/*  Title:      Pure/System/session.scala

     Author:     Makarius

     Options:    :folding=explicit:collapseFolds=1:

 Isabelle session, potentially with running prover.

 */

 package isabelle

 import scala.actors.TIMEOUT

 import scala.actors.Actor

 import scala.actors.Actor._

 object Session

 {

   /* events */

   case object Global_Settings

   case object Perspective

   case object Assignment

   case class Commands_Changed(set: Set[Command])

 }

 class Session(system: Isabelle_System)

 {

   /* real time parameters */  // FIXME properties or settings (!?)

   // user input (e.g. text edits, cursor movement)

   val input_delay = 300

   // prover output (markup, common messages)

   val output_delay = 100

   // GUI layout updates

   val update_delay = 500

   /* pervasive event buses */

   val global_settings = new Event_Bus[Session.Global_Settings.type]

   val raw_messages = new Event_Bus[Isabelle_Process.Result]

   val commands_changed = new Event_Bus[Session.Commands_Changed]

   val perspective = new Event_Bus[Session.Perspective.type]

   val assignments = new Event_Bus[Session.Assignment.type]

   /* unique ids */

   private var id_count: Document.ID = 0

   def new_id(): Document.ID = synchronized {

     require(id_count > java.lang.Long.MIN_VALUE)

     id_count -= 1

     id_count

   }

   /** buffered command changes (delay_first discipline) **/

   private case object Stop

   private val (_, command_change_buffer) =

     Simple_Thread.actor("command_change_buffer", daemon = true)

   //{{{

   {

     import scala.compat.Platform.currentTime

     var changed: Set[Command] = Set()

     var flush_time: Option[Long] = None

     def flush_timeout: Long =

       flush_time match {

         case None => 5000L

         case Some(time) => (time - currentTime) max 0

       }

     def flush()

     {

       if (!changed.isEmpty) commands_changed.event(Session.Commands_Changed(changed))

       changed = Set()

       flush_time = None

     }

     def invoke()

     {

       val now = currentTime

       flush_time match {

         case None => flush_time = Some(now + output_delay)

         case Some(time) => if (now >= time) flush()

       }

     }

     var finished = false

     while (!finished) {

       receiveWithin(flush_timeout) {

         case command: Command => changed += command; invoke()

         case TIMEOUT => flush()

         case Stop => finished = true

         case bad => System.err.println("command_change_buffer: ignoring bad message " + bad)

       }

     }

   }

   //}}}

   /** main protocol actor **/

   @volatile private var syntax = new Outer_Syntax(system.symbols)

   def current_syntax(): Outer_Syntax = syntax

   private val global_state = new Volatile(Document.State.init)

   def current_state(): Document.State = global_state.peek()

   private case object Interrupt_Prover

   private case class Edit_Version(edits: List[Document.Node_Text_Edit])

   private case class Started(timeout: Int, args: List[String])

   private val (_, session_actor) = Simple_Thread.actor("session_actor", daemon = true)

   {

     var prover: Isabelle_Process with Isar_Document = null

     /* document changes */

     def handle_change(change: Document.Change)

     //{{{

     {

       val previous = change.previous.get_finished

       val (node_edits, current) = change.result.get_finished

       var former_assignment = global_state.peek().the_assignment(previous).get_finished

       for {

         (name, Some(cmd_edits)) <- node_edits

         (prev, None) <- cmd_edits

         removed <- previous.nodes(name).commands.get_after(prev)

       } former_assignment -= removed

       val id_edits =

         node_edits map {

           case (name, None) => (name, None)

           case (name, Some(cmd_edits)) =>

             val ids =

               cmd_edits map {

                 case (c1, c2) =>

                   val id1 = c1.map(_.id)

                   val id2 =

                     c2 match {

                       case None => None

                       case Some(command) =>

                         if (global_state.peek().lookup_command(command.id).isEmpty) {

                           global_state.change(_.define_command(command))

                           prover.define_command(command.id, system.symbols.encode(command.source))

                         }

                         Some(command.id)

                     }

                   (id1, id2)

               }

             (name -> Some(ids))

         }

       global_state.change(_.define_version(current, former_assignment))

       prover.edit_version(previous.id, current.id, id_edits)

