H5P = H5P || {};

/**
 * Will render a Question with multiple choices for answers.
 *
 * Events provided:
 * - h5pQuestionSetFinished: Triggered when a question is finished. (User presses Finish-button)
 *
 * @param {Array} options
 * @param {int} contentId
 * @param {Object} contentData
 * @returns {H5P.QuestionSet} Instance
 */
H5P.QuestionSet = function (options, contentId, contentData) {
  if (!(this instanceof H5P.QuestionSet)) {
    return new H5P.QuestionSet(options, contentId, contentData);
  }
  H5P.EventDispatcher.call(this);
  var $ = H5P.jQuery;
  var self = this;
  this.contentId = contentId;

  var texttemplate =
          '<% if (introPage.showIntroPage) { %>' +
          '<div class="intro-page">' +
          '  <% if (introPage.title) { %>' +
          '    <div class="title"><span><%= introPage.title %></span></div>' +
          '  <% } %>' +
          '  <% if (introPage.introduction) { %>' +
          '    <div class="introduction"><%= introPage.introduction %></div>' +
          '  <% } %>' +
          '  <div class="buttons"><a class="qs-startbutton h5p-joubelui-button h5p-button"><%= introPage.startButtonText %></a></div>' +
          '</div>' +
          '<% } %>' +
          '<div tabindex="-1" class="qs-progress-announcer"></div>' +
          '<div class="questionset<% if (introPage.showIntroPage) { %> hidden<% } %>">' +
          '  <% for (var i=0; i<questions.length; i++) { %>' +
          '    <div class="question-container"></div>' +
          '  <% } %>' +
          '  <div class="qs-footer">' +
          '    <div class="qs-progress">' +
          '      <% if (progressType == "dots") { %>' +
          '        <ul class="dots-container" role="navigation">' +
          '          <% for (var i=0; i<questions.length; i++) { %>' +
          '           <li class="progress-item">' +
          '             <a href="#" ' +
          '               class="progress-dot unanswered<%' +
          '               if (disableBackwardsNavigation) { %> disabled <% } %>"' +
          '               aria-label="<%=' +
          '               texts.jumpToQuestion.replace("%d", i + 1).replace("%total", questions.length)' +
          '               + ", " + texts.unansweredText %>" tabindex="-1" ' +
          '               <% if (disableBackwardsNavigation) { %> aria-disabled="true" <% } %>' +
          '             ></a>' +
          '           </li>' +
          '          <% } %>' +
          '        </div>' +
          '      <% } else if (progressType == "textual") { %>' +
          '        <span class="progress-text"></span>' +
          '      <% } %>' +
          '    </div>' +
          '  </div>' +
          '</div>';

  var solutionButtonTemplate = options.endGame.showSolutionButton ?
          '    <button type="button" class="h5p-joubelui-button h5p-button qs-solutionbutton"><%= solutionButtonText %></button>':
          '';

  var resulttemplate =
          '<div class="questionset-results">' +
          '  <div class="greeting"><%= message %></div>' +
          '  <div class="feedback-section">' +
          '    <div class="feedback-scorebar"></div>' +
          '    <div class="feedback-text"></div>' +
          '  </div>' +
          '  <% if (comment) { %>' +
          '  <div class="result-header"><%= comment %></div>' +
          '  <% } %>' +
          '  <% if (resulttext) { %>' +
          '  <div class="result-text"><%= resulttext %></div>' +
          '  <% } %>' +
          '  <div class="buttons">' +
          '    <button type="button" class="h5p-joubelui-button h5p-button qs-finishbutton"><%= finishButtonText %></button>' +
          solutionButtonTemplate +
          '    <button type="button" class="h5p-joubelui-button h5p-button qs-retrybutton"><%= retryButtonText %></button>' +
          '  </div>' +
          '</div>';

  var defaults = {
    initialQuestion: 0,
    progressType: 'dots',
    passPercentage: 50,
    questions: [],
    introPage: {
      showIntroPage: false,
      title: '',
      introduction: '',
      startButtonText: 'Start'
    },
    texts: {
      prevButton: 'Previous question',
      nextButton: 'Next question',
      finishButton: 'Finish',
      textualProgress: 'Question: @current of @total questions',
      jumpToQuestion: 'Question %d of %total',
      questionLabel: 'Question',
      readSpeakerProgress: 'Question @current of @total',
      unansweredText: 'Unanswered',
      answeredText: 'Answered',
      currentQuestionText: 'Current question'
    },
    endGame: {
      showResultPage: true,
      noResultMessage: 'Finished',
      message: 'Your result:',
      oldFeedback: {
        successGreeting: '',
        successComment: '',
        failGreeting: '',
        failComment: ''
      },
      overallFeedback: [],
      finishButtonText: 'Finish',
      solutionButtonText: 'Show solution',
      retryButtonText: 'Retry',
      showAnimations: false,
      skipButtonText: 'Skip video'
    },
    disableBackwardsNavigation: false
  };

