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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   * Defines the base class for question import and export formats.
  19   *
  20   * @package    moodlecore
  21   * @subpackage questionbank
  22   * @copyright  1999 onwards Martin Dougiamas {@link http://moodle.com}
  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   * Base class for question import and export formats.
  32   *
  33   * @copyright  1999 onwards Martin Dougiamas {@link http://moodle.com}
  34   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  35   */
  36  class qformat_default {
  37  
  38      public $displayerrors = true;
  39      public $category = null;
  40      public $questions = array();
  41      public $course = null;
  42      public $filename = '';
  43      public $realfilename = '';
  44      public $matchgrades = 'error';
  45      public $catfromfile = 0;
  46      public $contextfromfile = 0;
  47      public $cattofile = 0;
  48      public $contexttofile = 0;
  49      public $questionids = array();
  50      public $importerrors = 0;
  51      public $stoponerror = true;
  52      public $translator = null;
  53      public $canaccessbackupdata = true;
  54  
  55      protected $importcontext = null;
  56  
  57      // functions to indicate import/export functionality
  58      // override to return true if implemented
  59  
  60      /** @return bool whether this plugin provides import functionality. */
  61      public function provide_import() {
  62          return false;
  63      }
  64  
  65      /** @return bool whether this plugin provides export functionality. */
  66      public function provide_export() {
  67          return false;
  68      }
  69  
  70      /** The string mime-type of the files that this plugin reads or writes. */
  71      public function mime_type() {
  72          return mimeinfo('type', $this->export_file_extension());
  73      }
  74  
  75      /**
  76       * @return string the file extension (including .) that is normally used for
  77       * files handled by this plugin.
  78       */
  79      public function export_file_extension() {
  80          return '.txt';
  81      }
  82  
  83      /**
  84       * Check if the given file is capable of being imported by this plugin.
  85       *
  86       * Note that expensive or detailed integrity checks on the file should
  87       * not be performed by this method. Simple file type or magic-number tests
  88       * would be suitable.
  89       *
  90       * @param stored_file $file the file to check
  91       * @return bool whether this plugin can import the file
  92       */
  93      public function can_import_file($file) {
  94          return ($file->get_mimetype() == $this->mime_type());
  95      }
  96  
  97      // Accessor methods
  98  
  99      /**
 100       * set the category
 101       * @param object category the category object
 102       */
 103      public function setCategory($category) {
 104          if (count($this->questions)) {
 105              debugging('You shouldn\'t call setCategory after setQuestions');
 106          }
 107          $this->category = $category;
 108          $this->importcontext = context::instance_by_id($this->category->contextid);
 109      }
 110  
 111      /**
 112       * Set the specific questions to export. Should not include questions with
 113       * parents (sub questions of cloze question type).
 114       * Only used for question export.
 115       * @param array of question objects
 116       */
 117      public function setQuestions($questions) {
 118          if ($this->category !== null) {
 119              debugging('You shouldn\'t call setQuestions after setCategory');
 120          }
 121          $this->questions = $questions;
 122      }
 123  
 124      /**
 125       * set the course class variable
 126       * @param course object Moodle course variable
 127       */
 128      public function setCourse($course) {
 129          $this->course = $course;
 130      }
 131  
 132      /**
 133       * set an array of contexts.
