/*  Title:      Pure/PIDE/text.scala

    Author:     Fabian Immler, TU Munich

    Author:     Makarius

Basic operations on plain text.

*/

package isabelle

import scala.collection.mutable

import scala.math.Ordering

import scala.util.Sorting

object Text

{

  /* offset */

  type Offset = Int

  /* range -- with total quasi-ordering */

  object Range

  {

    def apply(start: Offset): Range = Range(start, start)

    object Ordering extends scala.math.Ordering[Text.Range]

    {

      def compare(r1: Text.Range, r2: Text.Range): Int = r1 compare r2

    }

  }

  sealed case class Range(val start: Offset, val stop: Offset)

  {

    // denotation: {start} Un {i. start < i & i < stop}

    if (start > stop)

      error("Bad range: [" + start.toString + ":" + stop.toString + "]")

    override def toString = "[" + start.toString + ":" + stop.toString + "]"

    def map(f: Offset => Offset): Range = Range(f(start), f(stop))

    def +(i: Offset): Range = map(_ + i)

    def -(i: Offset): Range = map(_ - i)

    def is_singularity: Boolean = start == stop

    def contains(i: Offset): Boolean = start == i || start < i && i < stop

    def contains(that: Range): Boolean = this.contains(that.start) && that.stop <= this.stop

    def overlaps(that: Range): Boolean = this.contains(that.start) || that.contains(this.start)

    def compare(that: Range): Int = if (overlaps(that)) 0 else this.start compare that.start

    def apart(that: Range): Boolean =

      (this.start max that.start) > (this.stop min that.stop)

    def restrict(that: Range): Range =

      Range(this.start max that.start, this.stop min that.stop)

    def try_restrict(that: Range): Option[Range] =

      if (this apart that) None

      else Some(restrict(that))

    def try_join(that: Range): Option[Range] =

      if (this apart that) None

      else Some(Range(this.start min that.start, this.stop max that.stop))

  }

  /* perspective */

  object Perspective

  {

    val empty: Perspective = Perspective(Nil)

    def apply(ranges: Seq[Range]): Perspective =

    {

      val result = new mutable.ListBuffer[Text.Range]

      var last: Option[Text.Range] = None

      def ship(next: Option[Range]) { result ++= last; last = next }

      for (range <- ranges.sortBy(_.start))

      {

        last match {

          case None => ship(Some(range))

          case Some(last_range) =>

            last_range.try_join(range) match {

              case None => ship(Some(range))

              case joined => last = joined

            }

        }

      }

      ship(None)

      new Perspective(result.toList)

    }

  }

  class Perspective private(val ranges: List[Range]) // visible text partitioning in canonical order

  {

    def is_empty: Boolean = ranges.isEmpty

    def range: Range =

      if (is_empty) Range(0)

      else Range(ranges.head.start, ranges.last.stop)

    override def toString = ranges.toString

  }

  /* information associated with text range */

  sealed case class Info[A](val range: Text.Range, val info: A)

  {

    def restrict(r: Text.Range): Info[A] = Info(range.restrict(r), info)

    def try_restrict(r: Text.Range): Option[Info[A]] =

      try { Some(Info(range.restrict(r), info)) }

      catch { case ERROR(_) => None }

  }

  type Markup = Info[XML.Tree]

  /* editing */

  object Edit

  {

    def insert(start: Offset, text: String): Edit = new Edit(true, start, text)

    def remove(start: Offset, text: String): Edit = new Edit(false, start, text)

  }

  class Edit private(val is_insert: Boolean, val start: Offset, val text: String)

  {

    override def toString =

      (if (is_insert) "Insert(" else "Remove(") + (start, text).toString + ")"

    /* transform offsets */

    private def transform(do_insert: Boolean, i: Offset): Offset =

      if (i < start) i

      else if (do_insert) i + text.length

      else (i - text.length) max start

    def convert(i: Offset): Offset = transform(is_insert, i)

    def revert(i: Offset): Offset = transform(!is_insert, i)

    def convert(range: Range): Range = range.map(convert)

    def revert(range: Range): Range = range.map(revert)

    /* edit strings */

    private def insert(i: Offset, string: String): String =

      string.substring(0, i) + text + string.substring(i)

    private def remove(i: Offset, count: Int, string: String): String =

      string.substring(0, i) + string.substring(i + count)

    def can_edit(string: String, shift: Int): Boolean =

      shift <= start && start < shift + string.length

    def edit(string: String, shift: Int): (Option[Edit], String) =

      if (!can_edit(string, shift)) (Some(this), string)

      else if (is_insert) (None, insert(start - shift, string))

      else {

        val i = start - shift

        val count = text.length min (string.length - i)

        val rest =

          if (count == text.length) None

          else Some(Edit.remove(start, text.substring(count)))

        (rest, remove(i, count, string))

      }

  }

}