cleanupPasswordFile <- function(appDir) {

  check_directory(appDir)
  appDir <- normalizePath(appDir)

  # get data dir from appDir
  dataDir <- file.path(appDir, "shinyapps")

  # get password file
  passwordFile <- file.path(dataDir, paste("passwords", ".txt", sep = ""))

  # check if password file exists
  if (file.exists(passwordFile)) {
    message("WARNING: Password file found! This application is configured to use scrypt ",
            "authentication, which is no longer supported.\nIf you choose to proceed, ",
            "all existing users of this application will be removed, ",
            "and will NOT be recoverable.\nFor for more information please visit: ",
            "http://shiny.rstudio.com/articles/migration.html")
    response <- readline("Do you want to proceed? [Y/n]: ")
    if (tolower(substring(response, 1, 1)) != "y") {
      stop("Cancelled", call. = FALSE)
    } else {
      # remove old password file
      file.remove(passwordFile)
    }
  }

  invisible(TRUE)
}

#' Add authorized user to application
#'
#' @param email Email address of user to add.
#' @param appDir Directory containing application. Defaults to
#'   current working directory.
#' @param appName Name of application.
#' @inheritParams deployApp
#' @param sendEmail Send an email letting the user know the application
#'   has been shared with them.
#' @param emailMessage Optional character vector of length 1 containing a
#'   custom message to send in email invitation. Defaults to NULL, which
#'   will use default invitation message.
#' @seealso [removeAuthorizedUser()] and [showUsers()]
#' @note This function works only for ShinyApps servers.
#' @export
addAuthorizedUser <- function(email, appDir = getwd(), appName = NULL,
                              account = NULL, server = NULL, sendEmail = NULL,
                              emailMessage = NULL) {

  accountDetails <- accountInfo(account, server)
  checkShinyappsServer(accountDetails$server)

  # resolve application
  if (is.null(appName))
    appName <- basename(appDir)
  application <- resolveApplication(accountDetails, appName)

  # check for and remove password file
  cleanupPasswordFile(appDir)

  # fetch authoriztion list
  api <- clientForAccount(accountDetails)
  api$inviteApplicationUser(application$id, validateEmail(email), sendEmail,
                            emailMessage)

  message(paste("Added:", email, "to application", sep = " "))

  invisible(TRUE)
}

#' Remove authorized user from an application
#'
#' @param user The user to remove. Can be id or email address.
#' @param appDir Directory containing application. Defaults to
#' current working directory.
#' @param appName Name of application.
#' @inheritParams deployApp
#' @seealso [addAuthorizedUser()] and [showUsers()]
#' @note This function works only for ShinyApps servers.
#' @export
removeAuthorizedUser <- function(user, appDir = getwd(), appName = NULL,
                                 account = NULL, server = NULL) {

  accountDetails <- accountInfo(account, server)
  checkShinyappsServer(accountDetails$server)

  # resolve application
  if (is.null(appName))
    appName <- basename(appDir)
  application <- resolveApplication(accountDetails, appName)

  # check and remove password file
  cleanupPasswordFile(appDir)

  # get users
  users <- showUsers(appDir, appName, account, server)

  if (is.numeric(user)) {
    # lookup by id
    if (user %in% users$id) {
      user <- users[users$id == user, ]
    } else {
      stop("User ", user, " not found", call. = FALSE)
    }
  } else {
    # lookup by email
    if (user %in% users$email) {
      user <- users[users$email == user, ]
    } else {
      stop("User \"", user, "\" not found", call. = FALSE)
    }
  }

  # remove user
  api <- clientForAccount(accountDetails)
  api$removeApplicationUser(application$id, user$id)

  message(paste("Removed:", user$email, "from application", sep = " "))

  invisible(TRUE)
}

#' List authorized users for an application
#'
#' @param appDir Directory containing application. Defaults to
#'   current working directory.
#' @param appName Name of application.
#' @inheritParams deployApp
#' @seealso [addAuthorizedUser()] and [showInvited()]
#' @note This function works only for ShinyApps servers.
#' @export
showUsers <- function(appDir = getwd(), appName = NULL, account = NULL,
                      server = NULL) {

  accountDetails <- accountInfo(account, server)
  checkShinyappsServer(accountDetails$server)

  # resolve application
  if (is.null(appName))
    appName <- basename(appDir)
  application <- resolveApplication(accountDetails, appName)

  # fetch authoriztion list
  api <- clientForAccount(accountDetails)
  res <- api$listApplicationAuthorization(application$id)

