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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 file defines the question usage class, and a few related classes.
  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  
  30  /**
  31   * This class keeps track of a group of questions that are being attempted,
  32   * and which state, and so on, each one is currently in.
  33   *
  34   * A quiz attempt or a lesson attempt could use an instance of this class to
  35   * keep track of all the questions in the attempt and process student submissions.
  36   * It is basically a collection of {@question_attempt} objects.
  37   *
  38   * The questions being attempted as part of this usage are identified by an integer
  39   * that is passed into many of the methods as $slot. ($question->id is not
  40   * used so that the same question can be used more than once in an attempt.)
  41   *
  42   * Normally, calling code should be able to do everything it needs to be calling
  43   * methods of this class. You should not normally need to get individual
  44   * {@question_attempt} objects and play around with their inner workind, in code
  45   * that it outside the quetsion engine.
  46   *
  47   * Instances of this class correspond to rows in the question_usages table.
  48   *
  49   * @copyright  2009 The Open University
  50   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  51   */
  52  class question_usage_by_activity {
  53      /**
  54       * @var integer|string the id for this usage. If this usage was loaded from
  55       * the database, then this is the database id. Otherwise a unique random
  56       * string is used.
  57       */
  58      protected $id = null;
  59  
  60      /**
  61       * @var string name of an archetypal behaviour, that should be used
  62       * by questions in this usage if possible.
  63       */
  64      protected $preferredbehaviour = null;
  65  
  66      /** @var context the context this usage belongs to. */
  67      protected $context;
  68  
  69      /** @var string plugin name of the plugin this usage belongs to. */
  70      protected $owningcomponent;
  71  
  72      /** @var array {@link question_attempt}s that make up this usage. */
  73      protected $questionattempts = array();
  74  
  75      /** @var question_usage_observer that tracks changes to this usage. */
  76      protected $observer;
  77  
  78      /**
  79       * Create a new instance. Normally, calling code should use
  80       * {@link question_engine::make_questions_usage_by_activity()} or
  81       * {@link question_engine::load_questions_usage_by_activity()} rather than
  82       * calling this constructor directly.
  83       *
  84       * @param string $component the plugin creating this attempt. For example mod_quiz.
  85       * @param object $context the context this usage belongs to.
  86       */
  87      public function __construct($component, $context) {
  88          $this->owningcomponent = $component;
  89          $this->context = $context;
  90          $this->observer = new question_usage_null_observer();
  91      }
  92  
  93      /**
  94       * @param string $behaviour the name of an archetypal behaviour, that should
  95       * be used by questions in this usage if possible.
  96       */
  97      public function set_preferred_behaviour($behaviour) {
  98          $this->preferredbehaviour = $behaviour;
  99          $this->observer->notify_modified();
 100      }
 101  
 102      /** @return string the name of the preferred behaviour. */
 103      public function get_preferred_behaviour() {
 104          return $this->preferredbehaviour;
 105      }
 106  
 107      /** @return context the context this usage belongs to. */
 108      public function get_owning_context() {
 109          return $this->context;
 110      }
 111  
 112      /** @return string the name of the plugin that owns this attempt. */
 113      public function get_owning_component() {
 114          return $this->owningcomponent;
 115      }
 116  
 117      /** @return int|string If this usage came from the database, then the id
 118       * from the question_usages table is returned. Otherwise a random string is
 119       * returned. */
 120      public function get_id() {
 121          if (is_null($this->id)) {
 122              $this->id = random_string(10);
 123          }
 124          return $this->id;
 125      }
 126  
 127      /**
 128       * For internal use only. Used by {@link question_engine_data_mapper} to set
 129       * the id when a usage is saved to the database.
 130       * @param int $id the newly determined id for this usage.
 131       */
 132      public function set_id_from_database($id) {
 133          $this->id = $id;
 134          foreach ($this->questionattempts as $qa) {
 135              $qa->set_usage_id($id);
 136          }
 137      }
 138  
 139      /** @return question_usage_observer that is tracking changes made to this usage. */
 140      public function get_observer() {
 141          return $this->observer;
 142      }
 143  
 144      /**
 145       * You should almost certainly not call this method from your code. It is for
 146       * internal use only.
 147       * @param question_usage_observer that should be used to tracking changes made to this usage.
 148       */
 149      public function set_observer($observer) {
 150          $this->observer = $observer;
 151          foreach ($this->questionattempts as $qa) {
 152              $qa->set_observer($observer);
 153          }
 154      }
 155  
 156      /**
 157       * Add another question to this usage.
 158       *
 159       * The added question is not started until you call {@link start_question()}
 160       * on it.
 161       *
 162       * @param question_definition $question the question to add.
 163       * @param number $maxmark the maximum this question will be marked out of in
 164       *      this attempt (optional). If not given, $question->defaultmark is used.
 165       * @return int the number used to identify this question within this usage.
 166       */
 167      public function add_question(question_definition $question, $maxmark = null) {
 168          $qa = new question_attempt($question, $this->get_id(), $this->observer, $maxmark);
 169          $qa->set_slot($this->next_slot_number());
 170          $this->questionattempts[$this->next_slot_number()] = $qa;
 171          $this->observer->notify_attempt_added($qa);
 172          return $qa->get_slot();
 173      }
 174  
 175      /**
 176       * Add another question to this usage, in the place of an existing slot.
