Unique Thank-You Coupon in the Order Completed Email

$wpide_thanks_coupon = array(
    'type'    => 'percent', // percent or fixed_cart.
    'amount'  => 10,
    'days'    => 60,        // Days until it expires.
    'prefix'  => 'THANKS-',
);

add_action( 'woocommerce_order_status_completed', function ( $order_id, $order = null ) use ( $wpide_thanks_coupon ) {
    $order = $order instanceof WC_Order ? $order : wc_get_order( $order_id );

    if ( ! $order || $order->get_meta( '_wpide_thanks_coupon' ) || ! $order->get_billing_email() ) {
        return;
    }

    $code   = $wpide_thanks_coupon['prefix'] . strtoupper( wp_generate_password( 8, false, false ) );
    $coupon = new WC_Coupon();
    $coupon->set_code( $code );
    $coupon->set_discount_type( $wpide_thanks_coupon['type'] );
    $coupon->set_amount( $wpide_thanks_coupon['amount'] );
    $coupon->set_usage_limit( 1 );
    $coupon->set_individual_use( true );
    $coupon->set_email_restrictions( array( $order->get_billing_email() ) );
    $coupon->set_date_expires( time() + $wpide_thanks_coupon['days'] * DAY_IN_SECONDS );
    $coupon->set_description( 'Thank-you coupon for order #' . $order->get_order_number() );
    $coupon->save();

    $order->update_meta_data( '_wpide_thanks_coupon', $code );
    $order->save_meta_data();
}, 1, 2 );

add_action( 'woocommerce_email_after_order_table', function ( $order, $sent_to_admin, $plain_text, $email ) use ( $wpide_thanks_coupon ) {
    $code = $order->get_meta( '_wpide_thanks_coupon' );

    if ( $sent_to_admin || ! $code || ! $email || 'customer_completed_order' !== $email->id ) {
        return;
    }

    $offer = 'percent' === $wpide_thanks_coupon['type'] ? $wpide_thanks_coupon['amount'] . '%' : wp_strip_all_tags( wc_price( $wpide_thanks_coupon['amount'] ) );
    $text  = sprintf( 'Thank you! Here is %1$s off your next order with code %2$s, valid for %3$d days.', $offer, $code, $wpide_thanks_coupon['days'] );

    if ( $plain_text ) {
        echo esc_html( $text ) . "\n\n";
        return;
    }

    printf( '<div style="margin:20px 0;padding:16px;border:2px dashed #7f54b3;text-align:center"><p style="margin:0 0 8px">%1$s</p><p style="margin:0;font-size:22px;font-weight:700;letter-spacing:2px">%2$s</p></div>', esc_html( sprintf( 'Thank you! Enjoy %1$s off your next order (valid %2$d days):', $offer, $wpide_thanks_coupon['days'] ) ), esc_html( $code ) );
}, 10, 4 );