/*
 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/HttpMessage.java $
 * $Revision: 610823 $
 * $Date: 2008-01-10 07:53:53 -0800 (Thu, 10 Jan 2008) $
 *
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http;

import org.apache.http.params.HttpParams;

/**
 * A generic HTTP message.
 * Holds what is common between requests and responses.
 *
 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
 *
 * @version $Revision: 610823 $
 * 
 * @since 4.0
 */
public interface HttpMessage {
    
    /**
     * Returns the protocol version this message is compatible with.
     */
    ProtocolVersion getProtocolVersion();

    /**
     * Checks if a certain header is present in this message. Header values are
     * ignored.
     * 
     * @param name the header name to check for.
     * @return true if at least one header with this name is present.
     */
    boolean containsHeader(String name);
    
    /**
     * Returns all the headers with a specified name of this message. Header values
     * are ignored. Headers are orderd in the sequence they will be sent over a
     * connection.
     * 
     * @param name the name of the headers to return.
     * @return the headers whose name property equals <code>name</code>.
     */
    Header[] getHeaders(String name);

    /**
     * Returns the first header with a specified name of this message. Header
     * values are ignored. If there is more than one matching header in the
     * message the first element of {@link #getHeaders(String)} is returned.
     * If there is no matching header in the message <code>null</code> is 
     * returned.
     * 
     * @param name the name of the header to return.
     * @return the first header whose name property equals <code>name</code>
     *   or <code>null</code> if no such header could be found.
     */
    Header getFirstHeader(String name);

    /**
     * Returns the last header with a specified name of this message. Header values
     * are ignored. If there is more than one matching header in the message the
     * last element of {@link #getHeaders(String)} is returned. If there is no 
     * matching header in the message <code>null</code> is returned.
     * 
     * @param name the name of the header to return.
     * @return the last header whose name property equals <code>name</code>.
     *   or <code>null</code> if no such header could be found.
     */
    Header getLastHeader(String name);

    /**
     * Returns all the headers of this message. Headers are orderd in the sequence
     * they will be sent over a connection.
     * 
     * @return all the headers of this message
     */
    Header[] getAllHeaders();

    /**
     * Adds a header to this message. The header will be appended to the end of
     * the list.
     * 
     * @param header the header to append.
     */
    void addHeader(Header header);

    /**
     * Adds a header to this message. The header will be appended to the end of
     * the list.
     * 
     * @param name the name of the header.
     * @param value the value of the header.
     */
    void addHeader(String name, String value);

    /**
     * Overwrites the first header with the same name. The new header will be appended to 
     * the end of the list, if no header with the given name can be found.
     * 
     * @param header the header to set.
     */
    void setHeader(Header header);

    /**
     * Overwrites the first header with the same name. The new header will be appended to 
     * the end of the list, if no header with the given name can be found.
     * 
     * @param name the name of the header.
     * @param value the value of the header.
     */
    void setHeader(String name, String value);

    /**
     * Overwrites all the headers in the message.
     * 
     * @param headers the array of headers to set.
     */
    void setHeaders(Header[] headers);

    /**
     * Removes a header from this message.
     * 
     * @param header the header to remove.
     */
    void removeHeader(Header header);
    
    /**
     * Removes all headers with a certain name from this message.
     * 
     * @param name The name of the headers to remove.
     */
    void removeHeaders(String name);
    
    /**
     * Returns an iterator of all the headers.
     * 
     * @return Iterator that returns Header objects in the sequence they are
     *         sent over a connection.
     */
    HeaderIterator headerIterator();

    /**
     * Returns an iterator of the headers with a given name.
     *
     * @param name      the name of the headers over which to iterate, or
     *                  <code>null</code> for all headers
     *
     * @return Iterator that returns Header objects with the argument name
     *         in the sequence they are sent over a connection.
     */
    HeaderIterator headerIterator(String name);

    /**
     * Returns the parameters effective for this message as set by
     * {@link #setParams(HttpParams)}.
     */
    HttpParams getParams();

    /**
     * Provides parameters to be used for the processing of this message.
     * @param params the parameters
     */
    void setParams(HttpParams params);
        
}