add_action( 'plugins_loaded', 'mce_init' );

function mce_init(): void {
    if ( ! class_exists( 'WooCommerce' ) ) {
        add_action( 'admin_notices', function (): void {
            echo '<div class="error"><p>' .
                esc_html__( 'My Extension requires WooCommerce.', 'my-extension' ) .
                '</p></div>';
        } );
        return;
    }
    // Safe to use WooCommerce APIs from here.
}

/**
 * Plugin Name: My WooCommerce Extension
 * Plugin URI:  https://example.com/my-extension
 * Description: Extends WooCommerce with custom features.
 * Version:     1.0.0
 * Author:      Your Name
 * Requires Plugins: woocommerce
 * WC requires at least: 8.0
 * WC tested up to: 10.4
 * Requires PHP: 7.4
 */

add_action( 'before_woocommerce_init', function (): void {
    if ( class_exists( '\Automattic\WooCommerce\Utilities\FeaturesUtil' ) ) {
        // Declare HPOS compatibility.
        \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility(
            'custom_order_tables',
            __FILE__,
            true
        );
        // Declare Block Checkout compatibility.
        \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility(
            'cart_checkout_blocks',
            __FILE__,
            true
        );
    }
} );