/*
 * ====================================================================
 * 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.hc.client5.http;

import java.net.InetAddress;

import org.apache.hc.core5.http.HttpHost;

/**
 * Read-only interface for route information.
 *
 * @since 4.0
 */
public interface RouteInfo {

    /**
     * The tunnelling type of a route.
     * Plain routes are established by   connecting to the target or
     * the first proxy.
     * Tunnelled routes are established by connecting to the first proxy
     * and tunnelling through all proxies to the target.
     * Routes without a proxy cannot be tunnelled.
     */
    enum TunnelType { PLAIN, TUNNELLED }

    /**
     * The layering type of a route.
     * Plain routes are established by connecting or tunnelling.
     * Layered routes are established by layering a protocol such as TLS/SSL
     * over an existing connection.
     * Protocols can only be layered over a tunnel to the target, or
     * or over a direct connection without proxies.
     * <p>
     * Layering a protocol
     * over a direct connection makes little sense, since the connection
     * could be established with the new protocol in the first place.
     * But we don't want to exclude that use case.
     * </p>
     */
    enum LayerType  { PLAIN, LAYERED }

    /**
     * Obtains the target host.
     *
     * @return the target host
     */
    HttpHost getTargetHost();

    /**
     * Obtains the local address to connect from.
     *
     * @return  the local address,
     *          or {@code null}
     */
    InetAddress getLocalAddress();

    /**
     * Obtains the number of hops in this route.
     * A direct route has one hop. A route through a proxy has two hops.
     * A route through a chain of <i>n</i> proxies has <i>n+1</i> hops.
     *
     * @return  the number of hops in this route
     */
    int getHopCount();

    /**
     * Obtains the target of a hop in this route.
     * The target of the last hop is the {@link #getTargetHost target host},
     * the target of previous hops is the respective proxy in the chain.
     * For a route through exactly one proxy, target of hop 0 is the proxy
     * and target of hop 1 is the target host.
     *
     * @param hop       index of the hop for which to get the target,
     *                  0 for first
     *
     * @return  the target of the given hop
     *
     * @throws IllegalArgumentException
     *  if the argument is negative or not less than
     *  {@link #getHopCount getHopCount()}
     */
    HttpHost getHopTarget(int hop);

    /**
     * Obtains the first proxy host.
     *
     * @return the first proxy in the proxy chain, or
     *         {@code null} if this route is direct
     */
    HttpHost getProxyHost();

    /**
     * Obtains the tunnel type of this route.
     * If there is a proxy chain, only end-to-end tunnels are considered.
     *
     * @return  the tunnelling type
     */
    TunnelType getTunnelType();

    /**
     * Checks whether this route is tunnelled through a proxy.
     * If there is a proxy chain, only end-to-end tunnels are considered.
     *
     * @return  {@code true} if tunnelled end-to-end through at least
     *          one proxy,
     *          {@code false} otherwise
     */
    boolean isTunnelled();

    /**
     * Obtains the layering type of this route.
     * In the presence of proxies, only layering over an end-to-end tunnel
     * is considered.
     *
     * @return  the layering type
     */
    LayerType getLayerType();

    /**
     * Checks whether this route includes a layered protocol.
     * In the presence of proxies, only layering over an end-to-end tunnel
     * is considered.
     *
     * @return  {@code true} if layered,
     *          {@code false} otherwise
     */
    boolean isLayered();

    /**
     * Checks whether this route is secure.
     *
     * @return  {@code true} if secure,
     *          {@code false} otherwise
     */
    boolean isSecure();

}
