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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   * Common classes used by gradingform plugintypes are defined here
  19   *
  20   * @package    core_grading
  21   * @copyright  2011 David Mudrak <david@moodle.com>
  22   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23   */
  24  
  25  defined('MOODLE_INTERNAL') || die();
  26  
  27  /**
  28   * Class represents a grading form definition used in a particular area
  29   *
  30   * General data about definition is stored in the standard DB table
  31   * grading_definitions. A separate entry is created for each grading area
  32   * (i.e. for each module). Plugins may define and use additional tables
  33   * to store additional data about definitions.
  34   *
  35   * Advanced grading plugins must declare a class gradingform_xxxx_controller
  36   * extending this class and put it in lib.php in the plugin folder.
  37   *
  38   * See {@link gradingform_rubric_controller} as an example
  39   *
  40   * Except for overwriting abstract functions, plugin developers may want
  41   * to overwrite functions responsible for loading and saving of the
  42   * definition to include additional data stored.
  43   *
  44   * @package    core_grading
  45   * @copyright  2011 David Mudrak <david@moodle.com>
  46   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  47   * @category   grading
  48   */
  49  abstract class gradingform_controller {
  50  
  51      /** undefined definition status */
  52      const DEFINITION_STATUS_NULL = 0;
  53      /** the form is currently being edited and is not ready for usage yet */
  54      const DEFINITION_STATUS_DRAFT = 10;
  55      /** the form was marked as ready for actual usage */
  56      const DEFINITION_STATUS_READY = 20;
  57  
  58      /** @var stdClass the context */
  59      protected $context;
  60  
  61      /** @var string the frankenstyle name of the component */
  62      protected $component;
  63  
  64      /** @var string the name of the gradable area */
  65      protected $area;
  66  
  67      /** @var int the id of the gradable area record */
  68      protected $areaid;
  69  
  70      /** @var stdClass|false the definition structure */
  71      protected $definition = false;
  72  
  73      /** @var array graderange array of valid grades for this area. Use set_grade_range and get_grade_range to access this */
  74      private $graderange = null;
  75  
  76      /** @var bool if decimal values are allowed as grades. */
  77      private $allowgradedecimals = false;
  78  
  79      /** @var boolean|null cached result of function has_active_instances() */
  80      protected $hasactiveinstances = null;
  81  
  82      /**
  83       * Do not instantinate this directly, use {@link grading_manager::get_controller()}
  84       *
  85       * @param stdClass $context the context of the form
  86       * @param string $component the frankenstyle name of the component
  87       * @param string $area the name of the gradable area
  88       * @param int $areaid the id of the gradable area record
  89       */
  90      public function __construct(stdClass $context, $component, $area, $areaid) {
  91          global $DB;
  92  
  93          $this->context      = $context;
  94          list($type, $name)  = core_component::normalize_component($component);
  95          $this->component    = $type.'_'.$name;
  96          $this->area         = $area;
  97          $this->areaid       = $areaid;
  98  
  99          $this->load_definition();
 100      }
 101  
 102      /**
 103       * Returns controller context
 104       *
 105       * @return stdClass controller context
 106       */
 107      public function get_context() {
 108          return $this->context;
 109      }
 110  
 111      /**
 112       * Returns gradable component name
 113       *
 114       * @return string gradable component name
 115       */
 116      public function get_component() {
 117          return $this->component;
 118      }
 119  
 120      /**
 121       * Returns gradable area name
 122       *
 123       * @return string gradable area name
 124       */
 125      public function get_area() {
 126          return $this->area;
 127      }
 128  
 129      /**
 130       * Returns gradable area id
 131       *
 132       * @return int gradable area id
 133       */
 134      public function get_areaid() {
 135          return $this->areaid;
 136      }
 137  
 138      /**
 139       * Is the form definition record available?
 140       *
 141       * Note that this actually checks whether the process of defining the form ever started
 142       * and not whether the form definition should be considered as final.
 143       *
 144       * @return boolean
 145       */
 146      public function is_form_defined() {
 147          return ($this->definition !== false);
 148      }
 149  
 150      /**
 151       * Is the grading form defined and ready for usage?
 152       *
 153       * @return boolean
 154       */
 155      public function is_form_available() {
 156          return ($this->is_form_defined() && $this->definition->status == self::DEFINITION_STATUS_READY);
 157      }
 158  
 159      /**
 160       * Is the grading form saved as a shared public template?
 161       *
 162       * @return boolean
 163       */
 164      public function is_shared_template() {
 165          return ($this->get_context()->id == context_system::instance()->id
 166              and $this->get_component() == 'core_grading');
 167      }
 168  
 169      /**
 170       * Is the grading form owned by the given user?
