/*

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.net.http;

import java.io.IOException;

import java.net.ProtocolException;

import java.net.URI;

import java.nio.ByteBuffer;

import java.util.Map;

import java.util.Objects;

import java.util.Optional;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.CompletionStage;

import java.util.concurrent.TimeUnit;

import java.util.stream.Stream;

/**

 * A WebSocket client conforming to RFC 6455.

 *

 * <p> A {@code WebSocket} provides full-duplex communication over a TCP

 * connection.

 *

 * <p> To create a {@code WebSocket} use a {@linkplain #newBuilder(URI, Listener)

 * builder}. Once a {@code WebSocket} is obtained, it's ready to send and

 * receive messages. When the {@code WebSocket} is no longer

 * needed it must be closed: a Close message must both be {@linkplain

 * #sendClose() sent} and {@linkplain Listener#onClose(WebSocket, Optional,

 * String) received}. Or to close abruptly, {@link #abort()} is called. Once

 * closed it remains closed, cannot be reopened.

 *

 * <p> Messages of type {@code X} are sent through the {@code WebSocket.sendX}

 * methods and received through {@link WebSocket.Listener}{@code .onX} methods

 *

 * <p> Messages are received only if {@linkplain #request(long) requested}.

 *

 * <p> One outstanding send operation is permitted: if another send operation is

 * initiated before the previous one has completed, an {@link

 * IllegalStateException IllegalStateException} will be thrown. When sending, a

 * message should not be modified until the returned {@code CompletableFuture}

 * completes (either normally or exceptionally).

 *

 * <p> Messages can be sent and received as a whole or in parts. A whole message

 * is a sequence of one or more messages in which the last message is marked

 * when it is sent or received.

 *

 * <p> If the message is contained in a {@link ByteBuffer}, bytes are considered

 * arranged from the {@code buffer}'s {@link ByteBuffer#position() position} to

 * the {@code buffer}'s {@link ByteBuffer#limit() limit}.

 *

 * <p> All message exchange is run by the threads belonging to the {@linkplain

 * HttpClient#executorService() executor service} of {@code WebSocket}'s {@link

 * HttpClient}.

 *

 * <p> Unless otherwise noted, passing a {@code null} argument to a constructor

 * or method of this type will cause a {@link NullPointerException

 * NullPointerException} to be thrown.

 *

 * @since 9

 */

public interface WebSocket {

    /**

     * Creates a builder of {@code WebSocket}s connected to the given URI and

     * receiving events with the given {@code Listener}.

     *

     * <p> Equivalent to:

     * <pre>{@code

     *     WebSocket.newBuilder(uri, HttpClient.getDefault())

     * }</pre>

     *

     * @param uri

     *         the WebSocket URI as defined in the WebSocket Protocol

     *         (with "ws" or "wss" scheme)

     *

     * @param listener

     *         the listener

     *

     * @throws IllegalArgumentException

     *         if the {@code uri} is not a WebSocket URI

     * @throws SecurityException

     *         if running under a security manager and the caller does

     *         not have permission to access the

     *         {@linkplain HttpClient#getDefault() default HttpClient}

     *

     * @return a builder

     */

    static Builder newBuilder(URI uri, Listener listener) {

        return newBuilder(uri, HttpClient.getDefault(), listener);

    }

    /**

     * Creates a builder of {@code WebSocket}s connected to the given URI and

     * receiving events with the given {@code Listener}.

     *

     * <p> Providing a custom {@code client} allows for finer control over the

     * opening handshake.

     *

     * <p> <b>Example</b>

     * <pre>{@code

     *     HttpClient client = HttpClient.create()

     *             .proxy(ProxySelector.of(new InetSocketAddress("proxy.example.com", 80)))

     *             .build();

     *     ...

     *     WebSocket.newBuilder(URI.create("ws://websocket.example.com"), client, listener)...

     * }</pre>

     *

     * @param uri

     *         the WebSocket URI as defined in the WebSocket Protocol

     *         (with "ws" or "wss" scheme)

     *

     * @param client

     *         the HttpClient

     * @param listener

     *         the listener

     *

     * @throws IllegalArgumentException

     *         if the uri is not a WebSocket URI

     *

     * @return a builder

     */

    static Builder newBuilder(URI uri, HttpClient client, Listener listener) {

        return new WSBuilder(uri, client, listener);

    }

    /**

     * A builder for creating {@code WebSocket} instances.

