/*
 * 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.local;

import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.sshd.agent.SshAgent;
import org.apache.sshd.agent.SshAgentFactory;
import org.apache.sshd.agent.SshAgentServer;
import org.apache.sshd.agent.unix.AprLibrary;
import org.apache.sshd.agent.unix.UnixAgentFactory;
import org.apache.sshd.common.FactoryManager;
import org.apache.sshd.common.PropertyResolver;
import org.apache.sshd.common.PropertyResolverUtils;
import org.apache.sshd.common.channel.ChannelFactory;
import org.apache.sshd.common.session.ConnectionService;
import org.apache.sshd.common.session.Session;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.OsUtils;
import org.apache.sshd.common.util.ValidateUtils;
import org.apache.sshd.server.session.ServerSession;

/**
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public class ProxyAgentFactory implements SshAgentFactory {
    private final Map<String, AgentServerProxy> proxies = new ConcurrentHashMap<>();

    public ProxyAgentFactory() {
        super();
    }

    @Override
    public List<ChannelFactory> getChannelForwardingFactories(FactoryManager manager) {
        return isPreferredUnixAgent(manager)
            ? UnixAgentFactory.DEFAULT_FORWARDING_CHANNELS
            : LocalAgentFactory.DEFAULT_FORWARDING_CHANNELS;
    }

    @Override
    public SshAgent createClient(FactoryManager manager) throws IOException {
        String proxyId = manager.getString(SshAgent.SSH_AUTHSOCKET_ENV_NAME);
        if (GenericUtils.isEmpty(proxyId)) {
            throw new IllegalStateException("No " + SshAgent.SSH_AUTHSOCKET_ENV_NAME + " environment variable set");
        }

        AgentServerProxy proxy = proxies.get(proxyId);
        if (proxy == null) {
            throw new IllegalStateException("No ssh agent found for ID=" + proxyId);
        }

        return proxy.createClient();
    }

    @Override
    public SshAgentServer createServer(ConnectionService service) throws IOException {
        Session session = service.getSession();
        ValidateUtils.checkInstanceOf(session, ServerSession.class,
                "The session used to create an agent server proxy must be a server session: %s", session);

        AgentServerProxy proxy = new AgentServerProxy(service);
        proxies.put(proxy.getId(), proxy);
        return new SshAgentServer() {
            private final AtomicBoolean open = new AtomicBoolean(true);

            @Override
            public String getId() {
                return proxy.getId();
            }

            @Override
            public boolean isOpen() {
                return open.get() && proxy.isOpen();
            }

            @SuppressWarnings("synthetic-access")
            @Override
            public void close() throws IOException {
                if (open.getAndSet(false)) {
                    proxies.remove(proxy.getId());
                    proxy.close();
                }
            }
        };
    }

    public static boolean isPreferredUnixAgent(PropertyResolver resolver) {
        if (PropertyResolverUtils.getBooleanProperty(resolver, PREFER_UNIX_AGENT, OsUtils.isUNIX())) {
            try {
                if (AprLibrary.getInstance() != null) {
                    return true;
                }
            } catch (Exception ignore) {
                // ignored
            }
        }

        return false;
    }
}