 171       *
 172       * The form owner is the user who created this instance of the form.
 173       *
 174       * @param int $userid the user id to check, defaults to the current user
 175       * @return boolean|null null if the form not defined yet, boolean otherwise
 176       */
 177      public function is_own_form($userid = null) {
 178          global $USER;
 179  
 180          if (!$this->is_form_defined()) {
 181              return null;
 182          }
 183          if (is_null($userid)) {
 184              $userid = $USER->id;
 185          }
 186          return ($this->definition->usercreated == $userid);
 187      }
 188  
 189      /**
 190       * Returns a message why this form is unavailable. Maybe overriden by plugins to give more details.
 191       * @see is_form_available()
 192       *
 193       * @return string
 194       */
 195      public function form_unavailable_notification() {
 196          if ($this->is_form_available()) {
 197              return null;
 198          }
 199          return get_string('gradingformunavailable', 'grading');
 200      }
 201  
 202      /**
 203       * Returns URL of a page where the grading form can be defined and edited.
 204       *
 205       * @param moodle_url $returnurl optional URL of a page where the user should be sent once they are finished with editing
 206       * @return moodle_url
 207       */
 208      public function get_editor_url(moodle_url $returnurl = null) {
 209  
 210          $params = array('areaid' => $this->areaid);
 211  
 212          if (!is_null($returnurl)) {
 213              $params['returnurl'] = $returnurl->out(false);
 214          }
 215  
 216          return new moodle_url('/grade/grading/form/'.$this->get_method_name().'/edit.php', $params);
 217      }
 218  
 219      /**
 220       * Extends the module settings navigation
 221       *
 222       * This function is called when the context for the page is an activity module with the
 223       * FEATURE_ADVANCED_GRADING, the user has the permission moodle/grade:managegradingforms
 224       * and there is an area with the active grading method set to the given plugin.
 225       *
 226       * @param settings_navigation $settingsnav {@link settings_navigation}
 227       * @param navigation_node $node {@link navigation_node}
 228       */
 229      public function extend_settings_navigation(settings_navigation $settingsnav, navigation_node $node=null) {
 230          // do not extend by default
 231      }
 232  
 233      /**
 234       * Extends the module navigation
 235       *
 236       * This function is called when the context for the page is an activity module with the
 237       * FEATURE_ADVANCED_GRADING and there is an area with the active grading method set to the given plugin.
 238       *
 239       * @param global_navigation $navigation {@link global_navigation}
 240       * @param navigation_node $node {@link navigation_node}
 241       */
 242      public function extend_navigation(global_navigation $navigation, navigation_node $node=null) {
 243          // do not extend by default
 244      }
 245  
 246      /**
 247       * Returns the grading form definition structure
 248       *
 249       * @param boolean $force whether to force loading from DB even if it was already loaded
 250       * @return stdClass|false definition data or false if the form is not defined yet
 251       */
 252      public function get_definition($force = false) {
 253          if ($this->definition === false || $force) {
 254              $this->load_definition();
 255          }
 256          return $this->definition;
 257      }
 258  
 259      /**
 260       * Returns the form definition suitable for cloning into another area
 261       *
 262       * @param gradingform_controller $target the controller of the new copy
 263       * @return stdClass definition structure to pass to the target's {@link update_definition()}
 264       */
 265      public function get_definition_copy(gradingform_controller $target) {
 266  
 267          if (get_class($this) != get_class($target)) {
 268              throw new coding_exception('The source and copy controller mismatch');
 269          }
 270  
 271          if ($target->is_form_defined()) {
 272              throw new coding_exception('The target controller already contains a form definition');
 273          }
 274  
 275          $old = $this->get_definition();
 276          // keep our id
 277          $new = new stdClass();
 278          $new->copiedfromid = $old->id;
 279          $new->name = $old->name;
 280          // once we support files embedded into the description, we will want to
 281          // relink them into the new file area here (that is why we accept $target)
 282          $new->description = $old->description;
 283          $new->descriptionformat = $old->descriptionformat;
 284          $new->options = $old->options;
 285          $new->status = $old->status;
 286  
 287          return $new;
 288      }
 289  
 290      /**
 291       * Saves the defintion data into the database
 292       *
 293       * The implementation in this base class stores the common data into the record
 294       * into the {grading_definition} table. The plugins are likely to extend this
 295       * and save their data into own tables, too.