 134       * @param array $contexts Moodle course variable
 135       */
 136      public function setContexts($contexts) {
 137          $this->contexts = $contexts;
 138          $this->translator = new context_to_string_translator($this->contexts);
 139      }
 140  
 141      /**
 142       * set the filename
 143       * @param string filename name of file to import/export
 144       */
 145      public function setFilename($filename) {
 146          $this->filename = $filename;
 147      }
 148  
 149      /**
 150       * set the "real" filename
 151       * (this is what the user typed, regardless of wha happened next)
 152       * @param string realfilename name of file as typed by user
 153       */
 154      public function setRealfilename($realfilename) {
 155          $this->realfilename = $realfilename;
 156      }
 157  
 158      /**
 159       * set matchgrades
 160       * @param string matchgrades error or nearest for grades
 161       */
 162      public function setMatchgrades($matchgrades) {
 163          $this->matchgrades = $matchgrades;
 164      }
 165  
 166      /**
 167       * set catfromfile
 168       * @param bool catfromfile allow categories embedded in import file
 169       */
 170      public function setCatfromfile($catfromfile) {
 171          $this->catfromfile = $catfromfile;
 172      }
 173  
 174      /**
 175       * set contextfromfile
 176       * @param bool $contextfromfile allow contexts embedded in import file
 177       */
 178      public function setContextfromfile($contextfromfile) {
 179          $this->contextfromfile = $contextfromfile;
 180      }
 181  
 182      /**
 183       * set cattofile
 184       * @param bool cattofile exports categories within export file
 185       */
 186      public function setCattofile($cattofile) {
 187          $this->cattofile = $cattofile;
 188      }
 189  
 190      /**
 191       * set contexttofile
 192       * @param bool cattofile exports categories within export file
 193       */
 194      public function setContexttofile($contexttofile) {
 195          $this->contexttofile = $contexttofile;
 196      }
 197  
 198      /**
 199       * set stoponerror
 200       * @param bool stoponerror stops database write if any errors reported
 201       */
 202      public function setStoponerror($stoponerror) {
 203          $this->stoponerror = $stoponerror;
 204      }
 205  
 206      /**
 207       * @param bool $canaccess Whether the current use can access the backup data folder. Determines
 208       * where export files are saved.
 209       */
 210      public function set_can_access_backupdata($canaccess) {
 211          $this->canaccessbackupdata = $canaccess;
 212      }
 213  
 214      /***********************
 215       * IMPORTING FUNCTIONS
 216       ***********************/
 217  
 218      /**
 219       * Handle parsing error
 220       */
 221      protected function error($message, $text='', $questionname='') {
 222          $importerrorquestion = get_string('importerrorquestion', 'question');
 223  
 224          echo "<div class=\"importerror\">\n";
 225          echo "<strong>{$importerrorquestion} {$questionname}</strong>";
 226          if (!empty($text)) {
 227              $text = s($text);
 228              echo "<blockquote>{$text}</blockquote>\n";
 229          }
 230          echo "<strong>{$message}</strong>\n";
 231          echo "</div>";
 232  
 233          $this->importerrors++;
 234      }
 235  
 236      /**
 237       * Import for questiontype plugins
 238       * Do not override.
 239       * @param data mixed The segment of data containing the question
 240       * @param question object processed (so far) by standard import code if appropriate
 241       * @param extra mixed any additional format specific data that may be passed by the format
 242       * @param qtypehint hint about a question type from format
 243       * @return object question object suitable for save_options() or false if cannot handle
 244       */
 245      public function try_importing_using_qtypes($data, $question = null, $extra = null,
 246              $qtypehint = '') {
 247  
 248          // work out what format we are using
 249          $formatname = substr(get_class($this), strlen('qformat_'));
 250          $methodname = "import_from_{$formatname}";
 251  
 252          //first try importing using a hint from format
 253          if (!empty($qtypehint)) {
 254              $qtype = question_bank::get_qtype($qtypehint, false);
 255              if (is_object($qtype) && method_exists($qtype, $methodname)) {
 256                  $question = $qtype->$methodname($data, $question, $this, $extra);
 257                  if ($question) {
 258                      return $question;
 259                  }
 260              }
 261          }
 262  
 263          // loop through installed questiontypes checking for
 264          // function to handle this question
 265          foreach (question_bank::get_all_qtypes() as $qtype) {
 266              if (method_exists($qtype, $methodname)) {
 267                  if ($question = $qtype->$methodname($data, $question, $this, $extra)) {
 268                      return $question;
 269                  }
 270              }
 271          }
 272          return false;
 273      }
 274  
 275      /**
 276       * Perform any required pre-processing
 277       * @return bool success
 278       */
 279      public function importpreprocess() {
 280          return true;
 281      }
 282  
 283      /**
 284       * Process the file
 285       * This method should not normally be overidden
 286       * @param object $category
 287       * @return bool success
 288       */
 289      public function importprocess($category) {
 290          global $USER, $CFG, $DB, $OUTPUT;
 291  
 292          // Raise time and memory, as importing can be quite intensive.
