/*

 * 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.Authenticator;

import java.net.CookieHandler;

import java.net.InetSocketAddress;

import java.net.Proxy;

import java.net.ProxySelector;

import java.net.URI;

import java.util.Optional;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.Executor;

import java.util.concurrent.Executors;

import java.util.concurrent.ThreadFactory;

import javax.net.ssl.SSLContext;

import javax.net.ssl.SSLParameters;

/**

 * A container for configuration information common to multiple {@link

 * HttpRequest}s. All requests are sent through a {@code HttpClient}.

 * {@Incubating}

 *

 * <p> {@code HttpClient}s are immutable and created from a builder returned

 * from {@link HttpClient#newBuilder()}. Request builders are created by calling

 * {@link HttpRequest#newBuilder() }.

 * <p>

 * See {@link HttpRequest} for examples of usage of this API.

 *

 * @since 9

 */

public abstract class HttpClient {

    /**

     * Creates an HttpClient.

     */

    protected HttpClient() {}

    /**

     * Returns a new HttpClient with default settings.

     *

     * <p> Equivalent to {@code newBuilder().build()}.

     *

     * <p> The default settings include: the "GET" request method, a preference

     * of {@linkplain HttpClient.Version#HTTP_2 HTTP/2}, a redirection policy of

     * {@linkplain Redirect#NEVER NEVER}, the {@linkplain

     * ProxySelector#getDefault() default proxy selector}, and the {@linkplain

     * SSLContext#getDefault() default SSL context}.

     *

     * @implNote The system-wide default values are retrieved at the time the

     * {@code HttpClient} instance is constructed. Changing the system-wide

     * values after an {@code HttpClient} instance has been built, for

     * instance, by calling {@link ProxySelector#setDefault(ProxySelector)}

     * or {@link SSLContext#setDefault(SSLContext)}, has no effect on already

     * built instances.

     *

     * @return a new HttpClient

     */

    public static HttpClient newHttpClient() {

        return newBuilder().build();

    }

    /**

     * Creates a new {@code HttpClient} builder.

     *

     * @return a {@code HttpClient.Builder}

     */

    public static Builder newBuilder() {

        return new HttpClientBuilderImpl();

    }

    /**

     * A builder of immutable {@link HttpClient}s.

     * {@Incubating}

     *

     * <p> Builders are created by invoking {@linkplain HttpClient#newBuilder()

     * newBuilder}. Each of the setter methods modifies the state of the builder

     * and returns the same instance. Builders are not thread-safe and should not be

     * used concurrently from multiple threads without external synchronization.

     *

     * @since 9

     */

    public abstract static class Builder {

        /**

         * A proxy selector that always return {@link Proxy#NO_PROXY} implying

         * a direct connection.

         * This is a convenience object that can be passed to {@link #proxy(ProxySelector)}

         * in order to build an instance of {@link HttpClient} that uses no

         * proxy.

         */

        public static final ProxySelector NO_PROXY = ProxySelector.of(null);

        /**

         * Creates a Builder.

         */

        protected Builder() {}

        /**

         * Sets a cookie handler.

         *

         * @param cookieHandler the cookie handler

         * @return this builder

         */

        public abstract Builder cookieHandler(CookieHandler cookieHandler);

        /**

         * Sets an {@code SSLContext}.

         *

         * <p> If this method is not invoked prior to {@linkplain #build()

         * building}, then newly built clients will use the {@linkplain

         * SSLContext#getDefault() default context}, which is normally adequate

         * for client applications that do not need to specify protocols, or

         * require client authentication.

         *

         * @param sslContext the SSLContext

         * @return this builder

         */

        public abstract Builder sslContext(SSLContext sslContext);

        /**

         * Sets an {@code SSLParameters}.

         *

         * <p> If this method is not invoked prior to {@linkplain #build()

         * building}, then newly built clients will use a default,

         * implementation specific, set of parameters.

         *

         * <p> Some parameters which are used internally by the HTTP Client

         * implementation (such as the application protocol list) should not be

         * set by callers, as they may be ignored. The contents of the given

         * object are copied.

