Scala3 UByte

package smallui

import scala.util.FromDigits
import scala.util.FromDigits.*

object UByte:
  opaque type UByte = Byte

  // Code to support custom number literals for UByte.
  // Unfortunately, custom number literals aren't working in Scala prior to 3.2.2 at the moment of writing
  given FromDigits[UByte] = literal =>
    if literal.isBlank || literal.length > 4
    then throw MalformedNumber()

    val firstChar = literal.charAt(0)
    val firstDigit = firstChar.isDigit

    if !(firstDigit || firstChar == '+') then throw MalformedNumber()
    else if firstChar == '-' then throw NumberTooSmall()

    var int = if firstDigit then firstChar.toInt else 0
    var i = 1
    while i < literal.length do
      val char = literal.charAt(i)
      if char.isDigit
      then int = int * 10 + char.toInt
      else throw MalformedNumber()
      i += 1
    end while

    if int > 255 then throw NumberTooLarge()

    (int - 128).toByte
  end given

  extension (self: UByte) {

    inline def -(other: UByte): UByte =
      (self - other).toByte

    inline def +(other: UByte): UByte =
      (self + other).toByte

    inline def /(other: UByte): UByte =
      (self / other).toByte

    inline def *(other: UByte): UByte =
      (self * other).toByte

    inline def toString: String =
      (self + 128).toString

  }

  extension (self: String)
    inline def toUByte: UByte = summon[FromDigits[UByte]].fromDigits(self)

  extension (self: Byte)
    inline def toUByte: UByte = self

  extension (self: Char)
    inline def toUByte: UByte = self.toByte

  extension (self: Short)
    inline def toUByte: UByte = (self - 128).toByte

  extension (self: Int)
    inline def toUByte: UByte = (self - 128).toByte

  extension (self: Long)
    inline def toUByte: UByte = (self - 128).toByte

  extension (self: Float)
    inline def toUByte: UByte = (self - 128).toByte

  extension (self: Double)
    inline def toUByte: UByte = (self - 128).toByte

export UByte.UByte