String converter for camelCase <-> snake_case

StringFormatter.scala

object StringFormatter {
  private val spacesPattern = "[-\\s]".r
  private val firstPattern = "([A-Z]+)([A-Z][a-z])".r
  private val secondPattern = "([a-z\\d])([A-Z])".r
  private val replacementPattern = "$1_$2"

  implicit class stringFormatter(val word: String) extends AnyVal {
    def snakenize: String = {
      spacesPattern
        .replaceAllIn(secondPattern.replaceAllIn(
          firstPattern.replaceAllIn(word, replacementPattern),
          replacementPattern
        ),
          "_")
        .toLowerCase
    }

    def camelize: String = {
      @scala.annotation.tailrec
      def loop(left: List[Char] = Nil, right: List[Char] = word.toList): List[Char] =
        right match {
          case '_' :: c :: rest => loop(c.toUpper :: left, rest)
          case '_' :: Nil => left
          case c :: rest => loop(c :: left, rest)
          case Nil => left
        }
      loop().reverse.mkString
    }
  }
}

implemented as a library feature.
https://github.com/petitviolet/scala-operator/blob/master/modules/operator/src/main/scala/net/petitviolet/operator/StringOps.scala