Adding an action (reset) button to the R shiny DT table - r

Question

I modified the example here to include a save button as well. I want the user to be able to reset to the initial table after uploading a new file by adding a reset button (similar to the save button), but I wonder if it's possible to do so.
EDIT:
I want the button to be a part of the DT table and be placed next to the save.
library(shiny)
library(DT)
library(dplyr)
ui <- fluidPage(
fileInput("upload", NULL, accept = c(".csv")),
DTOutput("head")
)
server <- function(input, output, session) {
rv <- reactiveValues(
dataframe = data.frame(
x = seq(1:12),
y = LETTERS[1:12])
)
observe({
req(input$upload)
ext <- tools::file_ext(input$upload$name)
rv$dataframe <- switch(ext,
csv = read.csv(input$upload$datapath),
NULL)
})
output$head <- renderDT({
validate(need(!is.null(rv$dataframe)," Please upload a .csv file"))
datatable(rv$dataframe, extensions = 'Buttons',
options = list(
dom = 'Bfrtip',
buttons = list(list( extend = 'csv',
filename = '//public/comments/comments.csv',
text = 'Save'))))
})
}
shinyApp(ui, server)
Here is a snapshot of the current version:

Answer 1

There could be multiple ways to handle this. Here is one of it -
Used a fixed dataframe mtcars[1:6, 1:6] as the default dataframe instead of one which generates random numbers which is difficult to compare imo.
Added an actionButton for Reset feature.
Created another reactive variable called dataframe_copy which always holds the default dataframe.
library(shiny)
library(DT)
library(dplyr)
ui <- fluidPage(
fileInput("upload", NULL, accept = c(".csv")),
DTOutput("head"),
actionButton('reset', 'Reset')
)
server <- function(input, output, session) {
rv <- reactiveValues(
dataframe = mtcars[1:6, 1:6],
dataframe_copy = mtcars[1:6, 1:6]
)
observe({
req(input$upload)
ext <- tools::file_ext(input$upload$name)
rv$dataframe <- switch(ext,
csv = read.csv(input$upload$datapath),
NULL)
})
observeEvent(input$reset, {
rv$dataframe <- rv$dataframe_copy
})
output$head <- renderDT({
validate(need(!is.null(rv$dataframe)," Please upload a .csv file"))
datatable(rv$dataframe, extensions = 'Buttons',
options = list(
dom = 'Bfrtip',
buttons = list(list( extend = 'csv',
filename = '//public/comments/comments.csv',
text = 'Save'))))
})
}
shinyApp(ui, server)