/*  Title:      Pure/PIDE/document.scala

    Author:     Makarius

Document as editable list of commands.

*/

package isabelle

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(Outer_Lex.Token(Outer_Lex.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 */

    def parse_spans(commands: Linear_Set[Command]): Linear_Set[Command] =

    {

      // FIXME relative search!

      commands.iterator.find(is_unparsed) match {

        case Some(first_unparsed) =>

          val prefix = commands.prev(first_unparsed)

          val body = commands.iterator(first_unparsed).takeWhile(is_unparsed).toList

          val suffix = commands.next(body.last)

          val sources = (prefix.toList ::: body ::: suffix.toList).flatMap(_.span.map(_.source))

          val spans0 = Thy_Syntax.parse_spans(session.current_syntax.scan(sources.mkString))

          val (before_edit, spans1) =

            if (!spans0.isEmpty && Some(spans0.head) == prefix.map(_.span))

              (prefix, spans0.tail)

            else (if (prefix.isDefined) commands.prev(prefix.get) else None, spans0)

          val (after_edit, spans2) =

            if (!spans1.isEmpty && Some(spans1.last) == suffix.map(_.span))

              (suffix, spans1.take(spans1.length - 1))

            else (if (suffix.isDefined) commands.next(suffix.get) else None, 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 result = Library.timeit("text_edits") {

      val commands0 = old_doc.commands

      val commands1 = Library.timeit("edit_text") { edit_text(edits, commands0) }

      val commands2 = Library.timeit("parse_spans") { 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))

    }

    result

  }

}

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

  private val time0 = System.currentTimeMillis

  def assign_states(new_states: List[(Command, Command)])

  {

    assignment.fulfill(tmp_states ++ new_states)

    tmp_states = Map()

    System.err.println("assign_states: " + (System.currentTimeMillis - time0) + " ms elapsed time")

  }

  def current_state(cmd: Command): Option[State] =

  {

    require(assignment.is_finished)

    (assignment.join).get(cmd).map(_.current_state)

  }

}