 177       * The question_attempt that was in that slot is moved to the end at a new
 178       * slot number, which is returned.
 179       *
 180       * The added question is not started until you call {@link start_question()}
 181       * on it.
 182       *
 183       * @param int $slot the slot-number of the question to replace.
 184       * @param question_definition $question the question to add.
 185       * @param number $maxmark the maximum this question will be marked out of in
 186       *      this attempt (optional). If not given, the max mark from the $qa we
 187       *      are replacing is used.
 188       * @return int the new slot number of the question that was displaced.
 189       */
 190      public function add_question_in_place_of_other($slot, question_definition $question, $maxmark = null) {
 191          $newslot = $this->next_slot_number();
 192  
 193          $oldqa = $this->get_question_attempt($slot);
 194          $oldqa->set_slot($newslot);
 195          $this->questionattempts[$newslot] = $oldqa;
 196  
 197          if ($maxmark === null) {
 198              $maxmark = $oldqa->get_max_mark();
 199          }
 200  
 201          $qa = new question_attempt($question, $this->get_id(), $this->observer, $maxmark);
 202          $qa->set_slot($slot);
 203          $this->questionattempts[$slot] = $qa;
 204  
 205          $this->observer->notify_attempt_moved($oldqa, $slot);
 206          $this->observer->notify_attempt_added($qa);
 207  
 208          return $newslot;
 209      }
 210  
 211      /**
 212       * The slot number that will be allotted to the next question added.
 213       */
 214      public function next_slot_number() {
 215          return count($this->questionattempts) + 1;
 216      }
 217  
 218      /**
 219       * Get the question_definition for a question in this attempt.
 220       * @param int $slot the number used to identify this question within this usage.
 221       * @return question_definition the requested question object.
 222       */
 223      public function get_question($slot) {
 224          return $this->get_question_attempt($slot)->get_question();
 225      }
 226  
 227      /** @return array all the identifying numbers of all the questions in this usage. */
 228      public function get_slots() {
 229          return array_keys($this->questionattempts);
 230      }
 231  
 232      /** @return int the identifying number of the first question that was added to this usage. */
 233      public function get_first_question_number() {
 234          reset($this->questionattempts);
 235          return key($this->questionattempts);
 236      }
 237  
 238      /** @return int the number of questions that are currently in this usage. */
 239      public function question_count() {
 240          return count($this->questionattempts);
 241      }
 242  
 243      /**
 244       * Note the part of the {@link question_usage_by_activity} comment that explains
 245       * that {@link question_attempt} objects should be considered part of the inner
 246       * workings of the question engine, and should not, if possible, be accessed directly.
 247       *
 248       * @return question_attempt_iterator for iterating over all the questions being
 249       * attempted. as part of this usage.
 250       */
 251      public function get_attempt_iterator() {
 252          return new question_attempt_iterator($this);
 253      }
 254  
 255      /**
 256       * Check whether $number actually corresponds to a question attempt that is
 257       * part of this usage. Throws an exception if not.
 258       *
 259       * @param int $slot a number allegedly identifying a question within this usage.
 260       */
 261      protected function check_slot($slot) {
 262          if (!array_key_exists($slot, $this->questionattempts)) {
 263              throw new coding_exception('There is no question_attempt number ' . $slot .
 264                      ' in this attempt.');
 265          }
 266      }
 267  
 268      /**
 269       * Note the part of the {@link question_usage_by_activity} comment that explains
 270       * that {@link question_attempt} objects should be considered part of the inner
 271       * workings of the question engine, and should not, if possible, be accessed directly.
 272       *
 273       * @param int $slot the number used to identify this question within this usage.
 274       * @return question_attempt the corresponding {@link question_attempt} object.
 275       */
 276      public function get_question_attempt($slot) {
 277          $this->check_slot($slot);
 278          return $this->questionattempts[$slot];
 279      }
 280  
 281      /**
 282       * Get the current state of the attempt at a question.
 283       * @param int $slot the number used to identify this question within this usage.
 284       * @return question_state.
 285       */
 286      public function get_question_state($slot) {
 287          return $this->get_question_attempt($slot)->get_state();
 288      }
 289  
 290      /**
 291       * @param int $slot the number used to identify this question within this usage.
 292       * @param bool $showcorrectness Whether right/partial/wrong states should
 293       * be distinguised.
 294       * @return string A brief textual description of the current state.
 295       */
 296      public function get_question_state_string($slot, $showcorrectness) {
 297          return $this->get_question_attempt($slot)->get_state_string($showcorrectness);
 298      }
 299  
 300      /**
 301       * @param int $slot the number used to identify this question within this usage.
 302       * @param bool $showcorrectness Whether right/partial/wrong states should
 303       * be distinguised.
 304       * @return string a CSS class name for the current state.
 305       */
 306      public function get_question_state_class($slot, $showcorrectness) {
 307          return $this->get_question_attempt($slot)->get_state_class($showcorrectness);
 308      }
 309  
 310      /**
 311       * Whether this attempt at a given question could be completed just by the
 312       * student interacting with the question, before {@link finish_question()} is called.
 313       *
 314       * @param int $slot the number used to identify this question within this usage.
 315       * @return boolean whether the attempt at the given question can finish naturally.
 316       */
 317      public function can_question_finish_during_attempt($slot) {
 318          return $this->get_question_attempt($slot)->can_finish_during_attempt();
 319      }
 320  
 321      /**
 322       * Get the time of the most recent action performed on a question.