  var template = new EJS({text: texttemplate});
  var endTemplate = new EJS({text: resulttemplate});
  var params = $.extend(true, {}, defaults, options);

  var initialParams = $.extend(true, {}, defaults, options);
  var poolOrder; // Order of questions in a pool
  var currentQuestion = 0;
  var questionInstances = [];
  var questionOrder; //Stores order of questions to allow resuming of question set
  var $myDom;
  var scoreBar;
  var up;
  var renderSolutions = false;
  var showingSolutions = false;
  contentData = contentData || {};

  // Bring question set up to date when resuming
  if (contentData.previousState) {
    if (contentData.previousState.progress) {
      currentQuestion = contentData.previousState.progress;
    }
    questionOrder = contentData.previousState.order;
  }

  /**
   * Randomizes questions in an array and updates an array containing their order
   * @param  {array} questions
   * @return {Object.<array, array>} questionOrdering
   */
  var randomizeQuestionOrdering = function (questions) {

    // Save the original order of the questions in a multidimensional array [[question0,0],[question1,1]...
    var questionOrdering = questions.map(function (questionInstance, index) { return [questionInstance, index]; });

    // Shuffle the multidimensional array
    questionOrdering = H5P.shuffleArray(questionOrdering);

    // Retrieve question objects from the first index
    questions = [];
    for (var i = 0; i < questionOrdering.length; i++) {
      questions[i] = questionOrdering[i][0];
    }

    // Retrieve the new shuffled order from the second index
    var newOrder = [];
    for (var j = 0; j < questionOrdering.length; j++) {

      // Use a previous order if it exists
      if (contentData.previousState && contentData.previousState.questionOrder) {
        newOrder[j] = questionOrder[questionOrdering[j][1]];
      }
      else {
        newOrder[j] = questionOrdering[j][1];
      }
    }

    // Return the questions in their new order *with* their new indexes
    return {
      questions: questions,
      questionOrder: newOrder
    };
  };

  // Create a pool (a subset) of questions if necessary
  if (params.poolSize > 0) {

    // If a previous pool exists, recreate it
    if (contentData.previousState && contentData.previousState.poolOrder) {
      poolOrder = contentData.previousState.poolOrder;

      // Recreate the pool from the saved data
      var pool = [];
      for (var i = 0; i < poolOrder.length; i++) {
        pool[i] = params.questions[poolOrder[i]];
      }

      // Replace original questions with just the ones in the pool
      params.questions = pool;
    }
    else { // Otherwise create a new pool
      // Randomize and get the results
      var poolResult = randomizeQuestionOrdering(params.questions);
      var poolQuestions = poolResult.questions;
      poolOrder = poolResult.questionOrder;

      // Discard extra questions

      poolQuestions = poolQuestions.slice(0, params.poolSize);
      poolOrder = poolOrder.slice(0, params.poolSize);

      // Replace original questions with just the ones in the pool
      params.questions = poolQuestions;
    }
  }

  // Create the html template for the question container
  var $template = $(template.render(params));

  // Set overrides for questions
  var override;
  if (params.override.showSolutionButton || params.override.retryButton) {
    override = {};
    if (params.override.showSolutionButton) {
      // Force "Show solution" button to be on or off for all interactions
      override.enableSolutionsButton =
          (params.override.showSolutionButton === 'on' ? true : false);
    }

    if (params.override.retryButton) {
      // Force "Retry" button to be on or off for all interactions
      override.enableRetry =
          (params.override.retryButton === 'on' ? true : false);
    }
  }

