001/*
002 * ====================================================================
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *   http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing,
014 * software distributed under the License is distributed on an
015 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
016 * KIND, either express or implied.  See the License for the
017 * specific language governing permissions and limitations
018 * under the License.
019 * ====================================================================
020 *
021 * This software consists of voluntary contributions made by many
022 * individuals on behalf of the Apache Software Foundation.  For more
023 * information on the Apache Software Foundation, please see
024 * <http://www.apache.org/>.
025 *
026 */
027
028package org.apache.http.conn.routing;
029
030/**
031 * Provides directions on establishing a route.
032 * Implementations of this interface compare a planned route with
033 * a tracked route and indicate the next step required.
034 *
035 * @since 4.0
036 */
037public interface HttpRouteDirector {
038
039    /** Indicates that the route can not be established at all. */
040    public final static int UNREACHABLE = -1;
041
042    /** Indicates that the route is complete. */
043    public final static int COMPLETE = 0;
044
045    /** Step: open connection to target. */
046    public final static int CONNECT_TARGET = 1;
047
048    /** Step: open connection to proxy. */
049    public final static int CONNECT_PROXY = 2;
050
051    /** Step: tunnel through proxy to target. */
052    public final static int TUNNEL_TARGET = 3;
053
054    /** Step: tunnel through proxy to other proxy. */
055    public final static int TUNNEL_PROXY = 4;
056
057    /** Step: layer protocol (over tunnel). */
058    public final static int LAYER_PROTOCOL = 5;
059
060
061    /**
062     * Provides the next step.
063     *
064     * @param plan      the planned route
065     * @param fact      the currently established route, or
066     *                  {@code null} if nothing is established
067     *
068     * @return  one of the constants defined in this interface, indicating
069     *          either the next step to perform, or success, or failure.
070     *          0 is for success, a negative value for failure.
071     */
072    public int nextStep(RouteInfo plan, RouteInfo fact);
073
074}