/*  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

  val ID = Properties.Value.Long

  type Version_ID = ID

  type Command_ID = ID

  type Exec_ID = ID

  val no_id: ID = 0

  val new_id = new Counter

  /** document structure **/

  /* named nodes -- development graph */

  type Edit[A, B] = (String, Node.Edit[A, B])

  type Edit_Text = Edit[Text.Edit, Text.Perspective]

  type Edit_Command = Edit[(Option[Command], Option[Command]), Command.Perspective]

  type Node_Header = Exn.Result[Thy_Header]

  object Node

  {

    sealed abstract class Edit[A, B]

    {

      def foreach(f: A => Unit)

      {

        this match {

          case Edits(es) => es.foreach(f)

          case _ =>

        }

      }

    }

    case class Clear[A, B]() extends Edit[A, B]

    case class Edits[A, B](edits: List[A]) extends Edit[A, B]

    case class Header[A, B](header: Node_Header) extends Edit[A, B]

    case class Perspective[A, B](perspective: B) extends Edit[A, B]

    def norm_header(f: String => String, g: String => String, header: Node_Header): Node_Header =

      header match {

        case Exn.Res(h) => Exn.capture { h.norm_deps(f, g) }

        case exn => exn

      }

    val empty: Node =

      Node(Exn.Exn(ERROR("Bad theory header")), Command.Perspective.empty, Map(), Linear_Set())

    def command_starts(commands: Iterator[Command], offset: Text.Offset = 0)

      : Iterator[(Command, Text.Offset)] =

    {

      var i = offset

      for (command <- commands) yield {

        val start = i

        i += command.length

        (command, start)

      }

    }

  }

  private val block_size = 1024

  sealed case class Node(

    val header: Node_Header,

    val perspective: Command.Perspective,

    val blobs: Map[String, Blob],

    val commands: Linear_Set[Command])

  {

    def clear: Node = Node.empty.copy(header = header)

    /* commands */

    private lazy val full_index: (Array[(Command, Text.Offset)], Text.Range) =

    {

      val blocks = new mutable.ListBuffer[(Command, Text.Offset)]

      var next_block = 0

      var last_stop = 0

      for ((command, start) <- Node.command_starts(commands.iterator)) {

        last_stop = start + command.length

        while (last_stop + 1 > next_block) {

          blocks += (command -> start)

          next_block += block_size

        }

      }

      (blocks.toArray, Text.Range(0, last_stop))

    }

    def full_range: Text.Range = full_index._2

    def command_range(i: Text.Offset = 0): Iterator[(Command, Text.Offset)] =

    {

      if (!commands.isEmpty && full_range.contains(i)) {

        val (cmd0, start0) = full_index._1(i / block_size)

        Node.command_starts(commands.iterator(cmd0), start0) dropWhile {

          case (cmd, start) => start + cmd.length <= i }

      }

      else Iterator.empty

    }

    def command_range(range: Text.Range): Iterator[(Command, Text.Offset)] =

      command_range(range.start) takeWhile { case (_, start) => start < range.stop }

    def command_at(i: Text.Offset): Option[(Command, Text.Offset)] =

    {

      val range = command_range(i)

      if (range.hasNext) Some(range.next) else None

    }

    def proper_command_at(i: Text.Offset): Option[Command] =

      command_at(i) match {

        case Some((command, _)) =>

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

        case None => None

      }

    def command_start(cmd: Command): Option[Text.Offset] =

      command_starts.find(_._1 == cmd).map(_._2)

    def command_starts: Iterator[(Command, Text.Offset)] =

      Node.command_starts(commands.iterator)

  }

  /** versioning **/

  /* particular document versions */

  object Version

  {

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

  }

  type Nodes = Map[String, Node]

  sealed case class Version(val id: Version_ID, val nodes: Nodes)

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

  object Change

  {

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

  }

  sealed case class Change(

    val previous: Future[Version],

    val edits: List[Edit_Text],

    val version: Future[Version])

  {

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

  }

  /* history navigation */

  object History

  {

    val init: History = new History(List(Change.init))

  }

  // FIXME pruning, purging of state

  class History(val undo_list: List[Change])

  {

    require(!undo_list.isEmpty)

    def tip: Change = undo_list.head

    def +(change: Change): History = new History(change :: undo_list)

  }

  /** global state -- document structure, execution process, editing history **/

  abstract class Snapshot

  {

    val state: State

    val version: Version

    val node: Node

    val is_outdated: Boolean

    def command_state(command: Command): Command.State

    def convert(i: Text.Offset): Text.Offset

    def convert(range: Text.Range): Text.Range

    def revert(i: Text.Offset): Text.Offset

    def revert(range: Text.Range): Text.Range

    def select_markup[A](range: Text.Range)(result: Markup_Tree.Select[A])

      : Stream[Text.Info[Option[A]]]

  }

  type Assign =

   (List[(Document.Command_ID, Option[Document.Exec_ID])],  // exec state assignment

    List[(String, Option[Document.Command_ID])])  // last exec

  val no_assign: Assign = (Nil, Nil)

  object State

  {

    class Fail(state: State) extends Exception

    val init: State =

      State().define_version(Version.init, Assignment.init).assign(Version.init.id, no_assign)._2

    object Assignment

    {

      val init: Assignment = Assignment(Map.empty, Map.empty, false)

    }

    case class Assignment(

      val command_execs: Map[Command_ID, Exec_ID],

      val last_execs: Map[String, Option[Command_ID]],

      val is_finished: Boolean)

