/*
 * 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.karaf.shell.ssh;

import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.Duration;
import java.util.Collections;

import org.apache.karaf.shell.api.action.lifecycle.Manager;
import org.apache.karaf.shell.api.console.CommandLoggingFilter;
import org.apache.karaf.shell.api.console.Session;
import org.apache.karaf.shell.api.console.SessionFactory;
import org.apache.karaf.shell.ssh.keygenerator.OpenSSHKeyPairProvider;
import org.apache.karaf.shell.support.RegexCommandLoggingFilter;
import org.apache.karaf.util.tracker.BaseActivator;
import org.apache.karaf.util.tracker.annotation.Managed;
import org.apache.karaf.util.tracker.annotation.RequireService;
import org.apache.karaf.util.tracker.annotation.Services;
import org.apache.sshd.common.file.virtualfs.VirtualFileSystemFactory;
import org.apache.sshd.common.keyprovider.KeyPairProvider;
import org.apache.sshd.core.CoreModuleProperties;
import org.apache.sshd.scp.server.ScpCommandFactory;
import org.apache.sshd.server.SshServer;
import org.apache.sshd.server.forward.AcceptAllForwardingFilter;
import org.apache.sshd.sftp.server.SftpSubsystemFactory;
import org.osgi.framework.ServiceReference;
import org.osgi.service.cm.ConfigurationAdmin;
import org.osgi.service.cm.ManagedService;
import org.osgi.util.tracker.ServiceTracker;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Activate this bundle
 */
@Services(
        requires = { @RequireService(SessionFactory.class), @RequireService(ConfigurationAdmin.class) }
)
@Managed("org.apache.karaf.shell")
public class Activator extends BaseActivator implements ManagedService {

    static final Logger LOGGER = LoggerFactory.getLogger(Activator.class);

    ServiceTracker<Session, Session> sessionTracker;
    SessionFactory sessionFactory;
    SshServer server;

    @Override
    protected void doOpen() throws Exception {
        super.doOpen();

        sessionTracker = new ServiceTracker<Session, Session>(bundleContext, Session.class, null) {
            @Override
            public Session addingService(ServiceReference<Session> reference) {
                Session session = super.addingService(reference);
                KarafAgentFactory.getInstance().registerSession(session);
                return session;
            }
            @Override
            public void removedService(ServiceReference<Session> reference, Session session) {
                KarafAgentFactory.getInstance().unregisterSession(session);
                super.removedService(reference, session);
            }
        };
        sessionTracker.open();
    }

    @Override
    protected void doClose() {
        sessionTracker.close();
        super.doClose();
    }

    @Override
    protected void doStart() throws Exception {
        SessionFactory sf = getTrackedService(SessionFactory.class);
        if (sf == null) {
            return;
        }

        if (!ensureStartupConfiguration("org.apache.karaf.shell")) {
            return;
        }

        RegexCommandLoggingFilter filter = new RegexCommandLoggingFilter();
        filter.setPattern("ssh (.*?)-P +([^ ]+)");
        filter.setGroup(2);
        register(CommandLoggingFilter.class, filter);

        filter = new RegexCommandLoggingFilter();
        filter.setPattern("ssh (.*?)--password +([^ ]+)");
        filter.setGroup(2);
        register(CommandLoggingFilter.class, filter);

        sessionFactory = sf;
        sessionFactory.getRegistry().getService(Manager.class).register(SshAction.class);
        if (Boolean.parseBoolean(bundleContext.getProperty("karaf.startRemoteShell"))) {
            createAndRunSshServer();
        }
    }

    private void createAndRunSshServer() {
        server = createSshServer(sessionFactory);
        this.bundleContext.registerService(SshServer.class, server, null);
        if (server == null) {
            return; // can result from bad specification.
        }
        ClassLoader originalClassLoader = Thread.currentThread().getContextClassLoader();
        try {
            Thread.currentThread().setContextClassLoader(SshServer.class.getClassLoader());
            server.start();
        } catch (Exception e) {
            LOGGER.warn("Exception caught while starting SSH server", e);
        } finally {
            Thread.currentThread().setContextClassLoader(originalClassLoader);
        }
    }

