/*  Title:      Pure/System/isabelle_process.ML

    Author:     Makarius

    Options:    :folding=explicit:collapseFolds=1:

Isabelle process management -- always reactive due to multi-threaded I/O.

*/

package isabelle

import java.util.concurrent.LinkedBlockingQueue

import java.io.{BufferedReader, BufferedWriter, InputStreamReader, OutputStreamWriter,

  InputStream, OutputStream, IOException}

import scala.actors.Actor

import Actor._

object Isabelle_Process

{

  /* results */

  object Kind extends Enumeration {

    //{{{ values and codes

    // internal system notification

    val SYSTEM = Value("SYSTEM")

    // Posix channels/events

    val STDIN = Value("STDIN")

    val STDOUT = Value("STDOUT")

    val SIGNAL = Value("SIGNAL")

    val EXIT = Value("EXIT")

    // Isabelle messages

    val INIT = Value("INIT")

    val STATUS = Value("STATUS")

    val WRITELN = Value("WRITELN")

    val PRIORITY = Value("PRIORITY")

    val TRACING = Value("TRACING")

    val WARNING = Value("WARNING")

    val ERROR = Value("ERROR")

    val DEBUG = Value("DEBUG")

    // messages codes

    val code = Map(

      ('A' : Int) -> Kind.INIT,

      ('B' : Int) -> Kind.STATUS,

      ('C' : Int) -> Kind.WRITELN,

      ('D' : Int) -> Kind.PRIORITY,

      ('E' : Int) -> Kind.TRACING,

      ('F' : Int) -> Kind.WARNING,

      ('G' : Int) -> Kind.ERROR,

      ('H' : Int) -> Kind.DEBUG,

      ('0' : Int) -> Kind.SYSTEM,

      ('1' : Int) -> Kind.STDIN,

      ('2' : Int) -> Kind.STDOUT,

      ('3' : Int) -> Kind.SIGNAL,

      ('4' : Int) -> Kind.EXIT)

    // message markup

    val markup = Map(

      Kind.INIT -> Markup.INIT,

      Kind.STATUS -> Markup.STATUS,

      Kind.WRITELN -> Markup.WRITELN,

      Kind.PRIORITY -> Markup.PRIORITY,

      Kind.TRACING -> Markup.TRACING,

      Kind.WARNING -> Markup.WARNING,

      Kind.ERROR -> Markup.ERROR,

      Kind.DEBUG -> Markup.DEBUG,

      Kind.SYSTEM -> Markup.SYSTEM,

      Kind.STDIN -> Markup.STDIN,

      Kind.STDOUT -> Markup.STDOUT,

      Kind.SIGNAL -> Markup.SIGNAL,

      Kind.EXIT -> Markup.EXIT)

    //}}}

    def is_raw(kind: Value) =

      kind == STDOUT

    def is_control(kind: Value) =

      kind == SYSTEM ||

      kind == SIGNAL ||

      kind == EXIT

    def is_system(kind: Value) =

      kind == SYSTEM ||

      kind == STDIN ||

      kind == SIGNAL ||

      kind == EXIT ||

      kind == STATUS

  }

  class Result(val kind: Kind.Value, val props: List[(String, String)], val body: List[XML.Tree])

  {

    def message = XML.Elem(Markup.MESSAGE, (Markup.CLASS, Kind.markup(kind)) :: props, body)

    override def toString: String =

    {

      val res =

        if (kind == Kind.STATUS) body.map(_.toString).mkString

        else body.map(XML.content(_).mkString).mkString

      if (props.isEmpty)

        kind.toString + " [[" + res + "]]"

      else

        kind.toString + " " +

          (for ((x, y) <- props) yield x + "=" + y).mkString("{", ",", "}") + " [[" + res + "]]"

    }

    def is_raw = Kind.is_raw(kind)

    def is_control = Kind.is_control(kind)

    def is_system = Kind.is_system(kind)

    def cache(c: XML.Cache): Result =

      new Result(kind, c.cache_props(props), c.cache_trees(body))

