lift.scala

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
 }
}