Coupon Code shouldn't get mixed up with the customized Discount - php

Question

I have a Checkout page using Woocommerce where I have Discount added using the following code since I have a checkbox where user could check and the discount will apply. Here is the products page, please add any of them and proceed to Checkout page where you will get that Discount Checbox with label "Senior, Military, etc.". You can try entering "SAVE15" for the coupon code to apply.
// Add a custom checkbox fields after billing fields
function action_woocommerce_after_checkout_billing_form( $checkout ) {
// Add a custom checkbox field
echo '<h3 class="discount-type">' . __('DISCOUNT TYPE') . '</h3>';
woocommerce_form_field( 'discount30', array(
'type' => 'checkbox',
'label' => __( ' Senior, Military, Police, Firefighter, EMT Discount, Teacher',
'woocommerce' ),
'class' => array( 'form-row-wide' ),
), '' );
}
add_action( 'woocommerce_after_checkout_billing_form',
'action_woocommerce_after_checkout_billing_form', 10, 1 );
// Remove "(optional)" label on "discount30" field
function filter_woocommerce_form_field( $field, $key, $args, $value ) {
// Only on checkout page
if ( $key === 'discount30' && is_checkout() ) {
$optional = ' <span class="optional">(' . esc_html__( 'optional', 'woocommerce' ) .
')</span>';
$field = str_replace( $optional, '', $field );
}
return $field;
}
add_filter( 'woocommerce_form_field' , 'filter_woocommerce_form_field', 10, 4 );
// jQuery - Ajax script
function action_wp_footer() {
// Only on Checkout
if ( is_checkout() && ! is_wc_endpoint_url() ) :
if ( WC()->session->__isset('enable_fee') )
WC()->session->__unset('enable_fee')
?>
<script type="text/javascript">
jQuery( function($){
if ( typeof wc_checkout_params === 'undefined' )
return false;
$( 'form.checkout' ).on( 'change', 'input[name=discount30]', function(e) {
var fee = $(this).prop('checked') === true ? '1' : '';
$.ajax({
type: 'POST',
url: wc_checkout_params.ajax_url,
data: {
'action': 'enable_fee',
'enable_fee': fee,
},
success: function (result) {
$('body').trigger('update_checkout');
},
});
});
});
</script>
<?php
endif;
}
add_action( 'wp_footer', 'action_wp_footer' );
// Get Ajax request and saving to WC session
function get_enable_fee() {
if ( isset($_POST['enable_fee']) ) {
WC()->session->set( 'enable_fee', ( $_POST['enable_fee'] ? true : false ) );
}
die();
}
add_action( 'wp_ajax_enable_fee', 'get_enable_fee' );
add_action( 'wp_ajax_nopriv_enable_fee', 'get_enable_fee' );
// Add a custom 3 Cents Discount
function action_woocommerce_cart_calculate_fees( $cart ) {
// Only on checkout
if ( ( is_admin() && ! defined( 'DOING_AJAX' ) ) || ! is_checkout() )
return;
// Get number of items in the cart.
$items_in_cart = $cart->get_cart_contents_count();
// Calculate
$discount = 0.03 * $items_in_cart;
// Apply discount
if ( WC()->session->get('enable_fee') ) {
$cart->add_fee( __( 'Discount', 'woocommerce' ), -$discount );
}
}
add_action( 'woocommerce_cart_calculate_fees', 'action_woocommerce_cart_calculate_fees', 10, 1
);
Now, I'm using Coupon Code as well but don't want it to get mixed up so, how can I make a condition that if someone enter the Coupon Code, the discount that ABOVE code applies should be removed?