     }

     //}}}

     /* prover results */

     def bad_result(result: Isabelle_Process.Result)

     {

       System.err.println("Ignoring prover result: " + result.message.toString)

     }

     def handle_result(result: Isabelle_Process.Result)

     //{{{

     {

       raw_messages.event(result)

       result.properties match {

         case Position.Id(state_id) =>

           try {

             val st = global_state.change_yield(_.accumulate(state_id, result.message))

             command_change_buffer ! st.command

           }

           catch { case _: Document.State.Fail => bad_result(result) }

         case _ =>

           if (result.is_status) {

             result.body match {

               case List(Isar_Document.Assign(id, edits)) =>

                 try {

                   val cmds: List[Command] = global_state.change_yield(_.assign(id, edits))

                   for (cmd <- cmds) command_change_buffer ! cmd

                   assignments.event(Session.Assignment)

                 }

                 catch { case _: Document.State.Fail => bad_result(result) }

               case List(Keyword.Command_Decl(name, kind)) => syntax += (name, kind)

               case List(Keyword.Keyword_Decl(name)) => syntax += name

               case _ => if (!result.is_ready) bad_result(result)

             }

           }

           else if (result.is_exit) prover = null  // FIXME ??

           else if (!(result.is_init || result.is_exit || result.is_system || result.is_stdout))

             bad_result(result)

         }

     }

     //}}}

     /* prover startup */

     def startup_error(): String =

     {

       val buf = new StringBuilder

       while (

         receiveWithin(0) {

           case result: Isabelle_Process.Result =>

             if (result.is_system) {

               for (text <- XML.content(result.message))

                 buf.append(text)

             }

             true

           case TIMEOUT => false

         }) {}

       buf.toString

     }

     def prover_startup(timeout: Int): Option[String] =

     {

       receiveWithin(timeout) {

         case result: Isabelle_Process.Result if result.is_init =>

           handle_result(result)

           while (receive {

             case result: Isabelle_Process.Result =>

               handle_result(result); !result.is_ready

             }) {}

           None

         case result: Isabelle_Process.Result if result.is_exit =>

           handle_result(result)

           Some(startup_error())

         case TIMEOUT =>  // FIXME clarify

           prover.terminate; Some(startup_error())

       }

     }

     /* main loop */  // FIXME proper shutdown

     var finished = false

     while (!finished) {

       receive {

         case Interrupt_Prover =>

           if (prover != null) prover.interrupt

         case Edit_Version(edits) =>

           val previous = global_state.peek().history.tip.current

           val result = Future.fork { Thy_Syntax.text_edits(Session.this, previous.join, edits) }

           val change = global_state.change_yield(_.extend_history(previous, edits, result))

           val this_actor = self

           change.current.map(_ => {

             assignments.await { global_state.peek().is_assigned(previous.get_finished) }

             this_actor ! change })

           reply(())

         case change: Document.Change if prover != null =>

           handle_change(change)

         case result: Isabelle_Process.Result =>

           handle_result(result)

         case Started(timeout, args) =>

           if (prover == null) {

             prover = new Isabelle_Process(system, timeout, self, args:_*) with Isar_Document

             val origin = sender

             val opt_err = prover_startup(timeout + 500)

             if (opt_err.isDefined) prover = null

             origin ! opt_err

           }

           else reply(None)

         case Stop => // FIXME synchronous!?

           if (prover != null) {

             global_state.change(_ => Document.State.init)

             prover.terminate

             prover = null

           }

         case TIMEOUT =>  // FIXME clarify

         case bad if prover != null =>

           System.err.println("session_actor: ignoring bad message " + bad)

       }

     }

   }

   /** main methods **/

   def started(timeout: Int, args: List[String]): Option[String] =

     (session_actor !? Started(timeout, args)).asInstanceOf[Option[String]]

   def stop() { command_change_buffer ! Stop; session_actor ! Stop }

   def interrupt() { session_actor ! Interrupt_Prover }

   def edit_version(edits: List[Document.Node_Text_Edit]) { session_actor !? Edit_Version(edits) }

   def snapshot(name: String, pending_edits: List[Text.Edit]): Document.Snapshot =

     global_state.peek().snapshot(name, pending_edits)

 }