/*
    * Copyright (C) 2018, 2022 Thomas Wolf <thomas.wolf@paranor.ch> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.transport.sshd;
  
  import static java.text.MessageFormat.format;
  import static org.apache.sshd.common.SshConstants.SSH2_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE;
  import static org.apache.sshd.sftp.SftpModuleProperties.SFTP_CHANNEL_OPEN_TIMEOUT;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.net.URISyntaxException;
  import java.time.Duration;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Supplier;
  import java.util.regex.Pattern;
  
  import org.apache.sshd.client.SshClient;
  import org.apache.sshd.client.channel.ChannelExec;
  import org.apache.sshd.client.channel.ClientChannelEvent;
  import org.apache.sshd.client.config.hosts.HostConfigEntry;
  import org.apache.sshd.client.future.ConnectFuture;
  import org.apache.sshd.client.session.ClientSession;
  import org.apache.sshd.client.session.forward.PortForwardingTracker;
  import org.apache.sshd.common.AttributeRepository;
  import org.apache.sshd.common.SshException;
  import org.apache.sshd.common.future.CloseFuture;
  import org.apache.sshd.common.future.SshFutureListener;
  import org.apache.sshd.common.util.io.IoUtils;
  import org.apache.sshd.common.util.io.functors.IOFunction;
  import org.apache.sshd.common.util.net.SshdSocketAddress;
  import org.apache.sshd.sftp.client.SftpClient;
  import org.apache.sshd.sftp.client.SftpClient.CopyMode;
  import org.apache.sshd.sftp.client.SftpClientFactory;
  import org.apache.sshd.sftp.common.SftpException;
  import org.eclipse.jgit.annotations.NonNull;
  import org.eclipse.jgit.errors.TransportException;
  import org.eclipse.jgit.internal.transport.ssh.OpenSshConfigFile;
  import org.eclipse.jgit.internal.transport.sshd.AuthenticationCanceledException;
  import org.eclipse.jgit.internal.transport.sshd.AuthenticationLogger;
  import org.eclipse.jgit.internal.transport.sshd.JGitSshClient;
  import org.eclipse.jgit.internal.transport.sshd.SshdText;
  import org.eclipse.jgit.transport.FtpChannel;
  import org.eclipse.jgit.transport.RemoteSession2;
  import org.eclipse.jgit.transport.SshConstants;
  import org.eclipse.jgit.transport.URIish;
  import org.eclipse.jgit.util.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * An implementation of {@link org.eclipse.jgit.transport.RemoteSession
   * RemoteSession} based on Apache MINA sshd.
   *
   * @since 5.2
   */
  public class SshdSession implements RemoteSession2 {
  
  	private static final Logger LOG = LoggerFactory
  			.getLogger(SshdSession.class);
  
  	private static final Pattern SHORT_SSH_FORMAT = Pattern
  			.compile("[-\\w.]+(?:@[-\\w.]+)?(?::\\d+)?"); //$NON-NLS-1$
  
  	private static final int MAX_DEPTH = 10;
  
  	private final CopyOnWriteArrayList<SessionCloseListener> listeners = new CopyOnWriteArrayList<>();
  
  	private final URIish uri;
  
  	private SshClient client;
  
  	private ClientSession session;
  
  	SshdSession(URIish uri, Supplier<SshClient> clientFactory) {
  		this.uri = uri;
  		this.client = clientFactory.get();
  	}
  
  	void connect(Duration timeout) throws IOException {
  		if (!client.isStarted()) {
  			client.start();
  		}
 		try {
 			session = connect(uri, Collections.emptyList(),
 					future -> notifyCloseListeners(), timeout, MAX_DEPTH);
 		} catch (IOException e) {
 			disconnect(e);
 			throw e;
 		}
 	}
 
