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 * Copyright (c) 2015, 2018, 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 java.net.http;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStream;

import java.net.URI;

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.channels.FileChannel;

import java.nio.charset.StandardCharsets;

import java.nio.file.OpenOption;

import java.nio.file.Path;

import java.util.List;

import java.util.Objects;

import java.util.Optional;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.CompletionStage;

import java.util.concurrent.ConcurrentMap;

import java.util.concurrent.Flow;

import java.util.concurrent.Flow.Subscriber;

import java.util.function.Consumer;

import java.util.function.Function;

import java.util.stream.Stream;

import javax.net.ssl.SSLSession;

import jdk.internal.net.http.BufferingSubscriber;

import jdk.internal.net.http.LineSubscriberAdapter;

import jdk.internal.net.http.ResponseBodyHandlers.FileDownloadBodyHandler;

import jdk.internal.net.http.ResponseBodyHandlers.PathBodyHandler;

import jdk.internal.net.http.ResponseBodyHandlers.PushPromisesHandlerWithMap;

import jdk.internal.net.http.ResponseSubscribers;

import jdk.internal.net.http.ResponseSubscribers.PathSubscriber;

import static java.nio.file.StandardOpenOption.*;

import static jdk.internal.net.http.common.Utils.charsetFrom;

/**

 * An HTTP response.

 *

 * <p> An {@code HttpResponse} is not created directly, but rather returned as

 * a result of sending an {@link HttpRequest}. An {@code HttpResponse} is

 * made available when the response status code and headers have been received,

 * and typically after the response body has also been completely received.

 * Whether or not the {@code HttpResponse} is made available before the response

 * body has been completely received depends on the {@link BodyHandler

 * BodyHandler} provided when sending the {@code HttpRequest}.

 *

 * <p> This class provides methods for accessing the response status code,

 * headers, the response body, and the {@code HttpRequest} corresponding

 * to this response.

 *

 * <p> The following is an example of retrieving a response as a String:

 *

 * <pre>{@code    HttpResponse<String> response = client

 *     .send(request, BodyHandlers.ofString()); }</pre>

 *

 * <p> The class {@link BodyHandlers BodyHandlers} provides implementations

 * of many common response handlers. Alternatively, a custom {@code BodyHandler}

 * implementation can be used.

 *

 * @param <T> the response body type

 * @since 11

 */

public interface HttpResponse<T> {

    /**

     * Returns the status code for this response.

     *

     * @return the response code

     */

    public int statusCode();

    /**

     * Returns the {@link HttpRequest} corresponding to this response.

     *

     * <p> The returned {@code HttpRequest} may not be the initiating request

     * provided when {@linkplain HttpClient#send(HttpRequest, BodyHandler)

     * sending}. For example, if the initiating request was redirected, then the

     * request returned by this method will have the redirected URI, which will

     * be different from the initiating request URI.

     *

     * @see #previousResponse()

     *

     * @return the request

     */

    public HttpRequest request();

    /**

     * Returns an {@code Optional} containing the previous intermediate response

     * if one was received. An intermediate response is one that is received

     * as a result of redirection or authentication. If no previous response

     * was received then an empty {@code Optional} is returned.

     *

     * @return an Optional containing the HttpResponse, if any.

     */

    public Optional<HttpResponse<T>> previousResponse();

    /**

     * Returns the received response headers.

     *

     * @return the response headers

     */

    public HttpHeaders headers();

    /**

     * Returns the body. Depending on the type of {@code T}, the returned body

     * may represent the body after it was read (such as {@code byte[]}, or

     * {@code String}, or {@code Path}) or it may represent an object with

     * which the body is read, such as an {@link java.io.InputStream}.

     *

     * <p> If this {@code HttpResponse} was returned from an invocation of

     * {@link #previousResponse()} then this method returns {@code null}

     *

     * @return the body

     */

    public T body();

    /**

     * Returns an {@link Optional} containing the {@link SSLSession} in effect

     * for this response. Returns an empty {@code Optional} if this is not a

     * <i>HTTPS</i> response.

     *

     * @return an {@code Optional} containing the {@code SSLSession} associated

     *         with the response

     */

    public Optional<SSLSession> sslSession();

    /**

     * Returns the {@code URI} that the response was received from. This may be

     * different from the request {@code URI} if redirection occurred.

     *

     * @return the URI of the response

     */

     public URI uri();

    /**

     * Returns the HTTP protocol version that was used for this response.