  /**
   * Generates question instances from H5P objects
   *
   * @param  {object} questions H5P content types to be created as instances
   * @return {array} Array of questions instances
   */
  var createQuestionInstancesFromQuestions = function (questions) {
    var result = [];
    // Create question instances from questions
    // Instantiate question instances
    for (var i = 0; i < questions.length; i++) {

      var question;
      // If a previous order exists, use it
      if (questionOrder !== undefined) {
        question = questions[questionOrder[i]];
      }
      else {
        // Use a generic order when initialzing for the first time
        question = questions[i];
      }

      if (override) {
        // Extend subcontent with the overrided settings.
        $.extend(question.params.behaviour, override);
      }

      question.params = question.params || {};
      var hasAnswers = contentData.previousState && contentData.previousState.answers;
      var questionInstance = H5P.newRunnable(question, contentId, undefined, undefined,
        {
          previousState: hasAnswers ? contentData.previousState.answers[i] : undefined,
          parent: self
        });
      questionInstance.on('resize', function () {
        up = true;
        self.trigger('resize');
      });
      result.push(questionInstance);
    }

    return result;
  };

  // Create question instances from questions given by params
  questionInstances = createQuestionInstancesFromQuestions(params.questions);

  // Randomize questions only on instantiation
  if (params.randomQuestions && contentData.previousState === undefined) {
    var result = randomizeQuestionOrdering(questionInstances);
    questionInstances = result.questions;
    questionOrder = result.questionOrder;
  }

  // Resize all interactions on resize
  self.on('resize', function () {
    if (up) {
      // Prevent resizing the question again.
      up = false;
      return;
    }

    for (var i = 0; i < questionInstances.length; i++) {
      questionInstances[i].trigger('resize');
    }
  });

  // Update button state.
  var _updateButtons = function () {
    // Verify that current question is answered when backward nav is disabled
    if (params.disableBackwardsNavigation) {
      if (questionInstances[currentQuestion].getAnswerGiven() &&
          questionInstances.length-1 !== currentQuestion) {
        questionInstances[currentQuestion].showButton('next');
      }
      else {
        questionInstances[currentQuestion].hideButton('next');
      }
    }

    var answered = true;
    for (var i = questionInstances.length - 1; i >= 0; i--) {
      answered = answered && (questionInstances[i]).getAnswerGiven();
    }

    if (currentQuestion === (params.questions.length - 1) &&
        questionInstances[currentQuestion]) {
      if (answered) {
        questionInstances[currentQuestion].showButton('finish');
      }
      else {
        questionInstances[currentQuestion].hideButton('finish');
      }
    }
 };

  var _stopQuestion = function (questionNumber) {
    if (questionInstances[questionNumber]) {
      pauseMedia(questionInstances[questionNumber]);
    }
  };

  var _showQuestion = function (questionNumber, preventAnnouncement) {
    // Sanitize input.
    if (questionNumber < 0) {
      questionNumber = 0;
    }
    if (questionNumber >= params.questions.length) {
      questionNumber = params.questions.length - 1;
    }

    currentQuestion = questionNumber;

    handleAutoPlay(currentQuestion);

    // Hide all questions
    $('.question-container', $myDom).hide().eq(questionNumber).show();

    if (questionInstances[questionNumber]) {
      // Trigger resize on question in case the size of the QS has changed.
      var instance = questionInstances[questionNumber];
      instance.setActivityStarted();
      if (instance.$ !== undefined) {
        instance.trigger('resize');
      }
    }

    // Update progress indicator
    // Test if current has been answered.
    if (params.progressType === 'textual') {
      $('.progress-text', $myDom).text(params.texts.textualProgress.replace("@current", questionNumber+1).replace("@total", params.questions.length));
    }
    else {
      // Set currentNess
      var previousQuestion = $('.progress-dot.current', $myDom).parent().index();
      if (previousQuestion >= 0) {
        toggleCurrentDot(previousQuestion, false);
        toggleAnsweredDot(previousQuestion, questionInstances[previousQuestion].getAnswerGiven());
      }
      toggleCurrentDot(questionNumber, true);
    }

    if (!preventAnnouncement) {
      // Announce question number of total, must use timeout because of buttons logic
      setTimeout(function () {
        var humanizedProgress = params.texts.readSpeakerProgress
          .replace('@current', (currentQuestion + 1).toString())
          .replace('@total', questionInstances.length.toString());

        $('.qs-progress-announcer', $myDom)
          .html(humanizedProgress)
          .show().focus();

        if (instance && instance.readFeedback) {
          instance.readFeedback();
        }
      }, 0);
    }

    // Remember where we are
    _updateButtons();
    self.trigger('resize');
    return currentQuestion;
  };

