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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   * Code for handling and processing questions
  19   *
  20   * This is code that is module independent, i.e., can be used by any module that
  21   * uses questions, like quiz, lesson, ..
  22   * This script also loads the questiontype classes
  23   * Code for handling the editing of questions is in {@link question/editlib.php}
  24   *
  25   * TODO: separate those functions which form part of the API
  26   *       from the helper functions.
  27   *
  28   * @package moodlecore
  29   * @subpackage questionbank
  30   * @copyright 1999 onwards Martin Dougiamas and others {@link http://moodle.com}
  31   * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  32   */
  33  
  34  
  35  defined('MOODLE_INTERNAL') || die();
  36  
  37  require_once($CFG->dirroot . '/question/engine/lib.php');
  38  require_once($CFG->dirroot . '/question/type/questiontypebase.php');
  39  
  40  
  41  
  42  /// CONSTANTS ///////////////////////////////////
  43  
  44  /**
  45   * Constant determines the number of answer boxes supplied in the editing
  46   * form for multiple choice and similar question types.
  47   */
  48  define("QUESTION_NUMANS", 10);
  49  
  50  /**
  51   * Constant determines the number of answer boxes supplied in the editing
  52   * form for multiple choice and similar question types to start with, with
  53   * the option of adding QUESTION_NUMANS_ADD more answers.
  54   */
  55  define("QUESTION_NUMANS_START", 3);
  56  
  57  /**
  58   * Constant determines the number of answer boxes to add in the editing
  59   * form for multiple choice and similar question types when the user presses
  60   * 'add form fields button'.
  61   */
  62  define("QUESTION_NUMANS_ADD", 3);
  63  
  64  /**
  65   * Move one question type in a list of question types. If you try to move one element
  66   * off of the end, nothing will change.
  67   *
  68   * @param array $sortedqtypes An array $qtype => anything.
  69   * @param string $tomove one of the keys from $sortedqtypes
  70   * @param integer $direction +1 or -1
  71   * @return array an array $index => $qtype, with $index from 0 to n in order, and
  72   *      the $qtypes in the same order as $sortedqtypes, except that $tomove will
  73   *      have been moved one place.
  74   */
  75  function question_reorder_qtypes($sortedqtypes, $tomove, $direction) {
  76      $neworder = array_keys($sortedqtypes);
  77      // Find the element to move.
  78      $key = array_search($tomove, $neworder);
  79      if ($key === false) {
  80          return $neworder;
  81      }
  82      // Work out the other index.
  83      $otherkey = $key + $direction;
  84      if (!isset($neworder[$otherkey])) {
  85          return $neworder;
  86      }
  87      // Do the swap.
  88      $swap = $neworder[$otherkey];
  89      $neworder[$otherkey] = $neworder[$key];
  90      $neworder[$key] = $swap;
  91      return $neworder;
  92  }
  93  
  94  /**
  95   * Save a new question type order to the config_plugins table.
  96   * @global object
  97   * @param $neworder An arra $index => $qtype. Indices should start at 0 and be in order.
  98   * @param $config get_config('question'), if you happen to have it around, to save one DB query.
  99   */
 100  function question_save_qtype_order($neworder, $config = null) {
 101      global $DB;
 102  
 103      if (is_null($config)) {
 104          $config = get_config('question');
 105      }
 106  
 107      foreach ($neworder as $index => $qtype) {
 108          $sortvar = $qtype . '_sortorder';
 109          if (!isset($config->$sortvar) || $config->$sortvar != $index + 1) {
 110              set_config($sortvar, $index + 1, 'question');
 111          }
 112      }
 113  }
 114  
 115  /// FUNCTIONS //////////////////////////////////////////////////////
 116  
 117  /**
 118   * @param array $questionids of question ids.
 119   * @return boolean whether any of these questions are being used by any part of Moodle.
 120   */
 121  function questions_in_use($questionids) {
 122      global $CFG;
 123  
 124      if (question_engine::questions_in_use($questionids)) {
 125          return true;
 126      }
 127  
 128      foreach (core_component::get_plugin_list('mod') as $module => $path) {
 129          $lib = $path . '/lib.php';
 130          if (is_readable($lib)) {
 131              include_once($lib);
 132  
 133              $fn = $module . '_questions_in_use';
 134              if (function_exists($fn)) {
 135                  if ($fn($questionids)) {
 136                      return true;
 137                  }
 138              } else {
 139  
 140                  // Fallback for legacy modules.
 141                  $fn = $module . '_question_list_instances';
 142                  if (function_exists($fn)) {
 143                      foreach ($questionids as $questionid) {
 144                          $instances = $fn($questionid);
 145                          if (!empty($instances)) {
 146                              return true;
 147                          }
 148                      }
 149                  }
 150              }
 151          }
 152      }
 153  
 154      return false;
 155  }
 156  
 157  /**
 158   * Determine whether there arey any questions belonging to this context, that is whether any of its
 159   * question categories contain any questions. This will return true even if all the questions are
 160   * hidden.
 161   *
 162   * @param mixed $context either a context object, or a context id.
 163   * @return boolean whether any of the question categories beloning to this context have
 164   *         any questions in them.
 165   */
 166  function question_context_has_any_questions($context) {
 167      global $DB;
 168      if (is_object($context)) {
 169          $contextid = $context->id;
 170      } else if (is_numeric($context)) {
 171          $contextid = $context;
 172      } else {
 173          print_error('invalidcontextinhasanyquestions', 'question');
 174      }
 175      return $DB->record_exists_sql("SELECT *
 176                                       FROM {question} q
 177                                       JOIN {question_categories} qc ON qc.id = q.category
 178                                      WHERE qc.contextid = ? AND q.parent = 0", array($contextid));
 179  }
 180  
 181  /**
 182   * Check whether a given grade is one of a list of allowed options. If not,
 183   * depending on $matchgrades, either return the nearest match, or return false
 184   * to signal an error.
 185   * @param array $gradeoptionsfull list of valid options
 186   * @param int $grade grade to be tested
 187   * @param string $matchgrades 'error' or 'nearest'
 188   * @return mixed either 'fixed' value or false if error.
 189   */
 190  function match_grade_options($gradeoptionsfull, $grade, $matchgrades = 'error') {
 191  
 192      if ($matchgrades == 'error') {
 193          // (Almost) exact match, or an error.
 194          foreach ($gradeoptionsfull as $value => $option) {
 195              // Slightly fuzzy test, never check floats for equality.
 196              if (abs($grade - $value) < 0.00001) {
 197                  return $value; // Be sure the return the proper value.
 198              }
 199          }
 200          // Didn't find a match so that's an error.
 201          return false;
 202  
 203      } else if ($matchgrades == 'nearest') {
 204          // Work out nearest value
 205          $best = false;
 206          $bestmismatch = 2;
 207          foreach ($gradeoptionsfull as $value => $option) {
 208              $newmismatch = abs($grade - $value);
 209              if ($newmismatch < $bestmismatch) {
 210                  $best = $value;
 211                  $bestmismatch = $newmismatch;
 212              }
 213          }
 214          return $best;
 215  
 216      } else {
 217          // Unknow option passed.
 218          throw new coding_exception('Unknown $matchgrades ' . $matchgrades .
 219                  ' passed to match_grade_options');
 220      }
 221  }
 222  
 223  /**
 224   * Remove stale questions from a category.
 225   *
 226   * While questions should not be left behind when they are not used any more,
 227   * it does happen, maybe via restore, or old logic, or uncovered scenarios. When
 228   * this happens, the users are unable to delete the question category unless
 229   * they move those stale questions to another one category, but to them the
 230   * category is empty as it does not contain anything. The purpose of this function
 231   * is to detect the questions that may have gone stale and remove them.
 232   *
 233   * You will typically use this prior to checking if the category contains questions.
 234   *
 235   * The stale questions (unused and hidden to the user) handled are:
 236   * - hidden questions
 237   * - random questions
 238   *
 239   * @param int $categoryid The category ID.
 240   */
 241  function question_remove_stale_questions_from_category($categoryid) {
 242      global $DB;
 243  
 244      $select = 'category = :categoryid AND (qtype = :qtype OR hidden = :hidden)';
 245      $params = ['categoryid' => $categoryid, 'qtype' => 'random', 'hidden' => 1];
 246      $questions = $DB->get_recordset_select("question", $select, $params, '', 'id');
 247      foreach ($questions as $question) {
 248          // The function question_delete_question does not delete questions in use.
 249          question_delete_question($question->id);
 250      }
 251      $questions->close();
 252  }
 253  
 254  /**
 255   * Category is about to be deleted,
 256   * 1/ All questions are deleted for this question category.
 257   * 2/ Any questions that can't be deleted are moved to a new category
 258   * NOTE: this function is called from lib/db/upgrade.php
 259   *
 260   * @param object|coursecat $category course category object
 261   */
 262  function question_category_delete_safe($category) {
 263      global $DB;
 264      $criteria = array('category' => $category->id);
 265      $context = context::instance_by_id($category->contextid, IGNORE_MISSING);
 266      $rescue = null; // See the code around the call to question_save_from_deletion.
