 10];
 906      }
 907  
 908      /**
 909       * Typically, $mark will have come from optional_param($name, null, PARAM_RAW_TRIMMED).
 910       * This method copes with:
 911       *  - keeping null or '' input unchanged - important to let teaches set a question back to requries grading.
 912       *  - numbers that were typed as either 1.00 or 1,00 form.
 913       *  - invalid things, which get turned into null.
 914       *
 915       * @param string|null $mark raw use input of a mark.
 916       * @return float|string|null cleaned mark as a float if possible. Otherwise '' or null.
 917       */
 918      public static function clean_param_mark($mark) {
 919          if ($mark === '' || is_null($mark)) {
 920              return $mark;
 921          }
 922  
 923          $mark = str_replace(',', '.', $mark);
 924          // This regexp should match the one in validate_param.
 925          if (!preg_match('/^[\+-]?[0-9]*\.?[0-9]*(e[-+]?[0-9]+)?$/i', $mark)) {
 926              return null;
 927          }
 928  
 929          return clean_param($mark, PARAM_FLOAT);
 930      }
 931  
 932      /**
 933       * Get a sumitted variable (from the GET or POST data) that is a mark.
 934       * @param string $parname the submitted variable name.
 935       * @return float|string|null cleaned mark as a float if possible. Otherwise '' or null.
 936       */
 937      public static function optional_param_mark($parname) {
 938          return self::clean_param_mark(
 939                  optional_param($parname, null, PARAM_RAW_TRIMMED));
 940      }
 941  
 942      /**
 943       * Convert part of some question content to plain text.
 944       * @param string $text the text.
 945       * @param int $format the text format.
 946       * @param array $options formatting options. Passed to {@link format_text}.
 947       * @return float|string|null cleaned mark as a float if possible. Otherwise '' or null.
 948       */
 949      public static function to_plain_text($text, $format, $options = array('noclean' => 'true')) {
 950          // The following call to html_to_text uses the option that strips out
 951          // all URLs, but format_text complains if it finds @@PLUGINFILE@@ tokens.
 952          // So, we need to replace @@PLUGINFILE@@ with a real URL, but it doesn't
 953          // matter what. We use http://example.com/.
 954          $text = str_replace('@@PLUGINFILE@@/', 'http://example.com/', $text);
 955          return html_to_text(format_text($text, $format, $options), 0, false);
 956      }
 957  }
 958  
 959  
 960  /**
 961   * The interface for strategies for controlling which variant of each question is used.
 962   *
 963   * @copyright  2011 The Open University
 964   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 965   */
 966  interface question_variant_selection_strategy {
 967      /**
 968       * @param int $maxvariants the num
 969       * @param string $seed data that can be used to controls how the variant is selected
 970       *      in a semi-random way.
 971       * @return int the variant to use, a number betweeb 1 and $maxvariants inclusive.
 972       */
 973      public function choose_variant($maxvariants, $seed);
 974  }
 975  
 976  
 977  /**
 978   * A {@link question_variant_selection_strategy} that is completely random.
 979   *
 980   * @copyright  2011 The Open University
 981   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 982   */
 983  class question_variant_random_strategy implements question_variant_selection_strategy {
 984      public function choose_variant($maxvariants, $seed) {
 985          return rand(1, $maxvariants);
 986      }
 987  }
 988  
 989  
 990  /**
 991   * A {@link question_variant_selection_strategy} that is effectively random
 992   * for the first attempt, and then after that cycles through the available
 993   * variants so that the students will not get a repeated variant until they have
 994   * seen them all.
 995   *
 996   * @copyright  2011 The Open University
 997   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 998   */
 999  class question_variant_pseudorandom_no_repeats_strategy
1000          implements question_variant_selection_strategy {
1001  
1002      /** @var int the number of attempts this users has had, including the curent one. */
1003      protected $attemptno;
1004  
1005      /** @var int the user id the attempt belongs to. */
1006      protected $userid;
1007  
1008      /** @var string extra input fed into the pseudo-random code. */
1009      protected $extrarandomness = '';
1010  
1011      /**
1012       * Constructor.
