* limitations under the License.
 */

package okhttp3.internal.connection

import java.net.Inet6Address
import java.net.InetAddress
import okhttp3.internal.interleave

/**
 * Implementation of HappyEyeballs Sorting Addresses.
 *
 * The current implementation does not address any of:
 *  - Async DNS split by IP class
 *  - Stateful handling of connectivity results

 *
 * This nesting is typical but not strict. For example, when calls use "Expect: continue" the
 * request body start and end events occur within the response header events. Similarly,
 * [duplex calls][RequestBody.isDuplex] interleave the request and response bodies.
 *
 * Since connections may be reused, the proxy selection, DNS, and connect events may not be present
 * for a call. In future releases of OkHttp these events may also occur concurrently to permit

) {
  if (offset or count < 0L || offset > arrayLength || arrayLength - offset < count) {
    throw ArrayIndexOutOfBoundsException("length=$arrayLength, offset=$offset, count=$offset")
  }
}

internal fun <T> interleave(
  a: Iterable<T>,
  b: Iterable<T>,
): List<T> {
  val ia = a.iterator()
  val ib = b.iterator()

  return buildList {
    while (ia.hasNext() || ib.hasNext()) {
      if (ia.hasNext()) {

      if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        assertTrue(cancellationSuccess.get());
        // cancellation can interleave in 3 ways
        // 1. prior to setFuture
        // 2. after setFuture before set() on the future assigned
        // 3. after setFuture and set() are called but before the listener completes.

      if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        assertTrue(cancellationSuccess.get());
        // cancellation can interleave in 3 ways
        // 1. prior to setFuture
        // 2. after setFuture before set() on the future assigned
        // 3. after setFuture and set() are called but before the listener completes.

   *
   * ### Duplex Transmission
   *
   * With regular HTTP calls the request always completes sending before the response may begin
   * receiving. With duplex the request and response may be interleaved! That is, request body bytes
   * may be sent after response headers or body bytes have been received.
   *
   * Though any call may be initiated as a duplex call, only web servers that are specially

   *  * If it is a message frame this will result in a single call to [FrameCallback.onReadMessage].
   *    If the message spans multiple frames, each interleaved control frame will result in a
   *    corresponding call to [FrameCallback].
   */
  @Throws(IOException::class)
  fun processNextFrame() {
    readHeader()
    if (isControlFrame) {
      readControlFrame()

    // a multithreaded environment for a couple of reasons:
    //
    // 1. Subscribers to events posted on different threads can be interleaved with each other
    //    freely. (A event on one thread, B event on another could yield any of
    //    [a1, a2, a3, b1, b2], [a1, b2, a2, a3, b2], [a1, b2, b3, a2, a3], etc.)

#### Http2Writer

Socket writes are guarded by the Http2Writer. Only one stream can write at a time so that messages are not interleaved. Writes are either made by application-layer threads or the do-stuff-later pool.

### Holding multiple locks

   * We always do timeouts in the HTTP server role. For clients, we only do timeouts after the
   * request is transmitted. This is only interesting for duplex calls where the request and
   * response may be interleaved.
   *
   * Read this value only once for each enter/exit pair because its value can change.
   */
  private fun doReadTimeout() = !connection.client || sink.closed || sink.finished

  /**