 	private ClientSession connect(URIish target, List<URIish> jumps,
 			SshFutureListener<CloseFuture> listener, Duration timeout,
 			int depth) throws IOException {
 		if (--depth < 0) {
 			throw new IOException(
 					format(SshdText.get().proxyJumpAbort, target));
 		}
 		HostConfigEntry hostConfig = getHostConfig(target.getUser(),
 				target.getHost(), target.getPort());
 		String host = hostConfig.getHostName();
 		int port = hostConfig.getPort();
 		List<URIish> hops = determineHops(jumps, hostConfig, target.getHost());
 		ClientSession resultSession = null;
 		ClientSession proxySession = null;
 		PortForwardingTracker portForward = null;
 		AuthenticationLogger authLog = null;
 		try {
 			if (!hops.isEmpty()) {
 				URIish hop = hops.remove(0);
 				if (LOG.isDebugEnabled()) {
 					LOG.debug("Connecting to jump host {}", hop); //$NON-NLS-1$
 				}
 				proxySession = connect(hop, hops, null, timeout, depth);
 			}
 			AttributeRepository context = null;
 			if (proxySession != null) {
 				SshdSocketAddress remoteAddress = new SshdSocketAddress(host,
 						port);
 				portForward = proxySession.createLocalPortForwardingTracker(
 						SshdSocketAddress.LOCALHOST_ADDRESS, remoteAddress);
 				// We must connect to the locally bound address, not the one
 				// from the host config.
 				context = AttributeRepository.ofKeyValuePair(
 						JGitSshClient.LOCAL_FORWARD_ADDRESS,
 						portForward.getBoundAddress());
 			}
 			int timeoutInSec = OpenSshConfigFile.timeSpec(
 					hostConfig.getProperty(SshConstants.CONNECT_TIMEOUT));
 			resultSession = connect(hostConfig, context,
 					timeoutInSec > 0 ? Duration.ofSeconds(timeoutInSec)
 							: timeout);
 			if (proxySession != null) {
 				final PortForwardingTracker tracker = portForward;
 				final ClientSession pSession = proxySession;
 				resultSession.addCloseFutureListener(future -> {
 					IoUtils.closeQuietly(tracker);
 					String sessionName = pSession.toString();
 					try {
 						pSession.close();
 					} catch (IOException e) {
 						LOG.error(format(
 								SshdText.get().sshProxySessionCloseFailed,
 								sessionName), e);
 					}
 				});
 				portForward = null;
 				proxySession = null;
 			}
 			if (listener != null) {
 				resultSession.addCloseFutureListener(listener);
 			}
 			// Authentication timeout is by default 2 minutes.
 			authLog = new AuthenticationLogger(resultSession);
 			resultSession.auth().verify(resultSession.getAuthTimeout());
 			return resultSession;
 		} catch (IOException e) {
 			close(portForward, e);
 			close(proxySession, e);
 			close(resultSession, e);
 			if (e instanceof SshException && ((SshException) e)
 					.getDisconnectCode() == SSH2_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE) {
 				String message = format(SshdText.get().loginDenied, host,
 						Integer.toString(port));
 				throw new TransportException(target,
 						withAuthLog(message, authLog), e);
 			} else if (e instanceof SshException && e
 					.getCause() instanceof AuthenticationCanceledException) {
 				String message = e.getCause().getMessage();
 				throw new TransportException(target,
 						withAuthLog(message, authLog), e.getCause());
 			}
 			throw e;
 		} finally {
 			if (authLog != null) {
 				authLog.clear();
 			}
 		}
 	}
 
 	private String withAuthLog(String message, AuthenticationLogger authLog) {
 		if (authLog != null) {
 			String log = String.join(System.lineSeparator(), authLog.getLog());
 			if (!log.isEmpty()) {
 				return message + System.lineSeparator() + log;
 			}
 		}
 		return message;
 	}
 
 	private ClientSession connect(HostConfigEntry config,
 			AttributeRepository context, Duration timeout)
 			throws IOException {
 		ConnectFuture connected = client.connect(config, context, null);
 		long timeoutMillis = timeout.toMillis();
 		if (timeoutMillis <= 0) {
 			connected = connected.verify();
 		} else {
 			connected = connected.verify(timeoutMillis);
 		}
 		return connected.getSession();
 	}
 
 	private void close(Closeable toClose, Throwable error) {
 		if (toClose != null) {
 			try {
 				toClose.close();
 			} catch (IOException e) {
 				error.addSuppressed(e);
 			}
 		}
 	}
 
 	private HostConfigEntry getHostConfig(String username, String host,
 			int port) throws IOException {
 		HostConfigEntry entry = client.getHostConfigEntryResolver()
 				.resolveEffectiveHost(host, port, null, username, null, null);
 		if (entry == null) {
 			if (SshdSocketAddress.isIPv6Address(host)) {
 				return new HostConfigEntry("", host, port, username); //$NON-NLS-1$
 			}
 			return new HostConfigEntry(host, host, port, username);
 		}
 		return entry;
 	}
 
 	private List<URIish> determineHops(List<URIish> currentHops,
 			HostConfigEntry hostConfig, String host) throws IOException {
 		if (currentHops.isEmpty()) {
 			String jumpHosts = hostConfig.getProperty(SshConstants.PROXY_JUMP);
 			if (!StringUtils.isEmptyOrNull(jumpHosts)
 					&& !SshConstants.NONE.equals(jumpHosts)) {
 				try {
 					return parseProxyJump(jumpHosts);
 				} catch (URISyntaxException e) {
 					throw new IOException(
 							format(SshdText.get().configInvalidProxyJump, host,
 									jumpHosts),
 							e);
 				}
 			}
 		}
 		return currentHops;
 	}
 