 293          core_php_time_limit::raise();
 294          raise_memory_limit(MEMORY_EXTRA);
 295  
 296          // STAGE 1: Parse the file
 297          echo $OUTPUT->notification(get_string('parsingquestions', 'question'), 'notifysuccess');
 298  
 299          if (! $lines = $this->readdata($this->filename)) {
 300              echo $OUTPUT->notification(get_string('cannotread', 'question'));
 301              return false;
 302          }
 303  
 304          if (!$questions = $this->readquestions($lines)) {   // Extract all the questions
 305              echo $OUTPUT->notification(get_string('noquestionsinfile', 'question'));
 306              return false;
 307          }
 308  
 309          // STAGE 2: Write data to database
 310          echo $OUTPUT->notification(get_string('importingquestions', 'question',
 311                  $this->count_questions($questions)), 'notifysuccess');
 312  
 313          // check for errors before we continue
 314          if ($this->stoponerror and ($this->importerrors>0)) {
 315              echo $OUTPUT->notification(get_string('importparseerror', 'question'));
 316              return true;
 317          }
 318  
 319          // get list of valid answer grades
 320          $gradeoptionsfull = question_bank::fraction_options_full();
 321  
 322          // check answer grades are valid
 323          // (now need to do this here because of 'stop on error': MDL-10689)
 324          $gradeerrors = 0;
 325          $goodquestions = array();
 326          foreach ($questions as $question) {
 327              if (!empty($question->fraction) and (is_array($question->fraction))) {
 328                  $fractions = $question->fraction;
 329                  $invalidfractions = array();
 330                  foreach ($fractions as $key => $fraction) {
 331                      $newfraction = match_grade_options($gradeoptionsfull, $fraction,
 332                              $this->matchgrades);
 333                      if ($newfraction === false) {
 334                          $invalidfractions[] = $fraction;
 335                      } else {
 336                          $fractions[$key] = $newfraction;
 337                      }
 338                  }
 339                  if ($invalidfractions) {
 340                      echo $OUTPUT->notification(get_string('invalidgrade', 'question',
 341                              implode(', ', $invalidfractions)));
 342                      ++$gradeerrors;
 343                      continue;
 344                  } else {
 345                      $question->fraction = $fractions;
 346                  }
 347              }
 348              $goodquestions[] = $question;
 349          }
 350          $questions = $goodquestions;
 351  
 352          // check for errors before we continue
 353          if ($this->stoponerror && $gradeerrors > 0) {
 354              return false;
 355          }
 356  
 357          // count number of questions processed
 358          $count = 0;
 359  
 360          foreach ($questions as $question) {   // Process and store each question
 361              $transaction = $DB->start_delegated_transaction();
 362  
 363              // reset the php timeout
 364              core_php_time_limit::raise();
 365  
 366              // check for category modifiers
 367              if ($question->qtype == 'category') {
 368                  if ($this->catfromfile) {
 369                      // find/create category object
 370                      $catpath = $question->category;
 371                      $newcategory = $this->create_category_path($catpath);
 372                      if (!empty($newcategory)) {
 373                          $this->category = $newcategory;
 374                      }
 375                  }
 376                  $transaction->allow_commit();
 377                  continue;
 378              }
 379              $question->context = $this->importcontext;
 380  
 381              $count++;
 382  
 383              echo "<hr /><p><b>{$count}</b>. ".$this->format_question_text($question)."</p>";
 384  
 385              $question->category = $this->category->id;
 386              $question->stamp = make_unique_id_code();  // Set the unique code (not to be changed)
 387  
 388              $question->createdby = $USER->id;
 389              $question->timecreated = time();
 390              $question->modifiedby = $USER->id;
 391              $question->timemodified = time();
 392              $fileoptions = array(
 393                      'subdirs' => true,
 394                      'maxfiles' => -1,
 395                      'maxbytes' => 0,
 396                  );
 397  
 398              $question->id = $DB->insert_record('question', $question);
 399  
 400              if (isset($question->questiontextitemid)) {
 401                  $question->questiontext = file_save_draft_area_files($question->questiontextitemid,
 402                          $this->importcontext->id, 'question', 'questiontext', $question->id,