 267  
 268      // Deal with any questions in the category.
 269      if ($questions = $DB->get_records('question', $criteria, '', 'id,qtype')) {
 270  
 271          // Try to delete each question.
 272          foreach ($questions as $question) {
 273              question_delete_question($question->id);
 274          }
 275  
 276          // Check to see if there were any questions that were kept because
 277          // they are still in use somehow, even though quizzes in courses
 278          // in this category will already have been deleted. This could
 279          // happen, for example, if questions are added to a course,
 280          // and then that course is moved to another category (MDL-14802).
 281          $questionids = $DB->get_records_menu('question', $criteria, '', 'id, 1');
 282          if (!empty($questionids)) {
 283              $parentcontextid = SYSCONTEXTID;
 284              $name = get_string('unknown', 'question');
 285              if ($context !== false) {
 286                  $name = $context->get_context_name();
 287                  $parentcontext = $context->get_parent_context();
 288                  if ($parentcontext) {
 289                      $parentcontextid = $parentcontext->id;
 290                  }
 291              }
 292              question_save_from_deletion(array_keys($questionids), $parentcontextid, $name, $rescue);
 293          }
 294      }
 295  
 296      // Now delete the category.
 297      $DB->delete_records('question_categories', array('id' => $category->id));
 298  }
 299  
 300  /**
 301   * Tests whether any question in a category is used by any part of Moodle.
 302   *
 303   * @param integer $categoryid a question category id.
 304   * @param boolean $recursive whether to check child categories too.
 305   * @return boolean whether any question in this category is in use.
 306   */
 307  function question_category_in_use($categoryid, $recursive = false) {
 308      global $DB;
 309  
 310      //Look at each question in the category
 311      if ($questions = $DB->get_records_menu('question',
 312              array('category' => $categoryid), '', 'id, 1')) {
 313          if (questions_in_use(array_keys($questions))) {
 314              return true;
 315          }
 316      }
 317      if (!$recursive) {
 318          return false;
 319      }
 320  
 321      //Look under child categories recursively
 322      if ($children = $DB->get_records('question_categories',
 323              array('parent' => $categoryid), '', 'id, 1')) {
 324          foreach ($children as $child) {
 325              if (question_category_in_use($child->id, $recursive)) {
 326                  return true;
 327              }
 328          }
 329      }
 330  
 331      return false;
 332  }
 333  
 334  /**
 335   * Deletes question and all associated data from the database
 336   *
 337   * It will not delete a question if it is used by an activity module
 338   * @param object $question  The question being deleted
 339   */
 340  function question_delete_question($questionid) {
 341      global $DB;
 342  
 343      $question = $DB->get_record_sql('
 344              SELECT q.*, qc.contextid
 345              FROM {question} q
 346              JOIN {question_categories} qc ON qc.id = q.category
 347              WHERE q.id = ?', array($questionid));
 348      if (!$question) {
 349          // In some situations, for example if this was a child of a
 350          // Cloze question that was previously deleted, the question may already
 351          // have gone. In this case, just do nothing.
 352          return;
 353      }
 354  
 355      // Do not delete a question if it is used by an activity module
 356      if (questions_in_use(array($questionid))) {
 357          return;
 358      }
 359  
 360      $dm = new question_engine_data_mapper();
 361      $dm->delete_previews($questionid);
 362  
 363      // delete questiontype-specific data
 364      question_bank::get_qtype($question->qtype, false)->delete_question(
 365              $questionid, $question->contextid);
 366  
 367      // Delete all tag instances.
 368      core_tag_tag::remove_all_item_tags('core_question', 'question', $question->id);
 369  
 370      // Now recursively delete all child questions
 371      if ($children = $DB->get_records('question',
 372              array('parent' => $questionid), '', 'id, qtype')) {
 373          foreach ($children as $child) {
 374              if ($child->id != $questionid) {
 375                  question_delete_question($child->id);
 376              }
 377          }
 378      }
 379  
 380      // Finally delete the question record itself
 381      $DB->delete_records('question', array('id' => $questionid));
 382      question_bank::notify_question_edited($questionid);
 383  }
 384  
 385  /**
 386   * All question categories and their questions are deleted for this context id.
 387   *
 388   * @param object $contextid The contextid to delete question categories from
 389   * @return array Feedback from deletes (if any)
 390   */
 391  function question_delete_context($contextid) {
 392      global $DB;
 393  
 394      //To store feedback to be showed at the end of the process
 395      $feedbackdata   = array();
 396  
 397      //Cache some strings
 398      $strcatdeleted = get_string('unusedcategorydeleted', 'question');
 399      $fields = 'id, parent, name, contextid';
 400      if ($categories = $DB->get_records('question_categories', array('contextid' => $contextid), 'parent', $fields)) {
 401          //Sort categories following their tree (parent-child) relationships
 402          //this will make the feedback more readable
 403          $categories = sort_categories_by_tree($categories);
 404  
 405          foreach ($categories as $category) {
 406              question_category_delete_safe($category);
 407  
 408              //Fill feedback
 409              $feedbackdata[] = array($category->name, $strcatdeleted);
 410          }
 411      }
 412      return $feedbackdata;
 413  }
 414  
 415  /**
 416   * All question categories and their questions are deleted for this course.
 417   *
 418   * @param stdClass $course an object representing the activity
 419   * @param boolean $feedback to specify if the process must output a summary of its work
 420   * @return boolean
 421   */
 422  function question_delete_course($course, $feedback=true) {
 423      $coursecontext = context_course::instance($course->id);
 424      $feedbackdata = question_delete_context($coursecontext->id, $feedback);
 425  
 426      // Inform about changes performed if feedback is enabled.
 427      if ($feedback && $feedbackdata) {
 428          $table = new html_table();
 429          $table->head = array(get_string('category', 'question'), get_string('action'));
 430          $table->data = $feedbackdata;
 431          echo html_writer::table($table);
 432      }
 433      return true;
 434  }
 435  
 436  /**
 437   * Category is about to be deleted,
 438   * 1/ All question categories and their questions are deleted for this course category.
 439   * 2/ All questions are moved to new category
 440   *
 441   * @param object|coursecat $category course category object
 442   * @param object|coursecat $newcategory empty means everything deleted, otherwise id of
 443   *      category where content moved
 444   * @param boolean $feedback to specify if the process must output a summary of its work
 445   * @return boolean
 446   */
 447  function question_delete_course_category($category, $newcategory, $feedback=true) {
 448      global $DB, $OUTPUT;
 449  
 450      $context = context_coursecat::instance($category->id);
 451      if (empty($newcategory)) {
 452          $feedbackdata = question_delete_context($context->id, $feedback);
 453  
 454          // Output feedback if requested.
 455          if ($feedback && $feedbackdata) {
 456              $table = new html_table();
 457              $table->head = array(get_string('questioncategory', 'question'), get_string('action'));
 458              $table->data = $feedbackdata;
 459              echo html_writer::table($table);
 460          }
 461  
 462      } else {
 463          // Move question categories to the new context.
 464          if (!$newcontext = context_coursecat::instance($newcategory->id)) {
 465              return false;
 466          }
 467  
 468          // Update the contextid for any tag instances for questions in the old context.
 469          core_tag_tag::move_context('core_question', 'question', $context, $newcontext);
 470  
 471          $DB->set_field('question_categories', 'contextid', $newcontext->id, array('contextid' => $context->id));
 472  
 473          if ($feedback) {
 474              $a = new stdClass();
 475              $a->oldplace = $context->get_context_name();
 476              $a->newplace = $newcontext->get_context_name();
 477              echo $OUTPUT->notification(
 478                      get_string('movedquestionsandcategories', 'question', $a), 'notifysuccess');
 479          }
 480      }
 481  
 482      return true;
 483  }
 484  
 485  /**
 486   * Enter description here...
 487   *
 488   * @param array $questionids of question ids
 489   * @param object $newcontextid the context to create the saved category in.
 490   * @param string $oldplace a textual description of the think being deleted,
 491   *      e.g. from get_context_name
 492   * @param object $newcategory
 493   * @return mixed false on
 494   */
 495  function question_save_from_deletion($questionids, $newcontextid, $oldplace,
 496          $newcategory = null) {
 497      global $DB;
 498  
 499      // Make a category in the parent context to move the questions to.
 500      if (is_null($newcategory)) {
 501          $newcategory = new stdClass();
 502          $newcategory->parent = 0;
 503          $newcategory->contextid = $newcontextid;
 504          $newcategory->name = get_string('questionsrescuedfrom', 'question', $oldplace);
 505          $newcategory->info = get_string('questionsrescuedfrominfo', 'question', $oldplace);
 506          $newcategory->sortorder = 999;
 507          $newcategory->stamp = make_unique_id_code();
 508          $newcategory->id = $DB->insert_record('question_categories', $newcategory);
 509      }
 510  
 511      // Move any remaining questions to the 'saved' category.
