*
   * If there's nothing to read and no default value, this will throw an exception.
   */
  fun fromDer(reader: DerReader): T

  fun fromDer(byteString: ByteString): T {
    val buffer = Buffer().write(byteString)
    val reader = DerReader(buffer)
    return fromDer(reader)
  }

  /**
   * Writes [value] to this adapter, unless it is the default value and can be safely omitted.
   *

 * https://hc.apache.org/httpcomponents-client-5.0.x/httpclient5/examples/AsyncClientTlsAlpn.java
 *
 * Mainly intended to verify behaviour of popular clients across Android versions, similar
 * to observing Firefox or Chrome browser behaviour.
 */
class ApacheHttpClientHttp2Test {
  @Test
  fun testHttp2() {
    val client = HttpAsyncClients.createHttp2Default()

    client.use { client ->
      client.start()

    return result
  }
  synchronized(BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS) {
    for (i in 0 until BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS.size) {
      var format: DateFormat? = BROWSER_COMPATIBLE_DATE_FORMATS[i]
      if (format == null) {
        format =
          SimpleDateFormat(BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS[i], Locale.US).apply {

) : DerAdapter<T> {
  init {
    require(tagClass >= 0)
    require(tag >= 0)
  }

  override fun matches(header: DerHeader): Boolean = header.tagClass == tagClass && header.tag == tag

  override fun fromDer(reader: DerReader): T {
    val peekedHeader = reader.peekHeader()
    if (peekedHeader == null || peekedHeader.tagClass != tagClass || peekedHeader.tag != tag) {
      if (isOptional) return defaultValue as T

  private OAuthSessionFactory sessionFactory;

  /** Guarded by this. */
  private OAuthSession session;

  public SlackClient(SlackApi slackApi) {
    this.slackApi = slackApi;
  }

  /** Shows a browser URL to authorize this app to act as this user. */
  public void requestOauthSession(String scopes, String team) throws Exception {
    if (sessionFactory == null) {
      sessionFactory = new OAuthSessionFactory(slackApi);

Caching
=======

OkHttp implements an optional, off by default, Cache. OkHttp aims for RFC correct and
pragmatic caching behaviour, following common real-world browser like Firefox/Chrome and 
server behaviour when ambiguous.

# Basic Usage

```kotlin
  private val client: OkHttpClient = OkHttpClient.Builder()
      .cache(Cache(
          directory = File(application.cacheDir, "http_cache"),
          // $0.05 worth of phone storage in 2020

    byte[] bytes = new byte[16];
    secureRandom.nextBytes(bytes);
    return ByteString.of(bytes);
  }

  private HttpUrl redirectUrl() {
    return mockWebServer.url("/oauth/");
  }

  /** When the browser hits the redirect URL, use the provided code to ask Slack for a session. */
  @Override public MockResponse dispatch(RecordedRequest request) {
    HttpUrl requestUrl = mockWebServer.url(request.getPath());

  private var failFastResponse: MockResponse? = null

  @Throws(InterruptedException::class)
  override fun dispatch(request: RecordedRequest): MockResponse {
    // To permit interactive/browser testing, ignore requests for favicons.
    val requestLine = request.requestLine
    if (requestLine == "GET /favicon.ico HTTP/1.1") {
      logger.info("served $requestLine")