 403                          $fileoptions, $question->questiontext);
 404              } else if (isset($question->questiontextfiles)) {
 405                  foreach ($question->questiontextfiles as $file) {
 406                      question_bank::get_qtype($question->qtype)->import_file(
 407                              $this->importcontext, 'question', 'questiontext', $question->id, $file);
 408                  }
 409              }
 410              if (isset($question->generalfeedbackitemid)) {
 411                  $question->generalfeedback = file_save_draft_area_files($question->generalfeedbackitemid,
 412                          $this->importcontext->id, 'question', 'generalfeedback', $question->id,
 413                          $fileoptions, $question->generalfeedback);
 414              } else if (isset($question->generalfeedbackfiles)) {
 415                  foreach ($question->generalfeedbackfiles as $file) {
 416                      question_bank::get_qtype($question->qtype)->import_file(
 417                              $this->importcontext, 'question', 'generalfeedback', $question->id, $file);
 418                  }
 419              }
 420              $DB->update_record('question', $question);
 421  
 422              $this->questionids[] = $question->id;
 423  
 424              // Now to save all the answers and type-specific options
 425  
 426              $result = question_bank::get_qtype($question->qtype)->save_question_options($question);
 427  
 428              if (isset($question->tags)) {
 429                  core_tag_tag::set_item_tags('core_question', 'question', $question->id, $question->context, $question->tags);
 430              }
 431  
 432              if (!empty($result->error)) {
 433                  echo $OUTPUT->notification($result->error);
 434                  // Can't use $transaction->rollback(); since it requires an exception,
 435                  // and I don't want to rewrite this code to change the error handling now.
 436                  $DB->force_transaction_rollback();
 437                  return false;
 438              }
 439  
 440              $transaction->allow_commit();
 441  
 442              if (!empty($result->notice)) {
 443                  echo $OUTPUT->notification($result->notice);
 444                  return true;
 445              }
 446  
 447              // Give the question a unique version stamp determined by question_hash()
 448              $DB->set_field('question', 'version', question_hash($question),
 449                      array('id' => $question->id));
 450          }
 451          return true;
 452      }
 453  
 454      /**
 455       * Count all non-category questions in the questions array.
 456       *
 457       * @param array questions An array of question objects.
 458       * @return int The count.
 459       *
 460       */
 461      protected function count_questions($questions) {
 462          $count = 0;
 463          if (!is_array($questions)) {
 464              return $count;
 465          }
 466          foreach ($questions as $question) {
 467              if (!is_object($question) || !isset($question->qtype) ||
 468                      ($question->qtype == 'category')) {
 469                  continue;
 470              }
 471              $count++;
 472          }
 473          return $count;
 474      }
 475  
 476      /**
 477       * find and/or create the category described by a delimited list
 478       * e.g. $course$/tom/dick/harry or tom/dick/harry
 479       *
 480       * removes any context string no matter whether $getcontext is set
 481       * but if $getcontext is set then ignore the context and use selected category context.
 482       *
 483       * @param string catpath delimited category path
 484       * @param int courseid course to search for categories
 485       * @return mixed category object or null if fails
 486       */
 487      protected function create_category_path($catpath) {
 488          global $DB;
 489          $catnames = $this->split_category_path($catpath);
 490          $parent = 0;
 491          $category = null;
 492  
 493          // check for context id in path, it might not be there in pre 1.9 exports
 494          $matchcount = preg_match('/^\$([a-z]+)\$$/', $catnames[0], $matches);
 495          if ($matchcount == 1) {
 496              $contextid = $this->translator->string_to_context($matches[1]);
 497              array_shift($catnames);
 498          } else {
 499              $contextid = false;
 500          }
 501  
 502          if ($this->contextfromfile && $contextid !== false) {
 503              $context = context::instance_by_id($contextid);
 504              require_capability('moodle/question:add', $context);
 505          } else {
 506              $context = context::instance_by_id($this->category->contextid);
 507          }
 508          $this->importcontext = $context;
 509  
 510          // Now create any categories that need to be created.