 512      if (!question_move_questions_to_category($questionids, $newcategory->id)) {
 513          return false;
 514      }
 515      return $newcategory;
 516  }
 517  
 518  /**
 519   * All question categories and their questions are deleted for this activity.
 520   *
 521   * @param object $cm the course module object representing the activity
 522   * @param boolean $feedback to specify if the process must output a summary of its work
 523   * @return boolean
 524   */
 525  function question_delete_activity($cm, $feedback=true) {
 526      global $DB;
 527  
 528      $modcontext = context_module::instance($cm->id);
 529      $feedbackdata = question_delete_context($modcontext->id, $feedback);
 530      // Inform about changes performed if feedback is enabled.
 531      if ($feedback && $feedbackdata) {
 532          $table = new html_table();
 533          $table->head = array(get_string('category', 'question'), get_string('action'));
 534          $table->data = $feedbackdata;
 535          echo html_writer::table($table);
 536      }
 537      return true;
 538  }
 539  
 540  /**
 541   * This function should be considered private to the question bank, it is called from
 542   * question/editlib.php question/contextmoveq.php and a few similar places to to the
 543   * work of acutally moving questions and associated data. However, callers of this
 544   * function also have to do other work, which is why you should not call this method
 545   * directly from outside the questionbank.
 546   *
 547   * @param array $questionids of question ids.
 548   * @param integer $newcategoryid the id of the category to move to.
 549   */
 550  function question_move_questions_to_category($questionids, $newcategoryid) {
 551      global $DB;
 552  
 553      $newcontextid = $DB->get_field('question_categories', 'contextid',
 554              array('id' => $newcategoryid));
 555      list($questionidcondition, $params) = $DB->get_in_or_equal($questionids);
 556      $questions = $DB->get_records_sql("
 557              SELECT q.id, q.qtype, qc.contextid
 558                FROM {question} q
 559                JOIN {question_categories} qc ON q.category = qc.id
 560               WHERE  q.id $questionidcondition", $params);
 561      foreach ($questions as $question) {
 562          if ($newcontextid != $question->contextid) {
 563              question_bank::get_qtype($question->qtype)->move_files(
 564                      $question->id, $question->contextid, $newcontextid);
 565          }
 566      }
 567  
 568      // Move the questions themselves.
 569      $DB->set_field_select('question', 'category', $newcategoryid,
 570              "id $questionidcondition", $params);
 571  
 572      // Move any subquestions belonging to them.
 573      $DB->set_field_select('question', 'category', $newcategoryid,
 574              "parent $questionidcondition", $params);
 575  
 576      // Update the contextid for any tag instances that may exist for these questions.
 577      core_tag_tag::change_items_context('core_question', 'question', $questionids, $newcontextid);
 578  
 579      // TODO Deal with datasets.
 580  
 581      // Purge these questions from the cache.
 582      foreach ($questions as $question) {
 583          question_bank::notify_question_edited($question->id);
 584      }
 585  
 586      return true;
 587  }
 588  
 589  /**
 590   * This function helps move a question cateogry to a new context by moving all
 591   * the files belonging to all the questions to the new context.
 592   * Also moves subcategories.
 593   * @param integer $categoryid the id of the category being moved.
 594   * @param integer $oldcontextid the old context id.
 595   * @param integer $newcontextid the new context id.
 596   */
 597  function question_move_category_to_context($categoryid, $oldcontextid, $newcontextid) {
 598      global $DB;
 599  
 600      $questionids = $DB->get_records_menu('question',
 601              array('category' => $categoryid), '', 'id,qtype');
 602      foreach ($questionids as $questionid => $qtype) {
 603          question_bank::get_qtype($qtype)->move_files(
 604                  $questionid, $oldcontextid, $newcontextid);
 605          // Purge this question from the cache.
 606          question_bank::notify_question_edited($questionid);
 607      }
 608  
 609      core_tag_tag::change_items_context('core_question', 'question',
 610              array_keys($questionids), $newcontextid);
 611  
 612      $subcatids = $DB->get_records_menu('question_categories',
 613              array('parent' => $categoryid), '', 'id,1');
 614      foreach ($subcatids as $subcatid => $notused) {
 615          $DB->set_field('question_categories', 'contextid', $newcontextid,
 616                  array('id' => $subcatid));
 617          question_move_category_to_context($subcatid, $oldcontextid, $newcontextid);
 618      }
 619  }
 620  
 621  /**
 622   * Generate the URL for starting a new preview of a given question with the given options.
 623   * @param integer $questionid the question to preview.
 624   * @param string $preferredbehaviour the behaviour to use for the preview.
 625   * @param float $maxmark the maximum to mark the question out of.
 626   * @param question_display_options $displayoptions the display options to use.
 627   * @param int $variant the variant of the question to preview. If null, one will
 628   *      be picked randomly.
 629   * @param object $context context to run the preview in (affects things like
 630   *      filter settings, theme, lang, etc.) Defaults to $PAGE->context.
 631   * @return moodle_url the URL.
 632   */
 633  function question_preview_url($questionid, $preferredbehaviour = null,
 634          $maxmark = null, $displayoptions = null, $variant = null, $context = null) {
 635  
 636      $params = array('id' => $questionid);
 637  
 638      if (is_null($context)) {
 639          global $PAGE;
 640          $context = $PAGE->context;
 641      }
 642      if ($context->contextlevel == CONTEXT_MODULE) {
 643          $params['cmid'] = $context->instanceid;
 644      } else if ($context->contextlevel == CONTEXT_COURSE) {
 645          $params['courseid'] = $context->instanceid;
 646      }
 647  
 648      if (!is_null($preferredbehaviour)) {
 649          $params['behaviour'] = $preferredbehaviour;
 650      }
 651  
 652      if (!is_null($maxmark)) {
 653          $params['maxmark'] = $maxmark;
 654      }
 655  
 656      if (!is_null($displayoptions)) {
 657          $params['correctness']     = $displayoptions->correctness;
 658          $params['marks']           = $displayoptions->marks;
 659          $params['markdp']          = $displayoptions->markdp;
 660          $params['feedback']        = (bool) $displayoptions->feedback;
 661          $params['generalfeedback'] = (bool) $displayoptions->generalfeedback;
 662          $params['rightanswer']     = (bool) $displayoptions->rightanswer;
 663          $params['history']         = (bool) $displayoptions->history;
 664      }
 665  
 666      if ($variant) {
 667          $params['variant'] = $variant;
 668      }
 669  
 670      return new moodle_url('/question/preview.php', $params);
 671  }
 672  
 673  /**
 674   * @return array that can be passed as $params to the {@link popup_action} constructor.
 675   */
 676  function question_preview_popup_params() {
 677      return array(
 678          'height' => 600,
 679          'width' => 800,
 680      );
 681  }
 682  
 683  /**
 684   * Given a list of ids, load the basic information about a set of questions from
 685   * the questions table. The $join and $extrafields arguments can be used together
 686   * to pull in extra data. See, for example, the usage in mod/quiz/attemptlib.php, and
 687   * read the code below to see how the SQL is assembled. Throws exceptions on error.
 688   *
 689   * @param array $questionids array of question ids to load. If null, then all
 690   * questions matched by $join will be loaded.
 691   * @param string $extrafields extra SQL code to be added to the query.
 692   * @param string $join extra SQL code to be added to the query.
 693   * @param array $extraparams values for any placeholders in $join.
 694   * You must use named placeholders.
 695   * @param string $orderby what to order the results by. Optional, default is unspecified order.
 696   *
 697   * @return array partially complete question objects. You need to call get_question_options
 698   * on them before they can be properly used.
 699   */
 700  function question_preload_questions($questionids = null, $extrafields = '', $join = '',
 701          $extraparams = array(), $orderby = '') {
 702      global $DB;
 703  
 704      if ($questionids === null) {
 705          $where = '';
 706          $params = array();
 707      } else {
 708          if (empty($questionids)) {
 709              return array();
 710          }
 711  
 712          list($questionidcondition, $params) = $DB->get_in_or_equal(
 713                  $questionids, SQL_PARAMS_NAMED, 'qid0000');
 714          $where = 'WHERE q.id ' . $questionidcondition;
 715      }
 716  
 717      if ($join) {
 718          $join = 'JOIN ' . $join;
 719      }
 720  
 721      if ($extrafields) {
 722          $extrafields = ', ' . $extrafields;
 723      }
 724  
 725      if ($orderby) {
 726          $orderby = 'ORDER BY ' . $orderby;
 727      }
 728  
 729      $sql = "SELECT q.*, qc.contextid{$extrafields}
 730                FROM {question} q
 731                JOIN {question_categories} qc ON q.category = qc.id
 732                {$join}
 733               {$where}
 734            {$orderby}";
 735  
 736      // Load the questions.
 737      $questions = $DB->get_records_sql($sql, $extraparams + $params);
 738      foreach ($questions as $question) {
 739          $question->_partiallyloaded = true;
 740      }
 741  
 742      return $questions;
 743  }
 744  
 745  /**
 746   * Load a set of questions, given a list of ids. The $join and $extrafields arguments can be used
 747   * together to pull in extra data. See, for example, the usage in mod/quiz/attempt.php, and
 748   * read the code below to see how the SQL is assembled. Throws exceptions on error.
