/*

 * 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

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

 * questions.

 */

package jdk.incubator.http;

import java.io.IOException;

import java.io.InputStream;

import java.net.URI;

import jdk.incubator.http.ResponseSubscribers.MultiSubscriberImpl;

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.channels.FileChannel;

import java.nio.file.OpenOption;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.StandardOpenOption;

import java.security.AccessControlContext;

import java.util.Arrays;

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.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 subscribers</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 BodySubscriber} 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 subscriber types, or a custom

 * subscriber, or if the body is to be discarded it can call {@link

 * BodySubscriber#discard(Object) discard} and return a subscriber which

 * discards the response body. Static implementations of both handlers and

 * subscribers are provided in {@linkplain BodyHandler BodyHandler} and

 * {@linkplain BodySubscriber BodySubscriber} 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

 * BodySubscriber}.

 *

 * <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 {@link HttpRequest} corresponding to this response.

     *

     * <p> This may not be the original request provided by the caller,

     * for example, if that request was redirected.

     *

     * @see #previousResponse()

     *

     * @return the request

     */

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

    /**

     * Returns the received response headers.

     *

     * @return the response headers

     */

    public abstract 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 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();

    private static String pathForSecurityCheck(Path path) {

        return path.toFile().getPath();

    }

    /** A body handler that is further restricted by a given ACC. */

    interface UntrustedBodyHandler<T> extends BodyHandler<T> {

        void setAccessControlContext(AccessControlContext acc);

    }

    /**

     * A Path body handler.

     *

     * Note: Exists mainly too allow setting of the senders ACC post creation of

     * the handler.

     */

    static class PathBodyHandler implements UntrustedBodyHandler<Path> {

        private final Path file;

        private final OpenOption[]openOptions;

        private volatile AccessControlContext acc;

        PathBodyHandler(Path file, OpenOption... openOptions) {

            this.file = file;

            this.openOptions = openOptions;

        }

        @Override

        public void setAccessControlContext(AccessControlContext acc) {

            this.acc = acc;

        }

        @Override

        public BodySubscriber<Path> apply(int statusCode, HttpHeaders headers) {

            ResponseSubscribers.PathSubscriber bs = (ResponseSubscribers.PathSubscriber)

                    BodySubscriber.asFileImpl(file, openOptions);

            bs.setAccessControlContext(acc);

            return bs;

        }

    }

    // Similar to Path body handler, but for file download. Supports setting ACC.

    static class FileDownloadBodyHandler implements UntrustedBodyHandler<Path> {

        private final Path directory;

        private final OpenOption[]openOptions;

        private volatile AccessControlContext acc;

        FileDownloadBodyHandler(Path directory, OpenOption... openOptions) {

            this.directory = directory;

            this.openOptions = openOptions;

        }

        @Override

        public void setAccessControlContext(AccessControlContext acc) {

            this.acc = acc;

        }

        @Override

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

            ResponseSubscribers.PathSubscriber bs = (ResponseSubscribers.PathSubscriber)

                    BodySubscriber.asFileImpl(file, openOptions);

            bs.setAccessControlContext(acc);

            return bs;

        }

    }

    /**

     * 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 {@linkplain BodySubscriber}.

     * 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 #asString(java.nio.charset.Charset) asString(Charset)}</li>

     * <li>{@link #asFile(Path, OpenOption...)

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

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

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

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

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

     * <li>{@link #buffering(BodyHandler, int)

     * buffering(BodyHandler,int)}</li>

     * </ul>

     *

     * <p> These implementations return the equivalent {@link BodySubscriber}.

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

     * or headers and return different body subscribers as appropriate.

     *

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

     *

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

     * ignores 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 subscriber

     * depending on the status code.

     * <pre>

     * {@code

     *      HttpResponse<Path> resp1 = HttpRequest

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

     *              .GET()

     *              .response(

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

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

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

     * }

     * </pre>

     *

     * @param <T> the response body type

     */

    @FunctionalInterface

    public interface BodyHandler<T> {

        /**

         * Returns a {@link BodySubscriber BodySubscriber} 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

         * BodySubscriber} returned from {@link BodySubscriber#discard(Object)

         * discard}.

         *

         * @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);

        /**

         * 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, may be {@code null}

         * @return a response body handler

         */

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

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

        }

        /**

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

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

         * {@link BodySubscriber#asString(Charset) BodySubscriber.asString(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> asString(Charset charset) {

            Objects.requireNonNull(charset);

            return (status, headers) -> BodySubscriber.asString(charset);

        }

        /**

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

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

         * {@link BodySubscriber#asFile(Path, OpenOption...)

         * BodySubscriber.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

         * @throws SecurityException If a security manager has been installed

         *          and it denies {@link SecurityManager#checkWrite(String)

         *          write access} to the file. The {@link

         *          SecurityManager#checkDelete(String) checkDelete} method is

         *          invoked to check delete access if the file is opened with

         *          the {@code DELETE_ON_CLOSE} option.

         */

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

            Objects.requireNonNull(file);

            List<OpenOption> opts = List.of(openOptions);

            SecurityManager sm = System.getSecurityManager();

            if (sm != null) {

                String fn = pathForSecurityCheck(file);

                sm.checkWrite(fn);

                if (opts.contains(StandardOpenOption.DELETE_ON_CLOSE))

                    sm.checkDelete(fn);

                if (opts.contains(StandardOpenOption.READ))

                    sm.checkRead(fn);

            }

            return new PathBodyHandler(file, openOptions);

        }

        /**

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

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

         * {@link BodySubscriber#asFile(Path) BodySubscriber.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

         * @throws SecurityException if a security manager has been installed

         *          and it denies {@link SecurityManager#checkWrite(String)

         *          write access} to the file

         */

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

            return BodyHandler.asFile(file, StandardOpenOption.CREATE,

                                            StandardOpenOption.WRITE);

        }

        /**

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

         * {@link BodySubscriber BodySubscriber}<{@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).

         *

         * <p> 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