app.R

library(shiny)
library(shinyjs)
library(shinyalert)
library(tidyverse)
library(shinythemes)

val <- reactiveValues(txt = NULL, users = c(),
                      new_usr = NULL, usr_left =NULL)

intro <-"
##      ## ######## ##        ######   #######  ##     ## ########    
##  ##  ## ##       ##       ##    ## ##     ## ###   ### ##          
##  ##  ## ##       ##       ##       ##     ## #### #### ##          
##  ##  ## ######   ##       ##       ##     ## ## ### ## ######      
##  ##  ## ##       ##       ##       ##     ## ##     ## ##          
##  ##  ## ##       ##       ##    ## ##     ## ##     ## ##          
 ###  ###  ######## ########  ######   #######  ##     ## ########    
"

# intro <- "Welcome to my wonderland"

if (file.exists("chat_txt.Rds")) {
  val$txt <- readRDS("chat_txt.Rds")
} else {
  val$txt <- intro
}

jsCode <- "
// send message on enter
jQuery(document).ready(function(){
  jQuery('#text_msg').keypress(function(evt){
    if (evt.keyCode == 13){
      // Enter, simulate clicking send
      jQuery('#send').click();
      jQuery('#text_msg').html('hihihi');
    }
  });
})

// auto scroll to bottom
var oldContent = null;
window.setInterval(function() {
  var elem = document.getElementById('chat_window');
  if (oldContent != elem.innerHTML){
    scrollToBottom();
  }
  oldContent = elem.innerHTML;
}, 300);

// Scroll to the bottom of the chat window.
function scrollToBottom(){
  var elem = document.getElementById('chat_window');
  elem.scrollTop = elem.scrollHeight;
}"

ui <- fluidPage(
  theme = shinytheme("superhero"),
  shinyjs::useShinyjs(),
  useShinyalert(),
  tags$head(
    tags$link(rel = "stylesheet", type = "text/css", href = "style.css")
  ),
  extendShinyjs(text = jsCode, functions = c()),
  fluidRow(
    column(width = 6,
           h2("Anonymous chat")),
    column(
      width = 6,
      align = "right",
      br(),
      htmlOutput("logged_usr")
    )
  ),
  div(style = "height : 500px;",
      fluidRow(
        column(
          width = 9,
          verbatimTextOutput("chat_window"),
          tags$head(tags$style("")),
          uiOutput("notify")
        ),
        column(width = 3,
               h5("Active Users"),
               hr(),
               textOutput("users"))
      )
      ),
  fluidRow(column(
    width = 9,
    textInput("text_msg", "", 
              value = "", width = "100%",
              placeholder = "Enter you message"),
  ),
  column(width = 3,
         br(),
         actionButton("send", "Send",
                      width = "100%")))
)

server <- function(input, output, session) {
  
  # renaming your user name ----
  observeEvent("", {
    username <- paste0("Username", round(runif(1, 10000, 99999)))
    shinyalert(
      inputId = "username" ,
      "Welcome to Anonymous Chat",
      html = TRUE,
      text = tagList(
        textInput("uname", "Please rename yourself", value = username),
      ),
      closeOnEsc = FALSE,
      closeOnClickOutside = FALSE,
      showCancelButton = FALSE,
      showConfirmButton = TRUE
    )
  })
  # ----
  
  # to display new user joined ----
  observeEvent(input$username, {
    val$users <- c(val$users, input$uname)
    paste0("New user joined : ", input$uname) -> new_usr
    # showNotification(new_usr,
    #                  duration = 3,
    #                  type = "message")
    print(new_usr)
    print(val$users)
  })
  
  output$users <- renderText({paste(val$users, collapse = '\n')})
  # ----
  
  output$logged_usr <- renderText({
    paste("<b>", input$uname, "</b>")
  })

  # sending msg ----
  observeEvent(input$send, {
    
    # if the txt msg is empty
    if (input$text_msg == "") {
      shinyalert(
        "Oops!", "Can't send a blank message",
        type = "error", closeOnEsc = TRUE,
        timer = 3000, closeOnClickOutside = TRUE,
        showCancelButton = FALSE, showConfirmButton = TRUE
      )
    } else{
      if(object.size(val$txt)>50000){
        val$txt <- intro
      }
      new <- paste(Sys.time(), "#", input$uname, ":" , input$text_msg)
      
      val$txt <- paste(val$txt, new, sep = '\n')
      
      updateTextInput(session, "text_msg", value = "")
      
      saveRDS(val$txt, "chat_txt.Rds")
    }
  })
  
  output$chat_window <- renderText({val$txt })
  # ----
  
  # update the active user list on exit ----
  session$onSessionEnded(function(){
    isolate({
    val$users <- val$users[val$users != input$uname]
    paste0("user : ", input$uname, " left the room") -> usr_left
    print(usr_left)
    print(val$users)
    })
  })
  # ----
  
}

shinyApp(ui, server)