  /**
   * Handle autoplays, limit to one at a time
   *
   * @param {number} currentQuestionIndex
   */
  var handleAutoPlay = function (currentQuestionIndex) {
    for (var i = 0; i < questionInstances.length; i++) {
      questionInstances[i].pause();
    }

    var currentQuestion = params.questions[currentQuestionIndex];

    var hasAutoPlay = currentQuestion &&
        currentQuestion.params.media &&
        currentQuestion.params.media.params &&
        currentQuestion.params.media.params.playback &&
        currentQuestion.params.media.params.playback.autoplay;

    if (hasAutoPlay && typeof questionInstances[currentQuestionIndex].play === 'function') {
      questionInstances[currentQuestionIndex].play();
    }
  };



  /**
   * Show solutions for subcontent, and hide subcontent buttons.
   * Used for contracts with integrated content.
   * @public
   */
  var showSolutions = function () {
    showingSolutions = true;
    for (var i = 0; i < questionInstances.length; i++) {

      // Enable back and forth navigation in solution mode
      toggleDotsNavigation(true);
      if (i < questionInstances.length - 1) {
        questionInstances[i].showButton('next');
      }
      if (i > 0) {
        questionInstances[i].showButton('prev');
      }

      try {
        // Do not read answers
        questionInstances[i].toggleReadSpeaker(true);
        questionInstances[i].showSolutions();
        questionInstances[i].toggleReadSpeaker(false);
      }
      catch(error) {
        H5P.error("subcontent does not contain a valid showSolutions function");
        H5P.error(error);
      }
    }
  };

  /**
   * Toggles whether dots are enabled for navigation
   */
  var toggleDotsNavigation = function (enable) {
    $('.progress-dot', $myDom).each(function () {
      $(this).toggleClass('disabled', !enable);
      $(this).attr('aria-disabled', enable ? 'false' : 'true');
      // Remove tabindex
      if (!enable) {
        $(this).attr('tabindex', '-1');
      }
    });
  };

  /**
   * Resets the task and every subcontent task.
   * Used for contracts with integrated content.
   * @public
   */
  var resetTask = function () {

    // Clear previous state to ensure questions are created cleanly
    contentData.previousState = [];

    showingSolutions = false;

    for (var i = 0; i < questionInstances.length; i++) {
      try {
        questionInstances[i].resetTask();

        // Hide back and forth navigation in normal mode
        if (params.disableBackwardsNavigation) {
          toggleDotsNavigation(false);

          // Check if first question is answered by default
          if (i === 0 && questionInstances[i].getAnswerGiven()) {
            questionInstances[i].showButton('next');
          }
          else {
            questionInstances[i].hideButton('next');
          }

          questionInstances[i].hideButton('prev');
        }
      }
      catch(error) {
        H5P.error("subcontent does not contain a valid resetTask function");
        H5P.error(error);
      }
    }

    // Hide finish button
    questionInstances[questionInstances.length - 1].hideButton('finish');

    // Mark all tasks as unanswered:
    $('.progress-dot').each(function (idx) {
      toggleAnsweredDot(idx, false);
    });

    //Force the last page to be reRendered
    rendered = false;

    if (params.poolSize > 0) {

      // Make new pool from params.questions
      // Randomize and get the results
      var poolResult = randomizeQuestionOrdering(initialParams.questions);
      var poolQuestions = poolResult.questions;
      poolOrder = poolResult.questionOrder;

      // Discard extra questions
      poolQuestions = poolQuestions.slice(0, params.poolSize);
      poolOrder = poolOrder.slice(0, params.poolSize);

      // Replace original questions with just the ones in the pool
      params.questions = poolQuestions;

      // Recreate the question instances
      questionInstances = createQuestionInstancesFromQuestions(params.questions);

      // Update buttons
      initializeQuestion();

    } else if (params.randomQuestions) {
      randomizeQuestions();
    }

  };

  var rendered = false;

  this.reRender = function () {
    rendered = false;
  };

  /**
   * Randomizes question instances
   */
  var randomizeQuestions = function () {

    var result = randomizeQuestionOrdering(questionInstances);
    questionInstances = result.questions;
    questionOrder = result.questionOrder;

    replaceQuestionsInDOM(questionInstances);
  };

  /**
   * Empty the DOM of all questions, attach new questions and update buttons
   *
   * @param  {type} questionInstances Array of questions to be attached to the DOM
   */
  var replaceQuestionsInDOM = function (questionInstances) {

    // Find all question containers and detach questions from them
    $('.question-container', $myDom).each(function () {
      $(this).children().detach();
    });

    // Reattach questions and their buttons in the new order
    for (var i = 0; i < questionInstances.length; i++) {

      var question = questionInstances[i];

      // Make sure styles are not being added twice
      $('.question-container:eq(' + i + ')', $myDom).attr('class', 'question-container');

      question.attach($('.question-container:eq(' + i + ')', $myDom));

      //Show buttons if necessary
      if (questionInstances[questionInstances.length -1] === question &&
          question.hasButton('finish')) {
        question.showButton('finish');
      }

      if (questionInstances[questionInstances.length -1] !== question &&
          question.hasButton('next')) {
        question.showButton('next');
      }

      if (questionInstances[0] !== question &&
          question.hasButton('prev') &&
          !params.disableBackwardsNavigation) {
        question.showButton('prev');
      }

      // Hide relevant buttons since the order has changed
      if (questionInstances[0] === question) {
        question.hideButton('prev');
      }

      if (questionInstances[questionInstances.length-1] === question) {
        question.hideButton('next');
      }

      if (questionInstances[questionInstances.length-1] !== question) {
        question.hideButton('finish');
      }
    }
  };

  var moveQuestion = function (direction) {
    if (params.disableBackwardsNavigation && !questionInstances[currentQuestion].getAnswerGiven()) {
      questionInstances[currentQuestion].hideButton('next');
      questionInstances[currentQuestion].hideButton('finish');
      return;
    }

    _stopQuestion(currentQuestion);
    if (currentQuestion + direction >= questionInstances.length) {
      _displayEndGame();
    }
    else {
      // Allow movement if backward navigation enabled or answer given
      _showQuestion(currentQuestion + direction);
    }
  };

  /**
   * Toggle answered state of dot at given index
   * @param {number} dotIndex Index of dot
   * @param {boolean} isAnswered True if is answered, False if not answered
   */
  var toggleAnsweredDot = function (dotIndex, isAnswered) {
    var $el = $('.progress-dot:eq(' + dotIndex +')', $myDom);

    // Skip current button
    if ($el.hasClass('current')) {
      return;
    }

    // Ensure boolean
    isAnswered = !!isAnswered;

    var label = params.texts.jumpToQuestion
      .replace('%d', (dotIndex + 1).toString())
      .replace('%total', $('.progress-dot', $myDom).length) +
      ', ' +
      (isAnswered ? params.texts.answeredText : params.texts.unansweredText);

    $el.toggleClass('unanswered', !isAnswered)
      .toggleClass('answered', isAnswered)
      .attr('aria-label', label);
  };

  /**
   * Toggle current state of dot at given index
   * @param dotIndex
   * @param isCurrent
   */
  var toggleCurrentDot = function (dotIndex, isCurrent) {
    var $el = $('.progress-dot:eq(' + dotIndex +')', $myDom);
    var texts = params.texts;
    var label = texts.jumpToQuestion
      .replace('%d', (dotIndex + 1).toString())
      .replace('%total', $('.progress-dot', $myDom).length);

    if (!isCurrent) {
      var isAnswered = $el.hasClass('answered');
      label += ', ' + (isAnswered ? texts.answeredText : texts.unansweredText);
    }
    else {
      label += ', ' + texts.currentQuestionText;
    }

    var disabledTabindex = params.disableBackwardsNavigation && !showingSolutions;
    $el.toggleClass('current', isCurrent)
      .attr('aria-label', label)
      .attr('tabindex', isCurrent && !disabledTabindex ? 0 : -1);
  };

  var _displayEndGame = function () {
    $('.progress-dot.current', $myDom).removeClass('current');
    if (rendered) {
      $myDom.children().hide().filter('.questionset-results').show();
      self.trigger('resize');
      return;
    }
    //Remove old score screen.
    $myDom.children().hide().filter('.questionset-results').remove();
    rendered = true;

    // Get total score.
    var finals = self.getScore();
    var totals = self.getMaxScore();

    var scoreString = H5P.Question.determineOverallFeedback(params.endGame.overallFeedback, finals / totals).replace('@score', finals).replace('@total', totals);
    var success = ((100 * finals / totals) >= params.passPercentage);

    /**
     * Makes our buttons behave like other buttons.
     *
     * @private
     * @param {string} classSelector
     * @param {function} handler
     */
    var hookUpButton = function (classSelector, handler) {
      $(classSelector, $myDom).click(handler).keypress(function (e) {
        if (e.which === 32) {
          handler();
          e.preventDefault();
        }
      });
    };

    var displayResults = function () {
      self.triggerXAPICompleted(self.getScore(), self.getMaxScore(), success);

      var eparams = {
        message: params.endGame.showResultPage ? params.endGame.message : params.endGame.noResultMessage,
        comment: params.endGame.showResultPage ? (success ? params.endGame.oldFeedback.successGreeting : params.endGame.oldFeedback.failGreeting) : undefined,
        resulttext: params.endGame.showResultPage ? (success ? params.endGame.oldFeedback.successComment : params.endGame.oldFeedback.failComment) : undefined,
        finishButtonText: params.endGame.finishButtonText,
        solutionButtonText: params.endGame.solutionButtonText,
        retryButtonText: params.endGame.retryButtonText
      };

      // Show result page.
      $myDom.children().hide();
      $myDom.append(endTemplate.render(eparams));

      if (params.endGame.showResultPage) {
        hookUpButton('.qs-solutionbutton', function () {
          showSolutions();
          $myDom.children().hide().filter('.questionset').show();
          _showQuestion(params.initialQuestion);
        });
        hookUpButton('.qs-retrybutton', function () {
          resetTask();
          $myDom.children().hide();

          var $intro = $('.intro-page', $myDom);
          if ($intro.length) {
            // Show intro
            $('.intro-page', $myDom).show();
          }
          else {
            // Show first question
            $('.questionset', $myDom).show();
            _showQuestion(params.initialQuestion);
          }
        });

        if (scoreBar === undefined) {
          scoreBar = H5P.JoubelUI.createScoreBar(totals);
        }
        scoreBar.appendTo($('.feedback-scorebar', $myDom));
        scoreBar.setScore(finals);
        $('.feedback-text', $myDom).html(scoreString);

        // Announce that the question set is complete
        setTimeout(function () {
          $('.qs-progress-announcer', $myDom)
            .html(eparams.message + '.' +
                  scoreString + '.' +
                  eparams.comment + '.' +
                  eparams.resulttext)
            .show().focus();
        }, 0);
      }
      else {
        // Remove buttons and feedback section
        $('.qs-finishbutton, .qs-solutionbutton, .qs-retrybutton, .feedback-section', $myDom).remove();
      }

      self.trigger('resize');
    };

    if (params.endGame.showAnimations) {
      var videoData = success ? params.endGame.successVideo : params.endGame.failVideo;
      if (videoData) {
        $myDom.children().hide();
        var $videoContainer = $('<div class="video-container"></div>').appendTo($myDom);

        var video = new H5P.Video({
          sources: videoData,
          fitToWrapper: true,
          controls: false,
          autoplay: false
        }, contentId);
        video.on('stateChange', function (event) {
          if (event.data === H5P.Video.ENDED) {
            displayResults();
            $videoContainer.hide();
          }
        });
        video.attach($videoContainer);
        // Resize on video loaded
        video.on('loaded', function () {
          self.trigger('resize');
        });
        video.play();

        if (params.endGame.skippable) {
          $('<a class="h5p-joubelui-button h5p-button skip">' + params.endGame.skipButtonText + '</a>').click(function () {
            video.pause();
            $videoContainer.hide();
            displayResults();
          }).appendTo($videoContainer);
        }

        return;
      }
    }
    // Trigger finished event.
    displayResults();
    self.trigger('resize');
  };

  var registerImageLoadedListener = function (question) {
    H5P.on(question, 'imageLoaded', function () {
      self.trigger('resize');
    });
  };

  /**
   * Initialize a question and attach it to the DOM
   *
   */
  function initializeQuestion() {
    // Attach questions
    for (var i = 0; i < questionInstances.length; i++) {
      var question = questionInstances[i];

      // Make sure styles are not being added twice
      $('.question-container:eq(' + i + ')', $myDom).attr('class', 'question-container');

      question.attach($('.question-container:eq(' + i + ')', $myDom));

      // Listen for image resize
      registerImageLoadedListener(question);

      // Add finish button
      question.addButton('finish', params.texts.finishButton,
        moveQuestion.bind(this, 1), false);

      // Add next button
      question.addButton('next', '', moveQuestion.bind(this, 1),
        !params.disableBackwardsNavigation || !!question.getAnswerGiven(), {
          href: '#', // Use href since this is a navigation button
          'aria-label': params.texts.nextButton
        });

      // Add previous button
      question.addButton('prev', '', moveQuestion.bind(this, -1),
        !(questionInstances[0] === question || params.disableBackwardsNavigation), {
          href: '#', // Use href since this is a navigation button
          'aria-label': params.texts.prevButton
        });

      // Hide next button if it is the last question
      if (questionInstances[questionInstances.length -1] === question) {
        question.hideButton('next');
      }

      question.on('xAPI', function (event) {
        var shortVerb = event.getVerb();
        if (shortVerb === 'interacted' ||
          shortVerb === 'answered' ||
          shortVerb === 'attempted') {
          toggleAnsweredDot(currentQuestion,
            questionInstances[currentQuestion].getAnswerGiven());
          _updateButtons();
        }
        if (shortVerb === 'completed') {
          // An activity within this activity is not allowed to send completed events
          event.setVerb('answered');
        }
        if (event.data.statement.context.extensions === undefined) {
          event.data.statement.context.extensions = {};
        }
        event.data.statement.context.extensions['http://id.tincanapi.com/extension/ending-point'] = currentQuestion + 1;
      });

      // Mark question if answered
      toggleAnsweredDot(i, question.getAnswerGiven());
    }
  }

  this.attach = function (target) {
    if (this.isRoot()) {
      this.setActivityStarted();
    }
    if (typeof(target) === "string") {
      $myDom = $('#' + target);
    }
    else {
      $myDom = $(target);
    }

    // Render own DOM into target.
    $myDom.children().remove();
    $myDom.append($template);
    if (params.backgroundImage !== undefined) {
      $myDom.css({
        overflow: 'hidden',
        background: '#fff url("' + H5P.getPath(params.backgroundImage.path, contentId) + '") no-repeat 50% 50%',
        backgroundSize: '100% auto'
      });
    }

    if (params.introPage.backgroundImage !== undefined) {
      var $intro = $myDom.find('.intro-page');
      if ($intro.length) {
        var bgImg = params.introPage.backgroundImage;
        var bgImgRatio = (bgImg.height / bgImg.width);
        $intro.css({
          background: '#fff url("' + H5P.getPath(bgImg.path, contentId) + '") no-repeat 50% 50%',
          backgroundSize: 'auto 100%',
          minHeight: bgImgRatio * +window.getComputedStyle($intro[0]).width.replace('px','')
        });
      }
    }

    initializeQuestion();

    // Allow other libraries to add transitions after the questions have been inited
    $('.questionset', $myDom).addClass('started');

    $('.qs-startbutton', $myDom).click(function () {
      $(this).parents('.intro-page').hide();
      $('.questionset', $myDom).show();
      _showQuestion(params.initialQuestion);
    });

    /**
     * Triggers changing the current question.
     *
     * @private
     * @param {Object} [event]
     */
    var handleProgressDotClick = function (event) {
      // Disable dots when backward nav disabled
      event.preventDefault();
      if (params.disableBackwardsNavigation && !showingSolutions) {
        return;
      }
      _stopQuestion(currentQuestion);
      _showQuestion($(this).parent().index());
    };

    // Set event listeners.
    $('.progress-dot', $myDom).click(handleProgressDotClick).keydown(function (event) {
      var $this = $(this);
      switch (event.which) {
        case 13: // Enter
        case 32: // Space
          handleProgressDotClick.call(this, event);
          break;

        case 37: // Left Arrow
        case 38: // Up Arrow
          // Go to previous dot
          var $prev = $this.parent().prev();
          if ($prev.length) {
            $prev.children('a').attr('tabindex', '0').focus();
            $this.attr('tabindex', '-1');
          }
          break;

        case 39: // Right Arrow
        case 40: // Down Arrow
          // Go to next dot
          var $next = $this.parent().next();
          if ($next.length) {
            $next.children('a').attr('tabindex', '0').focus();
            $this.attr('tabindex', '-1');
          }
          break;
      }
    });



    // Hide all but current question
    _showQuestion(currentQuestion, true);

    if (renderSolutions) {
      showSolutions();
    }
    // Update buttons in case they have changed (restored user state)
    _updateButtons();

    this.trigger('resize');

    return this;
  };

  // Get current score for questionset.
  this.getScore = function () {
    var score = 0;
    for (var i = questionInstances.length - 1; i >= 0; i--) {
      score += questionInstances[i].getScore();
    }
    return score;
  };

  // Get total score possible for questionset.
  this.getMaxScore = function () {
    var score = 0;
    for (var i = questionInstances.length - 1; i >= 0; i--) {
      score += questionInstances[i].getMaxScore();
    }
    return score;
  };

  /**
   * @deprecated since version 1.9.2
   * @returns {number}
   */
  this.totalScore = function () {
    return this.getMaxScore();
  };

  /**
   * Gather copyright information for the current content.
   *
   * @returns {H5P.ContentCopyrights}
   */
  this.getCopyrights = function () {
    var info = new H5P.ContentCopyrights();