 323       * @param int $slot the number used to identify this question within this usage.
 324       * @return int timestamp.
 325       */
 326      public function get_question_action_time($slot) {
 327          return $this->get_question_attempt($slot)->get_last_action_time();
 328      }
 329  
 330      /**
 331       * Get the current fraction awarded for the attempt at a question.
 332       * @param int $slot the number used to identify this question within this usage.
 333       * @return number|null The current fraction for this question, or null if one has
 334       * not been assigned yet.
 335       */
 336      public function get_question_fraction($slot) {
 337          return $this->get_question_attempt($slot)->get_fraction();
 338      }
 339  
 340      /**
 341       * Get the current mark awarded for the attempt at a question.
 342       * @param int $slot the number used to identify this question within this usage.
 343       * @return number|null The current mark for this question, or null if one has
 344       * not been assigned yet.
 345       */
 346      public function get_question_mark($slot) {
 347          return $this->get_question_attempt($slot)->get_mark();
 348      }
 349  
 350      /**
 351       * Get the maximum mark possible for the attempt at a question.
 352       * @param int $slot the number used to identify this question within this usage.
 353       * @return number the available marks for this question.
 354       */
 355      public function get_question_max_mark($slot) {
 356          return $this->get_question_attempt($slot)->get_max_mark();
 357      }
 358  
 359      /**
 360       * Get the total mark for all questions in this usage.
 361       * @return number The sum of marks of all the question_attempts in this usage.
 362       */
 363      public function get_total_mark() {
 364          $mark = 0;
 365          foreach ($this->questionattempts as $qa) {
 366              if ($qa->get_max_mark() > 0 && $qa->get_state() == question_state::$needsgrading) {
 367                  return null;
 368              }
 369              $mark += $qa->get_mark();
 370          }
 371          return $mark;
 372      }
 373  
 374      /**
 375       * Get summary information about this usage.
 376       *
 377       * Some behaviours may be able to provide interesting summary information
 378       * about the attempt as a whole, and this method provides access to that data.
 379       * To see how this works, try setting a quiz to one of the CBM behaviours,
 380       * and then look at the extra information displayed at the top of the quiz
 381       * review page once you have sumitted an attempt.
 382       *
 383       * In the return value, the array keys are identifiers of the form
 384       * qbehaviour_behaviourname_meaningfullkey. For qbehaviour_deferredcbm_highsummary.
 385       * The values are arrays with two items, title and content. Each of these
 386       * will be either a string, or a renderable.
 387       *
 388       * @return array as described above.
 389       */
 390      public function get_summary_information(question_display_options $options) {
 391          return question_engine::get_behaviour_type($this->preferredbehaviour)
 392                  ->summarise_usage($this, $options);
 393      }
 394  
 395      /**
 396       * @return string a simple textual summary of the question that was asked.
 397       */
 398      public function get_question_summary($slot) {
 399          return $this->get_question_attempt($slot)->get_question_summary();
 400      }
 401  
 402      /**
 403       * @return string a simple textual summary of response given.
 404       */
 405      public function get_response_summary($slot) {
 406          return $this->get_question_attempt($slot)->get_response_summary();
 407      }
 408  
 409      /**
 410       * @return string a simple textual summary of the correct resonse.
 411       */
 412      public function get_right_answer_summary($slot) {
 413          return $this->get_question_attempt($slot)->get_right_answer_summary();
 414      }
 415  
 416      /**
 417       * Return one of the bits of metadata for a particular question attempt in
 418       * this usage.
 419       * @param int $slot the slot number of the question of inereest.
 420       * @param string $name the name of the metadata variable to return.
 421       * @return string the value of that metadata variable.
 422       */
 423      public function get_question_attempt_metadata($slot, $name) {
 424          return $this->get_question_attempt($slot)->get_metadata($name);
 425      }
 426  
 427      /**
 428       * Set some metadata for a particular question attempt in this usage.
 429       * @param int $slot the slot number of the question of inerest.
 430       * @param string $name the name of the metadata variable to return.
 431       * @param string $value the value to set that metadata variable to.
 432       */
 433      public function set_question_attempt_metadata($slot, $name, $value) {
 434          $this->get_question_attempt($slot)->set_metadata($name, $value);
 435      }
 436  
 437      /**
 438       * Get the {@link core_question_renderer}, in collaboration with appropriate
 439       * {@link qbehaviour_renderer} and {@link qtype_renderer} subclasses, to generate the
 440       * HTML to display this question.
 441       * @param int $slot the number used to identify this question within this usage.
 442       * @param question_display_options $options controls how the question is rendered.
 443       * @param string|null $number The question number to display. 'i' is a special
 444       *      value that gets displayed as Information. Null means no number is displayed.
 445       * @return string HTML fragment representing the question.
 446       */
 447      public function render_question($slot, $options, $number = null) {
 448          $options->context = $this->context;
 449          return $this->get_question_attempt($slot)->render($options, $number);
 450      }
 451  
 452      /**
 453       * Generate any bits of HTML that needs to go in the <head> tag when this question
 454       * is displayed in the body.
 455       * @param int $slot the number used to identify this question within this usage.
 456       * @return string HTML fragment.