 296       *
 297       * @param stdClass $definition data containing values for the {grading_definition} table
 298       * @param int|null $usermodified optional userid of the author of the definition, defaults to the current user
 299       */
 300      public function update_definition(stdClass $definition, $usermodified = null) {
 301          global $DB, $USER;
 302  
 303          if (is_null($usermodified)) {
 304              $usermodified = $USER->id;
 305          }
 306  
 307          if (!empty($this->definition->id)) {
 308              // prepare a record to be updated
 309              $record = new stdClass();
 310              // populate it with scalar values from the passed definition structure
 311              foreach ($definition as $prop => $val) {
 312                  if (is_array($val) or is_object($val)) {
 313                      // probably plugin's data
 314                      continue;
 315                  }
 316                  $record->{$prop} = $val;
 317              }
 318              // make sure we do not override some crucial values by accident
 319              if (!empty($record->id) and $record->id != $this->definition->id) {
 320                  throw new coding_exception('Attempting to update other definition record.');
 321              }
 322              $record->id = $this->definition->id;
 323              unset($record->areaid);
 324              unset($record->method);
 325              unset($record->timecreated);
 326              // set the modification flags
 327              $record->timemodified = time();
 328              $record->usermodified = $usermodified;
 329  
 330              $DB->update_record('grading_definitions', $record);
 331  
 332          } else if ($this->definition === false) {
 333              // prepare a record to be inserted
 334              $record = new stdClass();
 335              // populate it with scalar values from the passed definition structure
 336              foreach ($definition as $prop => $val) {
 337                  if (is_array($val) or is_object($val)) {
 338                      // probably plugin's data
 339                      continue;
 340                  }
 341                  $record->{$prop} = $val;
 342              }
 343              // make sure we do not override some crucial values by accident
 344              if (!empty($record->id)) {
 345                  throw new coding_exception('Attempting to create a new record while there is already one existing.');
 346              }
 347              unset($record->id);
 348              $record->areaid       = $this->areaid;
 349              $record->method       = $this->get_method_name();
 350              $record->timecreated  = time();
 351              $record->usercreated  = $usermodified;
 352              $record->timemodified = $record->timecreated;
 353              $record->usermodified = $record->usercreated;
 354              if (empty($record->status)) {
 355                  $record->status = self::DEFINITION_STATUS_DRAFT;
 356              }
 357              if (empty($record->descriptionformat)) {
 358                  $record->descriptionformat = FORMAT_MOODLE; // field can not be empty
 359              }
 360  
 361              $DB->insert_record('grading_definitions', $record);
 362  
 363          } else {
 364              throw new coding_exception('Unknown status of the cached definition record.');
 365          }
 366      }
 367  
 368      /**
 369       * Formats the definition description for display on page
 370       *
 371       * @return string
 372       */
 373      public function get_formatted_description() {
 374          if (!isset($this->definition->description)) {
 375              return '';
 376          }
 377          return format_text($this->definition->description, $this->definition->descriptionformat);
 378      }
 379  
 380      /**
 381       * Returns the current instance (either with status ACTIVE or NEEDUPDATE) for this definition for the
 382       * specified $raterid and $itemid (if multiple raters are allowed, or only for $itemid otherwise).
 383       *
 384       * @param int $raterid
 385       * @param int $itemid
 386       * @param boolean $idonly
 387       * @return mixed if $idonly=true returns id of the found instance, otherwise returns the instance object
 388       */
 389      public function get_current_instance($raterid, $itemid, $idonly = false) {
 390          global $DB;
 391          $params = array(
 392                  'definitionid'  => $this->definition->id,
 393                  'itemid' => $itemid,
 394                  'status1'  => gradingform_instance::INSTANCE_STATUS_ACTIVE,
 395                  'status2'  => gradingform_instance::INSTANCE_STATUS_NEEDUPDATE);
 396          $select = 'definitionid=:definitionid and itemid=:itemid and (status=:status1 or status=:status2)';
 397          if (false) {
 398              // TODO MDL-31237 should be: if ($manager->allow_multiple_raters())
 399              $select .= ' and raterid=:raterid';
 400              $params['raterid'] = $raterid;
 401          }
 402          if ($idonly) {
 403              if ($current = $DB->get_record_select('grading_instances', $select, $params, 'id', IGNORE_MISSING)) {
 404                  return $current->id;
 405              }
 406          } else {
 407              if ($current = $DB->get_record_select('grading_instances', $select, $params, '*', IGNORE_MISSING)) {
 408                  return $this->get_instance($current);
 409              }
 410          }
 411          return null;
 412      }
 413  
 414      /**
 415       * Returns list of ACTIVE instances for the specified $itemid
 416       * (intentionally does not return instances with status NEEDUPDATE)
 417       *
 418       * @param int $itemid
 419       * @return array of gradingform_instance objects
 420       */
 421      public function get_active_instances($itemid) {
 422          global $DB;
 423          $conditions = array('definitionid'  => $this->definition->id,
 424                      'itemid' => $itemid,
 425                      'status'  => gradingform_instance::INSTANCE_STATUS_ACTIVE);
 426          $records = $DB->get_recordset('grading_instances', $conditions);
 427          $rv = array();
 428          foreach ($records as $record) {
 429              $rv[] = $this->get_instance($record);
 430          }
 431          return $rv;
 432      }
 433  
 434      /**
 435       * Returns an array of all active instances for this definition.