 511          foreach ($catnames as $catname) {
 512              if ($category = $DB->get_record('question_categories',
 513                      array('name' => $catname, 'contextid' => $context->id, 'parent' => $parent))) {
 514                  $parent = $category->id;
 515              } else {
 516                  require_capability('moodle/question:managecategory', $context);
 517                  // create the new category
 518                  $category = new stdClass();
 519                  $category->contextid = $context->id;
 520                  $category->name = $catname;
 521                  $category->info = '';
 522                  $category->parent = $parent;
 523                  $category->sortorder = 999;
 524                  $category->stamp = make_unique_id_code();
 525                  $id = $DB->insert_record('question_categories', $category);
 526                  $category->id = $id;
 527                  $parent = $id;
 528              }
 529          }
 530          return $category;
 531      }
 532  
 533      /**
 534       * Return complete file within an array, one item per line
 535       * @param string filename name of file
 536       * @return mixed contents array or false on failure
 537       */
 538      protected function readdata($filename) {
 539          if (is_readable($filename)) {
 540              $filearray = file($filename);
 541  
 542              // If the first line of the file starts with a UTF-8 BOM, remove it.
 543              $filearray[0] = core_text::trim_utf8_bom($filearray[0]);
 544  
 545              // Check for Macintosh OS line returns (ie file on one line), and fix.
 546              if (preg_match("~\r~", $filearray[0]) AND !preg_match("~\n~", $filearray[0])) {
 547                  return explode("\r", $filearray[0]);
 548              } else {
 549                  return $filearray;
 550              }
 551          }
 552          return false;
 553      }
 554  
 555      /**
 556       * Parses an array of lines into an array of questions,
 557       * where each item is a question object as defined by
 558       * readquestion().   Questions are defined as anything
 559       * between blank lines.
 560       *
 561       * NOTE this method used to take $context as a second argument. However, at
 562       * the point where this method was called, it was impossible to know what
 563       * context the quetsions were going to be saved into, so the value could be
 564       * wrong. Also, none of the standard question formats were using this argument,
 565       * so it was removed. See MDL-32220.
 566       *
 567       * If your format does not use blank lines as a delimiter
 568       * then you will need to override this method. Even then
 569       * try to use readquestion for each question
 570       * @param array lines array of lines from readdata
 571       * @return array array of question objects
 572       */
 573      protected function readquestions($lines) {
 574  
 575          $questions = array();
 576          $currentquestion = array();
 577  
 578          foreach ($lines as $line) {
 579              $line = trim($line);
 580              if (empty($line)) {
 581                  if (!empty($currentquestion)) {
 582                      if ($question = $this->readquestion($currentquestion)) {
 583                          $questions[] = $question;
 584                      }
 585                      $currentquestion = array();
 586                  }
 587              } else {
 588                  $currentquestion[] = $line;
 589              }
 590          }
 591  
 592          if (!empty($currentquestion)) {  // There may be a final question
 593              if ($question = $this->readquestion($currentquestion)) {
 594                  $questions[] = $question;
 595              }
 596          }
 597  
 598          return $questions;
 599      }
 600  
 601      /**
 602       * return an "empty" question
 603       * Somewhere to specify question parameters that are not handled
 604       * by import but are required db fields.
 605       * This should not be overridden.
 606       * @return object default question
 607       */
 608      protected function defaultquestion() {
 609          global $CFG;
 610          static $defaultshuffleanswers = null;
 611          if (is_null($defaultshuffleanswers)) {
 612              $defaultshuffleanswers = get_config('quiz', 'shuffleanswers');
 613          }
 614  
 615          $question = new stdClass();
 616          $question->shuffleanswers = $defaultshuffleanswers;
 617          $question->defaultmark = 1;
 618          $question->image = "";
 619          $question->usecase = 0;
 620          $question->multiplier = array();
 621          $question->questiontextformat = FORMAT_MOODLE;
 622          $question->generalfeedback = '';
 623          $question->generalfeedbackformat = FORMAT_MOODLE;
 624          $question->correctfeedback = '';
 625          $question->partiallycorrectfeedback = '';
 626          $question->incorrectfeedback = '';
 627          $question->answernumbering = 'abc';
 628          $question->penalty = 0.3333333;
 629          $question->length = 1;
 630  
 631          // this option in case the questiontypes class wants
 632          // to know where the data came from
 633          $question->export_process = true;
 634          $question->import_process = true;
 635  
 636          return $question;
 637      }
 638  
 639      /**
 640       * Construct a reasonable default question name, based on the start of the question text.
