WooCommerce Coupon generator with limit

/**
 * Convert myCRED Points into WooCommerce Coupon
 * @version 1.2
 */
add_shortcode( 'mycred_to_woo_coupon', 'mycred_pro_render_points_to_coupon' );
function mycred_pro_render_points_to_coupon( $atts, $content = NULL ) {
    // Users must be logged in
    if ( ! is_user_logged_in() )
        return 'You must be logged in to generate store coupons.';

    // myCRED must be enabled
    if ( ! function_exists( 'mycred_get_settings' ) )
        return 'myCRED must be enabled to use this shortcode';

    extract( shortcode_atts( array(
        'exchange'     => 1,
        'type'         => 'mycred_default',
        'button_label' => 'Create Coupon'
    ), $atts ) );

    // Load myCRED
    $mycred = mycred( $type );

    // Prep
    $error = $code = false;
    $output = '';
    $user_id = get_current_user_id();

    // No need to show this for excluded users
    if ( $mycred->exclude_user( $user_id ) ) return;

    $balance = $mycred->get_users_balance( $user_id );

    // Form submission
    if ( isset( $_POST['mycred_to_woo'] ) && wp_verify_nonce( $_POST['mycred_to_woo']['token'], 'points-to-woo-coupon' ) ) {

        // Make sure amounts are always positive
        $amount = abs( $_POST['mycred_to_woo']['amount'] );

        // Exchange rate
        $value = $mycred->number( $amount*$exchange );

        // Make sure amount is not zero
        if ( $amount == $mycred->zero() )
            $error = 'Amount can not be zero';

        // Make sure user has enough points
        if ( $amount > $balance )
            $error = 'Insufficient Funds. Please try a lower amount';

        // If no errors
        if ( $error === false ) {

            // Deduct points from user
            $charge = $mycred->add_creds(
                'points_to_coupon',
                $user_id,
                0-$amount,
                '%plural% conversion into store coupon: %post_title%',
                $new_coupon_id,
                array( 'ref_type' => 'post', 'code' => $code ),
                $type
            );

            // If points were deducted create coupon
            if ( $charge === true ) {

                // Create Woo Coupon
                $code = wp_generate_password( 12, false, false );
                $new_coupon_id = wp_insert_post( array(
                    'post_title'   => $code,
                    'post_content' => '',
                    'post_status'  => 'publish',
                    'post_author'  => 1,
                    'post_type'    => 'shop_coupon'
                ) );

                $balance = $balance-$amount;
                $balance = $mycred->number( $balance );

                // Update Coupon details
                update_post_meta( $new_coupon_id, 'discount_type', 'fixed_cart' );
                update_post_meta( $new_coupon_id, 'coupon_amount', $value );
                update_post_meta( $new_coupon_id, 'individual_use', 'no' );
                update_post_meta( $new_coupon_id, 'product_ids', '' );
                update_post_meta( $new_coupon_id, 'exclude_product_ids', '' );

                // Make sure you set usage_limit to 1 to prevent duplicate usage!!!
                update_post_meta( $new_coupon_id, 'usage_limit', 1 );
                update_post_meta( $new_coupon_id, 'usage_limit_per_user', 1 );
                update_post_meta( $new_coupon_id, 'limit_usage_to_x_items', '' );
                update_post_meta( $new_coupon_id, 'usage_count', '' );
                update_post_meta( $new_coupon_id, 'expiry_date', '' );
                update_post_meta( $new_coupon_id, 'apply_before_tax', 'yes' );
                update_post_meta( $new_coupon_id, 'free_shipping', 'no' );
                update_post_meta( $new_coupon_id, 'product_categories', array() );
                update_post_meta( $new_coupon_id, 'exclude_product_categories', array() );
                update_post_meta( $new_coupon_id, 'exclude_sale_items', 'no' );
                update_post_meta( $new_coupon_id, 'minimum_amount', '' );
                update_post_meta( $new_coupon_id, 'customer_email', array() );

            }

            // Could not charge
            else {

                $error = 'You have reached your daily limit and can not create a coupon.';

            }

        }

    }

    // Show users current balance
    $output .= '
<p>Your current balance is: ' . $mycred->format_creds( $balance ) . '</p>';

    // Error
    if ( $error !== false )
        $output .= '<p style="color:red;">' . $error . '</p>';

    // Success
    elseif ( $code !== false )
        $output .= '<p>Your coupon code is: <strong>' . $code . '</strong></p>';

    // The form for those who have points
    if ( $balance > $mycred->zero() )
        $output .= '
<form action="" method="post">
    <input type="hidden" name="mycred_to_woo[token]" value="' . wp_create_nonce( 'points-to-woo-coupon' ) . '" />
    <label>Amount</label>
    <input type="text" size="5" name="mycred_to_woo[amount]" value="" />
    <input type="submit" name="submit" value="' . $button_label . '" />
</form>';

    // Not enough points
    else
        $output .= '<p>Not enough points to create coupons.</p>';

    return $output;
}