 457       */
 458      public function render_question_head_html($slot) {
 459          //$options->context = $this->context;
 460          return $this->get_question_attempt($slot)->render_head_html();
 461      }
 462  
 463      /**
 464       * Like {@link render_question()} but displays the question at the past step
 465       * indicated by $seq, rather than showing the latest step.
 466       *
 467       * @param int $slot the number used to identify this question within this usage.
 468       * @param int $seq the seq number of the past state to display.
 469       * @param question_display_options $options controls how the question is rendered.
 470       * @param string|null $number The question number to display. 'i' is a special
 471       *      value that gets displayed as Information. Null means no number is displayed.
 472       * @return string HTML fragment representing the question.
 473       */
 474      public function render_question_at_step($slot, $seq, $options, $number = null) {
 475          $options->context = $this->context;
 476          return $this->get_question_attempt($slot)->render_at_step(
 477                  $seq, $options, $number, $this->preferredbehaviour);
 478      }
 479  
 480      /**
 481       * Checks whether the users is allow to be served a particular file.
 482       * @param int $slot the number used to identify this question within this usage.
 483       * @param question_display_options $options the options that control display of the question.
 484       * @param string $component the name of the component we are serving files for.
 485       * @param string $filearea the name of the file area.
 486       * @param array $args the remaining bits of the file path.
 487       * @param bool $forcedownload whether the user must be forced to download the file.
 488       * @return bool true if the user can access this file.
 489       */
 490      public function check_file_access($slot, $options, $component, $filearea,
 491              $args, $forcedownload) {
 492          return $this->get_question_attempt($slot)->check_file_access(
 493                  $options, $component, $filearea, $args, $forcedownload);
 494      }
 495  
 496      /**
 497       * Replace a particular question_attempt with a different one.
 498       *
 499       * For internal use only. Used when reloading the state of a question from the
 500       * database.
 501       *
 502       * @param array $records Raw records loaded from the database.
 503       * @param int $questionattemptid The id of the question_attempt to extract.
 504       * @return question_attempt The newly constructed question_attempt_step.
 505       */
 506      public function replace_loaded_question_attempt_info($slot, $qa) {
 507          $this->check_slot($slot);
 508          $this->questionattempts[$slot] = $qa;
 509      }
 510  
 511      /**
 512       * You should probably not use this method in code outside the question engine.
 513       * The main reason for exposing it was for the benefit of unit tests.
 514       * @param int $slot the number used to identify this question within this usage.
 515       * @return string return the prefix that is pre-pended to field names in the HTML
 516       * that is output.
 517       */
 518      public function get_field_prefix($slot) {
 519          return $this->get_question_attempt($slot)->get_field_prefix();
 520      }
 521  
 522      /**
 523       * Get the number of variants available for the question in this slot.
 524       * @param int $slot the number used to identify this question within this usage.
 525       * @return int the number of variants available.
 526       */
 527      public function get_num_variants($slot) {
 528          return $this->get_question_attempt($slot)->get_question()->get_num_variants();
 529      }
 530  
 531      /**
 532       * Get the variant of the question being used in a given slot.
 533       * @param int $slot the number used to identify this question within this usage.
 534       * @return int the variant of this question that is being used.
 535       */
 536      public function get_variant($slot) {
 537          return $this->get_question_attempt($slot)->get_variant();
 538      }
 539  
 540      /**
 541       * Start the attempt at a question that has been added to this usage.
 542       * @param int $slot the number used to identify this question within this usage.
 543       * @param int $variant which variant of the question to use. Must be between
 544       *      1 and ->get_num_variants($slot) inclusive. If not give, a variant is
 545       *      chosen at random.
 546       * @param int $timestamp optional, the timstamp to record for this action. Defaults to now.
 547       */
 548      public function start_question($slot, $variant = null, $timenow = null) {
 549          if (is_null($variant)) {
 550              $variant = rand(1, $this->get_num_variants($slot));
 551          }
 552  
 553          $qa = $this->get_question_attempt($slot);
 554          $qa->start($this->preferredbehaviour, $variant, array(), $timenow);
 555          $this->observer->notify_attempt_modified($qa);
 556      }
 557  
 558      /**
 559       * Start the attempt at all questions that has been added to this usage.
 560       * @param question_variant_selection_strategy how to pick which variant of each question to use.
 561       * @param int $timestamp optional, the timstamp to record for this action. Defaults to now.
 562       * @param int $userid optional, the user to attribute this action to. Defaults to the current user.
 563       */
 564      public function start_all_questions(question_variant_selection_strategy $variantstrategy = null,
 565              $timestamp = null, $userid = null) {
 566          if (is_null($variantstrategy)) {
 567              $variantstrategy = new question_variant_random_strategy();
 568          }
 569  
 570          foreach ($this->questionattempts as $qa) {
 571              $qa->start($this->preferredbehaviour, $qa->select_variant($variantstrategy));
 572              $this->observer->notify_attempt_modified($qa);
 573          }
 574      }
 575  
 576      /**
 577       * Start the attempt at a question, starting from the point where the previous
 578       * question_attempt $oldqa had reached. This is used by the quiz 'Each attempt
 579       * builds on last' mode.
 580       * @param int $slot the number used to identify this question within this usage.
 581       * @param question_attempt $oldqa a previous attempt at this quetsion that
 582       *      defines the starting point.
 583       */
 584      public function start_question_based_on($slot, question_attempt $oldqa) {
 585          $qa = $this->get_question_attempt($slot);
 586          $qa->start_based_on($oldqa);
 587          $this->observer->notify_attempt_modified($qa);
 588      }
 589  
 590      /**
 591       * Process all the question actions in the current request.