 436       * (intentionally does not return instances with status NEEDUPDATE)
 437       *
 438       * @param int since only return instances with timemodified >= since
 439       * @return array of gradingform_instance objects
 440       */
 441      public function get_all_active_instances($since = 0) {
 442          global $DB;
 443          $conditions = array ($this->definition->id,
 444                               gradingform_instance::INSTANCE_STATUS_ACTIVE,
 445                               $since);
 446          $where = "definitionid = ? AND status = ? AND timemodified >= ?";
 447          $records = $DB->get_records_select('grading_instances', $where, $conditions);
 448          $rv = array();
 449          foreach ($records as $record) {
 450              $rv[] = $this->get_instance($record);
 451          }
 452          return $rv;
 453      }
 454  
 455      /**
 456       * Returns true if there are already people who has been graded on this definition.
 457       * In this case plugins may restrict changes of the grading definition
 458       *
 459       * @return boolean
 460       */
 461      public function has_active_instances() {
 462          global $DB;
 463          if (empty($this->definition->id)) {
 464              return false;
 465          }
 466          if ($this->hasactiveinstances === null) {
 467              $conditions = array('definitionid'  => $this->definition->id,
 468                          'status'  => gradingform_instance::INSTANCE_STATUS_ACTIVE);
 469              $this->hasactiveinstances = $DB->record_exists('grading_instances', $conditions);
 470          }
 471          return $this->hasactiveinstances;
 472      }
 473  
 474      /**
 475       * Returns the object of type gradingform_XXX_instance (where XXX is the plugin method name)
 476       *
 477       * @param mixed $instance id or row from grading_isntances table
 478       * @return gradingform_instance
 479       */
 480      protected function get_instance($instance) {
 481          global $DB;
 482          if (is_scalar($instance)) {
 483              // instance id is passed as parameter
 484              $instance = $DB->get_record('grading_instances', array('id'  => $instance), '*', MUST_EXIST);
 485          }
 486          if ($instance) {
 487              $class = 'gradingform_'. $this->get_method_name(). '_instance';
 488              return new $class($this, $instance);
 489          }
 490          return null;
 491      }
 492  
 493      /**
 494       * This function is invoked when user (teacher) starts grading.
 495       * It creates and returns copy of the current ACTIVE instance if it exists. If this is the
 496       * first grading attempt, a new instance is created.
 497       * The status of the returned instance is INCOMPLETE
 498       *
 499       * @param int $raterid
 500       * @param int $itemid
 501       * @return gradingform_instance
 502       */
 503      public function create_instance($raterid, $itemid = null) {
 504  
 505          // first find if there is already an active instance for this itemid
 506          if ($itemid && $current = $this->get_current_instance($raterid, $itemid)) {
 507              return $this->get_instance($current->copy($raterid, $itemid));
 508          } else {
 509              $class = 'gradingform_'. $this->get_method_name(). '_instance';
 510              return $this->get_instance($class::create_new($this->definition->id, $raterid, $itemid));
 511          }
 512      }
 513  
 514      /**
 515       * If instanceid is specified and grading instance exists and it is created by this rater for
 516       * this item, this instance is returned.
 517       * Otherwise new instance is created for the specified rater and itemid
 518       *
 519       * @param int $instanceid
 520       * @param int $raterid
 521       * @param int $itemid
 522       * @return gradingform_instance
 523       */
 524      public function get_or_create_instance($instanceid, $raterid, $itemid) {
 525          global $DB;
 526          if ($instanceid &&
 527                  $instance = $DB->get_record('grading_instances', array('id'  => $instanceid, 'raterid' => $raterid, 'itemid' => $itemid), '*', IGNORE_MISSING)) {
 528              return $this->get_instance($instance);
 529          }
 530          return $this->create_instance($raterid, $itemid);
 531      }
 532  
 533      /**
 534       * Returns the HTML code displaying the preview of the grading form
 535       *
 536       * Plugins are forced to override this. Ideally they should delegate
 537       * the task to their own renderer.
