What is the simplest way to make an interactive bar plot with multiple drop down filters with Shiny and ggplot combo?

I know it sounds a bit basic, but I would like to make an interactive barplot which can handle multiple x and y axis whether the user would like to use it.

I started it like this way however I know there are many things which are need to be added.

library(dplyr)
library(shiny)

# Sample workable data

sample <- data.frame("Country" = c("Australia", "Bangladesh",
                                     "Argentina", "Slovakia", "Greece", "Sweden"),
                       "Attribute1" = 57:62,
                       "Attribute2" = 13:18,
                       "Attribute3" = 5:10)

# Since I cannot enter the choices one by one..

Atts <- sample %>%
  select(Attribute1:Attribute3) %>%
  names() 

Ctrs <- unique(sample$Country)


# Define UI for application that draws a histogram
ui <- fluidPage(

  # Application title
  titlePanel("Sample Drop Down"),

  # Sidebar with dropdown

  sidebarLayout(
    sidebarPanel(
      selectInput(inputId = "selects", choices = Ctrs,
                  label = "Select Region", multiple = TRUE),
      selectInput(inputId = "selects2", choices = Atts, label = "select attribute",
                  multiple = TRUE)
    ),

    # Show a plot of the generated distribution
    mainPanel(
      plotOutput("Plot")
    )
  )
)



# Define server logic required to draw a histogram
server <- function(input, output) {

  output$Plot <- renderPlot({
    ggplot(data = sample, aes(x = input$selects, y= input$selects2)) + 
      geom_bar(stat = "identity", color = "blue", fill = "Country")
  })
}

# Run the application 
shinyApp(ui = ui, server = server)

So how do I link the UI and Server part together?