     *

     * <p> To build a {@code WebSocket}, instantiate a builder, configure it

     * as required by calling intermediate methods (the ones that return the

     * builder itself), then finally call {@link #buildAsync()} to get a {@link

     * CompletableFuture} with resulting {@code WebSocket}.

     *

     * <p> If an intermediate method has not been called, an appropriate

     * default value (or behavior) will be used. Unless otherwise noted, a

     * repeated call to an intermediate method overwrites the previous value (or

     * overrides the previous behaviour), if no exception is thrown.

     *

     * <p> Instances of {@code Builder} may not be safe for use by multiple

     * threads.

     *

     * @since 9

     */

    interface Builder {

        /**

         * Adds the given name-value pair to the list of additional headers for

         * the opening handshake.

         *

         * <p> Headers defined in WebSocket Protocol are not allowed to be added.

         *

         * @param name

         *         the header name

         * @param value

         *         the header value

         *

         * @return this builder

         *

         * @throws IllegalArgumentException

         *         if the {@code name} is a WebSocket defined header name

         */

        Builder header(String name, String value);

        /**

         * Includes a request for the given subprotocols during the opening

         * handshake.

         *

         * <p> Among the requested subprotocols at most one will be chosen by

         * the server. When the {@code WebSocket} is connected, the subprotocol

         * in use is available from {@link WebSocket#getSubprotocol}.

         * Subprotocols may be specified in the order of preference.

         *

         * <p> Each of the given subprotocols must conform to the relevant

         * rules defined in the WebSocket Protocol.

         *

         * @param mostPreferred

         *         the most preferred subprotocol

         * @param lesserPreferred

         *         the lesser preferred subprotocols, with the least preferred

         *         at the end

         *

         * @return this builder

         *

         * @throws IllegalArgumentException

         *         if any of the WebSocket Protocol rules relevant to

         *         subprotocols are violated

         */

        Builder subprotocols(String mostPreferred, String... lesserPreferred);

        /**

         * Sets a timeout for the opening handshake.

         *

         * <p> If the opening handshake is not finished within the specified

         * timeout then {@link #buildAsync()} completes exceptionally with a

         * {@code HttpTimeoutException}.

         *

         * <p> If the timeout is not specified then it's deemed infinite.

         *

         * @param timeout

         *         the maximum time to wait

         * @param unit

         *         the time unit of the timeout argument

         *

         * @return this builder

         *

         * @throws IllegalArgumentException

         *         if the {@code timeout} is negative

         */

        Builder connectTimeout(long timeout, TimeUnit unit);

        /**

         * Builds a {@code WebSocket}.

         *

         *

         * <p> {@code CompletableFuture} may complete exceptionally with the

         * following errors:

         * <ul>

         * <li> {@link IOException}

         *          if an I/O error occurs

         * <li> {@link InterruptedException}

         *          if the operation was interrupted

         * <li> {@link SecurityException}

         *          if a security manager is set, and the caller does not

         *          have a {@link java.net.URLPermission} for the WebSocket URI

         * <li> {@link WebSocketHandshakeException}

         *          if the opening handshake fails

         * </ul>

         *

         */

        CompletableFuture<WebSocket> buildAsync();

    }

    /**

     * A listener for events and messages on a {@code WebSocket}.

     *

     * <p> Each method below corresponds to a type of event.

     * <ul>

     * <li> {@link #onOpen onOpen} <br>

     * This method is always the first to be invoked.

     * <li> {@link #onText(WebSocket, CharSequence, WebSocket.MessagePart)

     * onText}, {@link #onBinary(WebSocket, ByteBuffer, WebSocket.MessagePart)

     * onBinary}, {@link #onPing(WebSocket, ByteBuffer) onPing} and {@link

     * #onPong(WebSocket, ByteBuffer) onPong} <br>

     * These methods are invoked zero or more times after {@code onOpen}.

     * <li> {@link #onClose(WebSocket, Optional, String) onClose}, {@link

     * #onError(WebSocket, Throwable) onError} <br>

     * Only one of these methods is invoked, and that method is invoked last and

     * at most once.

