Scala - Delete between defined region - scala

Question

I Have a series of tests that need to pass one of them includes deleting the buffer between the defined region (which is between the marker and cursor) and inserting the cut text in the paste. I then need to set the cursor and marker to the beginning of the cut text (see below code for a better understanding)
class Buffer(s: String) {
import scala.collection.mutable.StringBuilder
import scala.io.StdIn
private var buffer: StringBuilder = new StringBuilder(s)
private var cursor: Int = 0 // cursor is in between characters
private var marker: Int = 0 // marker is in between characters
private var paste: String = ""
private def end: Int = buffer.length // the end of the line
private def lwr: Int = Math.min(marker, cursor)
private def upr: Int = Math.max(marker, cursor)
/*
* Accessor methods to return aspects of the state
*/
def getCursor: Int = cursor
def getMarker: Int = marker
def getString: String = buffer.toString
def getPaste: String = paste
Delete the contents of the defined region and save the cut string in the paste
buffer. This operation re-sets the cursor and the marker to the start of the
cut text. For example:
B U F F E R marker = 1
^ ^ cursor = 4
Then perform xd()
B E R marker = 1
^ cursor = 1
*/
I have written some code:
def xd() {
paste = buffer.substring(lwr, upr)
buffer = buffer.delete(lwr, upr)
cursor = end
marker = end
}
this seems to pass the other tests but does not set the marker and cursor.
Any suggestions please?

Answer 1

First in Scala you would try to have no mutable state (var).
Here is a solution for cut and paste that is immutable:
case class Buffer(s: String, paste: String, private val cursor: Int = 0, private val marker: Int = 0) {
def mark(str: String): Buffer = {
val startIndex = s.indexOf(str)
val endIndex = startIndex + str.length
Buffer(s, startIndex, endIndex)
}
def cut(): Buffer = {
Buffer(s.take(cursor) + s.drop(marker), // rest of the String
s.take(marker).drop(cursor)) // paste of the String
}
}
You can use it like this:
Buffer("hello there") // > Buffer(hello there,,0,0)
.mark("o t") // > Buffer(hello there,,4,7)
.cut() // > Buffer(hellhere,o t,0,0)
You see the result of each line.
Let me know if you need more support or if I misunderstood you.