Scala Word case transformation (from json4s)

CaseTransformer.scala

import java.util.Locale

/** Exposing privates from MonadicJValue
 * https://github.com/json4s/json4s/blob/3daa876d2fdbc117f80cb1dfd65e7112eb109948/ast/shared/src/main/scala/org/json4s/MonadicJValue.scala#L411 
 */

object CaseTransformer {

  def camelize(word: String): String = {
    if (word.nonEmpty) {
      val w = pascalize(word)
      w.substring(0, 1).toLowerCase(Locale.ENGLISH) + w.substring(1)
    } else {
      word
    }
  }

  def pascalize(word: String): String = {
    val lst = word.split("_").filterNot(_.isEmpty).toList
    (lst.headOption.map(s => s.substring(0, 1).toUpperCase(Locale.ENGLISH) + s.substring(1)).get ::
      lst.tail.map(s => s.substring(0, 1).toUpperCase + s.substring(1))).mkString("")
  }

  def underscoreCamelCasesOnly(word: String): String = {
    val firstPattern       = "([A-Z]+)([A-Z][a-z])".r
    val secondPattern      = "([a-z\\d])([A-Z])".r
    val replacementPattern = "$1_$2"
    secondPattern
      .replaceAllIn(
        firstPattern.replaceAllIn(word, replacementPattern),
        replacementPattern
      )
      .toLowerCase
  }

  def underscore(word: String): String = {
    val spacesPattern = "[-\\s]".r
    spacesPattern.replaceAllIn(underscoreCamelCasesOnly(word), "_")
  }

}

Link:
https://github.com/json4s/json4s/blob/3daa876d2fdbc117f80cb1dfd65e7112eb109948/ast/shared/src/main/scala/org/json4s/MonadicJValue.scala#L411