/*
 * Copyright (C) 2008, 2017, Google Inc.
 * Copyright (C) 2017, 2018, Thomas Wolf <thomas.wolf@paranor.ch>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.internal.transport.ssh;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.time.Instant;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;

import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.errors.InvalidPatternException;
import org.eclipse.jgit.fnmatch.FileNameMatcher;
import org.eclipse.jgit.transport.SshConstants;
import org.eclipse.jgit.util.FS;
import org.eclipse.jgit.util.StringUtils;
import org.eclipse.jgit.util.SystemReader;

Fairly complete configuration parser for the openssh ~/.ssh/config file.

Both JSch 0.1.54 and Apache MINA sshd 2.1.0 have parsers for this, but both
are buggy. Therefore we implement our own parser to read an openssh
configuration file.


Limitations compared to the full openssh 7.5 parser:


This parser does not handle Match or Include keywords.
This parser does not do host name canonicalization.


Note that openssh's readconf.c is a validating parser; this parser does not
validate entries.


This config does %-substitutions for the following tokens:


%% - single %
%C - short-hand for %l%h%p%r.
%d - home directory path
%h - remote host name
%L - local host name without domain
%l - FQDN of the local host
%n - host name as specified in lookup(String, int, String) 
%p - port number; if not given in lookup(String, int, String) replaced only if set in the config 
%r - remote user name; if not given in lookup(String, int, String) replaced only if set in the config 
%u - local user name


%i is not handled; Java has no concept of a "user ID". %T is always replaced
by NONE.

See Also:
man
 *      ssh-config/**
 * Fairly complete configuration parser for the openssh ~/.ssh/config file.
 * <p>
 * Both JSch 0.1.54 and Apache MINA sshd 2.1.0 have parsers for this, but both
 * are buggy. Therefore we implement our own parser to read an openssh
 * configuration file.
 * </p>
 * <p>
 * Limitations compared to the full openssh 7.5 parser:
 * </p>
 * <ul>
 * <li>This parser does not handle Match or Include keywords.
 * <li>This parser does not do host name canonicalization.
 * </ul>
 * <p>
 * Note that openssh's readconf.c is a validating parser; this parser does not
 * validate entries.
 * </p>
 * <p>
 * This config does %-substitutions for the following tokens:
 * </p>
 * <ul>
 * <li>%% - single %
 * <li>%C - short-hand for %l%h%p%r.
 * <li>%d - home directory path
 * <li>%h - remote host name
 * <li>%L - local host name without domain
 * <li>%l - FQDN of the local host
 * <li>%n - host name as specified in {@link #lookup(String, int, String)}
 * <li>%p - port number; if not given in {@link #lookup(String, int, String)}
 * replaced only if set in the config
 * <li>%r - remote user name; if not given in
 * {@link #lookup(String, int, String)} replaced only if set in the config
 * <li>%u - local user name
 * </ul>
 * <p>
 * %i is not handled; Java has no concept of a "user ID". %T is always replaced
 * by NONE.
 * </p>
 *
 * @see <a href="http://man.openbsd.org/OpenBSD-current/man5/ssh_config.5">man
 *      ssh-config</a>
 */
public class OpenSshConfigFile {

	
"Host" name of the HostEntry for the default options before the first
host block in a config file.
/**
	 * "Host" name of the HostEntry for the default options before the first
	 * host block in a config file.
	 */
	private static final String DEFAULT_NAME = ""; //$NON-NLS-1$

	
The user's home directory, as key files may be relative to here. /** The user's home directory, as key files may be relative to here. */
	private final File home;

	
The .ssh/config file we read and monitor for updates. /** The .ssh/config file we read and monitor for updates. */
	private final File configFile;

	
User name of the user on the host OS. /** User name of the user on the host OS. */
	private final String localUserName;

	
Modification time of configFile when it was last loaded. /** Modification time of {@link #configFile} when it was last loaded. */
	private Instant lastModified;