 538       *
 539       * @param moodle_page $page the target page
 540       * @return string
 541       */
 542      abstract public function render_preview(moodle_page $page);
 543  
 544      /**
 545       * Deletes the form definition and all the associated data
 546       *
 547       * @see delete_plugin_definition()
 548       * @return void
 549       */
 550      public function delete_definition() {
 551          global $DB;
 552  
 553          if (!$this->is_form_defined()) {
 554              // nothing to do
 555              return;
 556          }
 557  
 558          // firstly, let the plugin delete everything from their own tables
 559          $this->delete_plugin_definition();
 560          // then, delete all instances left
 561          $DB->delete_records('grading_instances', array('definitionid' => $this->definition->id));
 562          // finally, delete the main definition record
 563          $DB->delete_records('grading_definitions', array('id' => $this->definition->id));
 564  
 565          $this->definition = false;
 566      }
 567  
 568      /**
 569       * Prepare the part of the search query to append to the FROM statement
 570       *
 571       * @param string $gdid the alias of grading_definitions.id column used by the caller
 572       * @return string
 573       */
 574      public static function sql_search_from_tables($gdid) {
 575          return '';
 576      }
 577  
 578      /**
 579       * Prepare the parts of the SQL WHERE statement to search for the given token
 580       *
 581       * The returned array cosists of the list of SQL comparions and the list of
 582       * respective parameters for the comparisons. The returned chunks will be joined
 583       * with other conditions using the OR operator.
 584       *
 585       * @param string $token token to search for
 586       * @return array
 587       */
 588      public static function sql_search_where($token) {
 589  
 590          $subsql = array();
 591          $params = array();
 592  
 593          return array($subsql, $params);
 594      }
 595  
 596      // //////////////////////////////////////////////////////////////////////////
 597  
 598      /**
 599       * Loads the form definition if it exists
 600       *
 601       * The default implementation just tries to load the record from the {grading_definitions}
 602       * table. The plugins are likely to override this with a more complex query that loads
 603       * all required data at once.
 604       */
 605      protected function load_definition() {
 606          global $DB;
 607          $this->definition = $DB->get_record('grading_definitions', array(
 608              'areaid' => $this->areaid,
 609              'method' => $this->get_method_name()), '*', IGNORE_MISSING);
 610      }
 611  
 612      /**
 613       * Deletes all plugin data associated with the given form definiton
 614       *
 615       * @see delete_definition()
 616       */
 617      abstract protected function delete_plugin_definition();
 618  
 619      /**
 620       * Returns the name of the grading method plugin, eg 'rubric'
 621       *
 622       * @return string the name of the grading method plugin, eg 'rubric'
 623       * @see PARAM_PLUGIN
 624       */
 625      protected function get_method_name() {
 626          if (preg_match('/^gradingform_([a-z][a-z0-9_]*[a-z0-9])_controller$/', get_class($this), $matches)) {
 627              return $matches[1];
 628          } else {
 629              throw new coding_exception('Invalid class name');
 630          }
 631      }
 632  
 633      /**
 634       * Returns html code to be included in student's feedback.
 635       *
 636       * @param moodle_page $page
 637       * @param int $itemid
 638       * @param array $gradinginfo result of function grade_get_grades if plugin want to use some of their info
 639       * @param string $defaultcontent default string to be returned if no active grading is found or for some reason can not be shown to a user
 640       * @param boolean $cangrade whether current user has capability to grade in this context
 641       * @return string
 642       */
 643      public function render_grade($page, $itemid, $gradinginfo, $defaultcontent, $cangrade) {
 644          return $defaultcontent;
 645      }
 646  
 647      /**
 648       * Sets the range of grades used in this area. This is usually either range like 0-100
 649       * or the scale where keys start from 1.
 650       *
 651       * Typically modules will call it:
 652       * $controller->set_grade_range(make_grades_menu($gradingtype), $gradingtype > 0);
 653       * Negative $gradingtype means that scale is used and the grade must be rounded
 654       * to the nearest int. Positive $gradingtype means that range 0..$gradingtype
 655       * is used for the grades and in this case grade does not have to be rounded.
 656       *
 657       * Sometimes modules always expect grade to be rounded (like mod_assignment does).
 658       *
 659       * @param array $graderange array where first _key_ is the minimum grade and the
 660       *     last key is the maximum grade.
 661       * @param bool $allowgradedecimals if decimal values are allowed as grades.
 662       */
 663      public final function set_grade_range(array $graderange, $allowgradedecimals = false) {
 664          $this->graderange = $graderange;
 665          $this->allowgradedecimals = $allowgradedecimals;
 666      }
 667  
 668      /**
 669       * Returns the range of grades used in this area
 670       *
 671       * @return array
 672       */
 673      public final function get_grade_range() {
 674          if (empty($this->graderange)) {
 675              return array();
 676          }
 677          return $this->graderange;
 678      }
 679  
 680      /**
 681       * Returns if decimal values are allowed as grades
 682       *
 683       * @return bool
 684       */
 685      public final function get_allow_grade_decimals() {
 686          return $this->allowgradedecimals;
 687      }
 688  
 689      /**
 690       * Overridden by sub classes that wish to make definition details available to web services.
