JSON reformat

fastest.scala

def reformat(json: String) = {
  val tab = "  "
  var inString = false
  var indentLevel = 0

  var index = 0;
  val stringLength = json.length
  val formatted = new StringBuilder

  while (index < stringLength) {
    val c = json.charAt(index)
    if (!inString && (c == '{' || c == '[')) {
      indentLevel += 1
      formatted.append(c).append("\n" + (tab * indentLevel))
    } else if (!inString && (c == '}' || c == ']')) {
      indentLevel -= 1
      formatted.append("\n" + (tab * indentLevel)).append(c)
    } else if (!inString && c == ',') {
      formatted.append(",\n" + (tab * indentLevel))
    } else if (!inString && c == ':') {
      formatted.append(": ")
    } else if (!inString && (c == ' ' || c == '\n' || c == '\t')) {

    } else if (c == '"') {
      formatted.append(c)
      if (index > 0 && json.charAt(index - 1) != '\'') inString = !inString
    } else {
      formatted.append(c)
    }
    index += 1
  }

  formatted.toString
}

stringbuilder.scala

def reformat(json: String) = {
  val tab = "  "

  @tailrec 
  def reformatIter(newJson: StringBuilder, original: String, previousChar: Char, inString: Boolean, indentLevel: Int): String = {
    if (original.length == 0) newJson.toString
    else {
      val currentChar = original.head
      val (formatted, newInString, newIndentLevel) = currentChar match {
        case '{' | '[' if !inString ⇒ (currentChar + "\n" + tab * (indentLevel + 1), inString, indentLevel + 1)
        case '}' | ']' if !inString ⇒ ("\n" + tab * (indentLevel - 1) + currentChar, inString, indentLevel - 1)
        case ',' if !inString ⇒ (",\n" + tab * indentLevel, inString, indentLevel)
        case ':' if !inString ⇒ (": ", inString, indentLevel)
        case ' ' | '\n' | '\t' if !inString ⇒ ("", inString, indentLevel)
        case '"' ⇒ (currentChar, if (previousChar == '\'') inString else !inString, indentLevel)
        case c ⇒ (currentChar, inString, indentLevel)
      }
      reformatIter(newJson.append(formatted), original.tail, currentChar, newInString, newIndentLevel)
    }
  }

  reformatIter(new StringBuilder, json, ' ', false, 0)
}