     * </ul>

     *

     * <pre><code>

     *     onOpen (onText|onBinary|onPing|onPong)* (onClose|onError)?

     * </code></pre>

     *

     * <p> Messages received by the {@code Listener} conform to the WebSocket

     * Protocol, otherwise {@code onError} with a {@link ProtocolException} is

     * invoked.

     *

     * <p> If a whole message is received, then the corresponding method

     * ({@code onText} or {@code onBinary}) will be invoked with {@link

     * WebSocket.MessagePart#WHOLE WHOLE} marker. Otherwise the method will be

     * invoked with {@link WebSocket.MessagePart#FIRST FIRST}, zero or more

     * times with {@link WebSocket.MessagePart#FIRST PART} and, finally, with

     * {@link WebSocket.MessagePart#LAST LAST} markers.

     *

     * <pre><code>

     *     WHOLE|(FIRST PART* LAST)

     * </code></pre>

     *

     * <p> All methods are invoked in a sequential (and

     * <a href="../../../java/util/concurrent/package-summary.html#MemoryVisibility">

     * happens-before</a>) order, one after another, possibly by different

     * threads. If any of the methods above throws an exception, {@code onError}

     * is then invoked with that exception. Exceptions thrown from {@code

     * onError} or {@code onClose} are ignored.

     *

     * <p> When the method returns, the message is deemed received. After this

     * another messages may be received.

     *

     * <p> These invocations begin asynchronous processing which might not end

     * with the invocation. To provide coordination, methods of {@code

     * Listener} return a {@link CompletionStage CompletionStage}. The {@code

     * CompletionStage} signals the {@code WebSocket} that the

     * processing of a message has ended. For

     * convenience, methods may return {@code null}, which means

     * the same as returning an already completed {@code CompletionStage}. If

     * the returned {@code CompletionStage} completes exceptionally, then {@link

     * #onError(WebSocket, Throwable) onError} will be invoked with the

     * exception.

     *

     * <p> Control of the message passes to the {@code Listener} with the

     * invocation of the method. Control of the message returns to the {@code

     * WebSocket} at the earliest of, either returning {@code null} from the

     * method, or the completion of the {@code CompletionStage} returned from

     * the method. The {@code WebSocket} does not access the message while it's

     * not in its control. The {@code Listener} must not access the message

     * after its control has been returned to the {@code WebSocket}.

     *

     * <p> It is the responsibility of the listener to make additional

     * {@linkplain WebSocket#request(long) message requests}, when ready, so

     * that messages are received eventually.

     *

     * <p> Methods above are never invoked with {@code null}s as their

     * arguments.

     *

     * @since 9

     */

    interface Listener {

        /**

         * Notifies the {@code Listener} that it is connected to the provided

         * {@code WebSocket}.

         *

         * <p> The {@code onOpen} method does not correspond to any message

         * from the WebSocket Protocol. It is a synthetic event. It is the first

         * {@code Listener}'s method to be invoked. No other {@code Listener}'s

         * methods are invoked before this one. The method is usually used to

         * make an initial {@linkplain WebSocket#request(long) request} for

         * messages.

         *

         * <p> If an exception is thrown from this method then {@link

         * #onError(WebSocket, Throwable) onError} will be invoked with the

         * exception.

         *

         * @implSpec The default implementation {@linkplain WebSocket#request(long)

         * requests one message}.

         *

         * @param webSocket

         *         the WebSocket

         */

        default void onOpen(WebSocket webSocket) { webSocket.request(1); }

        /**

         * Receives a Text message.

         *

         * <p> The {@code onText} method is invoked zero or more times between

         * {@code onOpen} and ({@code onClose} or {@code onError}).

         *

         * <p> This message may be a partial UTF-16 sequence. However, the

         * concatenation of all messages through the last will be a whole UTF-16

         * sequence.

         *

         * <p> If an exception is thrown from this method or the returned {@code

         * CompletionStage} completes exceptionally, then {@link

         * #onError(WebSocket, Throwable) onError} will be invoked with the

         * exception.

         *

         * @implSpec The default implementation {@linkplain WebSocket#request(long)

         * requests one more message}.