 691       * When not overridden, only definition data common to all grading methods is made available.
 692       * When overriding, the return value should be an array containing one or more key/value pairs.
 693       * These key/value pairs should match the definition returned by the get_definition() function.
 694       * For examples, look at:
 695       *    $gradingform_rubric_controller->get_external_definition_details()
 696       *    $gradingform_guide_controller->get_external_definition_details()
 697       * @return array An array of one or more key/value pairs containing the external_multiple_structure/s
 698       * corresponding to the definition returned by $controller->get_definition()
 699       * @since Moodle 2.5
 700       */
 701      public static function get_external_definition_details() {
 702          return null;
 703      }
 704  
 705      /**
 706       * Overridden by sub classes that wish to make instance filling details available to web services.
 707       * When not overridden, only instance filling data common to all grading methods is made available.
 708       * When overriding, the return value should be an array containing one or more key/value pairs.
 709       * These key/value pairs should match the filling data returned by the get_<method>_filling() function
 710       * in the gradingform_instance subclass.
 711       * For examples, look at:
 712       *    $gradingform_rubric_controller->get_external_instance_filling_details()
 713       *    $gradingform_guide_controller->get_external_instance_filling_details()
 714       *
 715       * @return array An array of one or more key/value pairs containing the external_multiple_structure/s
 716       * corresponding to the definition returned by $gradingform_<method>_instance->get_<method>_filling()
 717       * @since Moodle 2.6
 718       */
 719      public static function get_external_instance_filling_details() {
 720          return null;
 721      }
 722  }
 723  
 724  /**
 725   * Class to manage one gradingform instance.
 726   *
 727   * Gradingform instance is created for each evaluation of a student, using advanced grading.
 728   * It is stored as an entry in the DB table gradingform_instance.
 729   *
 730   * One instance (usually the latest) has the status INSTANCE_STATUS_ACTIVE. Sometimes it may
 731   * happen that a teacher wants to change the definition when some students have already been
 732   * graded. In this case their instances change status to INSTANCE_STATUS_NEEDUPDATE.
 733   *
 734   * To support future use of AJAX for background saving of incomplete evaluations the
 735   * status INSTANCE_STATUS_INCOMPLETE is introduced. If 'Cancel' is pressed this entry
 736   * is deleted.
 737   * When grade is updated the previous active instance receives status INSTANCE_STATUS_ACTIVE.
 738   *
 739   * Advanced grading plugins must declare a class gradingform_xxxx_instance
 740   * extending this class and put it in lib.php in the plugin folder.
 741   *
 742   * The reference to an instance of this class is passed to an advanced grading form element
 743   * included in the grading form, so this class must implement functions for rendering
 744   * and validation of this form element. See {@link MoodleQuickForm_grading}
 745   *
 746   * @package    core_grading
 747   * @copyright  2011 Marina Glancy
 748   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 749   * @category   grading
 750   */
 751  abstract class gradingform_instance {
 752      /** Valid istance status */
 753      const INSTANCE_STATUS_ACTIVE = 1;
 754      /** The grade needs to be updated by grader (usually because of changes is grading method) */
 755      const INSTANCE_STATUS_NEEDUPDATE = 2;
 756      /** The grader started grading but did clicked neither submit nor cancel */
 757      const INSTANCE_STATUS_INCOMPLETE = 0;
 758      /** Grader re-graded the student and this is the status for previous grade stored as history */
 759      const INSTANCE_STATUS_ARCHIVE = 3;
 760  
 761      /** @var stdClass record from table grading_instances */
 762      protected $data;
 763      /** @var gradingform_controller link to the corresponding controller */
 764      protected $controller;
 765  
 766      /**
 767       * Creates an instance
 768       *
 769       * @param gradingform_controller $controller
 770       * @param stdClass $data
 771       */
 772      public function __construct($controller, $data) {
 773          $this->data = (object)$data;
 774          $this->controller = $controller;
 775      }
 776  
 777      /**
 778       * Creates a new empty instance in DB and mark its status as INCOMPLETE
 779       *
 780       * @param int $definitionid
 781       * @param int $raterid
 782       * @param int $itemid
 783       * @return int id of the created instance
 784       */
 785      public static function create_new($definitionid, $raterid, $itemid) {
 786          global $DB;
 787          $instance = new stdClass();
