Translates between ASCII and unicode.

UnicodeTranslator.scala

import scala.annotation.tailrec

object UnicodeTranslator {

  private lazy val unicodeRegex = """(\\u[0-9a-fA-F]{4})""".r

  def escapeUnicode(stringToEscape:String) = stringToEscape.foldLeft("") { (escaped, char) =>
    if (char <= 127) {
      escaped + char
    } else {
      escaped + charToHex(char)
    }
  }

  def unescapeUnicode(stringToRemoveEscapesFrom:String):String = unescapeUnicode(stringToRemoveEscapesFrom, "")

  @tailrec
  private def unescapeUnicode(remainder:String, unescaped:String):String = remainder.take(6) match {
    case "" => unescaped;
    case unicodeRegex(hex) => unescapeUnicode(remainder.drop(6), unescaped + hexToChar(hex))
    case str => unescapeUnicode(remainder.tail, unescaped + str.head)
  }

  private def charToHex(c: Char) = {
    val hex = Integer.toHexString(c).toUpperCase.reverse.padTo(4, '0').reverse
    s"\\u$hex"
  }

  private def hexToChar(hex: String) = {
    val unicode = hex.drop(2)
    Integer.parseInt(unicode, 16).toChar
  }
}

UnicodeTranslatorTest.scala

import org.junit.runner.RunWith
import org.specs2.mutable.Specification
import org.specs2.runner.JUnitRunner

@RunWith(classOf[JUnitRunner])
class UnicodeTranslatorTest extends Specification {

  "escaping unicode" should {
    "not make any modifications for ASCII strings" in {
      UnicodeTranslator.escapeUnicode("Hello World") mustEqual "Hello World"
    }

    "replace a single character with it's unicode equivalent" in {
      UnicodeTranslator.escapeUnicode("ò") mustEqual "\\u00F2"
    }

    "replace the accented characters in a String" in {
      UnicodeTranslator.escapeUnicode("Bòrd na Gàidhlig") mustEqual "B\\u00F2rd na G\\u00E0idhlig"
    }
  }

  "unescaping unicode" should {
    "not make any modifications for ASCII strings" in {
      UnicodeTranslator.unescapeUnicode("Hello World") mustEqual "Hello World"
    }

    "replace a unicode with it's equivalent character" in {
      UnicodeTranslator.unescapeUnicode("\\u00F2") mustEqual "ò"
    }

    "replace unicodes in a string with the equivalent accented characters" in {
      UnicodeTranslator.unescapeUnicode("B\\u00F2rd na G\\u00E0idhlig") mustEqual "Bòrd na Gàidhlig"
    }
  }

}