src/Pure/PIDE/document.scala

explicit markup for forked goals, as indicated by Goal.fork;
accumulate pending forks within command state and hilight accordingly;
Isabelle_Process: enforce future_terminal_proof, which gives some impression of non-linear/parallel checking;

/*  Title:      Pure/PIDE/document.scala
    Author:     Makarius

Document as editable list of commands.
*/

package isabelle


import scala.annotation.tailrec


object Document
{
  /* command start positions */

  def command_starts(commands: Linear_Set[Command]): Iterator[(Command, Int)] =
  {
    var offset = 0
    for (cmd <- commands.iterator) yield {
      val start = offset
      offset += cmd.length
      (cmd, start)
    }
  }


  /* empty document */

  def empty(id: Isar_Document.Document_ID): Document =
  {
    val doc = new Document(id, Linear_Set(), Map())
    doc.assign_states(Nil)
    doc
  }



  /** document edits **/

  type Edit = (Option[Command], Option[Command])

  def text_edits(session: Session, old_doc: Document, new_id: Isar_Document.Document_ID,
    edits: List[Text_Edit]): (List[Edit], Document) =
  {
    require(old_doc.assignment.is_finished)


    /* unparsed dummy commands */

    def unparsed(source: String) =
      new Command(null, List(Token(Token.Kind.UNPARSED, source)))

    def is_unparsed(command: Command) = command.id == null


    /* phase 1: edit individual command source */

    def edit_text(eds: List[Text_Edit], commands: Linear_Set[Command]): Linear_Set[Command] =
    {
      eds match {
        case e :: es =>
          command_starts(commands).find {   // FIXME relative search!
            case (cmd, cmd_start) =>
              e.can_edit(cmd.source, cmd_start) || e.is_insert && e.start == cmd_start + cmd.length
          } match {
            case Some((cmd, cmd_start)) if e.can_edit(cmd.source, cmd_start) =>
              val (rest, text) = e.edit(cmd.source, cmd_start)
              val new_commands = commands.insert_after(Some(cmd), unparsed(text)) - cmd
              edit_text(rest.toList ::: es, new_commands)

            case Some((cmd, cmd_start)) =>
              edit_text(es, commands.insert_after(Some(cmd), unparsed(e.text)))

            case None =>
              require(e.is_insert && e.start == 0)
              edit_text(es, commands.insert_after(None, unparsed(e.text)))
          }
        case Nil => commands
      }
    }


    /* phase 2: recover command spans */

    @tailrec def parse_spans(commands: Linear_Set[Command]): Linear_Set[Command] =
    {
      commands.iterator.find(is_unparsed) match {
        case Some(first_unparsed) =>
          val first =
            commands.reverse_iterator(first_unparsed).find(_.is_command) getOrElse commands.head
          val last =
            commands.iterator(first_unparsed).find(_.is_command) getOrElse commands.last
          val range =
            commands.iterator(first).takeWhile(_ != last).toList ::: List(last)

          val sources = range.flatMap(_.span.map(_.source))
          val spans0 = Thy_Syntax.parse_spans(session.current_syntax.scan(sources.mkString))

          val (before_edit, spans1) =
            if (!spans0.isEmpty && first.is_command && first.span == spans0.head)
              (Some(first), spans0.tail)
            else (commands.prev(first), spans0)

          val (after_edit, spans2) =
            if (!spans1.isEmpty && last.is_command && last.span == spans1.last)
              (Some(last), spans1.take(spans1.length - 1))
            else (commands.next(last), spans1)

          val inserted = spans2.map(span => new Command(session.create_id(), span))
          val new_commands =
            commands.delete_between(before_edit, after_edit).append_after(before_edit, inserted)
          parse_spans(new_commands)

        case None => commands
      }
    }


    /* phase 3: resulting document edits */

    val commands0 = old_doc.commands
    val commands1 = edit_text(edits, commands0)
    val commands2 = parse_spans(commands1)

    val removed_commands = commands0.iterator.filter(!commands2.contains(_)).toList
    val inserted_commands = commands2.iterator.filter(!commands0.contains(_)).toList

    val doc_edits =
      removed_commands.reverse.map(cmd => (commands0.prev(cmd), None)) :::
      inserted_commands.map(cmd => (commands2.prev(cmd), Some(cmd)))

    val former_states = old_doc.assignment.join -- removed_commands

    (doc_edits, new Document(new_id, commands2, former_states))
  }
}


class Document(
    val id: Isar_Document.Document_ID,
    val commands: Linear_Set[Command],
    former_states: Map[Command, Command])
{
  /* command ranges */

  def command_starts: Iterator[(Command, Int)] = Document.command_starts(commands)

  def command_start(cmd: Command): Option[Int] =
    command_starts.find(_._1 == cmd).map(_._2)

  def command_range(i: Int): Iterator[(Command, Int)] =
    command_starts dropWhile { case (cmd, start) => start + cmd.length <= i }

  def command_range(i: Int, j: Int): Iterator[(Command, Int)] =
    command_range(i) takeWhile { case (_, start) => start < j }

  def command_at(i: Int): Option[(Command, Int)] =
  {
    val range = command_range(i)
    if (range.hasNext) Some(range.next) else None
  }


  /* command state assignment */

  val assignment = Future.promise[Map[Command, Command]]
  def await_assignment { assignment.join }

  @volatile private var tmp_states = former_states

  def assign_states(new_states: List[(Command, Command)])
  {
    assignment.fulfill(tmp_states ++ new_states)
    tmp_states = Map()
  }

  def current_state(cmd: Command): State =
  {
    require(assignment.is_finished)
    (assignment.join).get(cmd) match {
      case Some(cmd_state) => cmd_state.current_state
      case None => new State(cmd, Command.Status.UNDEFINED, 0, Nil, cmd.empty_markup)
    }
  }
}