 788          $instance->definitionid = $definitionid;
 789          $instance->raterid = $raterid;
 790          $instance->itemid = $itemid;
 791          $instance->status = self::INSTANCE_STATUS_INCOMPLETE;
 792          $instance->timemodified = time();
 793          $instance->feedbackformat = FORMAT_MOODLE;
 794          $instanceid = $DB->insert_record('grading_instances', $instance);
 795          return $instanceid;
 796      }
 797  
 798      /**
 799       * Duplicates the instance before editing (optionally substitutes raterid and/or itemid with
 800       * the specified values)
 801       * Plugins may want to override this function to copy data from additional tables as well
 802       *
 803       * @param int $raterid value for raterid in the duplicate
 804       * @param int $itemid value for itemid in the duplicate
 805       * @return int id of the new instance
 806       */
 807      public function copy($raterid, $itemid) {
 808          global $DB;
 809          $data = (array)$this->data; // Cast to array to make a copy
 810          unset($data['id']);
 811          $data['raterid'] = $raterid;
 812          $data['itemid'] = $itemid;
 813          $data['timemodified'] = time();
 814          $data['status'] = self::INSTANCE_STATUS_INCOMPLETE;
 815          $instanceid = $DB->insert_record('grading_instances', $data);
 816          return $instanceid;
 817      }
 818  
 819      /**
 820       * Returns the current (active or needupdate) instance for the same raterid and itemid as this
 821       * instance. This function is useful to find the status of the currently modified instance
 822       *
 823       * @return gradingform_instance
 824       */
 825      public function get_current_instance() {
 826          if ($this->get_status() == self::INSTANCE_STATUS_ACTIVE || $this->get_status() == self::INSTANCE_STATUS_NEEDUPDATE) {
 827              return $this;
 828          }
 829          return $this->get_controller()->get_current_instance($this->data->raterid, $this->data->itemid);
 830      }
 831  
 832      /**
 833       * Returns the controller
 834       *
 835       * @return gradingform_controller
 836       */
 837      public function get_controller() {
 838          return $this->controller;
 839      }
 840  
 841      /**
 842       * Returns the specified element from object $this->data
 843       *
 844       * @param string $key
 845       * @return mixed
 846       */
 847      public function get_data($key) {
 848          if (isset($this->data->$key)) {
 849              return $this->data->$key;
 850          }
 851          return null;
 852      }
 853  
 854      /**
 855       * Returns instance id
 856       *
 857       * @return int
 858       */
 859      public function get_id() {
 860          return $this->get_data('id');
 861      }
 862  
 863      /**
 864       * Returns instance status
 865       *
 866       * @return int
 867       */
 868      public function get_status() {
 869          return $this->get_data('status');
 870      }
 871  
 872      /**
 873       * Marks the instance as ACTIVE and current active instance (if exists) as ARCHIVE
 874       */
 875      protected function make_active() {
 876          global $DB;
 877          if ($this->data->status == self::INSTANCE_STATUS_ACTIVE) {
 878              // already active
 879              return;
 880          }
 881          if (empty($this->data->itemid)) {
 882              throw new coding_exception('You cannot mark active the grading instance without itemid');
 883          }
 884          $currentid = $this->get_controller()->get_current_instance($this->data->raterid, $this->data->itemid, true);
 885          if ($currentid && $currentid != $this->get_id()) {
 886              $DB->update_record('grading_instances', array('id' => $currentid, 'status' => self::INSTANCE_STATUS_ARCHIVE));
 887          }
 888          $DB->update_record('grading_instances', array('id' => $this->get_id(), 'status' => self::INSTANCE_STATUS_ACTIVE));
 889          $this->data->status = self::INSTANCE_STATUS_ACTIVE;
 890      }
 891  
 892      /**
 893       * Deletes this (INCOMPLETE) instance from database. This function is invoked on cancelling the
 894       * grading form and/or during cron cleanup.
 895       * Plugins using additional tables must override this method to remove additional data.
 896       * Note that if the teacher just closes the window or presses 'Back' button of the browser,
 897       * this function is not invoked.
 898       */
 899      public function cancel() {
 900          global $DB;
 901          // TODO MDL-31239 throw exception if status is not INSTANCE_STATUS_INCOMPLETE
 902          $DB->delete_records('grading_instances', array('id' => $this->get_id()));
 903      }
 904  
 905      /**
 906       * Updates the instance with the data received from grading form. This function may be
 907       * called via AJAX when grading is not yet completed, so it does not change the
 908       * status of the instance.