     *

     * @return HTTP protocol version

     */

    public HttpClient.Version version();

    /**

     * A handler for response bodies.  The class {@link BodyHandlers BodyHandlers}

     * provides implementations of many common body handlers.

     *

     * <p> The {@code BodyHandler} interface allows inspection of the response

     * code and headers, before the actual response body is received, and is

     * responsible for creating the response {@link BodySubscriber

     * BodySubscriber}. The {@code BodySubscriber} consumes the actual response

     * body bytes and, typically, converts them into a higher-level Java type.

     *

     * <p> A {@code BodyHandler} is a function that takes two parameters: the

     * response status code and the response headers; and which returns a

     * {@code BodySubscriber}. The {@code BodyHandler} is invoked when the

     * response status code and headers are available, but before the response

     * body bytes are received.

     *

     * <p> The following example uses one of the {@linkplain BodyHandlers

     * predefined body handlers} that always process the response body in the

     * same way ( streams the response body to a file ).

     *

     * <pre>{@code   HttpRequest request = HttpRequest.newBuilder()

     *        .uri(URI.create("http://www.foo.com/"))

     *        .build();

     *  client.sendAsync(request, BodyHandlers.ofFile(Paths.get("/tmp/f")))

     *        .thenApply(HttpResponse::body)

     *        .thenAccept(System.out::println); }</pre>

     *

     * Note, that even though the pre-defined handlers do not examine the

     * response code, the response code and headers are always retrievable from

     * the {@link HttpResponse}, when it is returned.

     *

     * <p> In the second example, the function returns a different subscriber

     * depending on the status code.

     * <pre>{@code   HttpRequest request = HttpRequest.newBuilder()

     *        .uri(URI.create("http://www.foo.com/"))

     *        .build();

     *  BodyHandler<Path> bodyHandler = (status, headers) -> status == 200

     *                      ? BodySubscribers.ofFile(Paths.get("/tmp/f"))

     *                      : BodySubscribers.replacing(Paths.get("/NULL"));

     *  client.sendAsync(request, bodyHandler)

     *        .thenApply(HttpResponse::body)

     *        .thenAccept(System.out::println); }</pre>

     *

     * @param <T> the response body type

     * @see BodyHandlers

     * @since 11

     */

    @FunctionalInterface

    public interface BodyHandler<T> {

        /**

         * Returns a {@link BodySubscriber BodySubscriber} considering the

         * given response status code and headers. This method is invoked before

         * the actual response body bytes are read and its implementation must

         * return a {@link BodySubscriber BodySubscriber} to consume the response

         * body bytes.

         *

         * <p> The response body can be discarded using one of {@link

         * BodyHandlers#discarding() discarding} or {@link

         * BodyHandlers#replacing(Object) replacing}.

         *

         * @param statusCode the HTTP status code received

         * @param responseHeaders the response headers received

         * @return a body subscriber

         */

        public BodySubscriber<T> apply(int statusCode, HttpHeaders responseHeaders);

    }

    /**

     * Implementations of {@link BodyHandler BodyHandler} that implement various

     * useful handlers, such as handling the response body as a String, or

     * streaming the response body to a file.

     *

     * <p> These implementations do not examine the status code, meaning the

     * body is always accepted. They typically return an equivalently named

     * {@code BodySubscriber}. Alternatively, a custom handler can be used to

     * examine the status code and headers, and return a different body

     * subscriber, of the same type, as appropriate.

     *

     * <p>The following are examples of using the predefined body handlers to

     * convert a flow of response body data into common high-level Java objects:

     *

     * <pre>{@code    // Receives the response body as a String

     *   HttpResponse<String> response = client

     *     .send(request, BodyHandlers.ofString());

     *

     *   // Receives the response body as a file

     *   HttpResponse<Path> response = client

     *     .send(request, BodyHandlers.ofFile(Paths.get("example.html")));

     *

     *   // Receives the response body as an InputStream

     *   HttpResponse<InputStream> response = client

     *     .send(request, BodyHandlers.ofInputStream());

     *

     *   // Discards the response body

     *   HttpResponse<Void> response = client

     *     .send(request, BodyHandlers.discarding());  }</pre>

     *

     * @since 11

     */

    public static class BodyHandlers {

        private BodyHandlers() { }

        /**

         * Returns a response body handler that returns a {@link BodySubscriber

         * BodySubscriber}{@code <Void>} obtained from {@link

         * BodySubscribers#fromSubscriber(Subscriber)}, with the given

         * {@code subscriber}.

