Fuck Yeah Reader Monad

fuckyeahreadermonad.scala

package examples.monads

case class User(id: Int, username: String, name: String)

trait UserRepository{
  def getById(id: Int) : Option[User]
  def save(user: Option[User]) : Unit
}

trait UserService{
  def updateName(id: Int, name: String) : Reader[UserServiceConfig, Unit]
  def deleteUser(id: Int) : Reader[UserServiceConfig, Unit]
}

trait UserServiceConfig{
  def Repository : UserRepository
}

sealed case class Reader[Environment,+Result](function: Environment => Result){
	def result(environment: Environment) : Result = function(environment)
	def map[T](f: Result => T) : Reader[Environment, T] = 
	  new Reader[Environment,T](Env => {
	    val prior = result(Env)
	    f(prior)
	  })
	def flatMap[T](f: Result => Reader[Environment,T]) : Reader[Environment,T] = 
	  new Reader[Environment,T](Env => {
	    val prior = result(Env)
	    f(prior).result(Env)
	  })
}

object ReaderMonadExamples {
	def run(){
	  
	  val service = new UserService(){
	    def updateName(id: Int, name: String) : Reader[UserServiceConfig, Unit] = {
	      new Reader(config => {
	        val repo = config.Repository
    		val updatedUser = repo.getById(id).map( x => x.copy(x.id,x.username,name) )
    		repo.save(updatedUser)
	      })
	    }
	    def deleteUser(id: Int) : Reader[UserServiceConfig, Unit] = {
	      new Reader(config => {
	    	  val repo = config.Repository
			  val user = repo.getById(id)
			  user.foreach(f => println("Deleting: " + f.toString))
	      })
	    }
	  }
	  
	  val configuration = new UserServiceConfig(){
	    def Repository = new UserRepository(){
	      def getById(id: Int) : Option[User] = {
	        id match{
	          case 1 => Some(User(1,"Tom", "Tom"))
	          case _ => None
	        }
	      }
	  	  def save(user: Option[User]) : Unit = {
	  	    user match{
	  	      case None => println("Nothing")
	  	      case Some(x) => println("Saving: " + x)
	  	    }
	  	  }
	    }
	  } 
	  
	  val reader = service.updateName(1, "Blair")
			  			  .flatMap(x => service.deleteUser(1))
	  					  .result(configuration)
	  
	}
}