 909       *
 910       * @param array $elementvalue
 911       */
 912      public function update($elementvalue) {
 913          global $DB;
 914          $newdata = new stdClass();
 915          $newdata->id = $this->get_id();
 916          $newdata->timemodified = time();
 917          if (isset($elementvalue['itemid']) && $elementvalue['itemid'] != $this->data->itemid) {
 918              $newdata->itemid = $elementvalue['itemid'];
 919          }
 920          // TODO MDL-31087 also update: rawgrade, feedback, feedbackformat
 921          $DB->update_record('grading_instances', $newdata);
 922          foreach ($newdata as $key => $value) {
 923              $this->data->$key = $value;
 924          }
 925      }
 926  
 927      /**
 928       * Calculates the grade to be pushed to the gradebook
 929       *
 930       * Returned grade must be in range $this->get_controller()->get_grade_range()
 931       * Plugins must returned grade converted to int unless
 932       * $this->get_controller()->get_allow_grade_decimals() is true.
 933       *
 934       * @return float|int
 935       */
 936      abstract public function get_grade();
 937  
 938      /**
 939       * Determines whether the submitted form was empty.
 940       *
 941       * @param array $elementvalue value of element submitted from the form
 942       * @return boolean true if the form is empty
 943       */
 944      public function is_empty_form($elementvalue) {
 945          return false;
 946      }
 947  
 948      /**
 949       * Removes the attempt from the gradingform_*_fillings table.
 950       * This function is not abstract as to not break plugins that might
 951       * use advanced grading.
 952       * @param array $data the attempt data
 953       */
 954      public function clear_attempt($data) {
 955          // This function is empty because the way to clear a grade
 956          // attempt will be different depending on the grading method.
 957          return;
 958      }
 959  
 960      /**
 961       * Called when teacher submits the grading form:
 962       * updates the instance in DB, marks it as ACTIVE and returns the grade to be pushed to the gradebook.
 963       * $itemid must be specified here (it was not required when the instance was
 964       * created, because it might not existed in draft)
 965       *
 966       * @param array $elementvalue
 967       * @param int $itemid
 968       * @return int the grade on 0-100 scale
 969       */
 970      public function submit_and_get_grade($elementvalue, $itemid) {
 971          $elementvalue['itemid'] = $itemid;
 972          if ($this->is_empty_form($elementvalue)) {
 973              $this->clear_attempt($elementvalue);
 974              $this->make_active();
 975              return -1;
 976          }
 977          $this->update($elementvalue);
 978          $this->make_active();
 979          return $this->get_grade();
 980      }
 981  
 982      /**
 983       * Returns html for form element of type 'grading'. If there is a form input element
 984       * it must have the name $gradingformelement->getName().
 985       * If there are more than one input elements they MUST be elements of array with
 986       * name $gradingformelement->getName().
 987       * Example: {NAME}[myelement1], {NAME}[myelement2][sub1], {NAME}[myelement2][sub2], etc.
 988       * ( {NAME} is a shortcut for $gradingformelement->getName() )
 989       * After submitting the form the value of $_POST[{NAME}] is passed to the functions
 990       * validate_grading_element() and submit_and_get_grade()
 991       *
 992       * Plugins may use $gradingformelement->getValue() to get the value passed on previous
 993       * form submit
 994       *
 995       * When forming html it is a plugin's responsibility to analyze flags
 996       * $gradingformelement->_flagFrozen and $gradingformelement->_persistantFreeze:
 997       *
 998       * (_flagFrozen == false) => form element is editable
 999       *
1000       * (_flagFrozen == false && _persistantFreeze == true) => form element is not editable
1001       * but all values are passed as hidden elements
1002       *
1003       * (_flagFrozen == false && _persistantFreeze == false) => form element is not editable
1004       * and no values are passed as hidden elements
1005       *
1006       * Plugins are welcome to use AJAX in the form element. But it is strongly recommended
1007       * that the grading only becomes active when teacher presses 'Submit' button (the
1008       * method submit_and_get_grade() is invoked)
1009       *
1010       * Also client-side JS validation may be implemented here
1011       *
1012       * @see MoodleQuickForm_grading in lib/form/grading.php
1013       *
1014       * @param moodle_page $page
1015       * @param MoodleQuickForm_grading $gradingformelement
1016       * @return string
1017       */
1018      abstract function render_grading_element($page, $gradingformelement);
1019  
1020      /**
1021       * Server-side validation of the data received from grading form.
1022       *
1023       * @param mixed $elementvalue is the scalar or array received in $_POST
1024       * @return boolean true if the form data is validated and contains no errors
1025       */
1026      public function validate_grading_element($elementvalue) {
1027          return true;
1028      }
1029  
1030      /**
1031       * Returns the error message displayed if validation failed.
1032       * If plugin wants to display custom message, the empty string should be returned here
1033       * and the custom message should be output in render_grading_element()
1034       *
1035       * Please note that in assignments grading in 2.2 the grading form is not validated
1036       * properly and this message is not being displayed.
1037       *
1038       * @see validate_grading_element()
1039       * @return string
1040       */
1041      public function default_validation_error_message() {
1042          return '';
1043      }
1044  }