WooCommerce - Set product featured images to cat image

<?php
  // For a given category, set all product featured images to the product's category image
  // relevant products must have one category only
  // version 1.2
  // usage: make a page with this shortcode: [set_product_images cat_name="my_cat_name"]
  // use "all" for my_cat_name to set all product featured images to their respective category images
  // load the page in a browser to run the script
  // code goes in your child theme's functions.php
  // For live shops, backup the database before using
  // THERE IS NO UNDO!

  add_shortcode('set_product_images', 'set_product_images');
  function set_product_images($attributes) {
    $defaults = array('cat_name' => 'None');
    $parameters = shortcode_atts( $defaults, $attributes);
    // get the cat_name
    $cat_name = $parameters['cat_name'];  // number of products to show
    switch ($cat_name) {
      case 'none':
        print '<p>Error: Category name not set in shortcode attributes.</p>'.PHP_EOL;
        break;
      case 'all':
        // get all product categories
        $product_cats = get_terms('product_cat', 'fields => "names"');
        foreach($product_cats as $product_cat){
          $this_cat_name = $product_cat->name;
          set_product_images_for_category($this_cat_name);
        }
        break;
      default:
        set_product_images_for_category($cat_name);
    }
  }

  function set_product_images_for_category($cat_name) {
    global $wpdb;
    echo '<p>Category name: '.$cat_name.'</p>'.PHP_EOL;
    // get the term
    $category = get_term_by('name', $cat_name, 'product_cat');
    if ($category === false) {
      print '<p>Error: The category name which was set in the shortcode\'s attributes was not found.</p>'.PHP_EOL;
    } else {
      $category_id = $category->term_id;
      echo '<p>Category ID: '.$category_id.'</p>';
      // get the category image
      $thumbnail_id = get_woocommerce_term_meta( $category_id, 'thumbnail_id', true );
      if (!$thumbnail_id) {
        print '<p>Error: There is no category image set for this category.</p>'.PHP_EOL;
      } else {
        echo '<p>Thumbnail ID: '.$thumbnail_id.'</p>'.PHP_EOL;
         $image_url = wp_get_attachment_url( $thumbnail_id );
        echo '<p>Category image url: '.$image_url.'</p>';
        if ($image_url) {
          echo '<img src="'.$image_url.'" alt="" />'.PHP_EOL;
        }
        // get all the products
        $nr_products = 0;
        $nr_products_changed = 0;
        $arguments = array('post_type' => 'product', 'posts_per_page' => -1);
        $the_query = new WP_Query( $arguments );
        // the loop
        if ( $the_query->have_posts() ) {
          while ( $the_query->have_posts() ) {
            $the_query->the_post();
            $nr_products++;
            // get the product categories
            $terms = get_the_terms( get_the_ID(), 'product_cat' );
            // "false" if the post contains no terms from the given taxonomy
            if ($terms !== false) {
              if(is_wp_error($terms)) {
                echo '<p>'.$return->get_error_message().'</p>';
              } else {
                // maybe 1 or many categories, we are only interested if there is 1 category
                if (count($terms) == 1) {
                  foreach ($terms as $term) {
                    // is it the category we are looking for?
                    if ($term->name == $cat_name) {
                      // found!
                      echo '<p>Post ID: '.get_the_ID().' Product category name: '.$term->name.'</p>'.PHP_EOL;
                      set_post_thumbnail( $post, $thumbnail_id);
                      echo '<p>Product featured image set to category image.</p>'.PHP_EOL;
                      $nr_products_changed++;
                    }
                  }
                }
              }
            }
          }
          echo '<p>Number of products found in the database: '.$nr_products.'</p>'.PHP_EOL;
          echo '<p>Number of products whose featured image was changed: '.$nr_products_changed.'</p>'.PHP_EOL;
        } else {
          // no posts found
        }
        // restore original Post Data
        wp_reset_postdata();
      }
    }
  }