 592       *
 593       * If there is a parameter slots included in the post data, then only
 594       * those question numbers will be processed, otherwise all questions in this
 595       * useage will be.
 596       *
 597       * This function also does {@link update_question_flags()}.
 598       *
 599       * @param int $timestamp optional, use this timestamp as 'now'.
 600       * @param array $postdata optional, only intended for testing. Use this data
 601       * instead of the data from $_POST.
 602       */
 603      public function process_all_actions($timestamp = null, $postdata = null) {
 604          foreach ($this->get_slots_in_request($postdata) as $slot) {
 605              if (!$this->validate_sequence_number($slot, $postdata)) {
 606                  continue;
 607              }
 608              $submitteddata = $this->extract_responses($slot, $postdata);
 609              $this->process_action($slot, $submitteddata, $timestamp);
 610          }
 611          $this->update_question_flags($postdata);
 612      }
 613  
 614      /**
 615       * Process all the question autosave data in the current request.
 616       *
 617       * If there is a parameter slots included in the post data, then only
 618       * those question numbers will be processed, otherwise all questions in this
 619       * useage will be.
 620       *
 621       * This function also does {@link update_question_flags()}.
 622       *
 623       * @param int $timestamp optional, use this timestamp as 'now'.
 624       * @param array $postdata optional, only intended for testing. Use this data
 625       * instead of the data from $_POST.
 626       */
 627      public function process_all_autosaves($timestamp = null, $postdata = null) {
 628          foreach ($this->get_slots_in_request($postdata) as $slot) {
 629              if (!$this->is_autosave_required($slot, $postdata)) {
 630                  continue;
 631              }
 632              $submitteddata = $this->extract_responses($slot, $postdata);
 633              $this->process_autosave($slot, $submitteddata, $timestamp);
 634          }
 635          $this->update_question_flags($postdata);
 636      }
 637  
 638      /**
 639       * Get the list of slot numbers that should be processed as part of processing
 640       * the current request.
 641       * @param array $postdata optional, only intended for testing. Use this data
 642       * instead of the data from $_POST.
 643       * @return array of slot numbers.
 644       */
 645      protected function get_slots_in_request($postdata = null) {
 646          // Note: we must not use "question_attempt::get_submitted_var()" because there is no attempt instance!!!
 647          if (is_null($postdata)) {
 648              $slots = optional_param('slots', null, PARAM_SEQUENCE);
 649          } else if (array_key_exists('slots', $postdata)) {
 650              $slots = clean_param($postdata['slots'], PARAM_SEQUENCE);
 651          } else {
 652              $slots = null;
 653          }
 654          if (is_null($slots)) {
 655              $slots = $this->get_slots();
 656          } else if (!$slots) {
 657              $slots = array();
 658          } else {
 659              $slots = explode(',', $slots);
 660          }
 661          return $slots;
 662      }
 663  
 664      /**
 665       * Get the submitted data from the current request that belongs to this
 666       * particular question.
 667       *
 668       * @param int $slot the number used to identify this question within this usage.
 669       * @param $postdata optional, only intended for testing. Use this data
 670       * instead of the data from $_POST.
 671       * @return array submitted data specific to this question.
 672       */
 673      public function extract_responses($slot, $postdata = null) {
 674          return $this->get_question_attempt($slot)->get_submitted_data($postdata);
 675      }
 676  
 677      /**
 678       * Transform an array of response data for slots to an array of post data as you would get from quiz attempt form.
 679       *
 680       * @param $simulatedresponses array keys are slot nos => contains arrays representing student
 681       *                                   responses which will be passed to question_definition::prepare_simulated_post_data method
 682       *                                   and then have the appropriate prefix added.
 683       * @return array simulated post data
 684       */
 685      public function prepare_simulated_post_data($simulatedresponses) {
 686          $simulatedpostdata = array();
 687          $simulatedpostdata['slots'] = implode(',', array_keys($simulatedresponses));
 688          foreach ($simulatedresponses as $slot => $responsedata) {
 689              $slotresponse = array();
 690  
 691              // Behaviour vars should not be processed by question type, just add prefix.
 692              $behaviourvars = $this->get_question_attempt($slot)->get_behaviour()->get_expected_data();
 693              foreach (array_keys($responsedata) as $responsedatakey) {
 694                  if ($responsedatakey{0} === '-') {
 695                      $behaviourvarname = substr($responsedatakey, 1);
 696                      if (isset($behaviourvars[$behaviourvarname])) {
 697                          // Expected behaviour var found.
 698                          if ($responsedata[$responsedatakey]) {
 699                              // Only set the behaviour var if the column value from the cvs file is non zero.
 700                              // The behaviours only look at whether the var is set or not they don't look at the value.
 701                              $slotresponse[$responsedatakey] = $responsedata[$responsedatakey];
 702                          }
 703                      }
 704                      // Remove both expected and unexpected vars from data passed to question type.
 705                      unset($responsedata[$responsedatakey]);
 706                  }
 707              }
 708  
 709              $slotresponse += $this->get_question($slot)->prepare_simulated_post_data($responsedata);
 710              $slotresponse[':sequencecheck'] = $this->get_question_attempt($slot)->get_sequence_check_count();
 711  
 712              // Add this slot's prefix to slot data.
