/*  Title:      Pure/System/session.scala

    Author:     Makarius

    Options:    :folding=explicit:collapseFolds=1:

Main Isabelle/Scala session, potentially with running prover process.

*/

package isabelle

import java.lang.System

import scala.actors.TIMEOUT

import scala.actors.Actor

import scala.actors.Actor._

object Session

{

  /* file store */

  abstract class File_Store

  {

    def read(path: Path): String

  }

  /* events */

  //{{{

  case object Global_Settings

  case object Perspective

  case object Assignment

  case class Commands_Changed(set: Set[Command])

  sealed abstract class Phase

  case object Inactive extends Phase

  case object Startup extends Phase  // transient

  case object Failed extends Phase

  case object Ready extends Phase

  case object Shutdown extends Phase  // transient

  //}}}

}

class Session(val file_store: Session.File_Store)

{

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

  val input_delay = Time.seconds(0.3)  // user input (e.g. text edits, cursor movement)

  val output_delay = Time.seconds(0.1)  // prover output (markup, common messages)

  val update_delay = Time.seconds(0.5)  // GUI layout updates

  /* pervasive event buses */

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

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

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

  val commands_changed = new Event_Bus[Session.Commands_Changed]

  val phase_changed = new Event_Bus[Session.Phase]

  val raw_messages = new Event_Bus[Isabelle_Process.Message]

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

  //{{{

  private case object Stop

  private val (_, command_change_buffer) =

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

  {

    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 - System.currentTimeMillis()) max 0

      }

    def flush()

    {

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

      changed = Set()

      flush_time = None

    }

    def invoke()

    {

      val now = System.currentTimeMillis()

      flush_time match {

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

        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; reply(())

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

      }

    }

  }

  //}}}

  /** main protocol actor **/

  /* global state */

  @volatile var verbose: Boolean = false

  @volatile private var loaded_theories: Set[String] = Set()

  @volatile private var syntax = new Outer_Syntax

  def current_syntax(): Outer_Syntax = syntax

  @volatile private var reverse_syslog = List[XML.Elem]()

  def syslog(): String = reverse_syslog.reverse.map(msg => XML.content(msg).mkString).mkString("\n")

  @volatile private var _phase: Session.Phase = Session.Inactive

  private def phase_=(new_phase: Session.Phase)

  {

    _phase = new_phase

    phase_changed.event(new_phase)

  }

  def phase = _phase

  def is_ready: Boolean = phase == Session.Ready

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

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

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

    global_state().snapshot(name, pending_edits)

  /* theory files */

  val thy_load = new Thy_Load

  {

    override def is_loaded(name: String): Boolean =

      loaded_theories.contains(name)

    override def check_thy(dir: Path, name: String): (String, Thy_Header.Header) =

    {

      val file = Isabelle_System.platform_file(dir + Thy_Header.thy_path(name))

      if (!file.exists || !file.isFile) error("No such file: " + quote(file.toString))

      val text = Standard_System.read_file(file)

      val header = Thy_Header.read(text)

      (text, header)

    }

  }

  val thy_info = new Thy_Info(thy_load)

  /* actor messages */

  private case class Start(timeout: Time, args: List[String])

  private case object Interrupt

  private case class Init_Node(name: String, header: Document.Node.Header, text: String)

  private case class Edit_Node(name: String, header: Document.Node.Header, edits: List[Text.Edit])

  private case class Change_Node(

    name: String,

    doc_edits: List[Document.Edit_Command],

    header_edits: List[(String, Thy_Header.Header)],

    previous: Document.Version,

    version: Document.Version)

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

  {

    val this_actor = self

    var prover: Option[Isabelle_Process with Isar_Document] = None

    /* incoming edits */

    def handle_edits(name: String,

        header: Document.Node.Header, edits: List[Document.Node.Edit[Text.Edit]])

    //{{{

    {

      val syntax = current_syntax()

      val previous = global_state().history.tip.version

      val doc_edits = edits.map(edit => (name, edit))

      val result = Future.fork {

        Thy_Syntax.text_edits(syntax, previous.join, doc_edits, List((name, header)))

      }

      val change =

        global_state.change_yield(_.extend_history(previous, doc_edits, result.map(_._3)))

      result.map {

        case (doc_edits, header_edits, _) =>

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

          this_actor !

