Try this or try that

Attention.md

Try this or try that (Scala)

• authenticate attempts to login the user into the Application. It does so as defined below:
  • It first attempts to log the user using the application user name and password.
  • In case appLogin fails, it attempts to log the user using user's Gmail Id and password.
  • In case gmailLogin fails, it attempts to log the user using user's Facebook Id and password.
  • In case fbLogin fails, it gives up and does not authenticate the user.
• Compare notes on your solutions after solving Part 1 and Part 2

Problem Part 1

• Look at login.scala and refactor this code using Try

Problem Part 2

• Look at login2.scala and implement the methods marked with ???
• Refactor authenticate using recoverWith

Problem Part 3

• Look at login3.scala and refactor this code using Future.
• Feel free to change other functions as you deem fit, but you are not allowed to change the signature of the authenticate function.

login.scala

class AuthenticationFailed private(message: String = "") extends Throwable(message) {
  def this(message: String, cause: Throwable) = {
    this(message)
    initCause(cause)
  }
  def this(cause: Throwable) = this(Option(cause).map(_.toString).orNull, cause)
}
// Companion Object
object AuthenticationFailed {
  def apply() = new AuthenticationFailed(null: String)
  def apply(message: String) = new AuthenticationFailed(message)
  def apply(cause: Throwable) = new AuthenticationFailed(cause)
  def apply(message: String, cause: Throwable) = new AuthenticationFailed(message, cause)

  def unapply(ex: AuthenticationFailed): Option[(String, Throwable)] = Some((ex.getMessage, ex.getCause))
}

def appLogin(name: String, password: String) = {
  if (name.equals("tester")) true
  else throw AuthenticationFailed(s"App. account with $name does not exist!")
}

def gmailLogin(name: String, password: String) = {
  if (name.equals("[email protected]")) true
  else throw AuthenticationFailed(s"Gmail account with $name does not exist!")
}

def fbLogin(name: String, password: String) = {
  if (name.equals("[email protected]")) true
  else throw AuthenticationFailed(s"Facebook with $name does not exist!")
}

// NOTE: printlns are given to help you grasp the flow very quickly,
// when you run the program.  They are not required to be present
// when refactoring.
//
def authenticate(name: String, password: String): Boolean = {
  try {
    println(s"Trying Application Login...")
    appLogin(name, password)
  } catch {
    case AuthenticationFailed(msg, cause) =>
    println(s"Failed App Login => $msg")
    try {
      println(s"Trying Gmail Login...")
      gmailLogin(name, password)
    } catch {
      case AuthenticationFailed(msg, cause) =>
      println(s"Failed Gmail Login => $msg")
      try {
        println(s"Trying Facebook Login...")
        fbLogin(name, password)
      } catch {
        case AuthenticationFailed(msg, cause) =>
          println(s"Failed Facebook Login => $msg")
          false
      }
    }
  }
}

println(authenticate("tester", "password"))            // true
println(authenticate("[email protected]", "aPassword")) // true
println(authenticate("[email protected]", "psswd"))        // true
println(authenticate("someone", "somepassword"))       // false

login2.scala

class AuthenticationFailed private(message: String = "") extends Throwable(message) {
  def this(message: String, cause: Throwable) = {
    this(message)
    initCause(cause)
  }
  def this(cause: Throwable) = this(Option(cause).map(_.toString).orNull, cause)
}
// Companion Object
object AuthenticationFailed {
  def apply() = new AuthenticationFailed(null: String)
  def apply(message: String) = new AuthenticationFailed(message)
  def apply(cause: Throwable) = new AuthenticationFailed(cause)
  def apply(message: String, cause: Throwable) = new AuthenticationFailed(message, cause)

  def unapply(ex: AuthenticationFailed): Option[(String, Throwable)] = Some((ex.getMessage, ex.getCause))
}

// Implement these
import scala.util.{Try, Success, Failure}
def appLogin(name: String, password: String): Try[Boolean] = ???
def gmailLogin(name: String, password: String): Try[Boolean] = ???
def fbLogin(name: String, password: String): Try[Boolean] = ???
def authenticate(name: String, password: String): Boolean = ???

println(authenticate("tester", "password"))            // true
println(authenticate("[email protected]", "aPassword")) // true
println(authenticate("[email protected]", "psswd"))        // true
println(authenticate("someone", "somepassword"))       // false

login3.scala

def appLogin(name: String, password: String) = {
  println(s"appLogin on => ${Thread.currentThread}")
  Thread.sleep(500)
  if (name.equals("tester")) true
  else throw AuthenticationFailed(s"App. account with $name does not exist!")
}

def gmailLogin(name: String, password: String) = {
  println(s"gmailLogin on => ${Thread.currentThread}")
  Thread.sleep(1000)
  if (name.equals("[email protected]")) true
  else throw AuthenticationFailed(s"Gmail account with $name does not exist!")
}

def fbLogin(name: String, password: String) = {
  println(s"gmailLogin on => ${Thread.currentThread}")
  Thread.sleep(1500)
  if (name.equals("[email protected]")) true
  else throw AuthenticationFailed(s"Facebook with $name does not exist!")
}

// NOTE: printlns are given to help you grasp the flow very quickly,
// when you run the program.  They are not required to be present
// when refactoring.
//
def authenticate(name: String, password: String): Boolean = {
  try {
    println(s"Trying Application Login...")
    appLogin(name, password)
  } catch {
    case AuthenticationFailed(msg, cause) =>
    println(s"Failed App Login => $msg")
    try {
      println(s"Trying Gmail Login...")
      gmailLogin(name, password)
    } catch {
      case AuthenticationFailed(msg, cause) =>
      println(s"Failed Gmail Login => $msg")
      try {
        println(s"Trying Facebook Login...")
        fbLogin(name, password)
      } catch {
        case AuthenticationFailed(msg, cause) =>
          println(s"Failed Facebook Login => $msg")
          false
      }
    }
  }
}

println(authenticate("tester", "password"))            // true
println(authenticate("[email protected]", "aPassword")) // true
println(authenticate("[email protected]", "psswd"))        // true
println(authenticate("someone", "somepassword"))       // false