  # get interesting fields
  users <- lapply(res, function(x) {
    a <- list()
    a$id <- x$user$id
    a$email <- x$user$email
    if (!is.null(x$account)) {
      a$account <- x$account
    } else {
      a$account <- NA
    }
    return(a)
  })

  # convert to data frame
  users <- do.call(rbind, users)
  df <- as.data.frame(users, stringsAsFactors = FALSE)
  return(df)
}

#' List invited users for an application
#'
#' @param appDir Directory containing application. Defaults to
#'   current working directory.
#' @param appName Name of application.
#' @inheritParams deployApp
#' @seealso [addAuthorizedUser()] and [showUsers()]
#' @note This function works only for ShinyApps servers.
#' @export
showInvited <- function(appDir = getwd(), appName = NULL, account = NULL,
                        server = NULL) {

  accountDetails <- accountInfo(account, server)
  checkShinyappsServer(accountDetails$server)

  # resolve application
  if (is.null(appName))
    appName <- basename(appDir)
  application <- resolveApplication(accountDetails, appName)

  # fetch invitation list
  api <- clientForAccount(accountDetails)
  res <- api$listApplicationInvitations(application$id)

  # get interesting fields
  users <- lapply(res, function(x) {
    a <- list()
    a$id <- x$id
    a$email <- x$email
    a$link <- x$link
    a$expired <- x$expired
    return(a)
  })

  # convert to data frame
  users <- do.call(rbind, users)
  df <- as.data.frame(users, stringsAsFactors = FALSE)
  return(df)
}

#' Resend invitation for invited users of an application
#'
#' @param invite The invitation to resend. Can be id or email address.
#' @param regenerate Regenerate the invite code. Can be helpful is the
#' invitation has expired.
#' @param appDir Directory containing application. Defaults to
#'   current working directory.
#' @param appName Name of application.
#' @inheritParams deployApp
#' @seealso [showInvited()]
#' @note This function works only for ShinyApps servers.
#' @export
resendInvitation <- function(invite, regenerate = FALSE,
                             appDir = getwd(), appName = NULL,
                             account = NULL, server = NULL) {

  accountDetails <- accountInfo(account, server)
  checkShinyappsServer(accountDetails$server)

  # get invitations
  invited <- showInvited(appDir, appName, account, server)

  if (is.numeric(invite)) {
    # lookup by id
    if (invite %in% invited$id) {
      invite <- invited[invited$id == invite, ]
    } else {
      stop("Invitation \"", invite, "\" not found", call. = FALSE)
    }
  } else {
    # lookup by email
    if (invite %in% invited$email) {
      invite <- invited[invited$email == invite, ]
    } else {
      stop("Invitiation for \"", invite, "\" not found", call. = FALSE)
    }
  }

  # resend invitation
  api <- clientForAccount(accountDetails)
  api$resendApplicationInvitation(invite$id, regenerate)

  message(paste("Sent invitation to", invite$email, "", sep = " "))

  invisible(TRUE)
}

#' (Deprecated) List authorized users for an application
#'
#' @param appDir Directory containing application. Defaults to current working
#'  directory.
#' @export
authorizedUsers <- function(appDir = getwd()) {
  .Deprecated("showUsers")

  # read password file
  path <- getPasswordFile(appDir)
  if (file.exists(path)) {
    passwords <- readPasswordFile(path)
  } else {
    passwords <- NULL
  }

  return(passwords)
}

validateEmail <- function(email) {

  if (is.null(email) || !grepl(".+\\@.+\\..+", email)) {
    stop("Invalid email address.", call. = FALSE)
  }

  invisible(email)
}

getPasswordFile <- function(appDir) {
  check_directory(appDir)

  file.path(normalizePath(appDir), "shinyapps", "passwords.txt")
}

readPasswordFile <- function(path) {
  # open and read file
  lines <- readLines(path)

  # extract fields
  fields <- do.call(rbind, strsplit(lines, ":"))
  users <- fields[, 1]
  hashes <- fields[, 2]

  # convert to data frame
  df <- data.frame(user = users, hash = hashes, stringsAsFactors = FALSE)

  # return data frame
  return(df)
}

writePasswordFile <- function(path, passwords) {

  # open and file
  f <- file(path, open = "w")
  defer(close(f))

  # write passwords
  apply(passwords, 1, function(r) {
    l <- paste(r[1], ":", r[2], "\n", sep = "")
    cat(l, file = f, sep = "")
  })
  message("Password file updated. You must deploy your application for these changes to take effect.")
}