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skinny-common

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package skinny.util

import scala.collection.mutable.ListBuffer
import java.util.Locale.ENGLISH

/**
 * String utility.
 */
object StringUtil {

  private[this] val acronymRegExpStr = "[A-Z]{2,}"
  private[this] val acronymRegExp = acronymRegExpStr.r
  private[this] val endsWithAcronymRegExpStr = "[A-Z]{2,}$"
  private[this] val singleUpperCaseRegExp = """[A-Z]""".r

  /**
   * Converts String value to snake_case'd value.
   *
   * @param str string value
   * @return snake_case'd value
   */
  def toSnakeCase(str: String): String = {
    Option(str).map { s =>
      // first, applies acronyms filter
      val acronymsFiltered = acronymRegExp.replaceAllIn(
        acronymRegExp.findFirstMatchIn(s).map { m =>
          s.replaceFirst(endsWithAcronymRegExpStr, "_" + m.matched.toLowerCase(ENGLISH))
        }.getOrElse(s), // might end with an acronym
        { m => "_" + m.matched.init.toLowerCase(ENGLISH) + "_" + m.matched.last.toString.toLowerCase(ENGLISH) }
      )
      // second, convert single upper case char to '_' + c.toLower
      val result = singleUpperCaseRegExp.replaceAllIn(acronymsFiltered, { m => "_" + m.matched.toLowerCase(ENGLISH) })
        .replaceFirst("^_", "")
        .replaceFirst("_$", "")

      if (str.startsWith("_")) "_" + result
      else if (str.endsWith("_")) result + "_"
      else result
    }.orNull[String]
  }

  /**
   * Converts String value to camelCase value.
   *
   * @param str string value
   * @return camelCase value
   */
  def toCamelCase(str: String): String = {
    Option(str).map { s =>
      val result = toUpperCamelCase(s)
      if (result.headOption.exists(c => c.isUpper)) result.head.toLower + result.tail
      else result
    }.orNull[String]
  }

  def toUpperCamelCase(str: String): String = {
    Option(str).map { s =>
      val result = s.foldLeft((ListBuffer[Char](), false)) {
        case ((cs, prevIs_), c) =>
          if (c == '_') (cs, true)
          else if (prevIs_) (cs += c.toUpper, false)
          else (cs += c, false)
      }._1.mkString
      if (result.headOption.exists(c => c.isLower)) result.head.toUpper + result.tail
      else result
    }.orNull[String]
  }

}