<?php

function h5pmods_alter_semantics(&$semantics, $library_name) {
  /*
   * Check if the library name matches the content type that should be changed.
   * We don't have to do anything to Multiple Choice Quizzes, for example.
   */
  if ($library_name === 'H5P.PersonalityQuiz') {
    /*
     * We are now basically crawling through the semantics.json file hierarchy.
     * There are other ways to do this, but this should suffice for now.
     * $semantics contains all fields of the top hierarchy, and you're
     * looking for the one that is named 'personalities'. So, you can loop
     * over all the fields of $semantics and can look at each of them individually.
     * The one that you're currently looking at will be $semantic_field.
     * You take the next one, and the next one, ..., until you arrive at the one
     * that has the correct name.
     */
    foreach ($semantics as $semantic_field) {
      if ($semantic_field->name === 'personalities') {
        /*
         * $semantic_field is now the one we need, and we can dig deeper.
         * Looking at the semantics.json file, you can see that the next
         * hierarchy level is "inside" the key 'field', and then the next
         * one that you need is "inside" the key 'fields'. You could now even
         * go directly to the one field that you want, but maybe a fields
         * get's added, and that would screw up this script.
         * You don't really need the next step, but this might be easier to
         * grasp. You could now store all the information about a personality
         * (name, description and image) in another variable.
         */
        $personality_fields = $semantic_field->field->fields;
        /*
         * As before, you can loop over all of these until you find the one
         * that is of interest -- it has the name 'description'.
         */
        foreach ($personality_fields as $personality_field) {
          if ($personality_field->name === "description") {
            /*
             * Now you are at the right spot! $personality_field now
             * contains the field and all its properties that you want to
             * change.
             * You cannot magically create a button here, but you could, e.g.
             * change the widget type. In semantics.json it says:
             *     "widget": "textarea"
             * That's how you tell the editor of H5P that it should create
             * a plain box where you can type into plain text. But H5P also
             * has these fancy editor boxes with lot's of buttons right?!
             * That's what's called the HTML-widget, and you can simply
             * change this by setting this ...
             */
            $personality_field->widget = 'html';
            /*
             * Now you have overridden semantics.
             */
          }
        }

      }
    }
  }
}

// You'll need something like the next line, too, if you're using WordPress
//add_action('h5p_alter_library_semantics', 'h5pmods_alter_semantics', 10, 4);