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

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 * 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,

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 *

 * 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.io.UncheckedIOException;

import java.net.URI;

import jdk.incubator.http.ResponseProcessors.MultiFile;

import jdk.incubator.http.ResponseProcessors.MultiProcessorImpl;

import static jdk.incubator.http.internal.common.Utils.unchecked;

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

import java.nio.ByteBuffer;

import java.nio.charset.Charset;

import java.nio.charset.StandardCharsets;

import java.nio.file.OpenOption;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.StandardOpenOption;

import java.util.Map;

import java.util.Optional;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.CompletionStage;

import java.util.concurrent.Flow;

import java.util.function.Consumer;

import java.util.function.Function;

import javax.net.ssl.SSLParameters;

/**

 * Represents a response to a {@link HttpRequest}.

 * {@Incubating}

 *

 * <p>A {@code HttpResponse} is available when the response status code and

 * headers have been received, and typically after the response body has also

 * been received. This depends on the response body handler provided when

 * sending the request. In all cases, the response body handler is invoked

 * before the body is read. This gives applications an opportunity to decide

 * how to handle the body.

 *

 * <p> Methods are provided in this class for accessing the response headers,

 * and response body.

 * <p>

 * <b>Response handlers and processors</b>

 * <p>

 * Response bodies are handled at two levels. Application code supplies a response

 * handler ({@link BodyHandler}) which may examine the response status code

 * and headers, and which then returns a {@link BodyProcessor} to actually read

 * (or discard) the body and convert it into some useful Java object type. The handler

 * can return one of the pre-defined processor types, or a custom processor, or

 * if the body is to be discarded, it can call {@link BodyProcessor#discard(Object)

 * BodyProcessor.discard()} and return a processor which discards the response body.

 * Static implementations of both handlers and processors are provided in

 * {@link BodyHandler BodyHandler} and {@link BodyProcessor BodyProcessor} respectively.

 * In all cases, the handler functions provided are convenience implementations

 * which ignore the supplied status code and

 * headers and return the relevant pre-defined {@code BodyProcessor}.

 * <p>

 * See {@link BodyHandler} for example usage.

 *

 * @param <T> the response body type

 * @since 9

 */

public abstract class HttpResponse<T> {

    /**

     * Creates an HttpResponse.

     */

    protected HttpResponse() { }

    /**

     * Returns the status code for this response.

     *

     * @return the response code

     */

    public abstract int statusCode();

    /**

     * Returns the initial {@link HttpRequest} that initiated the exchange.

     *

     * @return the request

     */

    public abstract HttpRequest request();

    /**

     * Returns the final {@link HttpRequest} that was sent on the wire for the

     * exchange ( may, or may not, be the same as the initial request ).

     *

     * @return the request

     */

    public abstract HttpRequest finalRequest();

    /**

     * Returns the received response headers.

     *

     * @return the response headers

     */

    public abstract HttpHeaders headers();

    /**

     * Returns the received response trailers, if there are any, when they

     * become available. For many response processor types this will be at the same

     * time as the {@code HttpResponse} itself is available. In such cases, the

     * returned {@code CompletableFuture} will be already completed.

     *

     * @return a CompletableFuture of the response trailers (may be empty)

     */

    public abstract CompletableFuture<HttpHeaders> trailers();

    /**

     * 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}.

     *

     * @return the body

     */

    public abstract T body();

    /**

     * Returns the {@link javax.net.ssl.SSLParameters} in effect for this

     * response. Returns {@code null} if this is not a HTTPS response.

     *

     * @return the SSLParameters associated with the response

     */

    public abstract SSLParameters sslParameters();

    /**

     * 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 abstract URI uri();

    /**

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

     *

     * @return HTTP protocol version

     */

    public abstract HttpClient.Version version();

    /**

     * A handler for response bodies.

     * {@Incubating}

     * <p>

     * This is a function that takes two parameters: the response status code,

     * and the response headers, and which returns a {@link BodyProcessor}.

     * The function is always called just before the response body is read. Its

     * implementation may examine the status code or headers and must decide,

     * whether to accept the response body or discard it, and if accepting it,

     * exactly how to handle it.