         *

         * @param sslParameters the SSLParameters

         * @return this builder

         */

        public abstract Builder sslParameters(SSLParameters sslParameters);

        /**

         * Sets the executor to be used for asynchronous and dependent tasks.

         *

         * <p> If this method is not invoked prior to {@linkplain #build()

         * building}, a default executor is created for each newly built {@code

         * HttpClient}. The default executor uses a {@linkplain

         * Executors#newCachedThreadPool(ThreadFactory) cached thread pool},

         * with a custom thread factory.

         *

         * @implNote If a security manager has been installed, the thread

         * factory creates threads that run with an access control context that

         * has no permissions.

         *

         * @param executor the Executor

         * @return this builder

         */

        public abstract Builder executor(Executor executor);

        /**

         * Specifies whether requests will automatically follow redirects issued

         * by the server.

         *

         * <p> If this method is not invoked prior to {@linkplain #build()

         * building}, then newly built clients will use a default redirection

         * policy of {@link Redirect#NEVER NEVER}.

         *

         * @param policy the redirection policy

         * @return this builder

         */

        public abstract Builder followRedirects(Redirect policy);

        /**

         * Requests a specific HTTP protocol version where possible.

         *

         * <p> If this method is not invoked prior to {@linkplain #build()

         * building}, then newly built clients will prefer {@linkplain

         * Version#HTTP_2 HTTP/2}.

         *

         * <p> If set to {@linkplain Version#HTTP_2 HTTP/2}, then each request

         * will attempt to upgrade to HTTP/2. If the upgrade succeeds, then the

         * response to this request will use HTTP/2 and all subsequent requests

         * and responses to the same

         * <a href="https://tools.ietf.org/html/rfc6454#section-4">origin server</a>

         * will use HTTP/2. If the upgrade fails, then the response will be

         * handled using HTTP/1.1

         *

         * @param version the requested HTTP protocol version

         * @return this builder

         */

        public abstract Builder version(HttpClient.Version version);

        /**

         * Sets the default priority for any HTTP/2 requests sent from this

         * client. The value provided must be between {@code 1} and {@code 256}

         * (inclusive).

         *

         * @param priority the priority weighting

         * @return this builder

         * @throws IllegalArgumentException if the given priority is out of range

         */

        public abstract Builder priority(int priority);

        /**

         * Sets a {@link java.net.ProxySelector}.

         *

         * @apiNote {@link ProxySelector#of(InetSocketAddress)}

         * provides a {@code ProxySelector} which uses a single proxy for all

         * requests. The system-wide proxy selector can be retrieved by

         * {@link ProxySelector#getDefault()}.

         *

         * @implNote

         * If this method is not invoked prior to {@linkplain #build()

         * building}, then newly built clients will use the {@linkplain

         * ProxySelector#getDefault() default proxy selector}, which

         * is normally adequate for client applications. This default

         * behavior can be turned off by supplying an explicit proxy

         * selector to this method, such as {@link #NO_PROXY} or one

         * returned by {@link ProxySelector#of(InetSocketAddress)},

         * before calling {@link #build()}.

         *

         * @param selector the ProxySelector

         * @return this builder

         */

        public abstract Builder proxy(ProxySelector selector);

        /**

         * Sets an authenticator to use for HTTP authentication.

         *

         * @param a the Authenticator

         * @return this builder

         */

        public abstract Builder authenticator(Authenticator a);

        /**

         * Returns a new {@link HttpClient} built from the current state of this

         * builder.

         *

         * @return this builder

         */

        public abstract HttpClient build();

    }

    /**

     * Returns an {@code Optional} containing this client's {@linkplain

     * CookieHandler}. If no {@code CookieHandler} was set in this client's

     * builder, then the {@code Optional} is empty.

     *

     * @return an {@code Optional} containing this client's {@code CookieHandler}

     */

    public abstract Optional<CookieHandler> cookieHandler();

    /**

     * Returns the follow redirects policy for this client. The default value

     * for client's built by builders that do not specify a redirect policy is

     * {@link HttpClient.Redirect#NEVER NEVER}.