         *

         * <p> The response body is not available through this, or the {@code

         * HttpResponse} API, but instead all response body is forwarded to the

         * given {@code subscriber}, which should make it available, if

         * appropriate, through some other mechanism, e.g. an entry in a

         * database, etc.

         *

         * @apiNote This method can be used as an adapter between {@code

         * BodySubscriber} and {@code Flow.Subscriber}.

         *

         * <p> For example:

         * <pre> {@code  TextSubscriber subscriber = new TextSubscriber();

         *  HttpResponse<Void> response = client.sendAsync(request,

         *      BodyHandlers.fromSubscriber(subscriber)).join();

         *  System.out.println(response.statusCode()); }</pre>

         *

         * @param subscriber the subscriber

         * @return a response body handler

         */

        public static BodyHandler<Void>

        fromSubscriber(Subscriber<? super List<ByteBuffer>> subscriber) {

            Objects.requireNonNull(subscriber);

            return (status, headers) -> BodySubscribers.fromSubscriber(subscriber,

                                                                       s -> null);

        }

        /**

         * Returns a response body handler that returns a {@link BodySubscriber

         * BodySubscriber}{@code <T>} obtained from {@link

         * BodySubscribers#fromSubscriber(Subscriber, Function)}, with the

         * given {@code subscriber} and {@code finisher} function.

         *

         * <p> The given {@code finisher} function is applied after the given

         * subscriber's {@code onComplete} has been invoked. The {@code finisher}

         * function is invoked with the given subscriber, and returns a value

         * that is set as the response's body.

         *

         * @apiNote This method can be used as an adapter between {@code

         * BodySubscriber} and {@code Flow.Subscriber}.

         *

         * <p> For example:

         * <pre> {@code  TextSubscriber subscriber = ...;  // accumulates bytes and transforms them into a String

         *  HttpResponse<String> response = client.sendAsync(request,

         *      BodyHandlers.fromSubscriber(subscriber, TextSubscriber::getTextResult)).join();

         *  String text = response.body(); }</pre>

         *

         * @param <S> the type of the Subscriber

         * @param <T> the type of the response body

         * @param subscriber the subscriber

         * @param finisher a function to be applied after the subscriber has completed

         * @return a response body handler

         */

        public static <S extends Subscriber<? super List<ByteBuffer>>,T> BodyHandler<T>

        fromSubscriber(S subscriber, Function<? super S,? extends T> finisher) {

            Objects.requireNonNull(subscriber);

            Objects.requireNonNull(finisher);

            return (status, headers) -> BodySubscribers.fromSubscriber(subscriber,

                                                                      finisher);

        }

        /**

         * Returns a response body handler that returns a {@link BodySubscriber

         * BodySubscriber}{@code <Void>} obtained from {@link

         * BodySubscribers#fromLineSubscriber(Subscriber, Function, Charset, String)

         * BodySubscribers.fromLineSubscriber(subscriber, s -> null, charset, null)},

         * with the given {@code subscriber}.

         * The {@link Charset charset} used to decode the response body bytes is

         * obtained from the HTTP response headers as specified by {@link #ofString()},

         * and lines are delimited in the manner of {@link BufferedReader#readLine()}.

         *

         * <p> The response body is not available through this, or the {@code

         * HttpResponse} API, but instead all response body is forwarded to the

         * given {@code subscriber}, which should make it available, if

         * appropriate, through some other mechanism, e.g. an entry in a

         * database, etc.

         *

         * @apiNote This method can be used as an adapter between a {@code

         * BodySubscriber} and a text based {@code Flow.Subscriber} that parses

         * text line by line.

         *

         * <p> For example:

         * <pre> {@code  // A PrintSubscriber that implements Flow.Subscriber<String>

         *  // and print lines received by onNext() on System.out

         *  PrintSubscriber subscriber = new PrintSubscriber(System.out);

         *  client.sendAsync(request, BodyHandlers.fromLineSubscriber(subscriber))

         *      .thenApply(HttpResponse::statusCode)

         *      .thenAccept((status) -> {

         *          if (status != 200) {

         *              System.err.printf("ERROR: %d status received%n", status);

         *          }

         *      }); }</pre>

         *

         * @param subscriber the subscriber

         * @return a response body handler

         */

        public static BodyHandler<Void>

        fromLineSubscriber(Subscriber<? super String> subscriber) {

            Objects.requireNonNull(subscriber);

            return (status, headers) ->

                        BodySubscribers.fromLineSubscriber(subscriber,

                                                           s -> null,

                                                           charsetFrom(headers),

                                                           null);

        }

        /**

         * Returns a response body handler that returns a {@link BodySubscriber

         * BodySubscriber}{@code <T>} obtained from {@link

         * BodySubscribers#fromLineSubscriber(Subscriber, Function, Charset, String)

         * BodySubscribers.fromLineSubscriber(subscriber, finisher, charset, lineSeparator)},

         * with the given {@code subscriber}, {@code finisher} function, and line separator.