 749   *
 750   * @param array $questionids array of question ids.
 751   * @param string $extrafields extra SQL code to be added to the query.
 752   * @param string $join extra SQL code to be added to the query.
 753   * @param array $extraparams values for any placeholders in $join.
 754   * You are strongly recommended to use named placeholder.
 755   *
 756   * @return array question objects.
 757   */
 758  function question_load_questions($questionids, $extrafields = '', $join = '') {
 759      $questions = question_preload_questions($questionids, $extrafields, $join);
 760  
 761      // Load the question type specific information
 762      if (!get_question_options($questions)) {
 763          return 'Could not load the question options';
 764      }
 765  
 766      return $questions;
 767  }
 768  
 769  /**
 770   * Private function to factor common code out of get_question_options().
 771   *
 772   * @param object $question the question to tidy.
 773   * @param boolean $loadtags load the question tags from the tags table. Optional, default false.
 774   */
 775  function _tidy_question($question, $loadtags = false) {
 776      global $CFG;
 777  
 778      // Load question-type specific fields.
 779      if (!question_bank::is_qtype_installed($question->qtype)) {
 780          $question->questiontext = html_writer::tag('p', get_string('warningmissingtype',
 781                  'qtype_missingtype')) . $question->questiontext;
 782      }
 783      question_bank::get_qtype($question->qtype)->get_question_options($question);
 784  
 785      // Convert numeric fields to float. (Prevents these being displayed as 1.0000000.)
 786      $question->defaultmark += 0;
 787      $question->penalty += 0;
 788  
 789      if (isset($question->_partiallyloaded)) {
 790          unset($question->_partiallyloaded);
 791      }
 792  
 793      if ($loadtags && core_tag_tag::is_enabled('core_question', 'question')) {
 794          $question->tags = core_tag_tag::get_item_tags_array('core_question', 'question', $question->id);
 795      }
 796  }
 797  
 798  /**
 799   * Updates the question objects with question type specific
 800   * information by calling {@link get_question_options()}
 801   *
 802   * Can be called either with an array of question objects or with a single
 803   * question object.
 804   *
 805   * @param mixed $questions Either an array of question objects to be updated
 806   *         or just a single question object
 807   * @param boolean $loadtags load the question tags from the tags table. Optional, default false.
 808   * @return bool Indicates success or failure.
 809   */
 810  function get_question_options(&$questions, $loadtags = false) {
 811      if (is_array($questions)) { // deal with an array of questions
 812          foreach ($questions as $i => $notused) {
 813              _tidy_question($questions[$i], $loadtags);
 814          }
 815      } else { // deal with single question
 816          _tidy_question($questions, $loadtags);
 817      }
 818      return true;
 819  }
 820  
 821  /**
 822   * Print the icon for the question type
 823   *
 824   * @param object $question The question object for which the icon is required.
 825   *       Only $question->qtype is used.
 826   * @return string the HTML for the img tag.
 827   */
 828  function print_question_icon($question) {
 829      global $PAGE;
 830      return $PAGE->get_renderer('question', 'bank')->qtype_icon($question->qtype);
 831  }
 832  
 833  /**
 834   * Creates a stamp that uniquely identifies this version of the question
 835   *
 836   * In future we want this to use a hash of the question data to guarantee that
 837   * identical versions have the same version stamp.
 838   *
 839   * @param object $question
 840   * @return string A unique version stamp
 841   */
 842  function question_hash($question) {
 843      return make_unique_id_code();
 844  }
 845  
 846  /// CATEGORY FUNCTIONS /////////////////////////////////////////////////////////////////
 847  
 848  /**
 849   * returns the categories with their names ordered following parent-child relationships
 850   * finally it tries to return pending categories (those being orphaned, whose parent is
 851   * incorrect) to avoid missing any category from original array.
 852   */
 853  function sort_categories_by_tree(&$categories, $id = 0, $level = 1) {
 854      global $DB;
 855  
 856      $children = array();
 857      $keys = array_keys($categories);
 858  
 859      foreach ($keys as $key) {
 860          if (!isset($categories[$key]->processed) && $categories[$key]->parent == $id) {
 861              $children[$key] = $categories[$key];
 862              $categories[$key]->processed = true;
 863              $children = $children + sort_categories_by_tree(
 864                      $categories, $children[$key]->id, $level+1);
 865          }
 866      }
 867      //If level = 1, we have finished, try to look for non processed categories
 868      // (bad parent) and sort them too
 869      if ($level == 1) {
 870          foreach ($keys as $key) {
 871              // If not processed and it's a good candidate to start (because its
 872              // parent doesn't exist in the course)
 873              if (!isset($categories[$key]->processed) && !$DB->record_exists('question_categories',
 874                      array('contextid' => $categories[$key]->contextid,
 875                              'id' => $categories[$key]->parent))) {
 876                  $children[$key] = $categories[$key];
 877                  $categories[$key]->processed = true;
 878                  $children = $children + sort_categories_by_tree(
 879                          $categories, $children[$key]->id, $level + 1);
 880              }
 881          }
 882      }
 883      return $children;
 884  }
 885  
 886  /**
 887   * Private method, only for the use of add_indented_names().
 888   *
 889   * Recursively adds an indentedname field to each category, starting with the category
 890   * with id $id, and dealing with that category and all its children, and
 891   * return a new array, with those categories in the right order.
 892   *
 893   * @param array $categories an array of categories which has had childids
 894   *          fields added by flatten_category_tree(). Passed by reference for
 895   *          performance only. It is not modfied.
 896   * @param int $id the category to start the indenting process from.
 897   * @param int $depth the indent depth. Used in recursive calls.
 898   * @return array a new array of categories, in the right order for the tree.
 899   */
 900  function flatten_category_tree(&$categories, $id, $depth = 0, $nochildrenof = -1) {
 901  
 902      // Indent the name of this category.
 903      $newcategories = array();
 904      $newcategories[$id] = $categories[$id];
 905      $newcategories[$id]->indentedname = str_repeat('&nbsp;&nbsp;&nbsp;', $depth) .
 906              $categories[$id]->name;
 907  
 908      // Recursively indent the children.
 909      foreach ($categories[$id]->childids as $childid) {
 910          if ($childid != $nochildrenof) {
 911              $newcategories = $newcategories + flatten_category_tree(
 912                      $categories, $childid, $depth + 1, $nochildrenof);
 913          }
 914      }
 915  
 916      // Remove the childids array that were temporarily added.
 917      unset($newcategories[$id]->childids);
 918  
 919      return $newcategories;
 920  }
 921  
 922  /**
 923   * Format categories into an indented list reflecting the tree structure.
 924   *
 925   * @param array $categories An array of category objects, for example from the.
 926   * @return array The formatted list of categories.
 927   */
 928  function add_indented_names($categories, $nochildrenof = -1) {
 929  
 930      // Add an array to each category to hold the child category ids. This array
 931      // will be removed again by flatten_category_tree(). It should not be used
 932      // outside these two functions.
 933      foreach (array_keys($categories) as $id) {
 934          $categories[$id]->childids = array();
 935      }
 936  
 937      // Build the tree structure, and record which categories are top-level.
 938      // We have to be careful, because the categories array may include published
 939      // categories from other courses, but not their parents.
 940      $toplevelcategoryids = array();
 941      foreach (array_keys($categories) as $id) {
 942          if (!empty($categories[$id]->parent) &&
 943                  array_key_exists($categories[$id]->parent, $categories)) {
 944              $categories[$categories[$id]->parent]->childids[] = $id;
 945          } else {
 946              $toplevelcategoryids[] = $id;
 947          }
 948      }
 949  
 950      // Flatten the tree to and add the indents.
 951      $newcategories = array();
 952      foreach ($toplevelcategoryids as $id) {
 953          $newcategories = $newcategories + flatten_category_tree(
 954                  $categories, $id, 0, $nochildrenof);
 955      }
 956  
 957      return $newcategories;
 958  }
 959  
 960  /**
 961   * Output a select menu of question categories.
 962   *
 963   * Categories from this course and (optionally) published categories from other courses
 964   * are included. Optionally, only categories the current user may edit can be included.
 965   *
 966   * @param integer $courseid the id of the course to get the categories for.
 967   * @param integer $published if true, include publised categories from other courses.
 968   * @param integer $only_editable if true, exclude categories this user is not allowed to edit.
 969   * @param integer $selected optionally, the id of a category to be selected by
 970   *      default in the dropdown.
 971   */
 972  function question_category_select_menu($contexts, $top = false, $currentcat = 0,
 973          $selected = "", $nochildrenof = -1) {
 974      global $OUTPUT;
 975      $categoriesarray = question_category_options($contexts, $top, $currentcat,
 976              false, $nochildrenof);
 977      if ($selected) {
 978          $choose = '';
 979      } else {
 980          $choose = 'choosedots';
 981      }
 982      $options = array();
 983      foreach ($categoriesarray as $group => $opts) {
 984          $options[] = array($group => $opts);
 985      }
 986      echo html_writer::label(get_string('questioncategory', 'core_question'), 'id_movetocategory', false, array('class' => 'accesshide'));
 987      echo html_writer::select($options, 'category', $selected, $choose, array('id' => 'id_movetocategory'));
 988  }
 989  
 990  /**
 991   * @param integer $contextid a context id.
