library(shiny)
library(bslib)

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

  # App title ----
  title = "Uploading Files",

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

    # Input: Select a file ----
    fileInput(
      "file1",
      "Choose CSV File",
      multiple = TRUE,
      accept = c(
        "text/csv",
        "text/comma-separated-values,text/plain",
        ".csv"
      )
    ),

    # Horizontal line ----
    tags$hr(),

    # Input: Checkbox if file has header ----
    checkboxInput("header", "Header", TRUE),

    # Input: Select separator ----
    radioButtons(
      "sep",
      "Separator",
      choices = c(
        Comma = ",",
        Semicolon = ";",
        Tab = "\t"
      ),
      selected = ","
    ),

    # Input: Select quotes ----
    radioButtons(
      "quote",
      "Quote",
      choices = c(
        None = "",
        "Double Quote" = '"',
        "Single Quote" = "'"
      ),
      selected = '"'
    ),

    # Horizontal line ----
    tags$hr(),

    # Input: Select number of rows to display ----
    radioButtons(
      "disp",
      "Display",
      choices = c(
        Head = "head",
        All = "all"
      ),
      selected = "head"
    )
  ),

  # Output: Data file ----
  tableOutput("contents")
)

# Define server logic to read selected file ----
server <- function(input, output) {
  output$contents <- renderTable({
    # input$file1 will be NULL initially. After the user selects
    # and uploads a file, head of that data file by default,
    # or all rows if selected, will be shown.

    req(input$file1)

    df <- read.csv(
      input$file1$datapath,
      header = input$header,
      sep = input$sep,
      quote = input$quote
    )

    if (input$disp == "head") {
      return(head(df))
    } else {
      return(df)
    }
  })
}

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