/* Title: Pure/Thy/text_edit.scala
Author: Fabian Immler, TU Munich
Author: Makarius
Basic edits on plain text.
*/
package isabelle
class Text_Edit(val is_insert: Boolean, val start: Int, val text: String)
{
override def toString =
(if (is_insert) "Insert(" else "Remove(") + (start, text).toString + ")"
/* transform offsets */
private def transform(do_insert: Boolean, offset: Int): Int =
if (offset < start) offset
else if (is_insert == do_insert) offset + text.length
else (offset - text.length) max start
def after(offset: Int): Int = transform(true, offset)
def before(offset: Int): Int = transform(false, offset)
/* edit strings */
private def insert(index: Int, string: String): String =
string.substring(0, index) + text + string.substring(index)
private def remove(index: Int, count: Int, string: String): String =
string.substring(0, index) + string.substring(index + count)
def can_edit(string: String, shift: Int): Boolean =
shift <= start && start < shift + string.length
def edit(string: String, shift: Int): (Option[Text_Edit], String) =
if (!can_edit(string, shift)) (Some(this), string)
else if (is_insert) (None, insert(start - shift, string))
else {
val index = start - shift
val count = text.length min (string.length - index)
val rest =
if (count == text.length) None
else Some(new Text_Edit(false, start, text.substring(count)))
(rest, remove(index, count, string))
}
}