 992   * @return object the default question category for that context, or false if none.
 993   */
 994  function question_get_default_category($contextid) {
 995      global $DB;
 996      $category = $DB->get_records('question_categories',
 997              array('contextid' => $contextid), 'id', '*', 0, 1);
 998      if (!empty($category)) {
 999          return reset($category);
1000      } else {
1001          return false;
1002      }
1003  }
1004  
1005  /**
1006   * Gets the default category in the most specific context.
1007   * If no categories exist yet then default ones are created in all contexts.
1008   *
1009   * @param array $contexts  The context objects for this context and all parent contexts.
1010   * @return object The default category - the category in the course context
1011   */
1012  function question_make_default_categories($contexts) {
1013      global $DB;
1014      static $preferredlevels = array(
1015          CONTEXT_COURSE => 4,
1016          CONTEXT_MODULE => 3,
1017          CONTEXT_COURSECAT => 2,
1018          CONTEXT_SYSTEM => 1,
1019      );
1020  
1021      $toreturn = null;
1022      $preferredness = 0;
1023      // If it already exists, just return it.
1024      foreach ($contexts as $key => $context) {
1025          if (!$exists = $DB->record_exists("question_categories",
1026                  array('contextid' => $context->id))) {
1027              // Otherwise, we need to make one
1028              $category = new stdClass();
1029              $contextname = $context->get_context_name(false, true);
1030              $category->name = get_string('defaultfor', 'question', $contextname);
1031              $category->info = get_string('defaultinfofor', 'question', $contextname);
1032              $category->contextid = $context->id;
1033              $category->parent = 0;
1034              // By default, all categories get this number, and are sorted alphabetically.
1035              $category->sortorder = 999;
1036              $category->stamp = make_unique_id_code();
1037              $category->id = $DB->insert_record('question_categories', $category);
1038          } else {
1039              $category = question_get_default_category($context->id);
1040          }
1041          $thispreferredness = $preferredlevels[$context->contextlevel];
1042          if (has_any_capability(array('moodle/question:usemine', 'moodle/question:useall'), $context)) {
1043              $thispreferredness += 10;
1044          }
1045          if ($thispreferredness > $preferredness) {
1046              $toreturn = $category;
1047              $preferredness = $thispreferredness;
1048          }
1049      }
1050  
1051      if (!is_null($toreturn)) {
1052          $toreturn = clone($toreturn);
1053      }
1054      return $toreturn;
1055  }
1056  
1057  /**
1058   * Get all the category objects, including a count of the number of questions in that category,
1059   * for all the categories in the lists $contexts.
1060   *
1061   * @param mixed $contexts either a single contextid, or a comma-separated list of context ids.
1062   * @param string $sortorder used as the ORDER BY clause in the select statement.
1063   * @return array of category objects.
1064   */
1065  function get_categories_for_contexts($contexts, $sortorder = 'parent, sortorder, name ASC') {
1066      global $DB;
1067      return $DB->get_records_sql("
1068              SELECT c.*, (SELECT count(1) FROM {question} q
1069                          WHERE c.id = q.category AND q.hidden='0' AND q.parent='0') AS questioncount
1070                FROM {question_categories} c
1071               WHERE c.contextid IN ($contexts)
1072            ORDER BY $sortorder");
1073  }
1074  
1075  /**
1076   * Output an array of question categories.
1077   */
1078  function question_category_options($contexts, $top = false, $currentcat = 0,
1079          $popupform = false, $nochildrenof = -1) {
1080      global $CFG;
1081      $pcontexts = array();
1082      foreach ($contexts as $context) {
1083          $pcontexts[] = $context->id;
1084      }
1085      $contextslist = join($pcontexts, ', ');
1086  
1087      $categories = get_categories_for_contexts($contextslist);
1088  
1089      $categories = question_add_context_in_key($categories);
1090  
1091      if ($top) {
1092          $categories = question_add_tops($categories, $pcontexts);
1093      }
1094      $categories = add_indented_names($categories, $nochildrenof);
1095  
1096      // sort cats out into different contexts
1097      $categoriesarray = array();
1098      foreach ($pcontexts as $contextid) {
1099          $context = context::instance_by_id($contextid);
1100          $contextstring = $context->get_context_name(true, true);
1101          foreach ($categories as $category) {
1102              if ($category->contextid == $contextid) {
1103                  $cid = $category->id;
1104                  if ($currentcat != $cid || $currentcat == 0) {
1105                      $countstring = !empty($category->questioncount) ?
1106                              " ($category->questioncount)" : '';
1107                      $categoriesarray[$contextstring][$cid] =
1108                              format_string($category->indentedname, true,
1109                                  array('context' => $context)) . $countstring;
1110                  }
1111              }
1112          }
1113      }
1114      if ($popupform) {
1115          $popupcats = array();
1116          foreach ($categoriesarray as $contextstring => $optgroup) {
1117              $group = array();
1118              foreach ($optgroup as $key => $value) {
1119                  $key = str_replace($CFG->wwwroot, '', $key);
1120                  $group[$key] = $value;
1121              }
1122              $popupcats[] = array($contextstring => $group);
1123          }
1124          return $popupcats;
1125      } else {
1126          return $categoriesarray;
1127      }
1128  }
1129  
1130  function question_add_context_in_key($categories) {
1131      $newcatarray = array();
1132      foreach ($categories as $id => $category) {
1133          $category->parent = "$category->parent,$category->contextid";
1134          $category->id = "$category->id,$category->contextid";
1135          $newcatarray["$id,$category->contextid"] = $category;
1136      }
1137      return $newcatarray;
1138  }
1139  
1140  function question_add_tops($categories, $pcontexts) {
1141      $topcats = array();
1142      foreach ($pcontexts as $context) {
1143          $newcat = new stdClass();
1144          $newcat->id = "0,$context";
1145          $newcat->name = get_string('top');
1146          $newcat->parent = -1;
1147          $newcat->contextid = $context;
1148          $topcats["0,$context"] = $newcat;
1149      }
1150      //put topcats in at beginning of array - they'll be sorted into different contexts later.
1151      return array_merge($topcats, $categories);
1152  }
1153  
1154  /**
1155   * @return array of question category ids of the category and all subcategories.
1156   */
1157  function question_categorylist($categoryid) {
1158      global $DB;
1159  
1160      // final list of category IDs
1161      $categorylist = array();
1162  
1163      // a list of category IDs to check for any sub-categories
1164      $subcategories = array($categoryid);
1165  
1166      while ($subcategories) {
1167          foreach ($subcategories as $subcategory) {
1168              // if anything from the temporary list was added already, then we have a loop
1169              if (isset($categorylist[$subcategory])) {
1170                  throw new coding_exception("Category id=$subcategory is already on the list - loop of categories detected.");
1171              }
1172              $categorylist[$subcategory] = $subcategory;
1173          }
1174  
1175          list ($in, $params) = $DB->get_in_or_equal($subcategories);
1176  
1177          $subcategories = $DB->get_records_select_menu('question_categories',
1178                  "parent $in", $params, NULL, 'id,id AS id2');
1179      }
1180  
1181      return $categorylist;
1182  }
1183  
1184  //===========================
1185  // Import/Export Functions
1186  //===========================
1187  
1188  /**
1189   * Get list of available import or export formats
1190   * @param string $type 'import' if import list, otherwise export list assumed
1191   * @return array sorted list of import/export formats available
1192   */
1193  function get_import_export_formats($type) {
1194      global $CFG;
1195      require_once($CFG->dirroot . '/question/format.php');
1196  
1197      $formatclasses = core_component::get_plugin_list_with_class('qformat', '', 'format.php');
1198  
1199      $fileformatname = array();
1200      foreach ($formatclasses as $component => $formatclass) {
1201  
1202          $format = new $formatclass();
1203          if ($type == 'import') {
1204              $provided = $format->provide_import();
1205          } else {
1206              $provided = $format->provide_export();
1207          }
1208  
1209          if ($provided) {
1210              list($notused, $fileformat) = explode('_', $component, 2);
1211              $fileformatnames[$fileformat] = get_string('pluginname', $component);
1212          }
1213      }
1214  
1215      core_collator::asort($fileformatnames);
1216      return $fileformatnames;
1217  }
1218  
1219  
1220  /**
1221   * Create a reasonable default file name for exporting questions from a particular
1222   * category.
1223   * @param object $course the course the questions are in.
1224   * @param object $category the question category.
1225   * @return string the filename.
1226   */
1227  function question_default_export_filename($course, $category) {
1228      // We build a string that is an appropriate name (questions) from the lang pack,
1229      // then the corse shortname, then the question category name, then a timestamp.