     *

     * @return this client's follow redirects setting

     */

    public abstract Redirect followRedirects();

    /**

     * Returns an {@code Optional} containing the {@code ProxySelector}

     * supplied to this client. If no proxy selector was set in this client's

     * builder, then the {@code Optional} is empty.

     *

     * <p> Even though this method may return an empty optional, the {@code

     * HttpClient} may still have an non-exposed {@linkplain

     * Builder#proxy(ProxySelector) default proxy selector} that is

     * used for sending HTTP requests.

     *

     * @return an {@code Optional} containing the proxy selector supplied

     *        to this client.

     */

    public abstract Optional<ProxySelector> proxy();

    /**

     * Returns this client's {@code SSLContext}.

     *

     * <p> If no {@code SSLContext} was set in this client's builder, then the

     * {@linkplain SSLContext#getDefault() default context} is returned.

     *

     * @return this client's SSLContext

     */

    public abstract SSLContext sslContext();

    /**

     * Returns a copy of this client's {@link SSLParameters}.

     *

     * <p> If no {@code SSLParameters} were set in the client's builder, then an

     * implementation specific default set of parameters, that the client will

     * use, is returned.

     *

     * @return this client's {@code SSLParameters}

     */

    public abstract SSLParameters sslParameters();

    /**

     * Returns an {@code Optional} containing the {@link Authenticator} set on

     * this client. If no {@code Authenticator} was set in the client's builder,

     * then the {@code Optional} is empty.

     *

     * @return an {@code Optional} containing this client's {@code Authenticator}

     */

    public abstract Optional<Authenticator> authenticator();

    /**

     * Returns the HTTP protocol version requested for this client. The default

     * value is {@link HttpClient.Version#HTTP_2}

     *

     * @return the HTTP protocol version requested

     */

    public abstract HttpClient.Version version();

    /**

     * Returns an {@code Optional} containing this client's {@linkplain

     * Executor}. If no {@code Executor} was set in the client's builder,

     * then the {@code Optional} is empty.

     *

     * <p> Even though this method may return an empty optional, the {@code

     * HttpClient} may still have an non-exposed {@linkplain

     * HttpClient.Builder#executor(Executor) default executor} that is used for

     * executing asynchronous and dependent tasks.

     *

     * @return an {@code Optional} containing this client's {@code Executor}

     */

    public abstract Optional<Executor> executor();

    /**

     * The HTTP protocol version.

     * {@Incubating}

     *

     * @since 9

     */

    public enum Version {

        /**

         * HTTP version 1.1

         */

        HTTP_1_1,

        /**

         * HTTP version 2

         */

        HTTP_2

    }

    /**

     * Defines automatic redirection policy.

     * {@Incubating}

     *

     * <p> This is checked whenever a {@code 3XX} response code is received. If

     * redirection does not happen automatically then the response is returned

     * to the user, where it can be handled manually.

     *

     * <p> {@code Redirect} policy is set via the {@link

     * HttpClient.Builder#followRedirects(HttpClient.Redirect)} method.

     *

     * @since 9

     */

    public enum Redirect {

        /**

         * Never redirect.

         */

        NEVER,

        /**

         * Always redirect.

         */

        ALWAYS,

        /**

         * Redirect to same protocol only. Redirection may occur from HTTP URLs

         * to other HTTP URLs, and from HTTPS URLs to other HTTPS URLs.

         */

        SAME_PROTOCOL,

        /**

         * Redirect always except from HTTPS URLs to HTTP URLs.

         */

        SECURE

    }

    /**

     * Sends the given request using this client, blocking if necessary to get

     * the response. The returned {@link HttpResponse}{@code <T>} contains the

     * response status, headers, and body ( as handled by given response body

     * handler ).

     *

     * @param <T> the response body type

     * @param req the request

     * @param responseBodyHandler the response body handler

     * @return the response body

     * @throws IOException if an I/O error occurs when sending or receiving

     * @throws InterruptedException if the operation is interrupted

     * @throws IllegalArgumentException if the request method is not supported

     * @throws SecurityException If a security manager has been installed

     *          and it denies {@link java.net.URLPermission access} to the

     *          URL in the given request, or proxy if one is configured.

