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/*  Title:      Pure/Thy/thy_syntax.scala
    Author:     Makarius

Superficial theory syntax: tokens and spans.
*/

package isabelle


import scala.collection.mutable
import scala.annotation.tailrec


object Thy_Syntax
{
  /** nested structure **/

  object Structure
  {
    sealed abstract class Entry { def length: Int }
    case class Block(val name: String, val body: List[Entry]) extends Entry
    {
      val length: Int = (0 /: body)(_ + _.length)
    }
    case class Atom(val command: Command) extends Entry
    {
      def length: Int = command.length
    }

    def parse(syntax: Outer_Syntax, node_name: Document.Node.Name, text: CharSequence): Entry =
    {
      /* stack operations */

      def buffer(): mutable.ListBuffer[Entry] = new mutable.ListBuffer[Entry]
      var stack: List[(Int, String, mutable.ListBuffer[Entry])] =
        List((0, node_name.toString, buffer()))

      @tailrec def close(level: Int => Boolean)
      {
        stack match {
          case (lev, name, body) :: (_, _, body2) :: rest if level(lev) =>
            body2 += Block(name, body.toList)
            stack = stack.tail
            close(level)
          case _ =>
        }
      }

      def result(): Entry =
      {
        close(_ => true)
        val (_, name, body) = stack.head
        Block(name, body.toList)
      }

      def add(command: Command)
      {
        syntax.heading_level(command) match {
          case Some(i) =>
            close(_ > i)
            stack = (i + 1, command.source, buffer()) :: stack
          case None =>
        }
        stack.head._3 += Atom(command)
      }


      /* result structure */

      val spans = parse_spans(syntax.scan(text))
      spans.foreach(span => add(Command(Document_ID.none, node_name, Nil, span)))
      result()
    }
  }



  /** parse spans **/

  def parse_spans(toks: List[Token]): List[List[Token]] =
  {
    val result = new mutable.ListBuffer[List[Token]]
    val span = new mutable.ListBuffer[Token]
    val improper = new mutable.ListBuffer[Token]

    def flush()
    {
      if (!span.isEmpty) { result += span.toList; span.clear }
      if (!improper.isEmpty) { result += improper.toList; improper.clear }
    }
    for (tok <- toks) {
      if (tok.is_command) { flush(); span += tok }
      else if (tok.is_improper) improper += tok
      else { span ++= improper; improper.clear; span += tok }
    }
    flush()

    result.toList
  }



  /** perspective **/

  def command_perspective(
      node: Document.Node,
      perspective: Text.Perspective,
      overlays: Document.Node.Overlays): (Command.Perspective, Command.Perspective) =
  {
    if (perspective.is_empty && overlays.is_empty)
      (Command.Perspective.empty, Command.Perspective.empty)
    else {
      val has_overlay = overlays.commands
      val visible = new mutable.ListBuffer[Command]
      val visible_overlay = new mutable.ListBuffer[Command]
      @tailrec
      def check_ranges(ranges: List[Text.Range], commands: Stream[(Command, Text.Offset)])
      {
        (ranges, commands) match {
          case (range :: more_ranges, (command, offset) #:: more_commands) =>
            val command_range = command.range + offset
            range compare command_range match {
              case 0 =>
                visible += command
                visible_overlay += command
                check_ranges(ranges, more_commands)
              case c =>
                if (has_overlay(command)) visible_overlay += command

                if (c < 0) check_ranges(more_ranges, commands)
                else check_ranges(ranges, more_commands)
            }

          case (Nil, (command, _) #:: more_commands) =>
            if (has_overlay(command)) visible_overlay += command

            check_ranges(Nil, more_commands)

          case _ =>
        }
      }

      val commands =
        (if (overlays.is_empty) node.command_iterator(perspective.range)
         else node.command_iterator()).toStream
      check_ranges(perspective.ranges, commands)
      (Command.Perspective(visible.toList), Command.Perspective(visible_overlay.toList))
    }
  }



  /** header edits: structure and outer syntax **/

  private def header_edits(
    resources: Resources,
    previous: Document.Version,
    edits: List[Document.Edit_Text]):
    (Prover.Syntax, Boolean, Boolean, List[Document.Node.Name], Document.Nodes,
      List[Document.Edit_Command]) =
  {
    var updated_imports = false
    var updated_keywords = false
    var nodes = previous.nodes
    val doc_edits = new mutable.ListBuffer[Document.Edit_Command]

    edits foreach {
      case (name, Document.Node.Deps(header)) =>
        val node = nodes(name)
        val update_header =
          !node.header.errors.isEmpty || !header.errors.isEmpty || node.header != header
        if (update_header) {
          val node1 = node.update_header(header)
          updated_imports = updated_imports || (node.header.imports != node1.header.imports)
          updated_keywords = updated_keywords || (node.header.keywords != node1.header.keywords)
          nodes += (name -> node1)
          doc_edits += (name -> Document.Node.Deps(header))
        }
      case _ =>
    }

    val (syntax, syntax_changed) =
      previous.syntax match {
        case Some(syntax) if !updated_keywords =>
          (syntax, false)
        case _ =>
          val syntax =
            (resources.base_syntax /: nodes.iterator) {
              case (syn, (_, node)) => syn.add_keywords(node.header.keywords)
            }
          (syntax, true)
      }

    val reparse =
      if (updated_imports || updated_keywords)
        nodes.descendants(doc_edits.iterator.map(_._1).toList)
      else Nil

