text: /**
   * jspsych-survey-likert
   * a jspsych plugin for measuring items on a likert scale
   *
   * Josh de Leeuw
   *
   * documentation: docs.jspsych.org
   *
   */
  
  jsPsych.plugins['survey-likert'] = (function() {
  
    var plugin = {};
  
    plugin.info = {
      name: 'survey-likert',
      description: '',
      parameters: {
        questions: {
          type: jsPsych.plugins.parameterType.COMPLEX,
          array: true,
          pretty_name: 'Questions',
          nested: {
            prompt: {type: jsPsych.plugins.parameterType.STRING,
                       pretty_name: 'Prompt',
                       default: undefined,
                       description: 'Questions that are associated with the slider.'},
            labels: {type: jsPsych.plugins.parameterType.STRING,
                     array: true,
                     pretty_name: 'Labels',
                     default: undefined,
                     description: 'Labels to display for individual question.'},
            required: {type: jsPsych.plugins.parameterType.BOOL,
                       pretty_name: 'Required',
                       default: false,
                       description: 'Makes answering questions required.'}
          }
        },
        preamble: {
          type: jsPsych.plugins.parameterType.STRING,
          pretty_name: 'Preamble',
          default: null,
          description: 'String to display at top of the page.'
        },
        button_label: {
          type: jsPsych.plugins.parameterType.STRING,
          pretty_name: 'Button label',
          default:  'Continue',
          description: 'Label of the button.'
        }
      }
    }
  
    plugin.trial = function(display_element, trial) {
  
  
      var html = "";
      // inject CSS for trial
      html += '<style id="jspsych-survey-likert-css">';
      html += ".jspsych-survey-likert-statement { display:block; font-size: 20px; padding-top: 40px; margin-bottom:10px; }"+
        ".jspsych-survey-likert-opts { list-style:none; width:100%; margin:0; padding:0 0 35px; display:block; font-size: 15px; line-height:1.1em; }"+
        ".jspsych-survey-likert-opt-label { line-height: 1.1em; color: #444; }"+
        ".jspsych-survey-likert-opts:before { content: ''; position:relative; top:11px; /*left:9.5%;*/ display:block; background-color:#efefef; height:4px; width:100%; }"+
        ".jspsych-survey-likert-opts:last-of-type { border-bottom: 0; }"+
        ".jspsych-survey-likert-opts li { display:inline-block; /*width:19%;*/ text-align:center; vertical-align: top; }"+
        ".jspsych-survey-likert-opts li input[type=radio] { display:block; position:relative; top:0; left:50%; margin-left:-6px; }"
      html += '</style>';
  
      // show preamble text
      if(trial.preamble !== null){
        html += '<div id="jspsych-survey-likert-preamble" class="jspsych-survey-likert-preamble">'+trial.preamble+'</div>';
      }
      html += '<form id="jspsych-survey-likert-form">';
  
      // add likert scale questions
      for (var i = 0; i < trial.questions.length; i++) {
        // add question
        html += '<label class="jspsych-survey-likert-statement">' + trial.questions[i].prompt + '</label>';
        // add options
        var width = 100 / trial.questions[i].labels.length;
        var options_string = '<ul class="jspsych-survey-likert-opts" data-radio-group="Q' + i + '">';
        for (var j = 0; j < trial.questions[i].labels.length; j++) {
          options_string += '<li style="width:' + width + '%"><input type="radio" name="Q' + i + '" value="' + j + '"';
          if(trial.questions[i].required){
            options_string += ' required';
          }
          options_string += '><label class="jspsych-survey-likert-opt-label">' + trial.questions[i].labels[j] + '</label></li>';
        }
        options_string += '</ul>';
        html += options_string;
      }
  
      // add submit button
      html += '<input type="submit" id="jspsych-survey-likert-next" class="jspsych-survey-likert jspsych-btn" value="'+trial.button_label+'"></input>';
  
      html += '</form>'
  
      display_element.innerHTML = html;
  
      display_element.querySelector('#jspsych-survey-likert-form').addEventListener('submit', function(e){
        e.preventDefault();
        // measure response time
        var endTime = (new Date()).getTime();
        var response_time = endTime - startTime;
  
        // create object to hold responses
        var question_data = {};
        var matches = display_element.querySelectorAll('#jspsych-survey-likert-form .jspsych-survey-likert-opts');
        for(var index = 0; index < matches.length; index++){
          var id = matches[index].dataset['radioGroup'];
          var el = display_element.querySelector('input[name="' + id + '"]:checked');
          if (el === null) {
            var response = "";
          } else {
            var response = parseInt(el.value);
          }
          var obje = {};
          obje[id] = response;
          Object.assign(question_data, obje);
        }
  
        // save data
        var trial_data = {
          "rt": response_time,
          "responses": JSON.stringify(question_data)
        };
  
        display_element.innerHTML = '';
  
        // next trial
        jsPsych.finishTrial(trial_data);
      });
  
      var startTime = (new Date()).getTime();
    };
  
    return plugin;
  })();
  