 	private List<URIish> parseProxyJump(String proxyJump)
 			throws URISyntaxException {
 		String[] hops = proxyJump.split(","); //$NON-NLS-1$
 		List<URIish> result = new LinkedList<>();
 		for (String hop : hops) {
 			// There shouldn't be any whitespace, but let's be lenient
 			hop = hop.trim();
 			if (SHORT_SSH_FORMAT.matcher(hop).matches()) {
 				// URIish doesn't understand the short SSH format
 				// user@host:port, only user@host:path
 				hop = SshConstants.SSH_SCHEME + "://" + hop; //$NON-NLS-1$
 			}
 			URIish to = new URIish(hop);
 			if (!SshConstants.SSH_SCHEME.equalsIgnoreCase(to.getScheme())) {
 				throw new URISyntaxException(hop,
 						SshdText.get().configProxyJumpNotSsh);
 			} else if (!StringUtils.isEmptyOrNull(to.getPath())) {
 				throw new URISyntaxException(hop,
 						SshdText.get().configProxyJumpWithPath);
 			}
 			result.add(to);
 		}
 		return result;
 	}
 
 	/**
 	 * Adds a {@link SessionCloseListener} to this session. Has no effect if the
 	 * given {@code listener} is already registered with this session.
 	 *
 	 * @param listener
 	 *            to add
 	 */
 	public void addCloseListener(@NonNull SessionCloseListener listener) {
 		listeners.addIfAbsent(listener);
 	}
 
 	/**
 	 * Removes the given {@code listener}; has no effect if the listener is not
 	 * currently registered with this session.
 	 *
 	 * @param listener
 	 *            to remove
 	 */
 	public void removeCloseListener(@NonNull SessionCloseListener listener) {
 		listeners.remove(listener);
 	}
 
 	private void notifyCloseListeners() {
 		for (SessionCloseListener l : listeners) {
 			try {
 				l.sessionClosed(this);
 			} catch (RuntimeException e) {
 				LOG.warn(SshdText.get().closeListenerFailed, e);
 			}
 		}
 	}
 
 	@Override
 	public Process exec(String commandName, int timeout) throws IOException {
 		return exec(commandName, Collections.emptyMap(), timeout);
 	}
 
 	@Override
 	public Process exec(String commandName, Map<String, String> environment,
 			int timeout) throws IOException {
 		@SuppressWarnings("resource")
 		ChannelExec exec = session.createExecChannel(commandName, null,
 				environment);
 		if (timeout <= 0) {
 			try {
 				exec.open().verify();
 			} catch (IOException | RuntimeException e) {
 				exec.close(true);
 				throw e;
 			}
 		} else {
 			try {
 				exec.open().verify(TimeUnit.SECONDS.toMillis(timeout));
 			} catch (IOException | RuntimeException e) {
 				exec.close(true);
 				throw new IOException(format(SshdText.get().sshCommandTimeout,
 						commandName, Integer.valueOf(timeout)), e);
 			}
 		}
 		return new SshdExecProcess(exec, commandName);
 	}
 
 	/**
 	 * Obtain an {@link FtpChannel} to perform SFTP operations in this
 	 * {@link SshdSession}.
 	 */
 	@Override
 	@NonNull
 	public FtpChannel getFtpChannel() {
 		return new SshdFtpChannel();
 	}
 
 	@Override
 	public void disconnect() {
 		disconnect(null);
 	}
 
 	private void disconnect(Throwable reason) {
 		try {
 			if (session != null) {
 				session.close();
 				session = null;
 			}
 		} catch (IOException e) {
 			if (reason != null) {
 				reason.addSuppressed(e);
 			} else {
 				LOG.error(SshdText.get().sessionCloseFailed, e);
 			}
 		} finally {
 			client.stop();
 			client = null;
 		}
 	}
 
 	private static class SshdExecProcess extends Process {
 
 		private final ChannelExec channel;
 
 		private final String commandName;
 
 		public SshdExecProcess(ChannelExec channel, String commandName) {
 			this.channel = channel;
 			this.commandName = commandName;
 		}
 
 		@Override
 		public OutputStream getOutputStream() {
 			return channel.getInvertedIn();
 		}
 
 		@Override
 		public InputStream getInputStream() {
 			return channel.getInvertedOut();
 		}
 
 		@Override
 		public InputStream getErrorStream() {
 			return channel.getInvertedErr();
 		}
 
 		@Override
 		public int waitFor() throws InterruptedException {
 			if (waitFor(-1L, TimeUnit.MILLISECONDS)) {
 				return exitValue();
 			}
 			return -1;
 		}
 
 		@Override
 		public boolean waitFor(long timeout, TimeUnit unit)
 				throws InterruptedException {
 			long millis = timeout >= 0 ? unit.toMillis(timeout) : -1L;
 			return channel
 					.waitFor(EnumSet.of(ClientChannelEvent.CLOSED), millis)
 					.contains(ClientChannelEvent.CLOSED);
 		}
 