  }

}

class Isabelle_Process(system: Isabelle_System, receiver: Actor, args: String*)

{

  import Isabelle_Process._

  /* demo constructor */

  def this(args: String*) =

    this(new Isabelle_System,

      new Actor { def act = loop { react { case res => Console.println(res) } } }.start, args: _*)

  /* process information */

  @volatile private var proc: Process = null

  @volatile private var closing = false

  @volatile private var pid: String = null

  @volatile private var the_session: String = null

  def session = the_session

  /* results */

  private def put_result(kind: Kind.Value, props: List[(String, String)], body: List[XML.Tree])

  {

    if (kind == Kind.INIT) {

      val map = Map(props: _*)

      if (map.isDefinedAt(Markup.PID)) pid = map(Markup.PID)

      if (map.isDefinedAt(Markup.SESSION)) the_session = map(Markup.SESSION)

    }

    receiver ! new Result(kind, props, body)

  }

  private def put_result(kind: Kind.Value, text: String)

  {

    put_result(kind, Nil, List(XML.Text(system.symbols.decode(text))))

  }

  /* signals */

  def interrupt() = synchronized {

    if (proc == null) error("Cannot interrupt Isabelle: no process")

    if (pid == null) put_result(Kind.SYSTEM, "Cannot interrupt: unknown pid")

    else {

      try {

        if (system.execute(true, "kill", "-INT", pid).waitFor == 0)

          put_result(Kind.SIGNAL, "INT")

        else

          put_result(Kind.SYSTEM, "Cannot interrupt: kill command failed")

      }

      catch { case e: IOException => error("Cannot interrupt Isabelle: " + e.getMessage) }

    }

  }

  def kill() = synchronized {

    if (proc == 0) error("Cannot kill Isabelle: no process")

    else {

      try_close()

      Thread.sleep(500)

      put_result(Kind.SIGNAL, "KILL")

      proc.destroy

      proc = null

      pid = null

    }

  }

  /* output being piped into the process */

  private val output = new LinkedBlockingQueue[String]

  private def output_raw(text: String) = synchronized {

    if (proc == null) error("Cannot output to Isabelle: no process")

    if (closing) error("Cannot output to Isabelle: already closing")

    output.put(text)

  }

  def output_sync(text: String) =

    output_raw(" \\<^sync>\n; " + text + " \\<^sync>;\n")

  def command(text: String) =

    output_sync("Isabelle.command " + Isabelle_Syntax.encode_string(text))

  def command(props: List[(String, String)], text: String) =

    output_sync("Isabelle.command " + Isabelle_Syntax.encode_properties(props) + " " +

      Isabelle_Syntax.encode_string(text))

  def ML(text: String) =

    output_sync("ML_val " + Isabelle_Syntax.encode_string(text))

  def close() = synchronized {    // FIXME watchdog/timeout

    output_raw("\u0000")

    closing = true

  }

  def try_close() = synchronized {

    if (proc != null && !closing) {

      try { close() }

      catch { case _: RuntimeException => }

    }

  }

  /* stdin */

  private class StdinThread(out_stream: OutputStream) extends Thread("isabelle: stdin") {

    override def run() = {

      val writer = new BufferedWriter(new OutputStreamWriter(out_stream, Isabelle_System.charset))

      var finished = false

      while (!finished) {

        try {

          //{{{

          val s = output.take

          if (s == "\u0000") {

            writer.close

            finished = true

          }

          else {

            put_result(Kind.STDIN, s)

            writer.write(s)

            writer.flush

          }

          //}}}

        }

        catch {

          case e: IOException => put_result(Kind.SYSTEM, "Stdin thread: " + e.getMessage)

        }

      }

      put_result(Kind.SYSTEM, "Stdin thread terminated")