1230  
1231      $base = clean_filename(get_string('exportfilename', 'question'));
1232  
1233      $dateformat = str_replace(' ', '_', get_string('exportnameformat', 'question'));
1234      $timestamp = clean_filename(userdate(time(), $dateformat, 99, false));
1235  
1236      $shortname = clean_filename($course->shortname);
1237      if ($shortname == '' || $shortname == '_' ) {
1238          $shortname = $course->id;
1239      }
1240  
1241      $categoryname = clean_filename(format_string($category->name));
1242  
1243      return "{$base}-{$shortname}-{$categoryname}-{$timestamp}";
1244  
1245      return $export_name;
1246  }
1247  
1248  /**
1249   * Converts contextlevels to strings and back to help with reading/writing contexts
1250   * to/from import/export files.
1251   *
1252   * @copyright 1999 onwards Martin Dougiamas  {@link http://moodle.com}
1253   * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
1254   */
1255  class context_to_string_translator{
1256      /**
1257       * @var array used to translate between contextids and strings for this context.
1258       */
1259      protected $contexttostringarray = array();
1260  
1261      public function __construct($contexts) {
1262          $this->generate_context_to_string_array($contexts);
1263      }
1264  
1265      public function context_to_string($contextid) {
1266          return $this->contexttostringarray[$contextid];
1267      }
1268  
1269      public function string_to_context($contextname) {
1270          $contextid = array_search($contextname, $this->contexttostringarray);
1271          return $contextid;
1272      }
1273  
1274      protected function generate_context_to_string_array($contexts) {
1275          if (!$this->contexttostringarray) {
1276              $catno = 1;
1277              foreach ($contexts as $context) {
1278                  switch ($context->contextlevel) {
1279                      case CONTEXT_MODULE :
1280                          $contextstring = 'module';
1281                          break;
1282                      case CONTEXT_COURSE :
1283                          $contextstring = 'course';
1284                          break;
1285                      case CONTEXT_COURSECAT :
1286                          $contextstring = "cat$catno";
1287                          $catno++;
1288                          break;
1289                      case CONTEXT_SYSTEM :
1290                          $contextstring = 'system';
1291                          break;
1292                  }
1293                  $this->contexttostringarray[$context->id] = $contextstring;
1294              }
1295          }
1296      }
1297  
1298  }
1299  
1300  /**
1301   * Check capability on category
1302   *
1303   * @param mixed $question object or id
1304   * @param string $cap 'add', 'edit', 'view', 'use', 'move'
1305   * @param integer $cachecat useful to cache all question records in a category
1306   * @return boolean this user has the capability $cap for this question $question?
1307   */
1308  function question_has_capability_on($question, $cap, $cachecat = -1) {
1309      global $USER, $DB;
1310  
1311      // these are capabilities on existing questions capabilties are
1312      //set per category. Each of these has a mine and all version. Append 'mine' and 'all'
1313      $question_questioncaps = array('edit', 'view', 'use', 'move');
1314      static $questions = array();
1315      static $categories = array();
1316      static $cachedcat = array();
1317      if ($cachecat != -1 && array_search($cachecat, $cachedcat) === false) {
1318          $questions += $DB->get_records('question', array('category' => $cachecat), '', 'id,category,createdby');
1319          $cachedcat[] = $cachecat;
1320      }
1321      if (!is_object($question)) {
1322          if (!isset($questions[$question])) {
1323              if (!$questions[$question] = $DB->get_record('question',
1324                      array('id' => $question), 'id,category,createdby')) {
1325                  print_error('questiondoesnotexist', 'question');
1326              }
1327          }
1328          $question = $questions[$question];
1329      }
1330      if (empty($question->category)) {
1331          // This can happen when we have created a fake 'missingtype' question to
1332          // take the place of a deleted question.
1333          return false;
1334      }
1335      if (!isset($categories[$question->category])) {
1336          if (!$categories[$question->category] = $DB->get_record('question_categories',
1337                  array('id'=>$question->category))) {
1338              print_error('invalidcategory', 'question');
1339          }
1340      }
1341      $category = $categories[$question->category];
1342      $context = context::instance_by_id($category->contextid);
1343  
1344      if (array_search($cap, $question_questioncaps)!== false) {
1345          if (!has_capability('moodle/question:' . $cap . 'all', $context)) {
1346              if ($question->createdby == $USER->id) {
1347                  return has_capability('moodle/question:' . $cap . 'mine', $context);
1348              } else {
1349                  return false;
1350              }
1351          } else {
1352              return true;
1353          }
1354      } else {
1355          return has_capability('moodle/question:' . $cap, $context);
1356      }
1357  
1358  }
1359  
1360  /**
1361   * Require capability on question.
1362   */
1363  function question_require_capability_on($question, $cap) {
1364      if (!question_has_capability_on($question, $cap)) {
1365          print_error('nopermissions', '', '', $cap);
1366      }
1367      return true;
1368  }
1369  
1370  /**
1371   * @param object $context a context
1372   * @return string A URL for editing questions in this context.
1373   */
1374  function question_edit_url($context) {
1375      global $CFG, $SITE;
1376      if (!has_any_capability(question_get_question_capabilities(), $context)) {
1377          return false;
1378      }
1379      $baseurl = $CFG->wwwroot . '/question/edit.php?';
1380      $defaultcategory = question_get_default_category($context->id);
1381      if ($defaultcategory) {
1382          $baseurl .= 'cat=' . $defaultcategory->id . ',' . $context->id . '&amp;';
1383      }
1384      switch ($context->contextlevel) {
1385          case CONTEXT_SYSTEM:
1386              return $baseurl . 'courseid=' . $SITE->id;
1387          case CONTEXT_COURSECAT:
1388              // This is nasty, becuase we can only edit questions in a course
1389              // context at the moment, so for now we just return false.
1390              return false;
1391          case CONTEXT_COURSE:
1392              return $baseurl . 'courseid=' . $context->instanceid;
1393          case CONTEXT_MODULE:
1394              return $baseurl . 'cmid=' . $context->instanceid;
1395      }
1396  
1397  }
1398  
1399  /**
1400   * Adds question bank setting links to the given navigation node if caps are met.
1401   *
1402   * @param navigation_node $navigationnode The navigation node to add the question branch to
1403   * @param object $context
1404   * @return navigation_node Returns the question branch that was added
1405   */
1406  function question_extend_settings_navigation(navigation_node $navigationnode, $context) {
1407      global $PAGE;
1408  
1409      if ($context->contextlevel == CONTEXT_COURSE) {
1410          $params = array('courseid'=>$context->instanceid);
1411      } else if ($context->contextlevel == CONTEXT_MODULE) {
1412          $params = array('cmid'=>$context->instanceid);
1413      } else {
1414          return;
1415      }
1416  
1417      if (($cat = $PAGE->url->param('cat')) && preg_match('~\d+,\d+~', $cat)) {
1418          $params['cat'] = $cat;
1419      }
1420  
1421      $questionnode = $navigationnode->add(get_string('questionbank', 'question'),
1422              new moodle_url('/question/edit.php', $params), navigation_node::TYPE_CONTAINER, null, 'questionbank');
1423  
1424      $contexts = new question_edit_contexts($context);
1425      if ($contexts->have_one_edit_tab_cap('questions')) {
1426          $questionnode->add(get_string('questions', 'question'), new moodle_url(
1427                  '/question/edit.php', $params), navigation_node::TYPE_SETTING, null, 'questions');
1428      }
1429      if ($contexts->have_one_edit_tab_cap('categories')) {
1430          $questionnode->add(get_string('categories', 'question'), new moodle_url(
1431                  '/question/category.php', $params), navigation_node::TYPE_SETTING, null, 'categories');
1432      }
1433      if ($contexts->have_one_edit_tab_cap('import')) {
1434          $questionnode->add(get_string('import', 'question'), new moodle_url(
1435                  '/question/import.php', $params), navigation_node::TYPE_SETTING, null, 'import');
1436      }
1437      if ($contexts->have_one_edit_tab_cap('export')) {
1438          $questionnode->add(get_string('export', 'question'), new moodle_url(
1439                  '/question/export.php', $params), navigation_node::TYPE_SETTING, null, 'export');
1440      }
1441  
1442      return $questionnode;
1443  }
1444  
1445  /**
1446   * @return array all the capabilities that relate to accessing particular questions.
1447   */
1448  function question_get_question_capabilities() {
1449      return array(
1450          'moodle/question:add',
1451          'moodle/question:editmine',
1452          'moodle/question:editall',
1453          'moodle/question:viewmine',
1454          'moodle/question:viewall',
1455          'moodle/question:usemine',
1456          'moodle/question:useall',
1457          'moodle/question:movemine',
1458          'moodle/question:moveall',
1459      );
1460  }
1461  
1462  /**
1463   * @return array all the question bank capabilities.
1464   */
1465  function question_get_all_capabilities() {
1466      $caps = question_get_question_capabilities();
1467      $caps[] = 'moodle/question:managecategory';
1468      $caps[] = 'moodle/question:flag';
1469      return $caps;
1470  }
1471  
1472  
1473  /**
1474   * Tracks all the contexts related to the one where we are currently editing
1475   * questions, and provides helper methods to check permissions.