    // Background
    if (params.backgroundImage !== undefined && params.backgroundImage.copyright !== undefined) {
      var background = new H5P.MediaCopyright(params.backgroundImage.copyright);
      background.setThumbnail(new H5P.Thumbnail(H5P.getPath(params.backgroundImage.path, contentId), params.backgroundImage.width, params.backgroundImage.height));
      info.addMedia(background);
    }

    // Questions
    var questionCopyrights;
    for (var i = 0; i < questionInstances.length; i++) {
      var instance = questionInstances[i];
      var qParams = params.questions[i].params;
      questionCopyrights = undefined;

      if (instance.getCopyrights !== undefined) {
        // Use the instance's own copyright generator
        questionCopyrights = instance.getCopyrights();
      }
      if (questionCopyrights === undefined) {
        // Create a generic flat copyright list
        questionCopyrights = new H5P.ContentCopyrights();
        H5P.findCopyrights(questionCopyrights, qParams, contentId);
      }

      // Determine label
      var label = (params.texts.questionLabel + ' ' + (i + 1));
      if (qParams.contentName !== undefined) {
        label += ': ' + qParams.contentName;
      }
      else if (instance.getTitle !== undefined) {
        label += ': ' + instance.getTitle();
      }
      questionCopyrights.setLabel(label);

      // Add info
      info.addContent(questionCopyrights);
    }

    // Success video
    var video;
    if (params.endGame.successVideo !== undefined && params.endGame.successVideo.length > 0) {
      video = params.endGame.successVideo[0];
      if (video.copyright !== undefined) {
        info.addMedia(new H5P.MediaCopyright(video.copyright));
      }
    }

    // Fail video
    if (params.endGame.failVideo !== undefined && params.endGame.failVideo.length > 0) {
      video = params.endGame.failVideo[0];
      if (video.copyright !== undefined) {
        info.addMedia(new H5P.MediaCopyright(video.copyright));
      }
    }

    return info;
  };
  this.getQuestions = function () {
    return questionInstances;
  };
  this.showSolutions = function () {
    renderSolutions = true;
  };

  /**
   * Stop the given element's playback if any.
   *
   * @param {object} instance
   */
  var pauseMedia = function (instance) {
    try {
      if (instance.pause !== undefined &&
        (instance.pause instanceof Function ||
        typeof instance.pause === 'function')) {
        instance.pause();
      }
    }
    catch (err) {
      // Prevent crashing, log error.
      H5P.error(err);
    }
  };

  /**
   * Returns the complete state of question set and sub-content
   *
   * @returns {Object} current state
   */
  this.getCurrentState = function () {
    return {
      progress: showingSolutions ? questionInstances.length - 1 : currentQuestion,
      answers: questionInstances.map(function (qi) {
        return qi.getCurrentState();
      }),
      order: questionOrder,
      poolOrder: poolOrder
    };
  };

  /**
   * Generate xAPI object definition used in xAPI statements.
   * @return {Object}
   */
  var getxAPIDefinition = function () {
    var definition = {};

    definition.interactionType = 'compound';
    definition.type = 'http://adlnet.gov/expapi/activities/cmi.interaction';
    definition.description = {
      'en-US': ''
    };

    return definition;
  };

  /**
   * Add the question itself to the definition part of an xAPIEvent
   */
  var addQuestionToXAPI = function (xAPIEvent) {
    var definition = xAPIEvent.getVerifiedStatementValue(['object', 'definition']);
    $.extend(definition, getxAPIDefinition());
  };

  /**
   * Get xAPI data from sub content types
   *
   * @param {Object} metaContentType
   * @returns {array}
   */
  var getXAPIDataFromChildren = function (metaContentType) {
    return metaContentType.getQuestions().map(function (question) {
      return question.getXAPIData();
    });
  };

  /**
   * Get xAPI data.
   * Contract used by report rendering engine.
   *
   * @see contract at {@link https://h5p.org/documentation/developers/contracts#guides-header-6}
   */
  this.getXAPIData = function () {
    var xAPIEvent = this.createXAPIEventTemplate('answered');
    addQuestionToXAPI(xAPIEvent);
    xAPIEvent.setScoredResult(this.getScore(),
      this.getMaxScore(),
      this,
      true,
      this.getScore() === this.getMaxScore()
    );
    return {
      statement: xAPIEvent.data.statement,
      children: getXAPIDataFromChildren(this)
    };
  };
};

H5P.QuestionSet.prototype = Object.create(H5P.EventDispatcher.prototype);
H5P.QuestionSet.prototype.constructor = H5P.QuestionSet;