 713              $prefix = $this->get_field_prefix($slot);
 714              foreach ($slotresponse as $key => $value) {
 715                  $simulatedpostdata[$prefix.$key] = $value;
 716              }
 717          }
 718          return $simulatedpostdata;
 719      }
 720  
 721      /**
 722       * Process a specific action on a specific question.
 723       * @param int $slot the number used to identify this question within this usage.
 724       * @param $submitteddata the submitted data that constitutes the action.
 725       */
 726      public function process_action($slot, $submitteddata, $timestamp = null) {
 727          $qa = $this->get_question_attempt($slot);
 728          $qa->process_action($submitteddata, $timestamp);
 729          $this->observer->notify_attempt_modified($qa);
 730      }
 731  
 732      /**
 733       * Process an autosave action on a specific question.
 734       * @param int $slot the number used to identify this question within this usage.
 735       * @param $submitteddata the submitted data that constitutes the action.
 736       */
 737      public function process_autosave($slot, $submitteddata, $timestamp = null) {
 738          $qa = $this->get_question_attempt($slot);
 739          if ($qa->process_autosave($submitteddata, $timestamp)) {
 740              $this->observer->notify_attempt_modified($qa);
 741          }
 742      }
 743  
 744      /**
 745       * Check that the sequence number, that detects weird things like the student
 746       * clicking back, is OK. If the sequence check variable is not present, returns
 747       * false. If the check variable is present and correct, returns true. If the
 748       * variable is present and wrong, throws an exception.
 749       * @param int $slot the number used to identify this question within this usage.
 750       * @param array $submitteddata the submitted data that constitutes the action.
 751       * @return bool true if the check variable is present and correct. False if it
 752       * is missing. (Throws an exception if the check fails.)
 753       */
 754      public function validate_sequence_number($slot, $postdata = null) {
 755          $qa = $this->get_question_attempt($slot);
 756          $sequencecheck = $qa->get_submitted_var(
 757                  $qa->get_control_field_name('sequencecheck'), PARAM_INT, $postdata);
 758          if (is_null($sequencecheck)) {
 759              return false;
 760          } else if ($sequencecheck != $qa->get_sequence_check_count()) {
 761              throw new question_out_of_sequence_exception($this->id, $slot, $postdata);
 762          } else {
 763              return true;
 764          }
 765      }
 766  
 767      /**
 768       * Check, based on the sequence number, whether this auto-save is still required.
 769       * @param int $slot the number used to identify this question within this usage.
 770       * @param array $submitteddata the submitted data that constitutes the action.
 771       * @return bool true if the check variable is present and correct, otherwise false.
 772       */
 773      public function is_autosave_required($slot, $postdata = null) {
 774          $qa = $this->get_question_attempt($slot);
 775          $sequencecheck = $qa->get_submitted_var(
 776                  $qa->get_control_field_name('sequencecheck'), PARAM_INT, $postdata);
 777          if (is_null($sequencecheck)) {
 778              return false;
 779          } else if ($sequencecheck != $qa->get_sequence_check_count()) {
 780              return false;
 781          } else {
 782              return true;
 783          }
 784      }
 785  
 786      /**
 787       * Update the flagged state for all question_attempts in this usage, if their
 788       * flagged state was changed in the request.
 789       *
 790       * @param $postdata optional, only intended for testing. Use this data
 791       * instead of the data from $_POST.
 792       */
 793      public function update_question_flags($postdata = null) {
 794          foreach ($this->questionattempts as $qa) {
 795              $flagged = $qa->get_submitted_var(
 796                      $qa->get_flag_field_name(), PARAM_BOOL, $postdata);
 797              if (!is_null($flagged) && $flagged != $qa->is_flagged()) {
 798                  $qa->set_flagged($flagged);
 799              }
 800          }
 801      }
 802  
 803      /**
 804       * Get the correct response to a particular question. Passing the results of
 805       * this method to {@link process_action()} will probably result in full marks.
 806       * If it is not possible to compute a correct response, this method should return null.
 807       * @param int $slot the number used to identify this question within this usage.
 808       * @return array that constitutes a correct response to this question.
 809       */
 810      public function get_correct_response($slot) {
 811          return $this->get_question_attempt($slot)->get_correct_response();
 812      }
 813  
 814      /**
 815       * Finish the active phase of an attempt at a question.
 816       *
 817       * This is an external act of finishing the attempt. Think, for example, of
 818       * the 'Submit all and finish' button in the quiz. Some behaviours,
 819       * (for example, immediatefeedback) give a way of finishing the active phase
 820       * of a question attempt as part of a {@link process_action()} call.
 821       *
 822       * After the active phase is over, the only changes possible are things like
 823       * manual grading, or changing the flag state.
 824       *
 825       * @param int $slot the number used to identify this question within this usage.
 826       */
 827      public function finish_question($slot, $timestamp = null) {
 828          $qa = $this->get_question_attempt($slot);
 829          $qa->finish($timestamp);
 830          $this->observer->notify_attempt_modified($qa);
 831      }
 832  
 833      /**
 834       * Finish the active phase of an attempt at a question. See {@link finish_question()}
 835       * for a fuller description of what 'finish' means.
 836       */
 837      public function finish_all_questions($timestamp = null) {
 838          foreach ($this->questionattempts as $qa) {
 839              $qa->finish($timestamp);
 840              $this->observer->notify_attempt_modified($qa);
 841          }
 842      }
 843  
 844      /**
 845       * Perform a manual grading action on a question attempt.