1476   *
1477   * @copyright 2007 Jamie Pratt me@jamiep.org
1478   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
1479   */
1480  class question_edit_contexts {
1481  
1482      public static $caps = array(
1483          'editq' => array('moodle/question:add',
1484              'moodle/question:editmine',
1485              'moodle/question:editall',
1486              'moodle/question:viewmine',
1487              'moodle/question:viewall',
1488              'moodle/question:usemine',
1489              'moodle/question:useall',
1490              'moodle/question:movemine',
1491              'moodle/question:moveall'),
1492          'questions'=>array('moodle/question:add',
1493              'moodle/question:editmine',
1494              'moodle/question:editall',
1495              'moodle/question:viewmine',
1496              'moodle/question:viewall',
1497              'moodle/question:movemine',
1498              'moodle/question:moveall'),
1499          'categories'=>array('moodle/question:managecategory'),
1500          'import'=>array('moodle/question:add'),
1501          'export'=>array('moodle/question:viewall', 'moodle/question:viewmine'));
1502  
1503      protected $allcontexts;
1504  
1505      /**
1506       * Constructor
1507       * @param context the current context.
1508       */
1509      public function __construct(context $thiscontext) {
1510          $this->allcontexts = array_values($thiscontext->get_parent_contexts(true));
1511      }
1512  
1513      /**
1514       * @return array all parent contexts
1515       */
1516      public function all() {
1517          return $this->allcontexts;
1518      }
1519  
1520      /**
1521       * @return object lowest context which must be either the module or course context
1522       */
1523      public function lowest() {
1524          return $this->allcontexts[0];
1525      }
1526  
1527      /**
1528       * @param string $cap capability
1529       * @return array parent contexts having capability, zero based index
1530       */
1531      public function having_cap($cap) {
1532          $contextswithcap = array();
1533          foreach ($this->allcontexts as $context) {
1534              if (has_capability($cap, $context)) {
1535                  $contextswithcap[] = $context;
1536              }
1537          }
1538          return $contextswithcap;
1539      }
1540  
1541      /**
1542       * @param array $caps capabilities
1543       * @return array parent contexts having at least one of $caps, zero based index
1544       */
1545      public function having_one_cap($caps) {
1546          $contextswithacap = array();
1547          foreach ($this->allcontexts as $context) {
1548              foreach ($caps as $cap) {
1549                  if (has_capability($cap, $context)) {
1550                      $contextswithacap[] = $context;
1551                      break; //done with caps loop
1552                  }
1553              }
1554          }
1555          return $contextswithacap;
1556      }
1557  
1558      /**
1559       * @param string $tabname edit tab name
1560       * @return array parent contexts having at least one of $caps, zero based index
1561       */
1562      public function having_one_edit_tab_cap($tabname) {
1563          return $this->having_one_cap(self::$caps[$tabname]);
1564      }
1565  
1566      /**
1567       * @return those contexts where a user can add a question and then use it.
1568       */
1569      public function having_add_and_use() {
1570          $contextswithcap = array();
1571          foreach ($this->allcontexts as $context) {
1572              if (!has_capability('moodle/question:add', $context)) {
1573                  continue;
1574              }
1575              if (!has_any_capability(array('moodle/question:useall', 'moodle/question:usemine'), $context)) {
1576                              continue;
1577              }
1578              $contextswithcap[] = $context;
1579          }
1580          return $contextswithcap;
1581      }
1582  
1583      /**
1584       * Has at least one parent context got the cap $cap?
1585       *
1586       * @param string $cap capability
1587       * @return boolean
1588       */
1589      public function have_cap($cap) {
1590          return (count($this->having_cap($cap)));
1591      }
1592  
1593      /**
1594       * Has at least one parent context got one of the caps $caps?
1595       *
1596       * @param array $caps capability
1597       * @return boolean
1598       */
1599      public function have_one_cap($caps) {
1600          foreach ($caps as $cap) {
1601              if ($this->have_cap($cap)) {
1602                  return true;
1603              }
1604          }
1605          return false;
1606      }
1607  
1608      /**
1609       * Has at least one parent context got one of the caps for actions on $tabname
1610       *
1611       * @param string $tabname edit tab name
1612       * @return boolean
1613       */
1614      public function have_one_edit_tab_cap($tabname) {
1615          return $this->have_one_cap(self::$caps[$tabname]);
1616      }
1617  
1618      /**
1619       * Throw error if at least one parent context hasn't got the cap $cap
1620       *
1621       * @param string $cap capability
1622       */
1623      public function require_cap($cap) {
1624          if (!$this->have_cap($cap)) {
1625              print_error('nopermissions', '', '', $cap);
1626          }
1627      }
1628  
1629      /**
1630       * Throw error if at least one parent context hasn't got one of the caps $caps
1631       *
1632       * @param array $cap capabilities
1633       */
1634      public function require_one_cap($caps) {
1635          if (!$this->have_one_cap($caps)) {
1636              $capsstring = join($caps, ', ');
1637              print_error('nopermissions', '', '', $capsstring);
1638          }
1639      }
1640  
1641      /**
1642       * Throw error if at least one parent context hasn't got one of the caps $caps
1643       *
1644       * @param string $tabname edit tab name
1645       */
1646      public function require_one_edit_tab_cap($tabname) {
1647          if (!$this->have_one_edit_tab_cap($tabname)) {
1648              print_error('nopermissions', '', '', 'access question edit tab '.$tabname);
1649          }
1650      }
1651  }
1652  
1653  
1654  /**
1655   * Helps call file_rewrite_pluginfile_urls with the right parameters.
1656   *
1657   * @package  core_question
1658   * @category files
1659   * @param string $text text being processed
1660   * @param string $file the php script used to serve files
1661   * @param int $contextid context ID
1662   * @param string $component component
1663   * @param string $filearea filearea
1664   * @param array $ids other IDs will be used to check file permission
1665   * @param int $itemid item ID
1666   * @param array $options options
1667   * @return string
1668   */
1669  function question_rewrite_question_urls($text, $file, $contextid, $component,
1670          $filearea, array $ids, $itemid, array $options=null) {
1671  
1672      $idsstr = '';
1673      if (!empty($ids)) {
1674          $idsstr .= implode('/', $ids);
1675      }
1676      if ($itemid !== null) {
1677          $idsstr .= '/' . $itemid;
1678      }
1679      return file_rewrite_pluginfile_urls($text, $file, $contextid, $component,
1680              $filearea, $idsstr, $options);
1681  }
1682  
1683  /**
1684   * Rewrite the PLUGINFILE urls in part of the content of a question, for use when
1685   * viewing the question outside an attempt (for example, in the question bank
1686   * listing or in the quiz statistics report).
1687   *
1688   * @param string $text the question text.
1689   * @param int $questionid the question id.
1690   * @param int $filecontextid the context id of the question being displayed.
1691   * @param string $filecomponent the component that owns the file area.
1692   * @param string $filearea the file area name.
1693   * @param int|null $itemid the file's itemid
1694   * @param int $previewcontextid the context id where the preview is being displayed.
1695   * @param string $previewcomponent component responsible for displaying the preview.
1696   * @param array $options text and file options ('forcehttps'=>false)
1697   * @return string $questiontext with URLs rewritten.
1698   */
1699  function question_rewrite_question_preview_urls($text, $questionid,
1700          $filecontextid, $filecomponent, $filearea, $itemid,
1701          $previewcontextid, $previewcomponent, $options = null) {
1702  
1703      $path = "preview/$previewcontextid/$previewcomponent/$questionid";
1704      if ($itemid) {
1705          $path .= '/' . $itemid;
1706      }
1707  
1708      return file_rewrite_pluginfile_urls($text, 'pluginfile.php', $filecontextid,
1709              $filecomponent, $filearea, $path, $options);
1710  }
1711  
1712  /**
1713   * Called by pluginfile.php to serve files related to the 'question' core
1714   * component and for files belonging to qtypes.
1715   *
1716   * For files that relate to questions in a question_attempt, then we delegate to
1717   * a function in the component that owns the attempt (for example in the quiz,
1718   * or in core question preview) to get necessary inforation.
1719   *
1720   * (Note that, at the moment, all question file areas relate to questions in
1721   * attempts, so the If at the start of the last paragraph is always true.)
1722   *
1723   * Does not return, either calls send_file_not_found(); or serves the file.
1724   *
1725   * @package  core_question
1726   * @category files
1727   * @param stdClass $course course settings object
1728   * @param stdClass $context context object
1729   * @param string $component the name of the component we are serving files for.
1730   * @param string $filearea the name of the file area.
1731   * @param array $args the remaining bits of the file path.
1732   * @param bool $forcedownload whether the user must be forced to download the file.
1733   * @param array $options additional options affecting the file serving
1734   */
1735  function question_pluginfile($course, $context, $component, $filearea, $args, $forcedownload, array $options=array()) {
1736      global $DB, $CFG;
1737  
1738      // Special case, sending a question bank export.