     * <p>

     * Some pre-defined implementations which do not utilize the status code

     * or headers (meaning the body is always accepted) are defined:

     * <ul><li>{@link #asByteArray() }</li>

     * <li>{@link #asByteArrayConsumer(java.util.function.Consumer)

     * asByteArrayConsumer(Consumer)}</li>

     * <li>{@link #asFileDownload(java.nio.file.Path,OpenOption...)

     * asFileDownload(Path,OpenOption...)}</li>

     * <li>{@link #discard(Object) }</li>

     * <li>{@link #asString(java.nio.charset.Charset)

     * asString(Charset)}</li></ul>

     * <p>

     * These implementations return the equivalent {@link BodyProcessor}.

     * Alternatively, the handler can be used to examine the status code

     * or headers and return different body processors as appropriate.

     * <p>

     * <b>Examples of handler usage</b>

     * <p>

     * The first example uses one of the predefined handler functions which

     * ignore the response headers and status, and always process the response

     * body in the same way.

     * <pre>

     * {@code

     *      HttpResponse<Path> resp = HttpRequest

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

     *              .GET()

     *              .response(BodyHandler.asFile(Paths.get("/tmp/f")));

     * }

     * </pre>

     * Note, that even though these pre-defined handlers ignore the status code

     * and headers, this information is still accessible from the {@code HttpResponse}

     * when it is returned.

     * <p>

     * In the second example, the function returns a different processor depending

     * on the status code.

     * <pre>

     * {@code

     *      HttpResponse<Path> resp1 = HttpRequest

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

     *              .GET()

     *              .response(

     *                  (status, headers) -> status == 200

     *                      ? BodyProcessor.asFile(Paths.get("/tmp/f"))

     *                      : BodyProcessor.discard(Paths.get("/NULL")));

     * }

     * </pre>

     *

     * @param <T> the response body type.

     */

    @FunctionalInterface

    public interface BodyHandler<T> {

        /**

         * Returns a {@link BodyProcessor BodyProcessor} considering the given response status

         * code and headers. This method is always called before the body is read

         * and its implementation can decide to keep the body and store it somewhere

         * or else discard it, by  returning the {@code BodyProcessor} returned

         * from {@link BodyProcessor#discard(java.lang.Object) discard()}.

         *

         * @param statusCode the HTTP status code received

         * @param responseHeaders the response headers received

         * @return a response body handler

         */

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

        /**

         * Returns a response body handler which discards the response body and

         * uses the given value as a replacement for it.

         *

         * @param <U> the response body type

         * @param value the value of U to return as the body

         * @return a response body handler

         */

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

            return (status, headers) -> BodyProcessor.discard(value);

        }

        /**

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

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

         * {@link BodyProcessor#asString(java.nio.charset.Charset)

         * BodyProcessor.asString(Charset)}. If a charset is provided, the

         * body is decoded using it. If charset is {@code null} then the processor

         * tries to determine the character set from the {@code Content-encoding}

         * header. If that charset is not supported then

         * {@link java.nio.charset.StandardCharsets#UTF_8 UTF_8} is used.

         *

         * @param charset the name of the charset to interpret the body as. If

         * {@code null} then charset determined from Content-encoding header

         * @return a response body handler

         */

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

            return (status, headers) -> {

                if (charset != null) {

                    return BodyProcessor.asString(charset);

                }

                return BodyProcessor.asString(charsetFrom(headers));

            };

        }

        /**

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

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

         * {@link BodyProcessor#asFile(Path) BodyProcessor.asFile(Path)}.

         * <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}.

         *

         * @param file the file to store the body in

         * @return a response body handler

         */

        public static BodyHandler<Path> asFile(Path file) {

            return (status, headers) -> BodyProcessor.asFile(file);

        }

        /**

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

         * {@link BodyProcessor BodyProcessor}<{@link Path}>

         * where the download directory is specified, but the filename is

         * obtained from the {@code Content-Disposition} response header. The

         * {@code Content-Disposition} header must specify the <i>attachment</i> type

         * and must also contain a

         * <i>filename</i> parameter. If the filename specifies multiple path

         * components only the final component is used as the filename (with the

         * given directory name). When the {@code HttpResponse} object is

         * returned, the body has been completely written to the file and {@link

         * #body()} returns a {@code Path} object for the file. The returned {@code Path} is the

         * combination of the supplied directory name and the file name supplied

         * by the server. If the destination directory does not exist or cannot

         * be written to, then the response will fail with an {@link IOException}.