    @Override
    protected void doStop() {
        if (sessionFactory != null) {
            sessionFactory.getRegistry().getService(Manager.class).unregister(SshAction.class);
            sessionFactory = null;
        }
        if (server != null) {
            try {
                server.stop(true);
            } catch (IOException e) {
                LOGGER.warn("Exception caught while stopping SSH server", e);
            }
            server = null;
        }
        super.doStop();
    }

    protected SshServer createSshServer(SessionFactory sessionFactory) {
        int sshPort                 = getInt("sshPort", 8101);
        String sshHost              = getString("sshHost", "0.0.0.0");
        long sshIdleTimeout         = getLong("sshIdleTimeout", 1800000);
        int nioWorkers              = getInt("nio-workers", 2);
        int maxConcurrentSessions  = getInt("max-concurrent-sessions", -1);
        String sshRealm             = getString("sshRealm", "karaf");
        Class<?>[] roleClasses      = getClassesArray("sshRoleTypes", "org.apache.karaf.jaas.boot.principal.RolePrincipal");
        String sshRole              = getString("sshRole", null);
        String privateHostKey       = getString("hostKey", System.getProperty("karaf.etc") + "/host.key");
        String privateKeyPassword   = getString("hostKeyPassword", null);
        String publicHostKey        = getString("hostKeyPub", System.getProperty("karaf.etc") + "/host.key.pub");
        String[] authMethods        = getStringArray("authMethods", "keyboard-interactive,password,publickey");
        int keySize                 = getInt("keySize", 2048);
        String algorithm            = getString("algorithm", "RSA");
        String[] macs               = getStringArray("macs", "hmac-sha2-512,hmac-sha2-256");
        String[] ciphers            = getStringArray("ciphers", "aes256-ctr,aes192-ctr,aes128-ctr");
        String[] kexAlgorithms      = getStringArray("kexAlgorithms", "ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256");
        String[] sigAlgorithms      = getStringArray("sigAlgorithms", "ssh-rsa,rsa-sha2-256,rsa-sha2-512,sk-ecdsa-sha2-nistp256@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521");
        String welcomeBanner        = getString("welcomeBanner", null);
        String moduliUrl            = getString("moduli-url", null);
        boolean sftpEnabled         = getBoolean("sftpEnabled", true);

        Path serverPrivateKeyPath = Paths.get(privateHostKey);
        Path serverPublicKeyPath = Paths.get(publicHostKey);
        KeyPairProvider keyPairProvider = new OpenSSHKeyPairProvider(serverPrivateKeyPath, serverPublicKeyPath, algorithm, keySize, privateKeyPassword);
        KarafJaasAuthenticator authenticator = new KarafJaasAuthenticator(sshRealm, sshRole, roleClasses);
        UserAuthFactoriesFactory authFactoriesFactory = new UserAuthFactoriesFactory();
        authFactoriesFactory.setAuthMethods(authMethods);

        SshServer server = SshServer.setUpDefaultServer();
        server.setPort(sshPort);
        server.setHost(sshHost);
        server.setMacFactories(SshUtils.buildMacs(macs));
        server.setCipherFactories(SshUtils.buildCiphers(ciphers));
        server.setKeyExchangeFactories(SshUtils.buildKexAlgorithms(kexAlgorithms));
        server.setSignatureFactories(SshUtils.buildSigAlgorithms(sigAlgorithms));
        server.setShellFactory(new ShellFactoryImpl(sessionFactory));

        if (sftpEnabled) {
            server.setCommandFactory(new ScpCommandFactory.Builder().withDelegate((channel, cmd) -> new ShellCommand(sessionFactory, cmd)).build());
            server.setSubsystemFactories(Collections.singletonList(new SftpSubsystemFactory()));
            server.setFileSystemFactory(new VirtualFileSystemFactory(Paths.get(System.getProperty("karaf.base"))));
        } else {
            server.setCommandFactory((channel, cmd) -> new ShellCommand(sessionFactory, cmd));
        }
        server.setKeyPairProvider(keyPairProvider);
        server.setPasswordAuthenticator(authenticator);
        server.setPublickeyAuthenticator(authenticator);
        server.setUserAuthFactories(authFactoriesFactory.getFactories());
        server.setAgentFactory(KarafAgentFactory.getInstance());
        server.setForwardingFilter(AcceptAllForwardingFilter.INSTANCE);
        CoreModuleProperties.IDLE_TIMEOUT.set(server, Duration.ofMillis(sshIdleTimeout));
        CoreModuleProperties.NIO_WORKERS.set(server, nioWorkers);
        if (maxConcurrentSessions != -1) {
            CoreModuleProperties.MAX_CONCURRENT_SESSIONS.set(server, maxConcurrentSessions);
        }
        if (moduliUrl != null) {
            CoreModuleProperties.MODULI_URL.set(server, moduliUrl);
        }
        if (welcomeBanner != null) {
            CoreModuleProperties.WELCOME_BANNER.set(server, welcomeBanner);
        }
        return server;
    }



}