    }

  }

  /* stdout */

  private class StdoutThread(in_stream: InputStream) extends Thread("isabelle: stdout") {

    override def run() = {

      val reader = new BufferedReader(new InputStreamReader(in_stream, Isabelle_System.charset))

      var result = new StringBuilder(100)

      var finished = false

      while (!finished) {

        try {

          //{{{

          var c = -1

          var done = false

          while (!done && (result.length == 0 || reader.ready)) {

            c = reader.read

            if (c >= 0) result.append(c.asInstanceOf[Char])

            else done = true

          }

          if (result.length > 0) {

            put_result(Kind.STDOUT, result.toString)

            result.length = 0

          }

          else {

            reader.close

            finished = true

            try_close()

          }

          //}}}

        }

        catch {

          case e: IOException => put_result(Kind.SYSTEM, "Stdout thread: " + e.getMessage)

        }

      }

      put_result(Kind.SYSTEM, "Stdout thread terminated")

    }

  }

  /* messages */

  private class MessageThread(fifo: String) extends Thread("isabelle: messages")

  {

    private class Protocol_Error(msg: String) extends Exception(msg)

    override def run()

    {

      val stream = system.fifo_stream(fifo)

      val default_buffer = new Array[Byte](65536)

      var c = -1

      def read_chunk(): List[XML.Tree] =

      {

        //{{{

        // chunk size

        var n = 0

        c = stream.read

        while (48 <= c && c <= 57) {

          n = 10 * n + (c - 48)

          c = stream.read

        }

        if (c != 10) throw new Protocol_Error("bad message chunk header")

        // chunk content

        val buf =

          if (n <= default_buffer.size) default_buffer

          else new Array[Byte](n)

        var i = 0

        var m = 0

        do {

          m = stream.read(buf, i, n - i)

          i += m

        } while (m > 0 && n > i)

        if (i != n) throw new Protocol_Error("bad message chunk content")

        YXML.parse_body_failsafe(YXML.decode_chars(system.symbols.decode, buf, 0, n))

        //}}}

      }

      do {

        try {

          //{{{

          c = stream.read

          var non_sync = 0

          while (c >= 0 && c != 2) {

            non_sync += 1

            c = stream.read

          }

          if (non_sync > 0)

            throw new Protocol_Error("lost synchronization -- skipping " + non_sync + " bytes")

          if (c == 2) {

            val header = read_chunk()

            val body = read_chunk()

            header match {

              case List(XML.Elem(name, props, Nil))

                  if name.size == 1 && Kind.code.isDefinedAt(name(0)) =>

                put_result(Kind.code(name(0)), props, body)

              case _ => throw new Protocol_Error("bad header: " + header.toString)

            }

          }

          //}}}

        }

        catch {

          case e: IOException =>

            put_result(Kind.SYSTEM, "Cannot read message:\n" + e.getMessage)

          case e: Protocol_Error =>

            put_result(Kind.SYSTEM, "Malformed message:\n" + e.getMessage)

        }

      } while (c != -1)

      stream.close

      try_close()

      put_result(Kind.SYSTEM, "Message thread terminated")

    }

  }

  /** main **/

  {

    /* isabelle version */

    {

      val (msg, rc) = system.isabelle_tool("version")

      if (rc != 0) error("Version check failed -- bad Isabelle installation:\n" + msg)

      put_result(Kind.SYSTEM, msg)

    }

    /* messages */

    val message_fifo = system.mk_fifo()

    def rm_fifo() = system.rm_fifo(message_fifo)

    val message_thread = new MessageThread(message_fifo)

    message_thread.start

    /* exec process */

    try {

      val cmdline = List(system.getenv_strict("ISABELLE_PROCESS"), "-W", message_fifo) ++ args

      proc = system.execute(true, cmdline: _*)

    }

    catch {

      case e: IOException =>

        rm_fifo()

        error("Failed to execute Isabelle process: " + e.getMessage)

    }

    /* stdin/stdout */

    new StdinThread(proc.getOutputStream).start

    new StdoutThread(proc.getInputStream).start

    /* exit */

    new Thread("isabelle: exit") {

      override def run() = {

        val rc = proc.waitFor()

        Thread.sleep(300)

        put_result(Kind.SYSTEM, "Exit thread terminated")

        put_result(Kind.EXIT, rc.toString)

        rm_fifo()

      }

    }.start

  }

}