    (syntax, syntax_changed, updated_imports, reparse, nodes, doc_edits.toList)
  }



  /** text edits **/

  /* edit individual command source */

  @tailrec def edit_text(eds: List[Text.Edit], commands: Linear_Set[Command]): Linear_Set[Command] =
  {
    eds match {
      case e :: es =>
        Document.Node.Commands.starts(commands.iterator).find {
          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), Command.unparsed(text)) - cmd
            edit_text(rest.toList ::: es, new_commands)

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

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


  /* inlined files */

  private def find_file(tokens: List[Token]): Option[String] =
  {
    def clean(toks: List[Token]): List[Token] =
      toks match {
        case t :: _ :: ts if t.is_keyword && (t.source == "%" || t.source == "--") => clean(ts)
        case t :: ts => t :: clean(ts)
        case Nil => Nil
      }
    clean(tokens.filter(_.is_proper)) match {
      case tok :: toks if tok.is_command => toks.find(_.is_name).map(_.content)
      case _ => None
    }
  }

  def span_files(syntax: Prover.Syntax, span: List[Token]): List[String] =
    syntax.load(span) match {
      case Some(exts) =>
        find_file(span) match {
          case Some(file) =>
            if (exts.isEmpty) List(file)
            else exts.map(ext => file + "." + ext)
          case None => Nil
        }
      case None => Nil
    }

  def resolve_files(
      resources: Resources,
      syntax: Prover.Syntax,
      node_name: Document.Node.Name,
      span: List[Token],
      get_blob: Document.Node.Name => Option[Document.Blob])
    : List[Command.Blob] =
  {
    span_files(syntax, span).map(file_name =>
      Exn.capture {
        val name =
          Document.Node.Name(resources.append(node_name.master_dir, Path.explode(file_name)))
        val blob = get_blob(name).map(blob => ((blob.bytes.sha1_digest, blob.chunk)))
        (name, blob)
      })
  }


  /* reparse range of command spans */

  @tailrec private def chop_common(
      cmds: List[Command],
      blobs_spans: List[(List[Command.Blob], List[Token])])
    : (List[Command], List[(List[Command.Blob], List[Token])]) =
  {
    (cmds, blobs_spans) match {
      case (cmd :: cmds, (blobs, span) :: rest) if cmd.blobs == blobs && cmd.span == span =>
        chop_common(cmds, rest)
      case _ => (cmds, blobs_spans)
    }
  }

  private def reparse_spans(
    resources: Resources,
    syntax: Prover.Syntax,
    get_blob: Document.Node.Name => Option[Document.Blob],
    name: Document.Node.Name,
    commands: Linear_Set[Command],
    first: Command, last: Command): Linear_Set[Command] =
  {
    val cmds0 = commands.iterator(first, last).toList
    val blobs_spans0 =
      parse_spans(syntax.scan(cmds0.iterator.map(_.source).mkString)).
        map(span => (resolve_files(resources, syntax, name, span, get_blob), span))

    val (cmds1, blobs_spans1) = chop_common(cmds0, blobs_spans0)

    val (rev_cmds2, rev_blobs_spans2) = chop_common(cmds1.reverse, blobs_spans1.reverse)
    val cmds2 = rev_cmds2.reverse
    val blobs_spans2 = rev_blobs_spans2.reverse

    cmds2 match {
      case Nil =>
        assert(blobs_spans2.isEmpty)
        commands
      case cmd :: _ =>
        val hook = commands.prev(cmd)
        val inserted =
          blobs_spans2.map({ case (blobs, span) => Command(Document_ID.make(), name, blobs, span) })
        (commands /: cmds2)(_ - _).append_after(hook, inserted)
    }
  }


  /* recover command spans after edits */

  // FIXME somewhat slow
  private def recover_spans(
    resources: Resources,
    syntax: Prover.Syntax,
    get_blob: Document.Node.Name => Option[Document.Blob],
    name: Document.Node.Name,
    perspective: Command.Perspective,
    commands: Linear_Set[Command]): Linear_Set[Command] =
  {
    val visible = perspective.commands.toSet

    def next_invisible_command(cmds: Linear_Set[Command], from: Command): Command =
      cmds.iterator(from).dropWhile(cmd => !cmd.is_command || visible(cmd))
        .find(_.is_command) getOrElse cmds.last

    @tailrec def recover(cmds: Linear_Set[Command]): Linear_Set[Command] =
      cmds.find(_.is_unparsed) match {
        case Some(first_unparsed) =>
          val first = next_invisible_command(cmds.reverse, first_unparsed)
          val last = next_invisible_command(cmds, first_unparsed)
          recover(reparse_spans(resources, syntax, get_blob, name, cmds, first, last))
        case None => cmds
      }
    recover(commands)
  }


