json.kt

fun JsonElement.appendTo(builder: StringBuilder) {
  when (this) {
    is JsonArray -> {
      builder.append("[")
      elements.forEachIndexed { index, element ->
        element.appendTo(builder)
        if (index != elements.size - 1) {
          builder.append(",")
        }
      }
      builder.append("]")
    }
    is JsonBoolean -> {
      builder.append(value)
    }
    JsonNull -> {
      builder.append("null")
    }
    is JsonNumber -> {
      var valueFormatted = value.toString()
      if ('.' in valueFormatted) {
        valueFormatted = value.toString().dropLastWhile { it == '0' }
          .dropLastWhile { it == '.' }
      }
      builder.append(valueFormatted)
    }
    is JsonObject -> {
      builder.append("{")
      fields.toList().forEachIndexed { index, (key, value) ->
        builder.append("\"${key}\":")
        value.appendTo(builder)
        if (index != fields.size - 1) {
          builder.append(",")
        }
      }
      builder.append("}")
    }
    is JsonString -> {
      builder.append("\"$value\"")
    }
  }
}

fun JsonElement.stringify(): String {
  val builder = StringBuilder()
  appendTo(builder)
  return builder.toString()
}