 641       * @param string $questiontext the question text.
 642       * @param string $default default question name to use if the constructed one comes out blank.
 643       * @return string a reasonable question name.
 644       */
 645      public function create_default_question_name($questiontext, $default) {
 646          $name = $this->clean_question_name(shorten_text($questiontext, 80));
 647          if ($name) {
 648              return $name;
 649          } else {
 650              return $default;
 651          }
 652      }
 653  
 654      /**
 655       * Ensure that a question name does not contain anything nasty, and will fit in the DB field.
 656       * @param string $name the raw question name.
 657       * @return string a safe question name.
 658       */
 659      public function clean_question_name($name) {
 660          $name = clean_param($name, PARAM_TEXT); // Matches what the question editing form does.
 661          $name = trim($name);
 662          $trimlength = 251;
 663          while (core_text::strlen($name) > 255 && $trimlength > 0) {
 664              $name = shorten_text($name, $trimlength);
 665              $trimlength -= 10;
 666          }
 667          return $name;
 668      }
 669  
 670      /**
 671       * Add a blank combined feedback to a question object.
 672       * @param object question
 673       * @return object question
 674       */
 675      protected function add_blank_combined_feedback($question) {
 676          $question->correctfeedback['text'] = '';
 677          $question->correctfeedback['format'] = $question->questiontextformat;
 678          $question->correctfeedback['files'] = array();
 679          $question->partiallycorrectfeedback['text'] = '';
 680          $question->partiallycorrectfeedback['format'] = $question->questiontextformat;
 681          $question->partiallycorrectfeedback['files'] = array();
 682          $question->incorrectfeedback['text'] = '';
 683          $question->incorrectfeedback['format'] = $question->questiontextformat;
 684          $question->incorrectfeedback['files'] = array();
 685          return $question;
 686      }
 687  
 688      /**
 689       * Given the data known to define a question in
 690       * this format, this function converts it into a question
 691       * object suitable for processing and insertion into Moodle.
 692       *
 693       * If your format does not use blank lines to delimit questions
 694       * (e.g. an XML format) you must override 'readquestions' too
 695       * @param $lines mixed data that represents question
 696       * @return object question object
 697       */
 698      protected function readquestion($lines) {
 699          // We should never get there unless the qformat plugin is broken.
 700          throw new coding_exception('Question format plugin is missing important code: readquestion.');
 701  
 702          return null;
 703      }
 704  
 705      /**
 706       * Override if any post-processing is required
 707       * @return bool success
 708       */
 709      public function importpostprocess() {
 710          return true;
 711      }
 712  
 713      /*******************
 714       * EXPORT FUNCTIONS
 715       *******************/
 716  
 717      /**
 718       * Provide export functionality for plugin questiontypes
 719       * Do not override
 720       * @param name questiontype name
 721       * @param question object data to export
 722       * @param extra mixed any addition format specific data needed
 723       * @return string the data to append to export or false if error (or unhandled)
 724       */
 725      protected function try_exporting_using_qtypes($name, $question, $extra=null) {
 726          // work out the name of format in use
 727          $formatname = substr(get_class($this), strlen('qformat_'));
 728          $methodname = "export_to_{$formatname}";
 729  
 730          $qtype = question_bank::get_qtype($name, false);
 731          if (method_exists($qtype, $methodname)) {
 732              return $qtype->$methodname($question, $this, $extra);
 733          }
 734          return false;
 735      }
 736  
 737      /**
 738       * Do any pre-processing that may be required
 739       * @param bool success
 740       */
 741      public function exportpreprocess() {
 742          return true;
 743      }
 744  
 745      /**
 746       * Enable any processing to be done on the content
 747       * just prior to the file being saved
 748       * default is to do nothing
 749       * @param string output text
 750       * @param string processed output text
 751       */
 752      protected function presave_process($content) {
 753          return $content;
 754      }
 755  
 756      /**
 757       * Do the export
 758       * For most types this should not need to be overrided
 759       * @return stored_file
 760       */
 761      public function exportprocess() {
