/*

 * Copyright (c) 2005, 2019, 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 com.sun.net.httpserver;

import java.io.*;

import java.nio.*;

import java.nio.channels.*;

import java.net.*;

import javax.net.ssl.*;

import java.util.*;

/**

 * This class encapsulates a HTTP request received and a

 * response to be generated in one exchange. It provides methods

 * for examining the request from the client, and for building and

 * sending the response.

 * <p>

 * The typical life-cycle of a HttpExchange is shown in the sequence

 * below.

 * <ol><li>{@link #getRequestMethod()} to determine the command

 * <li>{@link #getRequestHeaders()} to examine the request headers (if needed)

 * <li>{@link #getRequestBody()} returns a {@link java.io.InputStream} for reading the request body.

 *     After reading the request body, the stream should be closed.

 * <li>{@link #getResponseHeaders()} to set any response headers, except content-length

 * <li>{@link #sendResponseHeaders(int,long)} to send the response headers. Must be called before

 * next step.

 * <li>{@link #getResponseBody()} to get a {@link java.io.OutputStream} to send the response body.

 *      When the response body has been written, the stream must be closed to terminate the exchange.

 * </ol>

 * <b>Terminating exchanges</b>

 * <br>

 * Exchanges are terminated when both the request InputStream and response OutputStream are closed.

 * Closing the OutputStream, implicitly closes the InputStream (if it is not already closed).

 * However, it is recommended

 * to consume all the data from the InputStream before closing it.

 * The convenience method {@link #close()} does all of these tasks.

 * Closing an exchange without consuming all of the request body is not an error

 * but may make the underlying TCP connection unusable for following exchanges.

 * The effect of failing to terminate an exchange is undefined, but will typically

 * result in resources failing to be freed/reused.

 * @since 1.6

 */

public abstract class HttpExchange implements AutoCloseable {

    protected HttpExchange () {

    }

    /**

     * Returns an immutable Map containing the HTTP headers that were

     * included with this request. The keys in this Map will be the header

     * names, while the values will be a List of Strings containing each value

     * that was included (either for a header that was listed several times,

     * or one that accepts a comma-delimited list of values on a single line).

     * In either of these cases, the values for the header name will be

     * presented in the order that they were included in the request.

     * <p>

     * The keys in Map are case-insensitive.

     * @return a read-only Map which can be used to access request headers

     */

    public abstract Headers getRequestHeaders () ;

    /**

     * Returns a mutable Map into which the HTTP response headers can be stored

     * and which will be transmitted as part of this response. The keys in the

     * Map will be the header names, while the values must be a List of Strings

     * containing each value that should be included multiple times

     * (in the order that they should be included).

     * <p>

     * The keys in Map are case-insensitive.

     * @return a writable Map which can be used to set response headers.

     */

    public abstract Headers getResponseHeaders () ;

    /**

     * Get the request URI

     *

     * @return the request URI

     */

    public abstract URI getRequestURI () ;

    /**

     * Get the request method

     * @return the request method

     */

    public abstract String getRequestMethod ();

    /**

     * Get the HttpContext for this exchange

     * @return the HttpContext

     */

    public abstract HttpContext getHttpContext ();

    /**

     * Ends this exchange by doing the following in sequence:<ol>

     * <li>close the request InputStream, if not already closed;</li>

     * <li>close the response OutputStream, if not already closed.</li>

     * </ol>

     */

    public abstract void close () ;

    /**

     * returns a stream from which the request body can be read.

     * Multiple calls to this method will return the same stream.

     * It is recommended that applications should consume (read) all of the

     * data from this stream before closing it. If a stream is closed

     * before all data has been read, then the close() call will

     * read and discard remaining data (up to an implementation specific

     * number of bytes).

     * @return the stream from which the request body can be read.

     */

    public abstract InputStream getRequestBody () ;

    /**

     * returns a stream to which the response body must be

     * written. {@link #sendResponseHeaders(int,long)}) must be called prior to calling

     * this method. Multiple calls to this method (for the same exchange)

     * will return the same stream. In order to correctly terminate

     * each exchange, the output stream must be closed, even if no

     * response body is being sent.

     * <p>

     * Closing this stream implicitly

     * closes the InputStream returned from {@link #getRequestBody()}

     * (if it is not already closed).

     * <P>

     * If the call to sendResponseHeaders() specified a fixed response

     * body length, then the exact number of bytes specified in that

     * call must be written to this stream. If too many bytes are written,

     * then write() will throw an IOException. If too few bytes are written

     * then the stream close() will throw an IOException. In both cases,

     * the exchange is aborted and the underlying TCP connection closed.

