/*  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, doc_blobs, syntax_changed, deps_changed, doc_edits, version)

  }

}