/*  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(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 */

     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): 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, Nil, cmd.empty_markup)

     }

   }

 }