Generate SKU programmatically

<?php
/**
 * Generate SKU programmatically
 * https://example.com/wp-admin/edit.php?post_type=product&generate_sku
 */
function pm_generate_sku() {
    if(isset($_GET['generate_sku'])) {
        $query = new WC_Product_Query(array(
        'limit' => -1,
        'orderby' => 'date',
        'order' => 'DESC',
        ));

        $products = $query->get_products();

        foreach($products as $product) {
            // Get product ID and SKU (if exists)
            $product_id = $product->get_id();

            pm_generate_single_sku($product_id);
        }
    }
}
add_action('admin_init', 'pm_generate_sku');

/**
 * Add the SKU
 */
function pm_generate_single_sku($product_id, $post, $update) {
    global $permalink_manager_uris;

    // Trigger only when product is saved for the first time + ignore other post types
    if($update || $post->post_type !== 'product') { return; }

    // Get product object
    $product = wc_get_product($product_id);

    if(empty($product)) { return; }

    // Get current SKU
    $product_sku = $product->get_sku();

    // Add SKU only to products without them
    if(!empty($product_sku)) { return; }

    // Convert the product title to the number
    $product_title_encoded = sha1($product->get_title());

    // Generate the SKU based on unique product ID + encoded product title
    $product_sku = $product_id . $product_title_encoded;

    // Keep only digits
    $product_sku = preg_replace('/\D/', '', $product_sku);

    // Trim it to 7 characters to make sure that all SKU have the same length
    $product_sku = substr($product_sku, 0, 10);

    // Save SKU
    update_post_meta($product_id, '_sku', $product_sku);

    // Generate custom permalink with SKU
    $default_uri = Permalink_Manager_URI_Functions_Post::get_default_post_uri($product_id);

    if($default_uri) {
        $permalink_manager_uris[$product_id] = $default_uri;
        update_option('permalink-manager-uris', $permalink_manager_uris);
    }
}
add_action('wp_insert_post', 'pm_generate_single_sku', 99, 3);