 762          global $CFG, $OUTPUT, $DB, $USER;
 763  
 764          // get the questions (from database) in this category
 765          // only get q's with no parents (no cloze subquestions specifically)
 766          if ($this->category) {
 767              $questions = get_questions_category($this->category, true);
 768          } else {
 769              $questions = $this->questions;
 770          }
 771  
 772          $count = 0;
 773  
 774          // results are first written into string (and then to a file)
 775          // so create/initialize the string here
 776          $expout = "";
 777  
 778          // track which category questions are in
 779          // if it changes we will record the category change in the output
 780          // file if selected. 0 means that it will get printed before the 1st question
 781          $trackcategory = 0;
 782  
 783          // iterate through questions
 784          foreach ($questions as $question) {
 785              // used by file api
 786              $contextid = $DB->get_field('question_categories', 'contextid',
 787                      array('id' => $question->category));
 788              $question->contextid = $contextid;
 789  
 790              // do not export hidden questions
 791              if (!empty($question->hidden)) {
 792                  continue;
 793              }
 794  
 795              // do not export random questions
 796              if ($question->qtype == 'random') {
 797                  continue;
 798              }
 799  
 800              // check if we need to record category change
 801              if ($this->cattofile) {
 802                  if ($question->category != $trackcategory) {
 803                      $trackcategory = $question->category;
 804                      $categoryname = $this->get_category_path($trackcategory, $this->contexttofile);
 805  
 806                      // create 'dummy' question for category export
 807                      $dummyquestion = new stdClass();
 808                      $dummyquestion->qtype = 'category';
 809                      $dummyquestion->category = $categoryname;
 810                      $dummyquestion->name = 'Switch category to ' . $categoryname;
 811                      $dummyquestion->id = 0;
 812                      $dummyquestion->questiontextformat = '';
 813                      $dummyquestion->contextid = 0;
 814                      $expout .= $this->writequestion($dummyquestion) . "\n";
 815                  }
 816              }
 817  
 818              // export the question displaying message
 819              $count++;
 820  
 821              if (question_has_capability_on($question, 'view', $question->category)) {
 822                  $expout .= $this->writequestion($question, $contextid) . "\n";
 823              }
 824          }
 825  
 826          // continue path for following error checks
 827          $course = $this->course;
 828          $continuepath = "{$CFG->wwwroot}/question/export.php?courseid={$course->id}";
 829  
 830          // did we actually process anything
 831          if ($count==0) {
 832              print_error('noquestions', 'question', $continuepath);
 833          }
 834  
 835          // final pre-process on exported data
 836          $expout = $this->presave_process($expout);
 837          return $expout;
 838      }
 839  
 840      /**
 841       * get the category as a path (e.g., tom/dick/harry)
 842       * @param int id the id of the most nested catgory
 843       * @return string the path
 844       */
 845      protected function get_category_path($id, $includecontext = true) {
 846          global $DB;
 847  
 848          if (!$category = $DB->get_record('question_categories', array('id' => $id))) {
 849              print_error('cannotfindcategory', 'error', '', $id);
 850          }
 851          $contextstring = $this->translator->context_to_string($category->contextid);
 852  
 853          $pathsections = array();
 854          do {
 855              $pathsections[] = $category->name;
 856              $id = $category->parent;
 857          } while ($category = $DB->get_record('question_categories', array('id' => $id)));
 858  
 859          if ($includecontext) {
 860              $pathsections[] = '$' . $contextstring . '$';
 861          }
 862  
 863          $path = $this->assemble_category_path(array_reverse($pathsections));
 864  
 865          return $path;
 866      }
 867  
 868      /**
 869       * Convert a list of category names, possibly preceeded by one of the
 870       * context tokens like $course$, into a string representation of the
 871       * category path.
 872       *
 873       * Names are separated by / delimiters. And /s in the name are replaced by //.
 874       *
 875       * To reverse the process and split the paths into names, use
 876       * {@link split_category_path()}.