     * @return the stream to which the response body is written

     */

    public abstract OutputStream getResponseBody () ;

    /**

     * Starts sending the response back to the client using the current set of response headers

     * and the numeric response code as specified in this method. The response body length is also specified

     * as follows. If the response length parameter is greater than zero, this specifies an exact

     * number of bytes to send and the application must send that exact amount of data.

     * If the response length parameter is {@code zero}, then chunked transfer encoding is

     * used and an arbitrary amount of data may be sent. The application terminates the

     * response body by closing the OutputStream. If response length has the value {@code -1}

     * then no response body is being sent.

     * <p>

     * If the content-length response header has not already been set then

     * this is set to the appropriate value depending on the response length parameter.

     * <p>

     * This method must be called prior to calling {@link #getResponseBody()}.

     *

     * @implNote This implementation allows the caller to instruct the

     * server to force a connection close after the exchange terminates, by

     * supplying a {@code Connection: close} header to the {@linkplain

     * #getResponseHeaders() response headers} before {@code sendResponseHeaders}

     * is called.

     *

     * @param rCode the response code to send

     * @param responseLength if {@literal > 0}, specifies a fixed response

     *        body length and that exact number of bytes must be written

     *        to the stream acquired from getResponseBody(), or else

     *        if equal to 0, then chunked encoding is used,

     *        and an arbitrary number of bytes may be written.

     *        if {@literal <= -1}, then no response body length is specified and

     *        no response body may be written.

     * @see HttpExchange#getResponseBody()

     */

    public abstract void sendResponseHeaders (int rCode, long responseLength) throws IOException ;

    /**

     * Returns the address of the remote entity invoking this request

     * @return the InetSocketAddress of the caller

     */

    public abstract InetSocketAddress getRemoteAddress ();

    /**

     * Returns the response code, if it has already been set

     * @return the response code, if available. {@code -1} if not available yet.

     */

    public abstract int getResponseCode ();

    /**

     * Returns the local address on which the request was received

     * @return the InetSocketAddress of the local interface

     */

    public abstract InetSocketAddress getLocalAddress ();

    /**

     * Returns the protocol string from the request in the form

     * <i>protocol/majorVersion.minorVersion</i>. For example,

     * "HTTP/1.1"

     * @return the protocol string from the request

     */

    public abstract String getProtocol ();

    /**

     * Filter modules may store arbitrary objects with HttpExchange

     * instances as an out-of-band communication mechanism. Other Filters

     * or the exchange handler may then access these objects.

     * <p>

     * Each Filter class will document the attributes which they make

     * available.

     * @param name the name of the attribute to retrieve

     * @return the attribute object, or null if it does not exist

     * @throws NullPointerException if name is {@code null}

     */

    public abstract Object getAttribute (String name) ;

    /**

     * Filter modules may store arbitrary objects with HttpExchange

     * instances as an out-of-band communication mechanism. Other Filters

     * or the exchange handler may then access these objects.

     * <p>

     * Each Filter class will document the attributes which they make

     * available.

     * @param name the name to associate with the attribute value

     * @param value the object to store as the attribute value. {@code null}

     * value is permitted.

     * @throws NullPointerException if name is {@code null}

     */

    public abstract void setAttribute (String name, Object value) ;

    /**

     * Used by Filters to wrap either (or both) of this exchange's InputStream

     * and OutputStream, with the given filtered streams so

     * that subsequent calls to {@link #getRequestBody()} will

     * return the given {@link java.io.InputStream}, and calls to

     * {@link #getResponseBody()} will return the given

     * {@link java.io.OutputStream}. The streams provided to this

     * call must wrap the original streams, and may be (but are not

     * required to be) sub-classes of {@link java.io.FilterInputStream}

     * and {@link java.io.FilterOutputStream}.

     * @param i the filtered input stream to set as this object's inputstream,

     *          or {@code null} if no change.

     * @param o the filtered output stream to set as this object's outputstream,

     *          or {@code null} if no change.

     */

    public abstract void setStreams (InputStream i, OutputStream o);

    /**

     * If an authenticator is set on the HttpContext that owns this exchange,

     * then this method will return the {@link HttpPrincipal} that represents

     * the authenticated user for this HttpExchange.

     * @return the HttpPrincipal, or {@code null} if no authenticator is set.

     */

    public abstract HttpPrincipal getPrincipal ();

}