/*

 * Copyright (c) 2015, 2017, 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 java.io.IOException;

import java.net.ProtocolException;

import java.net.URI;

import java.nio.ByteBuffer;

import java.time.Duration;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.CompletionStage;

/**

 * A WebSocket client conforming to RFC 6455.

 * {@Incubating}

 *

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

 * connection.

 *

 * <p> To create a {@code WebSocket} use a {@linkplain HttpClient#newWebSocketBuilder(

 * URI, Listener) builder}. Once a {@code WebSocket} is built, 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, int, String) received}.

 * The {@code WebSocket} may be also closed {@linkplain #abort() abruptly}.

 *

 * <p> Once closed the {@code WebSocket} remains {@linkplain #isClosed() closed}

 * and cannot be reopened.

 *

 * <p> Messages of type {@code X} (where {@code X} is one of: Text, Binary,

 * Ping, Pong or Close) are sent and received asynchronously through the {@code

 * WebSocket.send{X}} and {@link WebSocket.Listener}{@code .on{X}} methods

 * respectively. Each method returns a {@link CompletionStage} which completes

 * when the operation has completed.

 *

 * <p> Note that messages (of any type) are received only if {@linkplain

 * #request(long) requested}.

 *

 * <p> One outstanding send operation is permitted. No further send operation

 * can be initiated before the previous one has completed. When sending, a

 * message must not be modified until the returned {@link CompletableFuture}

 * completes (either normally or exceptionally).

 *

 * <p> Text and Binary messages can be sent and received as a whole or in parts.

 * A whole message is transferred as a sequence of one or more invocations of a

 * corresponding method where the last invocation is identified via an

 * additional method argument.

 *

 * <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> Unless otherwise stated, {@code null} parameter values will cause methods

 * and constructors to throw {@link NullPointerException}.

 *

 * @implNote This implementation's methods do not block before returning

 * a {@code CompletableFuture}.

 *

 * @since 9

 */

public interface WebSocket {

    /**

     * The WebSocket Close message status code (<code>{@value}</code>),

     * indicating normal closure, meaning that the purpose for which the

     * connection was established has been fulfilled.

     *

     * @see #sendClose(int, String)

     * @see Listener#onClose(WebSocket, int, String)

     */

    int NORMAL_CLOSURE = 1000;

    /**

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

     * {@Incubating}

     *

     * <p> To build a {@code WebSocket}, {@linkplain HttpClient#newWebSocketBuilder(

     * URI, Listener) create} 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).

     *

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

     * without external synchronization.

     *

     * @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

         */

        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. This subprotocol will be available from {@link

         * WebSocket#getSubprotocol}. Subprotocols are specified in the order of

         * preference.

         *

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

         * rules defined in the WebSocket Protocol.

         *

         * <p> If this method is not invoked then no subprotocols are requested.

         *

         * @param mostPreferred

         *         the most preferred subprotocol

         * @param lesserPreferred

         *         the lesser preferred subprotocols, with the least preferred

         *         at the end

         *

         * @return this builder

         */

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

        /**

         * Sets a timeout for the opening handshake.

         *

         * <p> If the opening handshake does not complete within the specified

         * duration then the {@code CompletableFuture} returned from {@link

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

         * HttpTimeoutException}.

         *

         * <p> If this method is not invoked then the timeout is deemed infinite.

         *

         * @param timeout

         *         the timeout, non-{@linkplain Duration#isNegative() negative},

         *         non-{@linkplain Duration#ZERO ZERO}

         *

         * @return this builder

         */

        Builder connectTimeout(Duration timeout);

        /**

         * Builds a {@code WebSocket}.

         *

         * <p> Returns a {@code CompletableFuture<WebSocket>} which completes

         * normally with the {@code WebSocket} when it is connected or completes

         * exceptionally if an error occurs.

         *

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

         * following errors:

         * <ul>

         * <li> {@link IOException} -

         *          if an I/O error occurs

         * <li> {@link WebSocketHandshakeException} -

         *          if the opening handshake fails

         * <li> {@link HttpTimeoutException} -

         *          if the opening handshake does not complete within

         *          the specified {@linkplain #connectTimeout(Duration) duration}

         * <li> {@link InterruptedException} -

         *          if the operation was interrupted

         * <li> {@link SecurityException} -

         * <li> {@link IllegalArgumentException} -

         *          if any of the additional {@link #header(String, String)

         *          headers} are illegal;

         *          or if any of the WebSocket Protocol rules relevant to {@link

         *          #subprotocols(String, String...) subprotocols} are violated;

         *          or if the {@link #connectTimeout(Duration) connect timeout}

         *          is invalid;

         * </ul>

         *

         * @return a {@code CompletableFuture} with the {@code WebSocket}

         */

        CompletableFuture<WebSocket> buildAsync();

    }

    /**

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

     * {@Incubating}

     *

     * <p> Each method of {@code Listener} corresponds to a type of event or a

     * type of message. The {@code WebSocket} argument of the method is the

     * {@code WebSocket} the event has occurred (the message has been received)

     * on. All methods with the same {@code WebSocket} argument 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.