         * The {@link Charset charset} used to decode the response body bytes is

         * obtained from the HTTP response headers as specified by {@link #ofString()}.

         *

         * <p> The given {@code finisher} function is applied after the given

         * subscriber's {@code onComplete} has been invoked. The {@code finisher}

         * function is invoked with the given subscriber, and returns a value

         * that is set as the response's body.

         *

         * @apiNote This method can be used as an adapter between a {@code

         * BodySubscriber} and a text based {@code Flow.Subscriber} that parses

         * text line by line.

         *

         * <p> For example:

         * <pre> {@code  // A LineParserSubscriber that implements Flow.Subscriber<String>

         *  // and accumulates lines that match a particular pattern

         *  Pattern pattern = ...;

         *  LineParserSubscriber subscriber = new LineParserSubscriber(pattern);

         *  HttpResponse<List<String>> response = client.send(request,

         *      BodyHandlers.fromLineSubscriber(subscriber, s -> s.getMatchingLines(), "\n"));

         *  if (response.statusCode() != 200) {

         *      System.err.printf("ERROR: %d status received%n", response.statusCode());

         *  } }</pre>

         *

         *

         * @param <S> the type of the Subscriber

         * @param <T> the type of the response body

         * @param subscriber the subscriber

         * @param finisher a function to be applied after the subscriber has completed

         * @param lineSeparator an optional line separator: can be {@code null},

         *                      in which case lines will be delimited in the manner of

         *                      {@link BufferedReader#readLine()}.

         * @return a response body handler

         * @throws IllegalArgumentException if the supplied {@code lineSeparator}

         *         is the empty string

         */

        public static <S extends Subscriber<? super String>,T> BodyHandler<T>

        fromLineSubscriber(S subscriber,

                           Function<? super S,? extends T> finisher,

                           String lineSeparator) {

            Objects.requireNonNull(subscriber);

            Objects.requireNonNull(finisher);

            // implicit null check

            if (lineSeparator != null && lineSeparator.isEmpty())

                throw new IllegalArgumentException("empty line separator");

            return (status, headers) ->

                        BodySubscribers.fromLineSubscriber(subscriber,

                                                           finisher,

                                                           charsetFrom(headers),

                                                           lineSeparator);

        }

        /**

         * Returns a response body handler that discards the response body.

         *

         * @return a response body handler

         */

        public static BodyHandler<Void> discarding() {

            return (status, headers) -> BodySubscribers.discarding();

        }

        /**

         * Returns a response body handler that returns the given replacement

         * value, after discarding the response body.

         *

         * @param <U> the response body type

         * @param value the value of U to return as the body, may be {@code null}

         * @return a response body handler

         */

        public static <U> BodyHandler<U> replacing(U value) {

            return (status, headers) -> BodySubscribers.replacing(value);

        }

        /**

         * Returns a {@code BodyHandler<String>} that returns a

         * {@link BodySubscriber BodySubscriber}{@code <String>} obtained from

         * {@link BodySubscribers#ofString(Charset) BodySubscribers.ofString(Charset)}.

         * The body is decoded using the given character set.

         *

         * @param charset the character set to convert the body with

         * @return a response body handler

         */

        public static BodyHandler<String> ofString(Charset charset) {

            Objects.requireNonNull(charset);

            return (status, headers) -> BodySubscribers.ofString(charset);

        }

        /**

         * Returns a {@code BodyHandler<Path>} that returns a

         * {@link BodySubscriber BodySubscriber}{@code <Path>} obtained from

         * {@link BodySubscribers#ofFile(Path, OpenOption...)

         * BodySubscribers.ofFile(Path,OpenOption...)}.

         *

         * <p> When the {@code HttpResponse} object is returned, the body has

         * been completely written to the file, and {@link #body()} returns a

         * reference to its {@link Path}.

         *

         * <p> Security manager permission checks are performed in this factory

         * method, when the {@code BodyHandler} is created. Care must be taken

         * that the {@code BodyHandler} is not shared with untrusted code.

         *

         * @param file the file to store the body in

         * @param openOptions any options to use when opening/creating the file

         * @return a response body handler