zio.config.KeyConversionFunctions.scala Maven / Gradle / Ivy

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package zio.config

import scala.annotation.tailrec

private[config] trait KeyConversionFunctions {

  /**
   * Convert camelCase to any delimited string.
   * Example:
   *
   * {{{
   *   camelToDelimiter("abcDef", "-") === abc-def
   * }}}
   */
  def camelToDelimiter(input: String, delimiter: String): String = {
    def addToAcc(acc: List[String], current: List[Int]) = {
      def currentWord = current.reverse.flatMap(i => Character.toChars(i)).mkString.toLowerCase
      if (current.isEmpty) acc
      else if (acc.isEmpty) currentWord :: Nil
      else currentWord :: delimiter :: acc
    }

    @tailrec
    def loop(chars: List[Int], acc: List[String], current: List[Int], beginning: Boolean): String =
      chars match {
        case Nil                                         => addToAcc(acc, current).reverse.mkString
        case head :: tail if beginning                   =>
          loop(tail, acc, head :: current, Character.isUpperCase(head) || !Character.isLetter(head))
        case head :: tail if Character.isUpperCase(head) =>
          loop(tail, addToAcc(acc, current), head :: Nil, beginning = true)
        case head :: tail                                =>
          loop(tail, acc, head :: current, beginning = false)
      }

    loop(input.map(_.toInt).toList, Nil, Nil, beginning = true)
  }

  /**
   * Convert a camelCase key to kebab-case
   * val s = abcDef
   * toKebabCase(s) === abc-def
   */
  val toKebabCase: String => String =
    camelToDelimiter(_, "-")

  /**
   * Convert a camelCase key to snake_case
   */
  val toSnakeCase: String => String =
    camelToDelimiter(_, "_")

  /**
   * Add a prefix to an existing key
   */
  def addPrefixToKey(prefix: String): String => String =
    s => s"${prefix}${s}"

  /**
   * Add a post fix to an existing key
   */
  def addPostFixToKey(string: String): String => String =
    s => s"${s}${string}"
}