distinguish links and nodes in sankeyPlot using event_data

I am building a sankey plot using plotly package with R within a Shiny application.
At some point, I use event_data function which returns an index pointNumber which is an integer ranging from 0 to the number of pairwise nodes relationships.
When performing sankeyPlot in plotly you have to specify the node and link arguments. The problem is that pointNumber provides an index which I cannot distinguish between the node or the link.
I would like the app could identify if the user clicks on a node or on a link.

Here is a toy example. Note that when clicking on node "A", pointNumber returns 0, and the same when clicking on link connecting node "A" and node "B".

library(plotly); library(shiny)
ui <- fluidPage(
  plotlyOutput("plot"),
  verbatimTextOutput("index")
)
server <- function(input, output){
  output$index <- renderPrint({
    event_data("plotly_click", source="sankeyPlot")
  })
  output$plot <- renderPlotly({
    plot_ly(
      source = "sankeyPlot",
      type = "sankey",
      arrangement = "fixed",
      node = list(label = c("A","B","C","D"), hoverinfo="none"),
      link = list(source=c(0,0,1,2), target=c(1,2,3,3), value=c(2,5,2,1), hoverinfo="none")
    )
  })
}
shinyApp(ui, server)

Inizia con il semplice esempio Shiny che usa event_data("plotly_click") sul grafico sankey e analizza il pointNumber restituito per i clic sui nodi e sui link. Traccia il modo in cui vengono rappresentati gli eventi di sankeyPlot e determina come i dati restituiti possano distinguere l’elemento su cui è stato fatto clic. Il lavoro è completato quando l’app può identificare in modo affidabile se un clic ha come destinazione un nodo o un link.