SproutCore Todos backend in Unfiltered Scala

UnfilteredTodoServer.scala

package com.todos

import net.liftweb.json.JsonAST._
import net.liftweb.json.JsonDSL._

/**
 * Non-persistent Unfiltered implementation of the SproutCore back-end.
 * See <a href="http://wiki.sproutcore.com/w/page/12413020/Todos%2006-Building%20the%20Backend">SproutCore docs</a>
 */

case class Todo(id: String, description: String, isDone: Boolean) {
  def toJson = ("guid" -> url) ~ ("description" -> description) ~ ("isDone" -> isDone)
  def url = "/tasks/" + id
}

object Todo {
  def fromJson(id: String, body: JValue) : Option[Todo] = (for {
    JObject(todo) <- body
    JField("description", JString(desc)) <- todo
    JField("isDone", JBool(done)) <- todo
  } yield Todo(id, desc, done)) headOption
}

object TodosServer {

  import unfiltered.request._
  import unfiltered.response._

  def main(args: Array[String]) {
    unfiltered.jetty.Http(8080).filter(unfiltered.filter.Planify{

      case Path(Seg("tasks" :: Nil), r) => r match {

        case GET(_) => wrap(DB.findAll)

        case POST(r) => Todo.fromJson(DB.generateId, JsonBody(r)) match {
          case Some(todo) => Location(DB.add(todo).url)
          case _ => BadRequest
        }
      }

      case Path(Seg("tasks" :: id :: Nil), r) => r match {

        case GET(_) => DB.find(id) match {
          case Some(t) => t.toJson
          case None => NotFound
        }

        case DELETE(_) => DB.delete(id) match {
          case Some(todo) => todo.toJson
          case _ => NotFound
        }

        case PUT(r) =>
            (for {
              existing <- DB.find(id)
              updated <- Todo.fromJson(id, JsonBody(r))
            } yield updated) match {
              case Some(updated) => DB.add(updated).toJson
              case _ => BadRequest
            }
      }


    }).resources(new java.io.File("tmp/build/").toURL).run
  }

  implicit def jvalueToJsonResponder[T](json: JValue) : Responder[T] = JsonContent ~> ResponseString(compact(render(json)))
  type Convertable = {def toJson: JValue}
  def wrap(xs: Seq[Convertable]) : JValue = "content" -> xs.map(_.toJson)
}

object DB {
  private var todos: Map[String, Todo] = Map()
  private val counter = new java.util.concurrent.atomic.AtomicInteger

  def add(todo: Todo) = {
    todos = todos + (todo.id -> todo)
    todo
  }
  def find(id: String) = todos.get(id)
  def findAll = todos.values.toList
  def delete(id: String) : Option[Todo] = todos.get(id) match {
    case Some(todo) =>
      todos = todos - id
      Some(todo)
    case _ => None
  }

  def generateId = System.currentTimeMillis.toString + "-" + counter.addAndGet(1)
}

"Maybe a common UrlForTask extractor?"

Which part is that exactly?

I ended slapping one together (object TodoUrl). The previous revision had Path(Seg("tasks" :: id :: Nil)) repeated for GET, PUT and DELETE. Comparing to the other SproutCore back-end implementations, I'd argue that this quick and dirty one is among the most concise.

It still looks a little "asymmetric" and repetetive, though. I Inversed the Method and Path patterns (+ some other things). Maybe that's better...