shinyUI(
  uiOutput("ui")
)

shinyServer(function(input, output, session) {
  #### UI code --------------------------------------------------------------
  output$ui <- dashboardPage(dashboardHeader(title = "My Page"),
                             dashboardSidebar(
                               if (user_input$authenticated == FALSE) {
                                 NULL
                               } else {
                                 sidebarMenuOutput("sideBar_menu_UI")
                               }
                             ),
                             dashboardBody(
                               if (user_input$authenticated == FALSE) {
                                 ##### UI code for login page
                                 uiOutput("uiLogin")
                                 uiOutput("pass")
                               } else {
                                 #### Your app's UI code goes here!
                                 uiOutput("obs")
                                 plotOutput("distPlot")
                               }
                             ))

  #### YOUR APP'S SERVER CODE GOES HERE ----------------------------------------
  # slider input widget
  output$obs <- renderUI({
    sliderInput("obs", "Number of observations:",
                min = 1, max = 1000, value = 500)
  })

  # render histogram once slider input value exists
  output$distPlot <- renderPlot({
    req(input$obs)
    hist(rnorm(input$obs), main = "")
  })

  output$sideBar_menu_UI <- renderMenu({
    sidebarMenu(id = "sideBar_Menu",
                menuItem("Menu 1", tabName="menu1_tab", icon = icon("calendar")),
            menuItem("Menu 2", tabName="menu2_tab", icon = icon("database"))
)
  })

  #### PASSWORD server code ----------------------------------------------------
  # reactive value containing user's authentication status

  # user_input <- reactiveValues(authenticated = FALSE, valid_credentials = FALSE,
  #                              user_locked_out = FALSE, status = "")

  # authenticate user by:
  #   1. checking whether their user name and password are in the credentials
  #       data frame and on the same row (credentials are valid)
  #   2. if credentials are valid, retrieve their lockout status from the data frame
  #   3. if user has failed login too many times and is not currently locked out,
  #       change locked out status to TRUE in credentials DF and save DF to file
  #   4. if user is not authenticated, determine whether the user name or the password
  #       is bad (username precedent over pw) or he is locked out. set status value for
  #       error message code below

  observeEvent(input$login_button, {
    credentials <- readRDS("credentials/credentials.rds")

    row_username <- which(credentials$user == input$user_name)
    row_password <- which(credentials$pw == digest(input$password)) # digest() makes md5 hash of password

        # if user name row and password name row are same, credentials are valid
#   and retrieve locked out status
if (length(row_username) == 1 &&
    length(row_password) >= 1 &&  # more than one user may have same pw
    (row_username %in% row_password)) {
  user_input$valid_credentials <- TRUE
  user_input$user_locked_out <- credentials$locked_out[row_username]
}

# if user is not currently locked out but has now failed login too many times:
#   1. set current lockout status to TRUE
#   2. if username is present in credentials DF, set locked out status in
#     credentials DF to TRUE and save DF
if (input$login_button == num_fails_to_lockout &
    user_input$user_locked_out == FALSE) {

  user_input$user_locked_out <- TRUE

  if (length(row_username) == 1) {
    credentials$locked_out[row_username] <- TRUE

    saveRDS(credentials, "credentials/credentials.rds")
  }
}

# if a user has valid credentials and is not locked out, he is authenticated
if (user_input$valid_credentials == TRUE & user_input$user_locked_out == FALSE) {
  user_input$authenticated <- TRUE
} else {
  user_input$authenticated <- FALSE
}

# if user is not authenticated, set login status variable for error messages below
if (user_input$authenticated == FALSE) {
  if (user_input$user_locked_out == TRUE) {
    user_input$status <- "locked_out"
  } else if (length(row_username) > 1) {
    user_input$status <- "credentials_data_error"
  } else if (input$user_name == "" || length(row_username) == 0) {
    user_input$status <- "bad_user"
  } else if (input$password == "" || length(row_password) == 0) {
    user_input$status <- "bad_password"
  }
}
  })

  # password entry UI componenets:
  #   username and password text fields, login button
  output$uiLogin <- renderUI({
    wellPanel(
      textInput("user_name", "User Name:"),

      passwordInput("password", "Password:"),

      actionButton("login_button", "Log in")
    )
  })

  # red error message if bad credentials
  output$pass <- renderUI({
    if (user_input$status == "locked_out") {
      h5(strong(paste0("Your account is locked because of too manyn",
                       "failed login attempts. Contact administrator."), style = "color:red"), align = "center")
    } else if (user_input$status == "credentials_data_error") {
      h5(strong("Credentials data error - contact administrator!", style = "color:red"), align = "center")
    } else if (user_input$status == "bad_user") {
      h5(strong("User name not found!", style = "color:red"), align = "center")
    } else if (user_input$status == "bad_password") {
      h5(strong("Incorrect password!", style = "color:red"), align = "center")
    } else {
      ""
    }
  })
})