	
Encapsulates entries read out of the configuration file, and a cache of
fully resolved entries created from that.
/**
	 * Encapsulates entries read out of the configuration file, and a cache of
	 * fully resolved entries created from that.
	 */
	private static class State {
		// Keyed by pattern; if a "Host" line has multiple patterns, we generate
		// duplicate HostEntry objects
		Map<String, HostEntry> entries = new LinkedHashMap<>();

		// Keyed by user@hostname:port
		Map<String, HostEntry> hosts = new HashMap<>();

		@Override
		@SuppressWarnings("nls")
		public String toString() {
			return "State [entries=" + entries + ", hosts=" + hosts + "]";
		}
	}

	
State read from the config file, plus the cache. /** State read from the config file, plus the cache. */
	private State state;

	
Creates a new OpenSshConfigFile that will read the config from file config use the given file home as "home" directory. 
Params:
home – 
           user's home directory for the purpose of ~ replacement
config – 
           file to load.
localUserName – 
           user name of the current user on the local host OS/**
	 * Creates a new {@link OpenSshConfigFile} that will read the config from
	 * file {@code config} use the given file {@code home} as "home" directory.
	 *
	 * @param home
	 *            user's home directory for the purpose of ~ replacement
	 * @param config
	 *            file to load.
	 * @param localUserName
	 *            user name of the current user on the local host OS
	 */
	public OpenSshConfigFile(@NonNull File home, @NonNull File config,
			@NonNull String localUserName) {
		this.home = home;
		this.configFile = config;
		this.localUserName = localUserName;
		state = new State();
	}

	
Locate the configuration for a specific host request.
Params:
hostName – 
           the name the user has supplied to the SSH tool. This may be a
           real host name, or it may just be a "Host" block in the
           configuration file.
port – 
           the user supplied; <= 0 if none
userName –  the user supplied, may be null or empty if none given
Returns:
r configuration for the requested name./**
	 * Locate the configuration for a specific host request.
	 *
	 * @param hostName
	 *            the name the user has supplied to the SSH tool. This may be a
	 *            real host name, or it may just be a "Host" block in the
	 *            configuration file.
	 * @param port
	 *            the user supplied; <= 0 if none
	 * @param userName
	 *            the user supplied, may be {@code null} or empty if none given
	 * @return r configuration for the requested name.
	 */
	@NonNull
	public HostEntry lookup(@NonNull String hostName, int port,
			String userName) {
		final State cache = refresh();
		String cacheKey = toCacheKey(hostName, port, userName);
		HostEntry h = cache.hosts.get(cacheKey);
		if (h != null) {
			return h;
		}
		HostEntry fullConfig = new HostEntry();
		// Initialize with default entries at the top of the file, before the
		// first Host block.
		fullConfig.merge(cache.entries.get(DEFAULT_NAME));
		for (Map.Entry<String, HostEntry> e : cache.entries.entrySet()) {
			String pattern = e.getKey();
			if (isHostMatch(pattern, hostName)) {
				fullConfig.merge(e.getValue());
			}
		}
		fullConfig.substitute(hostName, port, userName, localUserName, home);
		cache.hosts.put(cacheKey, fullConfig);
		return fullConfig;
	}

	@NonNull
	private String toCacheKey(@NonNull String hostName, int port,
			String userName) {
		String key = hostName;
		if (port > 0) {
			key = key + ':' + Integer.toString(port);
		}
		if (userName != null && !userName.isEmpty()) {
			key = userName + '@' + key;
		}
		return key;
	}

	private synchronized State refresh() {
		final Instant mtime = FS.DETECTED.lastModifiedInstant(configFile);
		if (!mtime.equals(lastModified)) {
			State newState = new State();
			try (BufferedReader br = Files
					.newBufferedReader(configFile.toPath(), UTF_8)) {
				newState.entries = parse(br);
			} catch (IOException | RuntimeException none) {
				// Ignore -- we'll set and return an empty state
			}
			lastModified = mtime;
			state = newState;
		}
		return state;
	}

	private Map<String, HostEntry> parse(BufferedReader reader)
			throws IOException {
		final Map<String, HostEntry> entries = new LinkedHashMap<>();
		final List<HostEntry> current = new ArrayList<>(4);
		String line;

