Checkout Block custom fee checkbox

// Register Checkout Field
add_action( 'woocommerce_init', function() {

	if( ! function_exists( 'woocommerce_register_additional_checkout_field' ) ) {
		return;
	}

	woocommerce_register_additional_checkout_field(
		[
			'id' => 'ccom/custom_fee',
			'label' => 'Custom Fee +5%',
			'type' => 'checkbox',
			'location' => 'order',
			'required' => false,
		]
	);

} );

// Repopulate Field Value
add_filter(
	'woocommerce_get_default_value_for_ccom/custom_fee',
	function( $value, $group, $wc_object ) {
	if( WC()->session && WC()->session->get( 'ccom_custom_fee' ) ) {
		return WC()->session->get( 'ccom_custom_fee' );
	}
	return $value;
}, 10, 3 );

// AJAX To Process Field Dynamically
add_action( 'wp_footer', function() {

	if( ! is_checkout() ) {
		return;
	}

	?>
	<script type="text/javascript">

	document.addEventListener( 'DOMContentLoaded', function() {

		document.body.addEventListener( 'change', function( event ) {

			if( ! event.target || event.target.id !== 'order-ccom-custom_fee' ) {
				return;
			}

			if( ! window.wp || ! window.wp.data || ! window.wp.data.dispatch ) {
				return;
			}

			let checkbox = document.getElementById( 'order-ccom-custom_fee' );

			fetch( '/wp-json/ccom/v1/custom_fee', {
				method: 'POST',
				headers: {
					'Content-Type': 'application/json',
					'X-WP-Nonce': "<?php echo wp_create_nonce( 'wp_rest' ); ?>"
				},
				body: JSON.stringify( {
					apply: checkbox.checked
				} )
			} )
				.then( response => response.json() )
				.then( data => {
					if( data.success ) {
						const event = new CustomEvent( 'wc-blocks_added_to_cart' );
						document.body.dispatchEvent( event );
					}
				} )
				.catch( error => console.error( 'Error modifying cart fee:', error )
			);

		} );

	} );

	</script>
	<?php

} );

// Fee Line Item On Cart
add_action( 'woocommerce_cart_calculate_fees', function( $cart ) {

	if( is_admin() && ! defined( 'DOING_AJAX' ) ) {
		return;
	}

	$ccom_custom_fee = WC()->session->get( 'ccom_custom_fee' );

	if( $ccom_custom_fee ) {
		$cart->add_fee(
			'Custom Fee',
			(float) $cart->get_subtotal() * 0.05,
			false
		);
	}

} );

// REST API Endpoint
add_action( 'rest_api_init', function() {

    register_rest_route( 'ccom/v1', '/custom_fee', [

        'methods' => 'POST',
        'callback' => function( $request ) {

			$params = $request->get_json_params();
			$status = isset( $params['apply'] ) ? (bool) $params['apply'] : false;

			if( function_exists('WC') && null === WC()->session ) {
				WC()->frontend_includes();
				if( function_exists( 'wc_load_cart' ) ) {
					wc_load_cart();
				} else {
					WC()->session = new WC_Session_Handler;
					WC()->session->init();
				}
			}

			if( WC()->session ) {
				WC()->session->set( 'ccom_custom_fee', $status );
				WC()->cart->calculate_totals();
				return new WP_REST_Response(
					[ 'success' => true, 'fee_applied' => $status ],
					200
				);
			}

			return new WP_REST_Response( [ 'success' => false ], 400 );
		},
        'permission_callback' => '__return_true',

    ] );

} );