         *

         * @param directory the directory to store the file in

         * @param openOptions open options

         * @return a response body handler

         */

        public static BodyHandler<Path> asFileDownload(Path directory, OpenOption... openOptions) {

            return (status, headers) -> {

                String dispoHeader = headers.firstValue("Content-Disposition")

                        .orElseThrow(() -> unchecked(new IOException("No Content-Disposition")));

                if (!dispoHeader.startsWith("attachment;")) {

                    throw unchecked(new IOException("Unknown Content-Disposition type"));

                }

                int n = dispoHeader.indexOf("filename=");

                if (n == -1) {

                    throw unchecked(new IOException("Bad Content-Disposition type"));

                }

                int lastsemi = dispoHeader.lastIndexOf(';');

                String disposition;

                if (lastsemi < n) {

                    disposition = dispoHeader.substring(n + 9);

                } else {

                    disposition = dispoHeader.substring(n + 9, lastsemi);

                }

                Path file = Paths.get(directory.toString(), disposition);

                return BodyProcessor.asFile(file, openOptions);

            };

        }

        /**

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

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

         * {@link BodyProcessor#asFile(java.nio.file.Path, java.nio.file.OpenOption...)

         * BodyProcessor.asFile(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}.

         *

         * @param file the filename to store the body in

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

         * @return a response body handler

         */

        public static BodyHandler<Path> asFile(Path file, OpenOption... openOptions) {

            return (status, headers) -> BodyProcessor.asFile(file, openOptions);

        }

        /**

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

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

         * {@link BodyProcessor#asByteArrayConsumer(java.util.function.Consumer)

         * BodyProcessor.asByteArrayConsumer(Consumer)}.

         * <p>

         * When the {@code HttpResponse} object is returned, the body has been completely

         * written to the consumer.

         *

         * @param consumer a Consumer to accept the response body

         * @return a response body handler

         */

        public static BodyHandler<Void> asByteArrayConsumer(Consumer<Optional<byte[]>> consumer) {

            return (status, headers) -> BodyProcessor.asByteArrayConsumer(consumer);

        }

        /**

         * Returns a {@code BodyHandler<byte[]>} that returns a

         * {@link BodyProcessor BodyProcessor}<{@code byte[]}> obtained

         * from {@link BodyProcessor#asByteArray() BodyProcessor.asByteArray()}.

         * <p>

         * When the {@code HttpResponse} object is returned, the body has been completely

         * written to the byte array.

         *

         * @return a response body handler

         */

        public static BodyHandler<byte[]> asByteArray() {

            return (status, headers) -> BodyProcessor.asByteArray();

        }

        /**

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

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

         * {@link BodyProcessor#asString(java.nio.charset.Charset)

         * BodyProcessor.asString(Charset)}. The body is

         * decoded using the character set specified in

         * the {@code Content-encoding} response header. If there is no such

         * header, or the character set is not supported, then

         * {@link java.nio.charset.StandardCharsets#UTF_8 UTF_8} is used.

         * <p>

         * When the {@code HttpResponse} object is returned, the body has been completely

         * written to the string.

         *

         * @return a response body handler

         */

        public static BodyHandler<String> asString() {

            return (status, headers) -> BodyProcessor.asString(charsetFrom(headers));

        }

    }

    /**

     * A processor for response bodies.

     * {@Incubating}

     * <p>

     * The object acts as a {@link Flow.Subscriber}<{@link ByteBuffer}> to

     * the HTTP client implementation which publishes ByteBuffers containing the

     * response body. The processor converts the incoming buffers of data to

     * some user-defined object type {@code T}.

