/*  Title:      Pure/PIDE/document.scala

     Author:     Makarius

 Document as collection of named nodes, each consisting of an editable

 list of commands, associated with asynchronous execution process.

 */

 package isabelle

 import scala.collection.mutable

 object Document

 {

   /* formal identifiers */

   type ID = Long

   object ID {

     def apply(id: ID): String = Markup.Long.apply(id)

     def unapply(s: String): Option[ID] = Markup.Long.unapply(s)

   }

   type Version_ID = ID

   type Command_ID = ID

   type Exec_ID = ID

   val NO_ID: ID = 0

   /** named document nodes **/

   object Node

   {

     val empty: Node = new Node(Linear_Set())

     def command_starts(commands: Iterator[Command], offset: Int = 0): Iterator[(Command, Int)] =

     {

       var i = offset

       for (command <- commands) yield {

         val start = i

         i += command.length

         (command, start)

       }

     }

   }

   class Node(val commands: Linear_Set[Command])

   {

     /* command ranges */

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

       Node.command_starts(commands.iterator)

     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

     }

     def proper_command_at(i: Int): Option[Command] =

       command_at(i) match {

         case Some((command, _)) =>

           commands.reverse_iterator(command).find(cmd => !cmd.is_ignored)

         case None => None

       }

   }

   /* document versions */

   object Version

   {

     val init: Version = new Version(NO_ID, Map().withDefaultValue(Node.empty))

   }

   class Version(val id: Version_ID, val nodes: Map[String, Node])

   /** changes of plain text, eventually resulting in document edits **/

   type Node_Text_Edit = (String, List[Text_Edit])  // FIXME None: remove

   type Edit[C] =

    (String,  // node name

     Option[List[(Option[C], Option[C])]])  // None: remove, Some: insert/remove commands

   abstract class Snapshot

   {

     val version: Version

     val node: Node

     val is_outdated: Boolean

     def convert(offset: Int): Int

     def revert(offset: Int): Int

     def lookup_command(id: Command_ID): Option[Command]

     def state(command: Command): Command.State

   }

   object Change

   {

     val init = new Change(Future.value(Version.init), Nil, Future.value(Nil, Version.init))

   }

   class Change(

     val previous: Future[Version],

     val edits: List[Node_Text_Edit],

     val result: Future[(List[Edit[Command]], Version)])

   {

     val current: Future[Version] = result.map(_._2)

     def is_finished: Boolean = previous.is_finished && current.is_finished

   }

   /** global state -- document structure and execution process **/

   object State

   {

     class Fail(state: State) extends Exception

     val init = State().define_version(Version.init, Map()).assign(Version.init.id, Nil)

     class Assignment(former_assignment: Map[Command, Exec_ID])

     {

       @volatile private var tmp_assignment = former_assignment

       private val promise = Future.promise[Map[Command, Exec_ID]]

       def is_finished: Boolean = promise.is_finished

       def join: Map[Command, Exec_ID] = promise.join

       def assign(command_execs: List[(Command, Exec_ID)])

       {

         promise.fulfill(tmp_assignment ++ command_execs)

         tmp_assignment = Map()

       }

     }

   }

   case class State(

     val versions: Map[Version_ID, Version] = Map(),

     val commands: Map[Command_ID, Command.State] = Map(),

     val execs: Map[Exec_ID, (Command.State, Set[Version])] = Map(),

     val assignments: Map[Version, State.Assignment] = Map(),

     val disposed: Set[ID] = Set())  // FIXME unused!?

   {

     private def fail[A]: A = throw new State.Fail(this)

     def define_version(version: Version, former_assignment: Map[Command, Exec_ID]): State =

     {

       val id = version.id

       if (versions.isDefinedAt(id) || disposed(id)) fail

       copy(versions = versions + (id -> version),

         assignments = assignments + (version -> new State.Assignment(former_assignment)))

     }

     def define_command(command: Command): State =

     {

       val id = command.id

       if (commands.isDefinedAt(id) || disposed(id)) fail

       copy(commands = commands + (id -> command.empty_state))

     }

     def lookup_command(id: Command_ID): Option[Command] = commands.get(id).map(_.command)

     def the_version(id: Version_ID): Version = versions.getOrElse(id, fail)

     def the_command(id: Command_ID): Command.State = commands.getOrElse(id, fail)

     def the_exec_state(id: Exec_ID): Command.State = execs.getOrElse(id, fail)._1

     def the_assignment(version: Version): State.Assignment = assignments.getOrElse(version, fail)

     def accumulate(id: ID, message: XML.Tree): (Command.State, State) =

       execs.get(id) match {

         case Some((st, occs)) =>

           val new_st = st.accumulate(message)

           (new_st, copy(execs = execs + (id -> (new_st, occs))))

         case None =>

           commands.get(id) match {

             case Some(st) =>

               val new_st = st.accumulate(message)

               (new_st, copy(commands = commands + (id -> new_st)))

             case None => fail

           }

       }

     def assign(id: Version_ID, edits: List[(Command_ID, Exec_ID)]): State =

     {

       val version = the_version(id)

       val occs = Set(version)  // FIXME unused (!?)

       var new_execs = execs

       val assigned_execs =

         for ((cmd_id, exec_id) <- edits) yield {

           val st = the_command(cmd_id)

           if (new_execs.isDefinedAt(exec_id) || disposed(exec_id)) fail

           new_execs += (exec_id -> (st, occs))

           (st.command, exec_id)

         }

       the_assignment(version).assign(assigned_execs)  // FIXME explicit value instead of promise (!?)

       copy(execs = new_execs)

     }

     def is_assigned(version: Version): Boolean =

       assignments.get(version) match {

         case Some(assgn) => assgn.is_finished

         case None => false

       }

     def command_state(version: Version, command: Command): Command.State =

     {

       val assgn = the_assignment(version)

       require(assgn.is_finished)

       the_exec_state(assgn.join.getOrElse(command, fail))

     }

   }

 }