Switch Subscription - Add Directly To Cart

Here's what we got. We can add it to cart with specific URL arguments: Product, User Subscription ID, New Subscription ID, Subscription Order Line Number, and a nonce. Do not we did this on a single product with subscriptions as variations. This may need to be tweaked in other subscription cases but hopefully it's helpful to someone down the road:

/** * Generate cart button based on subscription variation ID * * @param Array $args * * @return void */function prefix_subscriptions_checkout_button( $args = array() ) {    $button_arr = wp_parse_args( $args, array(        'variation_id'  => 0,        'btn_class'     => array( 'button', 'button-primary' ),        'btn_text'      => __( 'Sign Up' ),        'btn_atts'      => array(),    ) );    $button_arr['btn_url'] = do_shortcode( '[add_to_cart_url id="' . intval( $button_arr['variation_id'] ) . '"]' );    if( is_user_logged_in() && function_exists( 'wcs_get_users_subscriptions' ) ) {        // Grab an array of user subscriptions        $user_subscriptions = wcs_get_users_subscriptions();        if( ! empty( $user_subscriptions ) ) {            // Array( 'Subscription ID' => WC_Subscriptions Object );            foreach( $user_subscriptions as $user_subscription_id => $subscription ) {                // Loop through the users subscription order items to get the subscription order line item                foreach( $subscription->get_items() as $item_line_number => $item_arr ) {                    if( $user_subscription_id == $item_arr['order_id'] ) {                        if( $item_arr['variation_id'] == $button_arr['variation_id'] ) {                            // Change button based on status                            switch( $subscription->get_status() ) {                                case 'on-hold':                                    $button_arr['btn_text']     = __( 'On Hold' );                                    $button_arr['btn_class']    = array( 'button', 'button-secondary' );                                    $button_arr['btn_url']      = 'javascript:void(0);';                                  break;                                case 'active':                                    $button_arr['btn_text']     = __( 'Current' );                                    $button_arr['btn_class']    = array( 'button', 'button-secondary' );                                    $button_arr['btn_url']      = 'javascript:void(0);';                                  break;                                default:                                    $button_arr['btn_url'] = add_query_arg( array(                                            'add-to-cart'           => $item_arr['product_id'],                                            'switch-subscription'   => $user_subscription_id,                                            'variation_id'          => $button_arr['variation_id'],                                            'item'                  => $item_line_number,                                            '_wcsnonce'             => wp_create_nonce( 'wcs_switch_request' )                                        ),                                        wc_get_cart_url()                                    );                            }                        }                    }                }            }        }    }    // Create button attributes    $button_atts = '';    if( ! empty( $button_arr['btn_atts'] ) && is_array( $button_arr['btn_atts'] ) ) {        foreach( $button_arr['btn_atts'] as $attribute => $value ) {            $button_atts .= sprintf( ' %1$s="%2$s"', esc_attr( $attribute ), esc_attr( $value ) );        }    }    // Create button Classes    if( ! empty( $button_arr['btn_class'] ) && is_array( $button_arr['btn_class'] ) ) {        array_walk( $button_arr['btn_class'], 'esc_attr' );        $button_arr['btn_class'] = implode( ' ', $button_arr['btn_class'] );    }    // Display Button    printf( '<a href="%1$s" class="%2$s"%3$s>%4$s</a>',        $button_arr['btn_url'],        esc_attr( $button_arr['btn_class'] ),        ( ! empty( $button_atts ) ) ? $button_atts : '',        $button_arr['btn_text']    );}