wenzelm@34276: /*  Title:      Pure/Thy/text_edit.scala
wenzelm@34276:     Author:     Fabian Immler, TU Munich
wenzelm@34276:     Author:     Makarius
wenzelm@34276: 
wenzelm@34276: Basic edits on plain text.
wenzelm@34276: */
wenzelm@34276: 
wenzelm@34276: package isabelle
wenzelm@34276: 
wenzelm@34276: 
wenzelm@34276: sealed abstract class Text_Edit
wenzelm@34276: {
wenzelm@34276:   val start: Int
wenzelm@34286:   def after(offset: Int): Int
wenzelm@34276:   def before(offset: Int): Int
wenzelm@34286:   def edit(string: String, shift: Int): (Option[Text_Edit], String)
wenzelm@34276: }
wenzelm@34276: 
wenzelm@34276: 
wenzelm@34276: object Text_Edit
wenzelm@34276: {
wenzelm@34286:   /* transform offsets */
wenzelm@34286: 
wenzelm@34286:   private def after_insert(start: Int, text: String, offset: Int): Int =
wenzelm@34286:     if (start <= offset) offset + text.length
wenzelm@34286:     else offset
wenzelm@34286: 
wenzelm@34286:   private def after_remove(start: Int, text: String, offset: Int): Int =
wenzelm@34286:     if (start > offset) offset
wenzelm@34286:     else (offset - text.length) max start
wenzelm@34286: 
wenzelm@34286: 
wenzelm@34286:   /* edit strings */
wenzelm@34286: 
wenzelm@34286:   private def insert(index: Int, text: String, string: String): String =
wenzelm@34286:     string.substring(0, index) + text + string.substring(index)
wenzelm@34286: 
wenzelm@34286:   private def remove(index: Int, count: Int, string: String): String =
wenzelm@34286:     string.substring(0, index) + string.substring(index + count)
wenzelm@34286: 
wenzelm@34286: 
wenzelm@34286:   /* explicit edits */
wenzelm@34286: 
wenzelm@34276:   case class Insert(start: Int, text: String) extends Text_Edit
wenzelm@34276:   {
wenzelm@34286:     def after(offset: Int): Int = after_insert(start, text, offset)
wenzelm@34286:     def before(offset: Int): Int = after_remove(start, text, offset)
wenzelm@34276: 
wenzelm@34286:     def can_edit(string_length: Int, shift: Int): Boolean =
wenzelm@34286:       shift <= start && start <= shift + string_length
wenzelm@34286: 
wenzelm@34286:     def edit(string: String, shift: Int): (Option[Insert], String) =
wenzelm@34286:       if (can_edit(string.length, shift)) (None, insert(start - shift, text, string))
wenzelm@34286:       else (Some(this), string)
wenzelm@34276:   }
wenzelm@34276: 
wenzelm@34276:   case class Remove(start: Int, text: String) extends Text_Edit
wenzelm@34276:   {
wenzelm@34286:     def after(offset: Int): Int = after_remove(start, text, offset)
wenzelm@34286:     def before(offset: Int): Int = after_insert(start, text, offset)
wenzelm@34286: 
wenzelm@34286:     def can_edit(string_length: Int, shift: Int): Boolean =
wenzelm@34286:       shift <= start && start < shift + string_length
wenzelm@34276: 
wenzelm@34286:     def edit(string: String, shift: Int): (Option[Remove], String) =
wenzelm@34286:       if (can_edit(string.length, shift)) {
wenzelm@34286:         val index = start - shift
wenzelm@34286:         val count = text.length min (string.length - index)
wenzelm@34286:         val rest =
wenzelm@34286:           if (count == text.length) None
wenzelm@34286:           else Some(Remove(start, text.substring(count)))
wenzelm@34286:         (rest, remove(index, count, string))
wenzelm@34286:       }
wenzelm@34286:       else (Some(this), string)
wenzelm@34276:   }
wenzelm@34276: }
wenzelm@34276: