library(shiny)
library(bslib)

# Define UI for slider demo app ----
ui <- page_sidebar(

  # App title ----
  title = "Downloading Data",

  # Sidebar panel for inputs ----
  sidebar = sidebar(

    # Input: Choose dataset ----
    selectInput(
      "dataset",
      "Choose a dataset:",
      choices = c("rock", "pressure", "cars")
    ),

    # Button
    downloadButton("downloadData", "Download")
  ),
  tableOutput("table")
)

# Define server logic to display and download selected file ----
server <- function(input, output) {

  # Reactive value for selected dataset ----
  datasetInput <- reactive({
    switch(
      input$dataset,
      "rock" = rock,
      "pressure" = pressure,
      "cars" = cars
    )
  })

  # Table of selected dataset ----
  output$table <- renderTable({
    datasetInput()
  })

  # Downloadable csv of selected dataset ----
  output$downloadData <- downloadHandler(
    filename = function() {
      paste(input$dataset, ".csv", sep = "")
    },
    content = function(file) {
      write.csv(datasetInput(), file, row.names = FALSE)
    }
  )
}

# Create Shiny app ----
shinyApp(ui, server)