  /* consolidate unfinished spans */

  private def consolidate_spans(
    resources: Resources,
    syntax: Prover.Syntax,
    get_blob: Document.Node.Name => Option[Document.Blob],
    reparse_limit: Int,
    name: Document.Node.Name,
    perspective: Command.Perspective,
    commands: Linear_Set[Command]): Linear_Set[Command] =
  {
    if (perspective.commands.isEmpty) commands
    else {
      commands.find(_.is_unfinished) match {
        case Some(first_unfinished) =>
          val visible = perspective.commands.toSet
          commands.reverse.find(visible) match {
            case Some(last_visible) =>
              val it = commands.iterator(last_visible)
              var last = last_visible
              var i = 0
              while (i < reparse_limit && it.hasNext) {
                last = it.next
                i += last.length
              }
              reparse_spans(resources, syntax, get_blob, name, commands, first_unfinished, last)
            case None => commands
          }
        case None => commands
      }
    }
  }


  /* main */

  def diff_commands(old_cmds: Linear_Set[Command], new_cmds: Linear_Set[Command])
    : List[Command.Edit] =
  {
    val removed = old_cmds.iterator.filter(!new_cmds.contains(_)).toList
    val inserted = new_cmds.iterator.filter(!old_cmds.contains(_)).toList

    removed.reverse.map(cmd => (old_cmds.prev(cmd), None)) :::
    inserted.map(cmd => (new_cmds.prev(cmd), Some(cmd)))
  }

  private def text_edit(
    resources: Resources,
    syntax: Prover.Syntax,
    get_blob: Document.Node.Name => Option[Document.Blob],
    reparse_limit: Int,
    node: Document.Node, edit: Document.Edit_Text): Document.Node =
  {
    edit match {
      case (_, Document.Node.Clear()) => node.clear

      case (_, Document.Node.Blob(blob)) => node.init_blob(blob)

      case (name, Document.Node.Edits(text_edits)) =>
        if (name.is_theory) {
          val commands0 = node.commands
          val commands1 = edit_text(text_edits, commands0)
          val commands2 =
            recover_spans(resources, syntax, get_blob, name, node.perspective.visible, commands1)
          node.update_commands(commands2)
        }
        else node

      case (_, Document.Node.Deps(_)) => node

      case (name, Document.Node.Perspective(required, text_perspective, overlays)) =>
        val (visible, visible_overlay) = command_perspective(node, text_perspective, overlays)
        val perspective: Document.Node.Perspective_Command =
          Document.Node.Perspective(required, visible_overlay, overlays)
        if (node.same_perspective(perspective)) node
        else
          node.update_perspective(perspective).update_commands(
            consolidate_spans(resources, syntax, get_blob, reparse_limit,
              name, visible, node.commands))
    }
  }

  def parse_change(
      resources: Resources,
      reparse_limit: Int,
      previous: Document.Version,
      doc_blobs: Document.Blobs,
      edits: List[Document.Edit_Text]): Session.Change =
  {
    def get_blob(name: Document.Node.Name) =
      doc_blobs.get(name) orElse previous.nodes(name).get_blob

    val (syntax, syntax_changed, deps_changed, reparse0, nodes0, doc_edits0) =
      header_edits(resources, previous, edits)

    val (doc_edits, version) =
      if (edits.isEmpty) (Nil, Document.Version.make(Some(syntax), previous.nodes))
      else {
        val reparse =
          (reparse0 /: nodes0.iterator)({
            case (reparse, (name, node)) =>
              if (node.load_commands.exists(_.blobs_changed(doc_blobs)))
                name :: reparse
              else reparse
            })
        val reparse_set = reparse.toSet

        var nodes = nodes0
        val doc_edits = new mutable.ListBuffer[Document.Edit_Command]; doc_edits ++= doc_edits0

        val node_edits =
          (edits ::: reparse.map((_, Document.Node.Edits(Nil)))).groupBy(_._1)
            .asInstanceOf[Map[Document.Node.Name, List[Document.Edit_Text]]]  // FIXME ???

        node_edits foreach {
          case (name, edits) =>
            val node = nodes(name)
            val commands = node.commands

            val node1 =
              if (reparse_set(name) && !commands.isEmpty)
                node.update_commands(
                  reparse_spans(resources, syntax, get_blob,
                    name, commands, commands.head, commands.last))
              else node
            val node2 =
              (node1 /: edits)(text_edit(resources, syntax, get_blob, reparse_limit, _, _))

            if (!(node.same_perspective(node2.perspective)))
              doc_edits += (name -> node2.perspective)

            doc_edits += (name -> Document.Node.Edits(diff_commands(commands, node2.commands)))

            nodes += (name -> node2)
        }
        (doc_edits.toList.filterNot(_._2.is_void), Document.Version.make(Some(syntax), nodes))
      }

    Session.Change(previous, syntax_changed, deps_changed, doc_edits, version)
  }
}