		// The man page doesn't say so, but the openssh parser (readconf.c)
		// starts out in active mode and thus always applies any lines that
		// occur before the first host block. We gather those options in a
		// HostEntry for DEFAULT_NAME.
		HostEntry defaults = new HostEntry();
		current.add(defaults);
		entries.put(DEFAULT_NAME, defaults);

		while ((line = reader.readLine()) != null) {
			line = line.trim();
			if (line.isEmpty() || line.startsWith("#")) { //$NON-NLS-1$
				continue;
			}
			String[] parts = line.split("[ \t]*[= \t]", 2); //$NON-NLS-1$
			// Although the ssh-config man page doesn't say so, the openssh
			// parser does allow quoted keywords.
			String keyword = dequote(parts[0].trim());
			// man 5 ssh-config says lines had the format "keyword arguments",
			// with no indication that arguments were optional. However, let's
			// not crap out on missing arguments. See bug 444319.
			String argValue = parts.length > 1 ? parts[1].trim() : ""; //$NON-NLS-1$

			if (StringUtils.equalsIgnoreCase(SshConstants.HOST, keyword)) {
				current.clear();
				for (String name : parseList(argValue)) {
					if (name == null || name.isEmpty()) {
						// null should not occur, but better be safe than sorry.
						continue;
					}
					HostEntry c = entries.get(name);
					if (c == null) {
						c = new HostEntry();
						entries.put(name, c);
					}
					current.add(c);
				}
				continue;
			}

			if (current.isEmpty()) {
				// We received an option outside of a Host block. We
				// don't know who this should match against, so skip.
				continue;
			}

			if (HostEntry.isListKey(keyword)) {
				List<String> args = validate(keyword, parseList(argValue));
				for (HostEntry entry : current) {
					entry.setValue(keyword, args);
				}
			} else if (!argValue.isEmpty()) {
				argValue = validate(keyword, dequote(argValue));
				for (HostEntry entry : current) {
					entry.setValue(keyword, argValue);
				}
			}
		}

		return entries;
	}

	
Splits the argument into a list of whitespace-separated elements.
Elements containing whitespace must be quoted and will be de-quoted.
Params:
argument – 
           argument part of the configuration line as read from the
           config file
Returns:
a List of elements, possibly empty and possibly containing empty elements, but not containing null/**
	 * Splits the argument into a list of whitespace-separated elements.
	 * Elements containing whitespace must be quoted and will be de-quoted.
	 *
	 * @param argument
	 *            argument part of the configuration line as read from the
	 *            config file
	 * @return a {@link List} of elements, possibly empty and possibly
	 *         containing empty elements, but not containing {@code null}
	 */
	private List<String> parseList(String argument) {
		List<String> result = new ArrayList<>(4);
		int start = 0;
		int length = argument.length();
		while (start < length) {
			// Skip whitespace
			if (Character.isSpaceChar(argument.charAt(start))) {
				start++;
				continue;
			}
			if (argument.charAt(start) == '"') {
				int stop = argument.indexOf('"', ++start);
				if (stop < start) {
					// No closing double quote: skip
					break;
				}
				result.add(argument.substring(start, stop));
				start = stop + 1;
			} else {
				int stop = start + 1;
				while (stop < length
						&& !Character.isSpaceChar(argument.charAt(stop))) {
					stop++;
				}
				result.add(argument.substring(start, stop));
				start = stop + 1;
			}
		}
		return result;
	}