 		@Override
 		public int exitValue() {
 			Integer exitCode = channel.getExitStatus();
 			if (exitCode == null) {
 				throw new IllegalThreadStateException(
 						format(SshdText.get().sshProcessStillRunning,
 								commandName));
 			}
 			return exitCode.intValue();
 		}
 
 		@Override
 		public void destroy() {
 			if (channel.isOpen()) {
 				channel.close(false);
 			}
 		}
 	}
 
 	private class SshdFtpChannel implements FtpChannel {
 
 		private SftpClient ftp;
 
 		/** Current working directory. */
 		private String cwd = ""; //$NON-NLS-1$
 
 		@Override
 		public void connect(int timeout, TimeUnit unit) throws IOException {
 			if (timeout <= 0) {
 				// This timeout must not be null!
 				SFTP_CHANNEL_OPEN_TIMEOUT.set(session,
 						Duration.ofMillis(Long.MAX_VALUE));
 			} else {
 				SFTP_CHANNEL_OPEN_TIMEOUT.set(session,
 						Duration.ofMillis(unit.toMillis(timeout)));
 			}
 			ftp = SftpClientFactory.instance().createSftpClient(session);
 			try {
 				cd(cwd);
 			} catch (IOException e) {
 				ftp.close();
 			}
 		}
 
 		@Override
 		public void disconnect() {
 			try {
 				ftp.close();
 			} catch (IOException e) {
 				LOG.error(SshdText.get().ftpCloseFailed, e);
 			}
 		}
 
 		@Override
 		public boolean isConnected() {
 			return session.isAuthenticated() && ftp.isOpen();
 		}
 
 		private String absolute(String path) {
 			if (path.isEmpty()) {
 				return cwd;
 			}
 			// Note: there is no path injection vulnerability here. If
 			// path has too many ".." components, we rely on the server
 			// catching it and returning an error.
 			if (path.charAt(0) != '/') {
 				if (cwd.charAt(cwd.length() - 1) == '/') {
 					return cwd + path;
 				}
 				return cwd + '/' + path;
 			}
 			return path;
 		}
 
 		private <T> T map(IOFunction<Void, T> op) throws IOException {
 			try {
 				return op.apply(null);
 			} catch (IOException e) {
 				if (e instanceof SftpException) {
 					throw new FtpChannel.FtpException(e.getLocalizedMessage(),
 							((SftpException) e).getStatus(), e);
 				}
 				throw e;
 			}
 		}
 
 		@Override
 		public void cd(String path) throws IOException {
 			cwd = map(x -> ftp.canonicalPath(absolute(path)));
 			if (cwd.isEmpty()) {
 				cwd += '/';
 			}
 		}
 
 		@Override
 		public String pwd() throws IOException {
 			return cwd;
 		}
 
 		@Override
 		public Collection<DirEntry> ls(String path) throws IOException {
 			return map(x -> {
 				List<DirEntry> result = new ArrayList<>();
 				for (SftpClient.DirEntry remote : ftp.readDir(absolute(path))) {
 					result.add(new DirEntry() {
 
 						@Override
 						public String getFilename() {
 							return remote.getFilename();
 						}
 
 						@Override
 						public long getModifiedTime() {
 							return remote.getAttributes().getModifyTime()
 									.toMillis();
 						}
 
 						@Override
 						public boolean isDirectory() {
 							return remote.getAttributes().isDirectory();
 						}
 
 					});
 				}
 				return result;
 			});
 		}
 
 		@Override
 		public void rmdir(String path) throws IOException {
 			map(x -> {
 				ftp.rmdir(absolute(path));
 				return null;
 			});
 
 		}
 
 		@Override
 		public void mkdir(String path) throws IOException {
 			map(x -> {
 				ftp.mkdir(absolute(path));
 				return null;
 			});
 		}
 
 		@Override
 		public InputStream get(String path) throws IOException {
 			return map(x -> ftp.read(absolute(path)));
 		}
 
 		@Override
 		public OutputStream put(String path) throws IOException {
 			return map(x -> ftp.write(absolute(path)));
 		}
 
 		@Override
 		public void rm(String path) throws IOException {
 			map(x -> {
 				ftp.remove(absolute(path));
 				return null;
 			});
 		}
 
 		@Override
 		public void rename(String from, String to) throws IOException {
 			map(x -> {
 				String src = absolute(from);
 				String dest = absolute(to);
 				try {
 					ftp.rename(src, dest, CopyMode.Atomic, CopyMode.Overwrite);
 				} catch (UnsupportedOperationException e) {
 					// Older server cannot do POSIX rename...
 					if (!src.equals(dest)) {
 						delete(dest);
 						ftp.rename(src, dest);
 					}
 				}
 				return null;
 			});
 		}
 	}
 }