     *          See HttpRequest for further information about

     *          <a href="HttpRequest.html#securitychecks">security checks</a>.

     */

    public abstract <T> HttpResponse<T>

    send(HttpRequest req, HttpResponse.BodyHandler<T> responseBodyHandler)

        throws IOException, InterruptedException;

    /**

     * Sends the given request asynchronously using this client and the given

     * response handler.

     *

     * <p> The returned completable future completes exceptionally with:

     * <ul>

     * <li>{@link IOException} - if an I/O error occurs when sending or receiving</li>

     * <li>{@link IllegalArgumentException} - if the request method is not supported</li>

     * <li>{@link SecurityException} - If a security manager has been installed

     *          and it denies {@link java.net.URLPermission access} to the

     *          URL in the given request, or proxy if one is configured.

     *          See HttpRequest for further information about

     *          <a href="HttpRequest.html#securitychecks">security checks</a>.</li>

     * </ul>

     *

     * @param <T> the response body type

     * @param req the request

     * @param responseBodyHandler the response body handler

     * @return a {@code CompletableFuture<HttpResponse<T>>}

     */

    public abstract <T> CompletableFuture<HttpResponse<T>>

    sendAsync(HttpRequest req, HttpResponse.BodyHandler<T> responseBodyHandler);

    /**

     * Sends the given request asynchronously using this client and the given

     * multi response handler.

     *

     * <p> The returned completable future completes exceptionally with:

     * <ul>

     * <li>{@link IOException} - if an I/O error occurs when sending or receiving</li>

     * <li>{@link IllegalArgumentException} - if the request method is not supported</li>

     * <li>{@link SecurityException} - If a security manager has been installed

     *          and it denies {@link java.net.URLPermission access} to the

     *          URL in the given request, or proxy if one is configured.

     *          See HttpRequest for further information about

     *          <a href="HttpRequest.html#securitychecks">security checks</a>.</li>

     * </ul>

     *

     * @param <U> a type representing the aggregated results

     * @param <T> a type representing all of the response bodies

     * @param req the request

     * @param multiSubscriber the multiSubscriber for the request

     * @return a {@code CompletableFuture<U>}

     */

    public abstract <U, T> CompletableFuture<U>

    sendAsync(HttpRequest req, HttpResponse.MultiSubscriber<U, T> multiSubscriber);

    /**

     * Creates a new {@code WebSocket} builder (optional operation).

     *

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

     * <pre>{@code

     *     HttpClient client = HttpClient.newHttpClient();

     *     CompletableFuture<WebSocket> ws = client.newWebSocketBuilder()

     *             .buildAsync(URI.create("ws://websocket.example.com"), listener);

     * }</pre>

     *

     * <p> Finer control over the WebSocket Opening Handshake can be achieved

     * by using a custom {@code HttpClient}.

     *

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

     * <pre>{@code

     *     InetSocketAddress addr = new InetSocketAddress("proxy.example.com", 80);

     *     HttpClient client = HttpClient.newBuilder()

     *             .proxy(ProxySelector.of(addr))

     *             .build();

     *     CompletableFuture<WebSocket> ws = client.newWebSocketBuilder()

     *             .buildAsync(URI.create("ws://websocket.example.com"), listener);

     * }</pre>

     *

     * <p> A {@code WebSocket.Builder} returned from this method is not safe for

     * use by multiple threads without external synchronization.

     *

     * @implSpec The default implementation of this method throws

     * {@code UnsupportedOperationException}. Clients obtained through

     * {@link HttpClient#newHttpClient()} or {@link HttpClient#newBuilder()}

     * return a {@code WebSocket} builder.

     *

     * @implNote Both builder and {@code WebSocket}s created with it operate in

     * a non-blocking fashion. That is, their methods do not block before

     * returning a {@code CompletableFuture}. Asynchronous tasks are executed in