	
Hook to perform validation on a single value, or to sanitize it. If this
throws an (unchecked) exception, parsing of the file is abandoned.
Params:
key – 
           of the entry
value – 
           as read from the config file
Returns:
the validated and possibly sanitized value/**
	 * Hook to perform validation on a single value, or to sanitize it. If this
	 * throws an (unchecked) exception, parsing of the file is abandoned.
	 *
	 * @param key
	 *            of the entry
	 * @param value
	 *            as read from the config file
	 * @return the validated and possibly sanitized value
	 */
	protected String validate(String key, String value) {
		if (String.CASE_INSENSITIVE_ORDER.compare(key,
				SshConstants.PREFERRED_AUTHENTICATIONS) == 0) {
			return stripWhitespace(value);
		}
		return value;
	}

	
Hook to perform validation on values, or to sanitize them. If this throws
an (unchecked) exception, parsing of the file is abandoned.
Params:
key – 
           of the entry
value – 
           list of arguments as read from the config file
Returns:
a List of values, possibly empty and possibly containing empty elements, but not containing null/**
	 * Hook to perform validation on values, or to sanitize them. If this throws
	 * an (unchecked) exception, parsing of the file is abandoned.
	 *
	 * @param key
	 *            of the entry
	 * @param value
	 *            list of arguments as read from the config file
	 * @return a {@link List} of values, possibly empty and possibly containing
	 *         empty elements, but not containing {@code null}
	 */
	protected List<String> validate(String key, List<String> value) {
		return value;
	}

	private static boolean isHostMatch(String pattern, String name) {
		if (pattern.startsWith("!")) { //$NON-NLS-1$
			return !patternMatchesHost(pattern.substring(1), name);
		} else {
			return patternMatchesHost(pattern, name);
		}
	}

	private static boolean patternMatchesHost(String pattern, String name) {
		if (pattern.indexOf('*') >= 0 || pattern.indexOf('?') >= 0) {
			final FileNameMatcher fn;
			try {
				fn = new FileNameMatcher(pattern, null);
			} catch (InvalidPatternException e) {
				return false;
			}
			fn.append(name);
			return fn.isMatch();
		} else {
			// Not a pattern but a full host name
			return pattern.equals(name);
		}
	}

	private static String dequote(String value) {
		if (value.startsWith("\"") && value.endsWith("\"") //$NON-NLS-1$ //$NON-NLS-2$
				&& value.length() > 1)
			return value.substring(1, value.length() - 1);
		return value;
	}

	private static String stripWhitespace(String value) {
		final StringBuilder b = new StringBuilder();
		for (int i = 0; i < value.length(); i++) {
			if (!Character.isSpaceChar(value.charAt(i)))
				b.append(value.charAt(i));
		}
		return b.toString();
	}

	private static File toFile(String path, File home) {
		if (path.startsWith("~/") || path.startsWith("~" + File.separator)) { //$NON-NLS-1$ //$NON-NLS-2$
			return new File(home, path.substring(2));
		}
		File ret = new File(path);
		if (ret.isAbsolute()) {
			return ret;
		}
		return new File(home, path);
	}

	
Converts a positive value into an int. 
Params:
value – 
           to convert
Returns:
the value, or -1 if it wasn't a positive integral value/**
	 * Converts a positive value into an {@code int}.
	 *
	 * @param value
	 *            to convert
	 * @return the value, or -1 if it wasn't a positive integral value
	 */
	public static int positive(String value) {
		if (value != null) {
			try {
				return Integer.parseUnsignedInt(value);
			} catch (NumberFormatException e) {
				// Ignore
			}
		}
		return -1;
	}

	
Converts a ssh config flag value (yes/true/on - no/false/off) into an boolean. 
Params:
value – 
           to convert
Returns:
true if value is "yes", "on", or "true"; false otherwise/**
	 * Converts a ssh config flag value (yes/true/on - no/false/off) into an
	 * {@code boolean}.
	 *
	 * @param value
	 *            to convert
	 * @return {@code true} if {@code value} is "yes", "on", or "true";
	 *         {@code false} otherwise
	 */
	public static boolean flag(String value) {
		if (value == null) {
			return false;
		}
		return SshConstants.YES.equals(value) || SshConstants.ON.equals(value)
				|| SshConstants.TRUE.equals(value);
	}

