Add a handling fee for CVR Payment Gateway

cvr-payment-gateway-handling-fee.php

<?php

if ( class_exists( 'WooCommerce' ) ) {
    add_action( 'woocommerce_cart_calculate_fees', 'yanco_cvr_calculate_totals' );
    function yanco_cvr_calculate_totals( ) {
		$available_gateways = WC()->payment_gateways->get_available_payment_gateways();
	    $current_gateway = '';
        $fee_title = __('CVR Handling Fee', 'woocommerce-cvr-payment-gateway'); // Change the title to fit your needs
        $cvr_handling_fee = 50; // Change the value to the amount you want to charge
        $fee_tax_class = 'zero rate'; // Change this to the tax class you wish to use for the fee
    		if ( ! empty( $available_gateways ) ) {
    	        // Chosen Method
    	        if ( isset( WC()->session->chosen_payment_method ) && isset( $available_gateways[ WC()->session->chosen_payment_method ] ) ) {
    				$current_gateway = $available_gateways[ WC()->session->chosen_payment_method ];
    	        } elseif ( isset( $available_gateways[ get_option( 'woocommerce_default_gateway' ) ] ) ) {
    	            $current_gateway = $available_gateways[ get_option( 'woocommerce_default_gateway' ) ];
    	        } else {
    	            $current_gateway = current( $available_gateways );
    	        }
    	    }
    		if ( $current_gateway->id == 'yanco_wc_cvr_payment_gateway' ) {
    			WC()->cart->add_fee( $fee_title, $cvr_handling_fee, true, $fee_tax_class );
    		}
    }
}