<?php
//Display Fields
add_action( 'woocommerce_product_after_variable_attributes', 'variable_fields', 10, 2 );
//JS to add fields for new variations
add_action( 'woocommerce_product_after_variable_attributes_js', 'variable_fields_js' );
//Save variation fields
add_action( 'woocommerce_process_product_meta_variable', 'save_variable_fields', 10, 1 );

/**
 * For each role create new price field for variations
 *
*/
function variable_fields( $loop, $variation_data ) {
$specific_prices = unserialize($variation_data['_specific_price'][0]);

$roles = get_editable_roles();
echo '<tr><h3>Roles and prices</h3></tr>';

foreach ($roles as $key => $role) {

?>
    <tr>
    <td><?php echo $role['name']?></td>
        <td>

            <?php
            // Text Field
            woocommerce_wp_text_input(
                array(
                    'id'          => '_specific_price['.$loop.']['.$key.']',
                    'desc_tip'    => 'false',
                    'value'       => $specific_prices[$key]
                )
            );
            ?>
        </td>
    </tr>
<?php
}
}

/**
 * Create new fields for new variations
 *
*/
function variable_fields_js() {
$roles = get_editable_roles();
echo '<h3>Ceny pro skupiny zákazníků</h3>';
foreach ($roles as $key => $role) {

?>

    <tr>
    <td><?php echo $role['name']?></td>
        <td>

            <?php
            // Text Field
            woocommerce_wp_text_input(
                array(
                    'id'          => '_specific_price['.$loop.']['.$key.']',
                    'desc_tip'    => 'false',
                    'value'       => $specific_prices[$key]
                )
            );
            ?>
        </td>
    </tr>
<?php
}

}

/**
 * Save new fields for variations
 *
*/
function save_variable_fields( $post_id ) {
    if (isset( $_POST['variable_sku'] ) ) :

        $variable_sku          = $_POST['variable_sku'];
        $variable_post_id      = $_POST['variable_post_id'];

        // Text Field
        $_text_field = $_POST['_specific_price'];

    for ( $i = 0; $i < sizeof( $variable_sku ); $i++ ) :
            $variation_id = (int) $variable_post_id[$i];

      if ( isset( $_text_field[$i] ) ) {
            update_post_meta( $variation_id, '_specific_price', $_text_field[$i] );


        }
        endfor;
    endif;
}


// display the role prices in frontend
add_filter( 'woocommerce_variation_price_html', 'w4dev_woocommerce_variation_prices_html', 10, 2);
add_filter( 'woocommerce_variation_sale_price_html', 'w4dev_woocommerce_variation_prices_html', 10, 2);
add_filter( 'woocommerce_get_price', 'w4dev_woocommerce_variation_prices_html', 10, 2);

function w4dev_woocommerce_variation_prices_html( $price, $product )
{

    $specific_prices = unserialize($product->product_custom_fields['_specific_price'][0]);
    $role = get_user_role();
    if (isset($specific_prices[$role]) && $specific_prices[$role] != '')
      $price = $specific_prices[$role];

    return $price;
}


// Get user role
function get_user_role() {
    global $current_user;
    $user_roles = $current_user->roles;
    $user_role = array_shift($user_roles);

    return $user_role;
}