 846       * @param int $slot the number used to identify this question within this usage.
 847       * @param string $comment the comment being added to the question attempt.
 848       * @param number $mark the mark that is being assigned. Can be null to just
 849       * add a comment.
 850       * @param int $commentformat one of the FORMAT_... constants. The format of $comment.
 851       */
 852      public function manual_grade($slot, $comment, $mark, $commentformat = null) {
 853          $qa = $this->get_question_attempt($slot);
 854          $qa->manual_grade($comment, $mark, $commentformat);
 855          $this->observer->notify_attempt_modified($qa);
 856      }
 857  
 858      /**
 859       * Regrade a question in this usage. This replays the sequence of submitted
 860       * actions to recompute the outcomes.
 861       * @param int $slot the number used to identify this question within this usage.
 862       * @param bool $finished whether the question attempt should be forced to be finished
 863       *      after the regrade, or whether it may still be in progress (default false).
 864       * @param number $newmaxmark (optional) if given, will change the max mark while regrading.
 865       */
 866      public function regrade_question($slot, $finished = false, $newmaxmark = null) {
 867          $oldqa = $this->get_question_attempt($slot);
 868          if (is_null($newmaxmark)) {
 869              $newmaxmark = $oldqa->get_max_mark();
 870          }
 871  
 872          $newqa = new question_attempt($oldqa->get_question(), $oldqa->get_usage_id(),
 873                  $this->observer, $newmaxmark);
 874          $newqa->set_database_id($oldqa->get_database_id());
 875          $newqa->set_slot($oldqa->get_slot());
 876          $newqa->regrade($oldqa, $finished);
 877  
 878          $this->questionattempts[$slot] = $newqa;
 879          $this->observer->notify_attempt_modified($newqa);
 880      }
 881  
 882      /**
 883       * Regrade all the questions in this usage (without changing their max mark).
 884       * @param bool $finished whether each question should be forced to be finished
 885       *      after the regrade, or whether it may still be in progress (default false).
 886       */
 887      public function regrade_all_questions($finished = false) {
 888          foreach ($this->questionattempts as $slot => $notused) {
 889              $this->regrade_question($slot, $finished);
 890          }
 891      }
 892  
 893      /**
 894       * Change the max mark for this question_attempt.
 895       * @param int $slot the slot number of the question of inerest.
 896       * @param float $maxmark the new max mark.
 897       */
 898      public function set_max_mark($slot, $maxmark) {
 899          $this->get_question_attempt($slot)->set_max_mark($maxmark);
 900      }
 901  
 902      /**
 903       * Create a question_usage_by_activity from records loaded from the database.
 904       *
 905       * For internal use only.
 906       *
 907       * @param Iterator $records Raw records loaded from the database.
 908       * @param int $questionattemptid The id of the question_attempt to extract.
 909       * @return question_usage_by_activity The newly constructed usage.
 910       */
 911      public static function load_from_records($records, $qubaid) {
 912          $record = $records->current();
 913          while ($record->qubaid != $qubaid) {
 914              $records->next();
 915              if (!$records->valid()) {
 916                  throw new coding_exception("Question usage {$qubaid} not found in the database.");
 917              }
 918              $record = $records->current();
 919          }
 920  
 921          $quba = new question_usage_by_activity($record->component,
 922              context::instance_by_id($record->contextid, IGNORE_MISSING));
 923          $quba->set_id_from_database($record->qubaid);
 924          $quba->set_preferred_behaviour($record->preferredbehaviour);
 925  
 926          $quba->observer = new question_engine_unit_of_work($quba);
 927  
 928          // If slot is null then the current pointer in $records will not be
 929          // advanced in the while loop below, and we get stuck in an infinite loop,
 930          // since this method is supposed to always consume at least one record.
 931          // Therefore, in this case, advance the record here.
 932          if (is_null($record->slot)) {
 933              $records->next();
 934          }
 935  
 936          while ($record && $record->qubaid == $qubaid && !is_null($record->slot)) {
 937              $quba->questionattempts[$record->slot] =
 938                      question_attempt::load_from_records($records,
 939                      $record->questionattemptid, $quba->observer,
 940                      $quba->get_preferred_behaviour());
 941              if ($records->valid()) {
 942                  $record = $records->current();
 943              } else {
 944                  $record = false;
 945              }
 946          }
 947  
 948          return $quba;
 949      }
 950  }
 951  
 952  
 953  /**
 954   * A class abstracting access to the
 955   * {@link question_usage_by_activity::$questionattempts} array.
 956   *
 957   * This class snapshots the list of {@link question_attempts} to iterate over
 958   * when it is created. If a question is added to the usage mid-iteration, it
 959   * will now show up.
 960   *
 961   * To create an instance of this class, use
 962   * {@link question_usage_by_activity::get_attempt_iterator()}
 963   *
 964   * @copyright  2009 The Open University
 965   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 966   */
 967  class question_attempt_iterator implements Iterator, ArrayAccess {
 968      /** @var question_usage_by_activity that we are iterating over. */
 969      protected $quba;
 970      /** @var array of question numbers. */
 971      protected $slots;
 972  
 973      /**
 974       * To create an instance of this class, use
 975       * {@link question_usage_by_activity::get_attempt_iterator()}.