1739      if ($filearea === 'export') {
1740          list($context, $course, $cm) = get_context_info_array($context->id);
1741          require_login($course, false, $cm);
1742  
1743          require_once($CFG->dirroot . '/question/editlib.php');
1744          $contexts = new question_edit_contexts($context);
1745          // check export capability
1746          $contexts->require_one_edit_tab_cap('export');
1747          $category_id = (int)array_shift($args);
1748          $format      = array_shift($args);
1749          $cattofile   = array_shift($args);
1750          $contexttofile = array_shift($args);
1751          $filename    = array_shift($args);
1752  
1753          // load parent class for import/export
1754          require_once($CFG->dirroot . '/question/format.php');
1755          require_once($CFG->dirroot . '/question/editlib.php');
1756          require_once($CFG->dirroot . '/question/format/' . $format . '/format.php');
1757  
1758          $classname = 'qformat_' . $format;
1759          if (!class_exists($classname)) {
1760              send_file_not_found();
1761          }
1762  
1763          $qformat = new $classname();
1764  
1765          if (!$category = $DB->get_record('question_categories', array('id' => $category_id))) {
1766              send_file_not_found();
1767          }
1768  
1769          $qformat->setCategory($category);
1770          $qformat->setContexts($contexts->having_one_edit_tab_cap('export'));
1771          $qformat->setCourse($course);
1772  
1773          if ($cattofile == 'withcategories') {
1774              $qformat->setCattofile(true);
1775          } else {
1776              $qformat->setCattofile(false);
1777          }
1778  
1779          if ($contexttofile == 'withcontexts') {
1780              $qformat->setContexttofile(true);
1781          } else {
1782              $qformat->setContexttofile(false);
1783          }
1784  
1785          if (!$qformat->exportpreprocess()) {
1786              send_file_not_found();
1787              print_error('exporterror', 'question', $thispageurl->out());
1788          }
1789  
1790          // export data to moodle file pool
1791          if (!$content = $qformat->exportprocess(true)) {
1792              send_file_not_found();
1793          }
1794  
1795          send_file($content, $filename, 0, 0, true, true, $qformat->mime_type());
1796      }
1797  
1798      // Normal case, a file belonging to a question.
1799      $qubaidorpreview = array_shift($args);
1800  
1801      // Two sub-cases: 1. A question being previewed outside an attempt/usage.
1802      if ($qubaidorpreview === 'preview') {
1803          $previewcontextid = (int)array_shift($args);
1804          $previewcomponent = array_shift($args);
1805          $questionid = (int) array_shift($args);
1806          $previewcontext = context_helper::instance_by_id($previewcontextid);
1807  
1808          $result = component_callback($previewcomponent, 'question_preview_pluginfile', array(
1809                  $previewcontext, $questionid,
1810                  $context, $component, $filearea, $args,
1811                  $forcedownload, $options), 'callbackmissing');
1812  
1813          if ($result === 'callbackmissing') {
1814              throw new coding_exception("Component {$previewcomponent} does not define the callback " .
1815                      "{$previewcomponent}_question_preview_pluginfile callback. " .
1816                      "Which is required if you are using question_rewrite_question_preview_urls.", DEBUG_DEVELOPER);
1817          }
1818  
1819          send_file_not_found();
1820      }
1821  
1822      // 2. A question being attempted in the normal way.
1823      $qubaid = (int)$qubaidorpreview;
1824      $slot = (int)array_shift($args);
1825  
1826      $module = $DB->get_field('question_usages', 'component',
1827              array('id' => $qubaid));
1828      if (!$module) {
1829          send_file_not_found();
1830      }
1831  
1832      if ($module === 'core_question_preview') {
1833          require_once($CFG->dirroot . '/question/previewlib.php');
1834          return question_preview_question_pluginfile($course, $context,
1835                  $component, $filearea, $qubaid, $slot, $args, $forcedownload, $options);
1836  
1837      } else {
1838          $dir = core_component::get_component_directory($module);
1839          if (!file_exists("$dir/lib.php")) {
1840              send_file_not_found();
1841          }
1842          include_once("$dir/lib.php");
1843  
1844          $filefunction = $module . '_question_pluginfile';
1845          if (function_exists($filefunction)) {
1846              $filefunction($course, $context, $component, $filearea, $qubaid, $slot,
1847                  $args, $forcedownload, $options);
1848          }
1849  
1850          // Okay, we're here so lets check for function without 'mod_'.
1851          if (strpos($module, 'mod_') === 0) {
1852              $filefunctionold  = substr($module, 4) . '_question_pluginfile';
1853              if (function_exists($filefunctionold)) {
1854                  $filefunctionold($course, $context, $component, $filearea, $qubaid, $slot,
1855                      $args, $forcedownload, $options);
1856              }
1857          }
1858  
1859          send_file_not_found();
1860      }
1861  }
1862  
1863  /**
1864   * Serve questiontext files in the question text when they are displayed in this report.
1865   *
1866   * @package  core_files
1867   * @category files
1868   * @param context $previewcontext the context in which the preview is happening.
1869   * @param int $questionid the question id.
1870   * @param context $filecontext the file (question) context.
1871   * @param string $filecomponent the component the file belongs to.
1872   * @param string $filearea the file area.
1873   * @param array $args remaining file args.
1874   * @param bool $forcedownload.
1875   * @param array $options additional options affecting the file serving.
1876   */
1877  function core_question_question_preview_pluginfile($previewcontext, $questionid,
1878          $filecontext, $filecomponent, $filearea, $args, $forcedownload, $options = array()) {
1879      global $DB;
1880  
1881      // Verify that contextid matches the question.
1882      $question = $DB->get_record_sql('
1883              SELECT q.*, qc.contextid
1884                FROM {question} q
1885                JOIN {question_categories} qc ON qc.id = q.category
1886               WHERE q.id = :id AND qc.contextid = :contextid',
1887              array('id' => $questionid, 'contextid' => $filecontext->id), MUST_EXIST);
1888  
1889      // Check the capability.
1890      list($context, $course, $cm) = get_context_info_array($previewcontext->id);
1891      require_login($course, false, $cm);
1892  
1893      question_require_capability_on($question, 'use');
1894  
1895      $fs = get_file_storage();
1896      $relativepath = implode('/', $args);
1897      $fullpath = "/{$filecontext->id}/{$filecomponent}/{$filearea}/{$relativepath}";
1898      if (!$file = $fs->get_file_by_hash(sha1($fullpath)) or $file->is_directory()) {
1899          send_file_not_found();
1900      }
1901  
1902      send_stored_file($file, 0, 0, $forcedownload, $options);
1903  }
1904  
1905  /**
1906   * Create url for question export
1907   *
1908   * @param int $contextid, current context
1909   * @param int $categoryid, categoryid
1910   * @param string $format
1911   * @param string $withcategories
1912   * @param string $ithcontexts
1913   * @param moodle_url export file url
1914   */
1915  function question_make_export_url($contextid, $categoryid, $format, $withcategories,
1916          $withcontexts, $filename) {
1917      global $CFG;
1918      $urlbase = "$CFG->httpswwwroot/pluginfile.php";
1919      return moodle_url::make_file_url($urlbase,
1920              "/$contextid/question/export/{$categoryid}/{$format}/{$withcategories}" .
1921              "/{$withcontexts}/{$filename}", true);
1922  }
1923  
1924  /**
1925   * Return a list of page types
1926   * @param string $pagetype current page type
1927   * @param stdClass $parentcontext Block's parent context
1928   * @param stdClass $currentcontext Current context of block
1929   */
1930  function question_page_type_list($pagetype, $parentcontext, $currentcontext) {
1931      global $CFG;
1932      $types = array(
1933          'question-*'=>get_string('page-question-x', 'question'),
1934          'question-edit'=>get_string('page-question-edit', 'question'),
1935          'question-category'=>get_string('page-question-category', 'question'),
1936          'question-export'=>get_string('page-question-export', 'question'),
1937          'question-import'=>get_string('page-question-import', 'question')
1938      );
1939      if ($currentcontext->contextlevel == CONTEXT_COURSE) {
1940          require_once($CFG->dirroot . '/course/lib.php');
1941          return array_merge(course_page_type_list($pagetype, $parentcontext, $currentcontext), $types);
1942      } else {
1943          return $types;
1944      }
1945  }
1946  
1947  /**
1948   * Does an activity module use the question bank?
1949   *
1950   * @param string $modname The name of the module (without mod_ prefix).
1951   * @return bool true if the module uses questions.
1952   */
1953  function question_module_uses_questions($modname) {
1954      if (plugin_supports('mod', $modname, FEATURE_USES_QUESTIONS)) {
1955          return true;
1956      }
1957  
1958      $component = 'mod_'.$modname;
1959      if (component_callback_exists($component, 'question_pluginfile')) {
1960          debugging("{$component} uses questions but doesn't declare FEATURE_USES_QUESTIONS", DEBUG_DEVELOPER);
1961          return true;
1962      }
1963  
1964      return false;
1965  }