/*
 * 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.
 */
package org.apache.sshd.agent;

import java.io.IOException;
import java.util.List;

import org.apache.sshd.common.FactoryManager;
import org.apache.sshd.common.channel.ChannelFactory;
import org.apache.sshd.common.session.ConnectionService;

/**
 * The <code>SshAgentFactory</code> is used to communicate with an SshAgent.
 */
public interface SshAgentFactory {
    /**
     * Value that can be set in order to control the type of authentication
     * channel being requested when forwarding a PTY session. If not defined
     * then {@link #DEFAULT_PROXY_AUTH_CHANNEL_TYPE} is used
     */
    String PROXY_AUTH_CHANNEL_TYPE = "ssh-agent-factory-proxy-auth-channel-type";
    // see also https://tools.ietf.org/html/draft-ietf-secsh-agent-02
    String DEFAULT_PROXY_AUTH_CHANNEL_TYPE = "auth-agent-req@openssh.com";

    // See ProxyAgentFactory#getChannelForwardingFactories
    String PREFER_UNIX_AGENT = "ssh-prefer-unix-agent";

    /**
     * The channels are requested by the ssh server when forwarding a client request.
     * The channel will receive agent requests and need to forward them to the agent,
     * either local or through another proxy.
     *
     * @param manager The {@link FactoryManager} through which the request is made
     * @return The {@link ChannelFactory}-ies used to create channels on the client side
     */
    List<ChannelFactory> getChannelForwardingFactories(FactoryManager manager);

    /**
     * Create an SshAgent that can be used on the client side by the authentication
     * process to send possible keys.
     *
     * @param manager The {@link FactoryManager} instance
     * @return The {@link SshAgent} instance
     * @throws IOException If failed to create the client
     */
    SshAgent createClient(FactoryManager manager) throws IOException;

    /**
     * Create the server side that will be used by other SSH clients.
     * It will usually create a channel that will forward the requests
     * to the original client.
     *
     * @param service The {@link ConnectionService} to use
     * @return The {@link SshAgentServer} instance
     * @throws IOException If failed to create the server
     */
    SshAgentServer createServer(ConnectionService service) throws IOException;
}
