gistfile1.scala

package code.comet

import net.liftweb._
import http._
import actor._
import js._
import JsCmds._
import js.jquery.JqJsCmds.{AppendHtml, FadeOut, Hide, FadeIn}
import java.util.Date
import scala.xml._
import util.Helpers._
import util.Log

object ChatServer extends LiftActor with ListenerManager {

  private var messages: List[ChatCmd] = List("Welcome")

  def createUpdate = messages

  override def lowPriority = {
    case s: String => messages ::= s ; updateListeners()
    case d: RemoveMessage => messages ::= d ; updateListeners()
  }
}

sealed trait ChatCmd

object ChatCmd {
  implicit def strToMsg(msg: String): ChatCmd =
    new AddMessage(nextFuncName, msg, new Date)
}

final case class AddMessage(guid: String, msg: String, date: Date) extends ChatCmd
final case class RemoveMessage(guid: String) extends ChatCmd

class Chat extends CometActor with CometListener {
  private var msgs: List[ChatCmd] = Nil
  private var bindLine: NodeSeq = Nil

  def registerWith = ChatServer

  override def lowPriority = {
    case m: List[ChatCmd] => {
      val delta = m diff msgs
      msgs = m
      updateDeltas(delta)
    }
  }

  def updateDeltas(what: List[ChatCmd]) {
    partialUpdate(what.foldRight(Noop) {
      case (m: AddMessage , x) =>
        x & AppendHtml("ul_dude", doLine(m)) &
      Hide(m.guid) & FadeIn(m.guid, TimeSpan(0),TimeSpan(500))
      case (RemoveMessage(guid), x) =>
        x & FadeOut(guid,TimeSpan(0),TimeSpan(500)) &
      After(TimeSpan(500),Replace(guid, NodeSeq.Empty))
    })
  }

  def render =
    bind("chat", // the namespace for binding                                                                                                                                                                
         "line" -> lines _, // bind the function lines                                                                                                                                                       
         "input" -> SHtml.text("", s => ChatServer ! s)) // the input                                                                                                                                        

  private def lines(xml: NodeSeq): NodeSeq = {
    bindLine = xml
    val deleted = Set((for {
      RemoveMessage(guid) <- msgs
    } yield guid) :_*)

    for {
      m @ AddMessage(guid, msg, date) <- msgs.reverse if !deleted.contains(guid)
      node <- doLine(m)
    } yield node
  }


  private def doLine(m: AddMessage): NodeSeq =
    bind("chat", addId(bindLine, m.guid),
         "msg" -> m.msg,
         "btn" -> SHtml.ajaxButton("delete",
                                   () => {
                                     ChatServer !
                                     RemoveMessage(m.guid)
                                     Noop}))

  private def addId(in: NodeSeq, id: String): NodeSeq = in map {
    case e: Elem => e % ("id" -> id)
    case x => x
  }
}