    {

      def check_finished: Assignment = { require(is_finished); this }

      def unfinished: Assignment = copy(is_finished = false)

      def assign(add_command_execs: List[(Command_ID, Option[Exec_ID])],

        add_last_execs: List[(String, Option[Command_ID])]): Assignment =

      {

        require(!is_finished)

        val command_execs1 =

          (command_execs /: add_command_execs) {

            case (res, (command_id, None)) => res - command_id

            case (res, (command_id, Some(exec_id))) => res + (command_id -> exec_id)

          }

        Assignment(command_execs1, last_execs ++ add_last_execs, true)

      }

    }

  }

  sealed case class State(

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

    val commands: Map[Command_ID, Command.State] = Map(),  // static markup from define_command

    val execs: Map[Exec_ID, Command.State] = Map(),  // dynamic markup from execution

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

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

    val history: History = History.init)

  {

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

    def define_version(version: Version, assignment: State.Assignment): State =

    {

      val id = version.id

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

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

        assignments = assignments + (id -> assignment.unfinished))

    }

    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 defined_command(id: Command_ID): Boolean = commands.isDefinedAt(id)

    def find_command(version: Version, id: ID): Option[(String, Node, Command)] =

      commands.get(id) orElse execs.get(id) match {

        case None => None

        case Some(st) =>

          val command = st.command

          version.nodes.find({ case (_, node) => node.commands(command) })

            .map({ case (name, node) => (name, node, command) })

      }

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

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

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

    def the_assignment(version: Version): State.Assignment =

      assignments.getOrElse(version.id, fail)

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

      execs.get(id) match {

        case Some(st) =>

          val new_st = st.accumulate(message)

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

        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, arg: Assign): (List[Command], State) =

    {

      val version = the_version(id)

      val (command_execs, last_execs) = arg

      val (changed_commands, new_execs) =

        ((Nil: List[Command], execs) /: command_execs) {

          case ((commands1, execs1), (cmd_id, exec)) =>

            val st = the_command(cmd_id)

            val commands2 = st.command :: commands1

            val execs2 =

              exec match {

                case None => execs1

                case Some(exec_id) => execs1 + (exec_id -> st)

              }

            (commands2, execs2)

        }

      val new_assignment = the_assignment(version).assign(command_execs, last_execs)

      val new_state = copy(assignments = assignments + (id -> new_assignment), execs = new_execs)

      (changed_commands, new_state)

    }

    def is_assigned(version: Version): Boolean =

      assignments.get(version.id) match {

        case Some(assgn) => assgn.is_finished

        case None => false

      }

    def is_stable(change: Change): Boolean =

      change.is_finished && is_assigned(change.version.get_finished)

    def recent_stable: Option[Change] = history.undo_list.find(is_stable)

    def tip_stable: Boolean = is_stable(history.tip)

    def tip_version: Version = history.tip.version.get_finished

    def last_exec_offset(name: String): Text.Offset =

    {

      val version = tip_version

      the_assignment(version).last_execs.get(name) match {

        case Some(Some(id)) =>

          val node = version.nodes(name)

          val cmd = the_command(id).command

          node.command_start(cmd) match {

            case None => 0

            case Some(start) => start + cmd.length

          }

        case _ => 0

      }

    }

    def continue_history(

        previous: Future[Version],

        edits: List[Edit_Text],

        version: Future[Version]): (Change, State) =

    {

      val change = Change(previous, edits, version)

      (change, copy(history = history + change))

    }

    // persistent user-view

    def snapshot(name: String, pending_edits: List[Text.Edit]): Snapshot =

    {

      val stable = recent_stable.get

      val latest = history.tip

      // FIXME proper treatment of removed nodes

      val edits =

        (pending_edits /: history.undo_list.takeWhile(_ != stable))((edits, change) =>

            (for ((a, Node.Edits(es)) <- change.edits if a == name) yield es).flatten ::: edits)

      lazy val reverse_edits = edits.reverse

      new Snapshot

      {

        val state = State.this

        val version = stable.version.get_finished

        val node = version.nodes(name)

        val is_outdated = !(pending_edits.isEmpty && latest == stable)

        def command_state(command: Command): Command.State =

          try {

            the_exec(the_assignment(version).check_finished.command_execs

              .getOrElse(command.id, fail))

          }

          catch { case _: State.Fail => command.empty_state }

        def convert(offset: Text.Offset) = (offset /: edits)((i, edit) => edit.convert(i))

        def revert(offset: Text.Offset) = (offset /: reverse_edits)((i, edit) => edit.revert(i))

        def convert(range: Text.Range) = (range /: edits)((r, edit) => edit.convert(r))

        def revert(range: Text.Range) = (range /: reverse_edits)((r, edit) => edit.revert(r))

        def select_markup[A](range: Text.Range)(result: Markup_Tree.Select[A])

          : Stream[Text.Info[Option[A]]] =

        {

          val former_range = revert(range)

          for {

            (command, command_start) <- node.command_range(former_range).toStream

            Text.Info(r0, x) <- command_state(command).markup.

              select((former_range - command_start).restrict(command.range)) {

                case Text.Info(r0, info)

                if result.isDefinedAt(Text.Info(convert(r0 + command_start), info)) =>

                  result(Text.Info(convert(r0 + command_start), info))

              }

          } yield Text.Info(convert(r0 + command_start), x)

        }

      }

    }

  }

}