         *

         * @implNote This implementation passes only complete UTF-16 sequences

         * to the {@code onText} method.

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         * @param part

         *         the part

         *

         * @return a CompletionStage that completes when the message processing

         * is done; or {@code null} if already done

         */

        default CompletionStage<?> onText(WebSocket webSocket,

                                          CharSequence message,

                                          MessagePart part) {

            webSocket.request(1);

            return null;

        }

        /**

         * Receives a Binary message.

         *

         * <p> The {@code onBinary} method is invoked zero or more times

         * between {@code onOpen} and ({@code onClose} or {@code onError}).

         *

         * <p> If an exception is thrown from this method or the returned {@code

         * CompletionStage} completes exceptionally, then {@link

         * #onError(WebSocket, Throwable) onError} will be invoked with this

         * exception.

         *

         * @implSpec The default implementation {@linkplain WebSocket#request(long)

         * requests one more message}.

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         * @param part

         *         the part

         *

         * @return a CompletionStage that completes when the message processing

         * is done; or {@code null} if already done

         */

        default CompletionStage<?> onBinary(WebSocket webSocket,

                                            ByteBuffer message,

                                            MessagePart part) {

            webSocket.request(1);

            return null;

        }

        /**

         * Receives a Ping message.

         *

         * <p> A Ping message may be sent or received by either client or

         * server. It may serve either as a keepalive or as a means to verify

         * that the remote endpoint is still responsive.

         *

         * <p> The message will consist of not more than {@code 125} bytes:

         * {@code message.remaining() <= 125}.

         *

         * <p> The {@code onPing} is invoked zero or more times in between

         * {@code onOpen} and ({@code onClose} or {@code onError}).

         *

         * <p> If an exception is thrown from this method or the returned {@code

         * CompletionStage} completes exceptionally, then {@link

         * #onError(WebSocket, Throwable) onError} will be invoked with this

         * exception.

         *

         * @implNote

         *

         * <p> Replies with a Pong message and requests one more message when

         * the Pong has been sent.

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         *

         * @return a CompletionStage that completes when the message processing

         * is done; or {@code null} if already done

         */

        default CompletionStage<?> onPing(WebSocket webSocket,

                                          ByteBuffer message) {

            return webSocket.sendPong(message).thenRun(() -> webSocket.request(1));

        }

        /**

         * Receives a Pong message.

         *

         * <p> A Pong message may be unsolicited or may be received in response

         * to a previously sent Ping. In the latter case, the contents of the

         * Pong is identical to the originating Ping.

         *

         * <p> The message will consist of not more than {@code 125} bytes:

         * {@code message.remaining() <= 125}.

         *

         * <p> The {@code onPong} method is invoked zero or more times in

         * between {@code onOpen} and ({@code onClose} or {@code onError}).

         *

         * <p> If an exception is thrown from this method or the returned {@code

         * CompletionStage} completes exceptionally, then {@link

         * #onError(WebSocket, Throwable) onError} will be invoked with this

         * exception.

         *

         * @implSpec The default implementation {@linkplain WebSocket#request(long)

         * requests one more message}.

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         *

         * @return a CompletionStage that completes when the message processing

         * is done; or {@code null} if already done

         */

        default CompletionStage<?> onPong(WebSocket webSocket,

                                          ByteBuffer message) {

            webSocket.request(1);

            return null;

        }

        /**

         * Receives a Close message.

         *

         * <p> Once a Close message is received, the server will not send any

         * more messages.

         *

         * <p> A Close message may consist of a close code and a reason for

         * closing. The reason will have a UTF-8 representation not longer than

         * {@code 123} bytes. The reason may be useful for debugging or passing

         * information relevant to the connection but is not necessarily human

         * readable.

         *

         * <p> {@code onClose} is the last invocation on the {@code Listener}.

         * It is invoked at most once, but after {@code onOpen}. If an exception

         * is thrown from this method, it is ignored.

         *

         * @implSpec The default implementation does nothing.

         *

         * @param webSocket

         *         the WebSocket

         * @param code

         *         an {@code Optional} describing the close code, or

         *         an empty {@code Optional} if the message doesn't contain it

         * @param reason

         *         the reason of close; can be empty