text: // This file is part of Moodle - http://moodle.org/
  //
  // Moodle is free software: you can redistribute it and/or modify
  // it under the terms of the GNU General Public License as published by
  // the Free Software Foundation, either version 3 of the License, or
  // (at your option) any later version.
  //
  // Moodle is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  // GNU General Public License for more details.
  //
  // You should have received a copy of the GNU General Public License
  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  
  /**
   * JavaScript required by the question engine.
   *
   * @package    moodlecore
   * @subpackage questionengine
   * @copyright  2008 The Open University
   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
   */
  
  
  /**
   * Scroll manager is a class that help with saving the scroll positing when you
   * click on an action icon, and then when the page is reloaded after processing
   * the action, it scrolls you to exactly where you were. This is much nicer for
   * the user.
   *
   * To use this in your code, you need to ensure that:
   * 1. The button that triggers the action has to have a click event handler that
   *    calls M.core_scroll_manager.save_scroll_pos
   * 2. The script that process the action has to grab the scrollpos parameter
   *    using $scrollpos = optional_param('scrollpos', 0, PARAM_INT);
   * 3. After doing the processing, it must add ->param('scrollpos', $scrollpos)
   *    to the URL that it redirects to.
   * 4. Finally, on the page that is reloaded (which should be the same as the one
   *    the user started on) you need to call M.core_scroll_manager.scroll_to_saved_pos
   *    on page load.
   */
  M.core_scroll_manager = M.core_scroll_manager || {};
  
  /**
   * In the form that contains the element, set the value of the form field with
   * name scrollpos to the current scroll position. If there is no element with
   * that name, it creates a hidden form field wiht that name within the form.
   * @param element the element in the form. Should be something that can be
   *      passed to Y.one.
   */
  M.core_scroll_manager.save_scroll_pos = function(Y, element) {
      if (typeof(element) == 'string') {
          // Have to use getElementById here because element id can contain :.
          element = Y.one(document.getElementById(element));
      }
      var form = element.ancestor('form');
      if (!form) {
          return;
      }
      var scrollpos = form.one('input[name=scrollpos]');
      if (!scrollpos) {
          scrollpos = form.appendChild(form.create('<input type="hidden" name="scrollpos" />'));
      }
      scrollpos.set('value', form.get('docScrollY'));
  }
  
  /**
   * Event handler that can be used on a link. Assumes that the link already
   * contains at least one URL parameter.
   */
  M.core_scroll_manager.save_scroll_action = function(e) {
      var link = e.target.ancestor('a[href]');
      if (!link) {
          M.core_scroll_manager.save_scroll_pos({}, e.target);
          return;
      }
      link.set('href', link.get('href') + '&scrollpos=' + link.get('docScrollY'));
  }
  
  /**
   * If there is a parameter like scrollpos=123 in the URL, scroll to that saved position.
   */
  M.core_scroll_manager.scroll_to_saved_pos = function(Y) {
      var matches = window.location.href.match(/^.*[?&]scrollpos=(\d*)(?:&|$|#).*$/, '$1');
      if (matches) {
          // onDOMReady is the effective one here. I am leaving the immediate call to
          // window.scrollTo in case it reduces flicker.
          window.scrollTo(0, matches[1]);
          Y.on('domready', function() { window.scrollTo(0, matches[1]); });
  
          // And the following horror is necessary to make it work in IE 8.
          // Note that the class ie8 on body is only there in Moodle 2.0 and OU Moodle.
          if (Y.one('body').hasClass('ie')) {
              M.core_scroll_manager.force_ie_to_scroll(Y, matches[1])
          }
      }
  }
  
  /**
   * Beat IE into submission.
   * @param targetpos the target scroll position.
   */
  M.core_scroll_manager.force_ie_to_scroll = function(Y, targetpos) {
      var hackcount = 25;
      function do_scroll() {
          window.scrollTo(0, targetpos);
          hackcount -= 1;
          if (hackcount > 0) {
              setTimeout(do_scroll, 10);
          }
      }
      Y.on('load', do_scroll, window);
  }
  
  M.core_question_engine = M.core_question_engine || {};
  
  /**
   * Flag used by M.core_question_engine.prevent_repeat_submission.
   */
  M.core_question_engine.questionformalreadysubmitted = false;
  
  /**
   * Initialise a question submit button. This saves the scroll position and
   * sets the fragment on the form submit URL so the page reloads in the right place.
   * @param button the id of the button in the HTML.
   */
  M.core_question_engine.init_submit_button = function(Y, button) {
      require(['core_form/submit'], function(submit) {
          submit.init(button);
      });
      var totalQuestionsInPage = document.querySelectorAll('div.que').length;
      var buttonel = document.getElementById(button);
      var outeruniqueid = buttonel.closest('.que').id;
      Y.on('click', function(e) {
          M.core_scroll_manager.save_scroll_pos(Y, button);
          if (totalQuestionsInPage > 1) {
              // Only change the form action if the page have more than one question.
              buttonel.form.action = buttonel.form.action + '#' + outeruniqueid;
          }
      }, buttonel);
  }
  
  /**
   * Initialise a form that contains questions printed using print_question.
   * This has the effect of:
   * 1. Turning off browser autocomlete.
   * 2. Stopping enter from submitting the form (or toggling the next flag) unless
   *    keyboard focus is on the submit button or the flag.
   * 3. Removes any '.questionflagsavebutton's, since we have JavaScript to toggle
   *    the flags using ajax.
   * 4. Scroll to the position indicated by scrollpos= in the URL, if it is there.
   * 5. Prevent the user from repeatedly submitting the form.
   * @param Y the Yahoo object. Needs to have the DOM and Event modules loaded.
   * @param form something that can be passed to Y.one, to find the form element.
   */
  M.core_question_engine.init_form = function(Y, form) {
      Y.one(form).setAttribute('autocomplete', 'off');
  
      Y.on('submit', M.core_question_engine.prevent_repeat_submission, form, form, Y);
  
      Y.on('key', function (e) {
          if (!e.target.test('a') && !e.target.test('input[type=submit]') &&
                  !e.target.test('input[type=img]') && !e.target.test('textarea') && !e.target.test('[contenteditable=true]')) {
              e.preventDefault();
          }
      }, form, 'press:13');
  
      Y.one(form).all('.questionflagsavebutton').remove();
  
      M.core_scroll_manager.scroll_to_saved_pos(Y);
  }
  
  /**
   * Event handler to stop a question form being submitted more than once.
   * @param e the form submit event.
   * @param form the form element.
   */
  M.core_question_engine.prevent_repeat_submission = function(e, Y) {
      if (M.core_question_engine.questionformalreadysubmitted) {
          e.halt();
          return;
      }
  
      setTimeout(function() {
          Y.all('input[type=submit]').set('disabled', true);
      }, 0);
      M.core_question_engine.questionformalreadysubmitted = true;
  }
  