     *

     * <ul>

     * <li> {@link #onOpen(WebSocket) onOpen} <br>

     * This method is invoked first.

     * <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, int, String) onClose}, {@link

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

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

     * </ul>

     *

     * <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#PART PART} and, finally, with

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

     *

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

     * invoked with the same {@code WebSocket} and this exception. Exceptions

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

     *

     * <p> When the method returns, the message is deemed received (in

     * particular, if contained in a {@code ByteBuffer buffer}, the data is

     * deemed received completely regardless of the result {@code

     * buffer.hasRemaining()} upon the method's return. After this further

     * 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 (by convention) means the same as returning an

     * already completed (normally) {@code CompletionStage}.

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

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

     * same {@code WebSocket} and this 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> A {@code WebSocket} implementation never invokes {@code Listener}'s

     * methods 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 and the first {@code

         * Listener}'s method to be invoked.

         *

         * <p> This 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 same

         * {@code WebSocket} and this exception.

         *

         * @implSpec The default implementation of this method behaves as if:

         *

         * <pre>{@code

         *     webSocket.request(1);

         * }</pre>

         *

         * @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 same

         * {@code WebSocket} and this exception.

         *

         * @implSpec The default implementation of this method behaves as if:

         *

         * <pre>{@code

         *     webSocket.request(1);

         *     return null;

         * }</pre>

         *

         * @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 {@code CompletionStage} which 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 the same

         * {@code WebSocket} and this exception.

         *

         * @implSpec The default implementation of this method behaves as if:

         *

         * <pre>{@code

         *     webSocket.request(1);

         *     return null;

         * }</pre>

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         * @param part

         *         the part

         *

         * @return a {@code CompletionStage} which 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 {@code WebSocket} handles Ping messages by replying with

         * appropriate Pong messages using a strategy of its choice, but within

         * the boundaries of the WebSocket Protocol. The {@code WebSocket} may

         * invoke {@code onPing} after handling a Ping message, before doing so

         * or in parallel with it. In other words no particular ordering is

         * guaranteed. If an error occurs while implementation handles this Ping

         * message, then {@code onError} will be invoked with this error. For

         * more details on handling Ping messages see RFC 6455 sections

         * <a href="https://tools.ietf.org/html/rfc6455#section-5.5.2">5.5.2. Ping</a>

         * and

         * <a href="https://tools.ietf.org/html/rfc6455#section-5.5.3">5.5.3. Pong</a>.

         *

         * <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.

         *

         * @implSpec The default implementation of this method behaves as if:

         *

         * <pre>{@code

         *     webSocket.request(1);

         *     return null;

         * }</pre>

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         *

         * @return a {@code CompletionStage} which completes when the message

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

         */

        default CompletionStage<?> onPing(WebSocket webSocket,

                                          ByteBuffer message) {

            webSocket.request(1);

            return null;

        }

        /**

         * 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 of this method behaves as if:

         *

         * <pre>{@code

         *     webSocket.request(1);

         *     return null;

         * }</pre>

         *

         * @param webSocket

         *         the WebSocket

         * @param message

         *         the message

         *

         * @return a {@code CompletionStage} which 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> A Close message consists of a status code and a reason for

         * closing. The status code is an integer in the range {@code 1000 <=

         * code <= 65535}. The {@code reason} is a short string that has an

         * UTF-8 representation not longer than {@code 123} bytes. For more

         * details on Close message, status codes and reason see RFC 6455 sections

         * <a href="https://tools.ietf.org/html/rfc6455#section-5.5.1">5.5.1. Close</a>

         * and

         * <a href="https://tools.ietf.org/html/rfc6455#section-7.4">7.4. Status Codes</a>.

         *

         * <p> After the returned {@code CompletionStage} has completed

         * (normally or exceptionally), the {@code WebSocket} completes the

         * closing handshake by replying with an appropriate Close message.

         *

         * <p> This implementation replies with a Close message that has the

         * same code this message has and an empty reason.

         *

         * <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.

         *

         * <p> The {@code WebSocket} will close at the earliest of completion of

         * the returned {@code CompletionStage} or sending a Close message. In

         * particular, if a Close message has been {@linkplain WebSocket#sendClose

         * sent} before, then this invocation completes the closing handshake

         * and by the time this method is invoked, the {@code WebSocket} will

         * have been closed.

         *

         * @implSpec The default implementation of this method behaves as if:

         *

         * <pre>{@code

         *     return null;

         * }</pre>

         *

         * @param webSocket

         *         the WebSocket

         * @param statusCode

         *         the status code

         * @param reason

         *         the reason

         *

         * @return a {@code CompletionStage} which completes when the {@code

         * WebSocket} can be closed; or {@code null} if it can be closed immediately

         *

         * @see #NORMAL_CLOSURE

         */