            Change_Node(name, doc_edits, header_edits, previous.join, change.version.join)

      }

    }

    //}}}

    /* resulting changes */

    def handle_change(change: Change_Node)

    //{{{

    {

      val previous = change.previous

      val version = change.version

      val name = change.name

      val doc_edits = change.doc_edits

      val header_edits = change.header_edits

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

      for {

        (name, Document.Node.Edits(cmd_edits)) <- doc_edits  // FIXME proper coverage!?

        (prev, None) <- cmd_edits

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

      } former_assignment -= removed

      def id_command(command: Command): Document.Command_ID =

      {

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

          global_state.change(_.define_command(command))

          prover.get.define_command(command.id, Symbol.encode(command.source))

        }

        command.id

      }

      val id_edits =

        doc_edits map {

          case (name, edit) =>

            (name, edit.map({ case (c1, c2) => (c1.map(id_command), c2.map(id_command)) }))

        }

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

      prover.get.edit_version(previous.id, version.id, id_edits, header_edits)

    }

    //}}}

    /* prover results */

    def handle_result(result: Isabelle_Process.Result)

    //{{{

    {

      def bad_result(result: Isabelle_Process.Result)

      {

        if (verbose)

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

      }

      result.properties match {

        case Position.Id(state_id) if !result.is_raw =>

          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 Markup.Invoke_Scala(name, id) if result.is_raw =>

          Future.fork {

            val arg = XML.content(result.body).mkString

            val (tag, res) = Invoke_Scala.method(name, arg)

            prover.get.invoke_scala(id, tag, res)

          }

        case _ =>

          if (result.is_syslog) {

            reverse_syslog ::= result.message

            if (result.is_ready) {

              // FIXME move to ML side (!?)

              syntax += ("hence", Keyword.PRF_ASM_GOAL, "then have")

              syntax += ("thus", Keyword.PRF_ASM_GOAL, "then show")

              phase = Session.Ready

            }

            else if (result.is_exit && phase == Session.Startup) phase = Session.Failed

            else if (result.is_exit) phase = Session.Inactive

          }

          else if (result.is_stdout) { }

          else 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 List(Thy_Info.Loaded_Theory(name)) => loaded_theories += name

              case _ => bad_result(result)

            }

          }

          else bad_result(result)

      }

    }

    //}}}

    /* main loop */

    //{{{

    var finished = false

    while (!finished) {

      receive {

        case Start(timeout, args) if prover.isEmpty =>

          if (phase == Session.Inactive || phase == Session.Failed) {

            phase = Session.Startup

            prover = Some(new Isabelle_Process(timeout, this_actor, args:_*) with Isar_Document)

          }

        case Stop =>

          if (phase == Session.Ready) {

            global_state.change(_ => Document.State.init)  // FIXME event bus!?

            phase = Session.Shutdown

            prover.get.terminate

            prover = None

            phase = Session.Inactive

          }

          finished = true

          reply(())

        case Interrupt if prover.isDefined =>

          prover.get.interrupt

        case Init_Node(name, header, text) if prover.isDefined =>

          // FIXME compare with existing node

          handle_edits(name, header,

            List(Document.Node.Remove(), Document.Node.Edits(List(Text.Edit.insert(0, text)))))

          reply(())

        case Edit_Node(name, header, text_edits) if prover.isDefined =>

          handle_edits(name, header, List(Document.Node.Edits(text_edits)))

          reply(())

        case change: Change_Node if prover.isDefined =>

          handle_change(change)

        case input: Isabelle_Process.Input =>

          raw_messages.event(input)

        case result: Isabelle_Process.Result =>

          handle_result(result)

          raw_messages.event(result)

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

      }

    }

    //}}}

  }

  /* actions */

  def start(timeout: Time, args: List[String]) { session_actor ! Start(timeout, args) }

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

  def interrupt() { session_actor ! Interrupt }

  def init_node(name: String, header: Document.Node.Header, text: String)

  { session_actor !? Init_Node(name, header, text) }

  def edit_node(name: String, header: Document.Node.Header, edits: List[Text.Edit])

  { session_actor !? Edit_Node(name, header, edits) }

}