 877       *
 878       * @param array $names
 879       * @return string
 880       */
 881      protected function assemble_category_path($names) {
 882          $escapednames = array();
 883          foreach ($names as $name) {
 884              $escapedname = str_replace('/', '//', $name);
 885              if (substr($escapedname, 0, 1) == '/') {
 886                  $escapedname = ' ' . $escapedname;
 887              }
 888              if (substr($escapedname, -1) == '/') {
 889                  $escapedname = $escapedname . ' ';
 890              }
 891              $escapednames[] = $escapedname;
 892          }
 893          return implode('/', $escapednames);
 894      }
 895  
 896      /**
 897       * Convert a string, as returned by {@link assemble_category_path()},
 898       * back into an array of category names.
 899       *
 900       * Each category name is cleaned by a call to clean_param(, PARAM_TEXT),
 901       * which matches the cleaning in question/category_form.php.
 902       *
 903       * @param string $path
 904       * @return array of category names.
 905       */
 906      protected function split_category_path($path) {
 907          $rawnames = preg_split('~(?<!/)/(?!/)~', $path);
 908          $names = array();
 909          foreach ($rawnames as $rawname) {
 910              $names[] = clean_param(trim(str_replace('//', '/', $rawname)), PARAM_TEXT);
 911          }
 912          return $names;
 913      }
 914  
 915      /**
 916       * Do an post-processing that may be required
 917       * @return bool success
 918       */
 919      protected function exportpostprocess() {
 920          return true;
 921      }
 922  
 923      /**
 924       * convert a single question object into text output in the given
 925       * format.
 926       * This must be overriden
 927       * @param object question question object
 928       * @return mixed question export text or null if not implemented
 929       */
 930      protected function writequestion($question) {
 931          // if not overidden, then this is an error.
 932          throw new coding_exception('Question format plugin is missing important code: writequestion.');
 933          return null;
 934      }
 935  
 936      /**
 937       * Convert the question text to plain text, so it can safely be displayed
 938       * during import to let the user see roughly what is going on.
 939       */
 940      protected function format_question_text($question) {
 941          return question_utils::to_plain_text($question->questiontext,
 942                  $question->questiontextformat);
 943      }
 944  }
 945  
 946  class qformat_based_on_xml extends qformat_default {
 947  
 948      /**
 949       * A lot of imported files contain unwanted entities.
 950       * This method tries to clean up all known problems.
 951       * @param string str string to correct
 952       * @return string the corrected string
 953       */
 954      public function cleaninput($str) {
 955  
 956          $html_code_list = array(
 957              "&#039;" => "'",
 958              "&#8217;" => "'",
 959              "&#8220;" => "\"",
 960              "&#8221;" => "\"",
 961              "&#8211;" => "-",
 962              "&#8212;" => "-",
 963          );
 964          $str = strtr($str, $html_code_list);
 965          // Use core_text entities_to_utf8 function to convert only numerical entities.
 966          $str = core_text::entities_to_utf8($str, false);
 967          return $str;
 968      }
 969  
 970      /**
 971       * Return the array moodle is expecting
 972       * for an HTML text. No processing is done on $text.
 973       * qformat classes that want to process $text
 974       * for instance to import external images files
 975       * and recode urls in $text must overwrite this method.
 976       * @param array $text some HTML text string
 977       * @return array with keys text, format and files.
 978       */
 979      public function text_field($text) {
 980          return array(
 981              'text' => trim($text),
 982              'format' => FORMAT_HTML,
 983              'files' => array(),
 984          );
 985      }
 986  
 987      /**
 988       * Return the value of a node, given a path to the node
 989       * if it doesn't exist return the default value.
 990       * @param array xml data to read
 991       * @param array path path to node expressed as array
 992       * @param mixed default
 993       * @param bool istext process as text
 994       * @param string error if set value must exist, return false and issue message if not
 995       * @return mixed value
 996       */
 997      public function getpath($xml, $path, $default, $istext=false, $error='') {
 998          foreach ($path as $index) {
 999              if (!isset($xml[$index])) {
1000                  if (!empty($error)) {
1001                      $this->error($error);
1002                      return false;
1003                  } else {
1004                      return $default;
1005                  }
1006              }
1007  
1008              $xml = $xml[$index];
1009          }
1010  
1011          if ($istext) {
1012              if (!is_string($xml)) {
1013                  $this->error(get_string('invalidxml', 'qformat_xml'));
1014              }
1015              $xml = trim($xml);
1016          }
1017  
1018          return $xml;
1019      }
1020  }