/**
 * Throws an [InvalidInputException] if the [response][Response] [status][Status] is
 * [400][Status.BAD_REQUEST]. Otherwise, apply the [BiDiBodyLens] to the [response][Response].
 *
 * @see validate
 */
@Throws(InvalidInputException::class)
fun <FINAL> BiDiBodyLens<FINAL>.getOrThrow(response: Response): FINAL {
    if (response.status == Status.BAD_REQUEST) throw InvalidInputException(response.body.toString())
    response.validate()
    return this(response)
}

/**
 * If the [response][Response] is [204][Status.NO_CONTENT], return `null`. Otherwise, apply the
 * [BiDiBodyLens] to the [response][Response].
 *
 * @see validate
 */
fun <FINAL> BiDiBodyLens<FINAL>.optional(response: Response): FINAL? {
    response.validate()
    return if (response.status == Status.NO_CONTENT) null else this(response)
}

/**
 * If the [response][Response] is [204][Status.NO_CONTENT], return an empty [List][emptyList].
 * Otherwise, apply the [BiDiBodyLens] to the [response][Response].
 *
 * @see validate
 */
fun <FINAL> BiDiBodyLens<List<FINAL>>.optional(response: Response): List<FINAL> {
    response.validate()
    return if (response.status == Status.NO_CONTENT) emptyList() else this(response)
}

/**
 * Throws a [ResponseException] if the [Response] [status][Status] is not [200][Status.OK] or
 * [204][Status.NO_CONTENT].
 */
@Throws(ResponseException::class)
fun Response.validate() {
    if (status !in listOf(Status.OK, Status.NO_CONTENT)) throw ResponseException(status)
}