/*

 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.incubator.http;

import jdk.incubator.http.internal.common.ByteBufferReference;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.util.function.Consumer;

import java.util.function.Supplier;

/**

 * Implemented by classes that offer an asynchronous interface.

 *

 * PlainHttpConnection, AsyncSSLConnection AsyncSSLDelegate.

 *

 * setAsyncCallbacks() is called to set the callback for reading

 * and error notification. Reads all happen on the selector thread, which

 * must not block.

 *

 * Writing uses the same write() methods as used in blocking mode.

 * Queues are employed on the writing side to buffer data while it is waiting

 * to be sent. This strategy relies on HTTP/2 protocol flow control to stop

 * outgoing queue from continually growing. Writes can be initiated by the

 * calling thread, but if socket becomes full then the queue is emptied by

 * the selector thread

 */

interface AsyncConnection {

    /**

     * Enables asynchronous sending and receiving mode. The given async

     * receiver will receive all incoming data. asyncInput() will be called

     * to trigger reads. asyncOutput() will be called to drive writes.

     *

     * The errorReceiver callback must be called when any fatal exception

     * occurs. Connection is assumed to be closed afterwards.

     */

    void setAsyncCallbacks(Consumer<ByteBufferReference> asyncReceiver,

                           Consumer<Throwable> errorReceiver,

                           Supplier<ByteBufferReference> readBufferSupplier);

    /**

     * Does whatever is required to start reading. Usually registers

     * an event with the selector thread.

     */

    void startReading();

    /**

     * Cancel asynchronous reading. Used to downgrade a HTTP/2 connection to HTTP/1

     */

    void stopAsyncReading();

    /**

     * In async mode, this method puts buffers at the end of the send queue.

     * When in async mode, calling this method should later be followed by

     * subsequent flushAsync invocation.

     * That allows multiple threads to put buffers into the queue while some other

     * thread is writing.

     */

    void writeAsync(ByteBufferReference[] buffers) throws IOException;

    /**

     * Re-enable asynchronous reads through the callback

     */

    void enableCallback();

    /**

     * In async mode, this method may put buffers at the beginning of send queue,

     * breaking frames sequence and allowing to write these buffers before other

     * buffers in the queue.

     * When in async mode, calling this method should later be followed by

     * subsequent flushAsync invocation.

     * That allows multiple threads to put buffers into the queue while some other

     * thread is writing.

     */

    void writeAsyncUnordered(ByteBufferReference[] buffers) throws IOException;

    /**

     * This method should be called after any writeAsync/writeAsyncUnordered

     * invocation.

     * If there is a race to flushAsync from several threads one thread

     * (race winner) capture flush operation and write the whole queue content.

     * Other threads (race losers) exits from the method (not blocking)

     * and continue execution.

     */

    void flushAsync() throws IOException;

}