1013       * @param int $attemptno The attempt number.
1014       * @param int $userid the user the attempt is for (defaults to $USER->id).
1015       */
1016      public function __construct($attemptno, $userid = null, $extrarandomness = '') {
1017          $this->attemptno = $attemptno;
1018          if (is_null($userid)) {
1019              global $USER;
1020              $this->userid = $USER->id;
1021          } else {
1022              $this->userid = $userid;
1023          }
1024  
1025          if ($extrarandomness) {
1026              $this->extrarandomness = '|' . $extrarandomness;
1027          }
1028      }
1029  
1030      public function choose_variant($maxvariants, $seed) {
1031          if ($maxvariants == 1) {
1032              return 1;
1033          }
1034  
1035          $hash = sha1($seed . '|user' . $this->userid . $this->extrarandomness);
1036          $randint = hexdec(substr($hash, 17, 7));
1037  
1038          return ($randint + $this->attemptno) % $maxvariants + 1;
1039      }
1040  }
1041  
1042  /**
1043   * A {@link question_variant_selection_strategy} designed ONLY for testing.
1044   * For selected questions it wil return a specific variants. For the other
1045   * slots it will use a fallback strategy.
1046   *
1047   * @copyright  2013 The Open University
1048   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
1049   */
1050  class question_variant_forced_choices_selection_strategy
1051      implements question_variant_selection_strategy {
1052  
1053      /** @var array seed => variant to select. */
1054      protected $forcedchoices;
1055  
1056      /** @var question_variant_selection_strategy strategy used to make the non-forced choices. */
1057      protected $basestrategy;
1058  
1059      /**
1060       * Constructor.
1061       * @param array $forcedchoices array seed => variant to select.
1062       * @param question_variant_selection_strategy $basestrategy strategy used
1063       *      to make the non-forced choices.
1064       */
1065      public function __construct(array $forcedchoices, question_variant_selection_strategy $basestrategy) {
1066          $this->forcedchoices = $forcedchoices;
1067          $this->basestrategy  = $basestrategy;
1068      }
1069  
1070      public function choose_variant($maxvariants, $seed) {
1071          if (array_key_exists($seed, $this->forcedchoices)) {
1072              if ($this->forcedchoices[$seed] > $maxvariants) {
1073                  throw new coding_exception('Forced variant out of range.');
1074              }
1075              return $this->forcedchoices[$seed];
1076          } else {
1077              return $this->basestrategy->choose_variant($maxvariants, $seed);
1078          }
1079      }
1080  
1081      /**
1082       * Helper method for preparing the $forcedchoices array.
1083       * @param array                      $variantsbyslot slot number => variant to select.
1084       * @param question_usage_by_activity $quba           the question usage we need a strategy for.
1085       * @throws coding_exception when variant cannot be forced as doesn't work.
1086       * @return array that can be passed to the constructor as $forcedchoices.
1087       */
1088      public static function prepare_forced_choices_array(array $variantsbyslot,
1089                                                          question_usage_by_activity $quba) {
1090  
1091          $forcedchoices = array();
1092  
1093          foreach ($variantsbyslot as $slot => $varianttochoose) {
1094              $question = $quba->get_question($slot);
1095              $seed = $question->get_variants_selection_seed();
1096              if (array_key_exists($seed, $forcedchoices) && $forcedchoices[$seed] != $varianttochoose) {
1097                  throw new coding_exception('Inconsistent forced variant detected at slot ' . $slot);
1098              }
1099              if ($varianttochoose > $question->get_num_variants()) {
1100                  throw new coding_exception('Forced variant out of range at slot ' . $slot);
1101              }
1102              $forcedchoices[$seed] = $varianttochoose;
1103          }
1104          return $forcedchoices;
1105      }
1106  }