 976       * @param $quba the usage to iterate over.
 977       */
 978      public function __construct(question_usage_by_activity $quba) {
 979          $this->quba = $quba;
 980          $this->slots = $quba->get_slots();
 981          $this->rewind();
 982      }
 983  
 984      /** @return question_attempt_step */
 985      public function current() {
 986          return $this->offsetGet(current($this->slots));
 987      }
 988      /** @return int */
 989      public function key() {
 990          return current($this->slots);
 991      }
 992      public function next() {
 993          next($this->slots);
 994      }
 995      public function rewind() {
 996          reset($this->slots);
 997      }
 998      /** @return bool */
 999      public function valid() {
1000          return current($this->slots) !== false;
1001      }
1002  
1003      /** @return bool */
1004      public function offsetExists($slot) {
1005          return in_array($slot, $this->slots);
1006      }
1007      /** @return question_attempt_step */
1008      public function offsetGet($slot) {
1009          return $this->quba->get_question_attempt($slot);
1010      }
1011      public function offsetSet($slot, $value) {
1012          throw new coding_exception('You are only allowed read-only access to ' .
1013                  'question_attempt::states through a question_attempt_step_iterator. Cannot set.');
1014      }
1015      public function offsetUnset($slot) {
1016          throw new coding_exception('You are only allowed read-only access to ' .
1017                  'question_attempt::states through a question_attempt_step_iterator. Cannot unset.');
1018      }
1019  }
1020  
1021  
1022  /**
1023   * Interface for things that want to be notified of signficant changes to a
1024   * {@link question_usage_by_activity}.
1025   *
1026   * A question behaviour controls the flow of actions a student can
1027   * take as they work through a question, and later, as a teacher manually grades it.
1028   *
1029   * @copyright  2009 The Open University
1030   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
1031   */
1032  interface question_usage_observer {
1033      /** Called when a field of the question_usage_by_activity is changed. */
1034      public function notify_modified();
1035  
1036      /**
1037       * Called when a new question attempt is added to this usage.
1038       * @param question_attempt $qa the newly added question attempt.
1039       */
1040      public function notify_attempt_added(question_attempt $qa);
1041  
1042      /**
1043       * Called when the fields of a question attempt in this usage are modified.
1044       * @param question_attempt $qa the newly added question attempt.
1045       */
1046      public function notify_attempt_modified(question_attempt $qa);
1047  
1048      /**
1049       * Called when a question_attempt has been moved to a new slot.
1050       * @param question_attempt $qa The question attempt that was moved.
1051       * @param int $oldslot The previous slot number of that attempt.
1052       */
1053      public function notify_attempt_moved(question_attempt $qa, $oldslot);
1054  
1055      /**
1056       * Called when a new step is added to a question attempt in this usage.
1057       * @param question_attempt_step $step the new step.
1058       * @param question_attempt $qa the usage it is being added to.
1059       * @param int $seq the sequence number of the new step.
1060       */
1061      public function notify_step_added(question_attempt_step $step, question_attempt $qa, $seq);
1062  
1063      /**
1064       * Called when a new step is updated in a question attempt in this usage.
1065       * @param question_attempt_step $step the step that was updated.
1066       * @param question_attempt $qa the usage it is being added to.
1067       * @param int $seq the sequence number of the new step.
1068       */
1069      public function notify_step_modified(question_attempt_step $step, question_attempt $qa, $seq);
1070  
1071      /**
1072       * Called when a new step is updated in a question attempt in this usage.
1073       * @param question_attempt_step $step the step to delete.
1074       * @param question_attempt $qa the usage it is being added to.
1075       */
1076      public function notify_step_deleted(question_attempt_step $step, question_attempt $qa);
1077  
1078      /**
1079       * Called when a new metadata variable is set on a question attempt in this usage.
1080       * @param question_attempt $qa the question attempt the metadata is being added to.
1081       * @param int $name the name of the metadata variable added.
1082       */
1083      public function notify_metadata_added(question_attempt $qa, $name);
1084  
1085      /**
1086       * Called when a metadata variable on a question attempt in this usage is updated.
1087       * @param question_attempt $qa the question attempt where the metadata is being modified.
1088       * @param int $name the name of the metadata variable modified.
1089       */
1090      public function notify_metadata_modified(question_attempt $qa, $name);
1091  }
1092  
1093  
1094  /**
1095   * Null implmentation of the {@link question_usage_watcher} interface.
1096   * Does nothing.
1097   *
1098   * @copyright  2009 The Open University
1099   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
1100   */
1101  class question_usage_null_observer implements question_usage_observer {
1102      public function notify_modified() {
1103      }
1104      public function notify_attempt_added(question_attempt $qa) {
1105      }
1106      public function notify_attempt_modified(question_attempt $qa) {
1107      }
1108      public function notify_attempt_moved(question_attempt $qa, $oldslot) {
1109      }
1110      public function notify_step_added(question_attempt_step $step, question_attempt $qa, $seq) {
1111      }
1112      public function notify_step_modified(question_attempt_step $step, question_attempt $qa, $seq) {
1113      }
1114      public function notify_step_deleted(question_attempt_step $step, question_attempt $qa) {
1115      }
1116      public function notify_metadata_added(question_attempt $qa, $name) {
1117      }
1118      public function notify_metadata_modified(question_attempt $qa, $name) {
1119      }
1120  }