     * <p>

     * The {@link #getBody()} method returns a {@link CompletionStage}{@code <T>}

     * that provides the response body object. The {@code CompletionStage} must

     * be obtainable at any time. When it completes depends on the nature

     * of type {@code T}. In many cases, when {@code T} represents the entire body after being

     * read then it completes after the body has been read. If {@code T} is a streaming

     * type such as {@link java.io.InputStream} then it completes before the

     * body has been read, because the calling code uses it to consume the data.

     *

     * @param <T> the response body type

     */

    public interface BodyProcessor<T>

            extends Flow.Subscriber<ByteBuffer> {

        /**

         * Returns a {@code CompletionStage} which when completed will return the

         * response body object.

         *

         * @return a CompletionStage for the response body

         */

        public CompletionStage<T> getBody();

        /**

         * Returns a body processor which stores the response body as a {@code

         * String} converted using the given {@code Charset}.

         * <p>

         * The {@link HttpResponse} using this processor is available after the

         * entire response has been read.

         *

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

         * @return a body processor

         */

        public static BodyProcessor<String> asString(Charset charset) {

            return new ResponseProcessors.ByteArrayProcessor<>(

                    bytes -> new String(bytes, charset)

            );

        }

        /**

         * Returns a {@code BodyProcessor} which stores the response body as a

         * byte array.

         * <p>

         * The {@link HttpResponse} using this processor is available after the

         * entire response has been read.

         *

         * @return a body processor

         */

        public static BodyProcessor<byte[]> asByteArray() {

            return new ResponseProcessors.ByteArrayProcessor<>(

                    Function.identity() // no conversion

            );

        }

        /**

         * Returns a {@code BodyProcessor} which stores the response body in a

         * file opened with the given options and name. The file will be opened

         * with the given options using

         * {@link java.nio.channels.FileChannel#open(java.nio.file.Path,java.nio.file.OpenOption...)

         * FileChannel.open} just before the body is read. Any exception thrown will be returned

         * or thrown from {@link HttpClient#send(jdk.incubator.http.HttpRequest,

         * jdk.incubator.http.HttpResponse.BodyHandler) HttpClient::send}

         * or {@link HttpClient#sendAsync(jdk.incubator.http.HttpRequest,

         * jdk.incubator.http.HttpResponse.BodyHandler) HttpClient::sendAsync}

         * as appropriate.

         * <p>

         * The {@link HttpResponse} using this processor is available after the

         * entire response has been read.

         *

         * @param file the file to store the body in

         * @param openOptions the list of options to open the file with

         * @return a body processor

         */

        public static BodyProcessor<Path> asFile(Path file, OpenOption... openOptions) {

            return new ResponseProcessors.PathProcessor(file, openOptions);

        }

        /**

         * Returns a {@code BodyProcessor} which provides the incoming body

         * data to the provided Consumer of {@code Optional<byte[]>}. Each

         * call to {@link Consumer#accept(java.lang.Object) Consumer.accept()}

         * will contain a non empty {@code Optional}, except for the final invocation after

         * all body data has been read, when the {@code Optional} will be empty.

         * <p>

         * The {@link HttpResponse} using this processor is available after the

         * entire response has been read.

         *

         * @param consumer a Consumer of byte arrays

         * @return a BodyProcessor

         */

        public static BodyProcessor<Void> asByteArrayConsumer(Consumer<Optional<byte[]>> consumer) {

            return new ResponseProcessors.ConsumerProcessor(consumer);

        }

        /**

         * Returns a {@code BodyProcessor} which stores the response body in a

         * file opened with the given name. Has the same effect as calling

         * {@link #asFile(java.nio.file.Path, java.nio.file.OpenOption...) asFile}

         * with the standard open options {@code CREATE} and {@code WRITE}

         * <p>

         * The {@link HttpResponse} using this processor is available after the

         * entire response has been read.

         *

         * @param file the file to store the body in

         * @return a body processor

         */

        public static BodyProcessor<Path> asFile(Path file) {

            return new ResponseProcessors.PathProcessor(

                    file,

                    StandardOpenOption.CREATE, StandardOpenOption.WRITE);

        }

        /**

         * Returns a response processor which discards the response body. The

         * supplied value is the value that will be returned from

         * {@link HttpResponse#body()}.