Add custom stock status to products in WooCommerce

// Add new stock status options
function filter_woocommerce_product_stock_status_options( $status ) {
    // Add new statuses
    $status['pre_order'] = __( 'Pre order', 'woocommerce' );
    $status['contact_us'] = __( 'Contact us', 'woocommerce' );

    return $status;
}
add_filter( 'woocommerce_product_stock_status_options', 'filter_woocommerce_product_stock_status_options', 10, 1 );

// Availability text
function filter_woocommerce_get_availability_text( $availability, $product ) {
    switch( $product->get_stock_status() ) {
        case 'pre_order':
            $availability = __( 'Pre order', 'woocommerce' );
        break;
        case 'contact_us':
            $availability = __( 'Contact us', 'woocommerce' ); 
        break;
    }

    return $availability; 
}
add_filter( 'woocommerce_get_availability_text', 'filter_woocommerce_get_availability_text', 10, 2 );

// Availability class
function filter_woocommerce_get_availability_class( $class, $product ) {
    switch( $product->get_stock_status() ) {
        case 'pre_order':
            $class = 'pre-order'; 
        break;
        case 'contact_us':
            $class = 'contact-us'; 
        break;
    }

    return $class;
}
add_filter( 'woocommerce_get_availability_class', 'filter_woocommerce_get_availability_class', 10, 2 );

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