	
Retrieves the local user name as given in the constructor.
Returns:
the user name/**
	 * Retrieves the local user name as given in the constructor.
	 *
	 * @return the user name
	 */
	public String getLocalUserName() {
		return localUserName;
	}

	
A host entry from the ssh config file. Any merging of global values and
of several matching host entries, %-substitutions, and ~ replacement have
all been done.
/**
	 * A host entry from the ssh config file. Any merging of global values and
	 * of several matching host entries, %-substitutions, and ~ replacement have
	 * all been done.
	 */
	public static class HostEntry {

		
Keys that can be specified multiple times, building up a list. (I.e.,
those are the keys that do not follow the general rule of "first
occurrence wins".)
/**
		 * Keys that can be specified multiple times, building up a list. (I.e.,
		 * those are the keys that do not follow the general rule of "first
		 * occurrence wins".)
		 */
		private static final Set<String> MULTI_KEYS = new TreeSet<>(
				String.CASE_INSENSITIVE_ORDER);

		static {
			MULTI_KEYS.add(SshConstants.CERTIFICATE_FILE);
			MULTI_KEYS.add(SshConstants.IDENTITY_FILE);
			MULTI_KEYS.add(SshConstants.LOCAL_FORWARD);
			MULTI_KEYS.add(SshConstants.REMOTE_FORWARD);
			MULTI_KEYS.add(SshConstants.SEND_ENV);
		}

		
Keys that take a whitespace-separated list of elements as argument.
Because the dequote-handling is different, we must handle those in
the parser. There are a few other keys that take comma-separated
lists as arguments, but for the parser those are single arguments
that must be quoted if they contain whitespace, and taking them apart
is the responsibility of the user of those keys.
/**
		 * Keys that take a whitespace-separated list of elements as argument.
		 * Because the dequote-handling is different, we must handle those in
		 * the parser. There are a few other keys that take comma-separated
		 * lists as arguments, but for the parser those are single arguments
		 * that must be quoted if they contain whitespace, and taking them apart
		 * is the responsibility of the user of those keys.
		 */
		private static final Set<String> LIST_KEYS = new TreeSet<>(
				String.CASE_INSENSITIVE_ORDER);

		static {
			LIST_KEYS.add(SshConstants.CANONICAL_DOMAINS);
			LIST_KEYS.add(SshConstants.GLOBAL_KNOWN_HOSTS_FILE);
			LIST_KEYS.add(SshConstants.SEND_ENV);
			LIST_KEYS.add(SshConstants.USER_KNOWN_HOSTS_FILE);
		}

		private Map<String, String> options;

		private Map<String, List<String>> multiOptions;

		private Map<String, List<String>> listOptions;

		
Retrieves the value of a single-valued key, or the first is the key has multiple values. Keys are case-insensitive, so getValue("HostName") == getValue("HOSTNAME"). 
Params:
key – 
           to get the value of
Returns:
the value, or null if none/**
		 * Retrieves the value of a single-valued key, or the first is the key
		 * has multiple values. Keys are case-insensitive, so
		 * {@code getValue("HostName") == getValue("HOSTNAME")}.
		 *
		 * @param key
		 *            to get the value of
		 * @return the value, or {@code null} if none
		 */
		public String getValue(String key) {
			String result = options != null ? options.get(key) : null;
			if (result == null) {
				// Let's be lenient and return at least the first value from
				// a list-valued or multi-valued key.
				List<String> values = listOptions != null ? listOptions.get(key)
						: null;
				if (values == null) {
					values = multiOptions != null ? multiOptions.get(key)
							: null;
				}
				if (values != null && !values.isEmpty()) {
					result = values.get(0);
				}
			}
			return result;
		}

		
Retrieves the values of a multi or list-valued key. Keys are case-insensitive, so getValue("HostName") == getValue("HOSTNAME"). 
Params:
key – 
           to get the values of
Returns:
a possibly empty list of values/**
		 * Retrieves the values of a multi or list-valued key. Keys are
		 * case-insensitive, so
		 * {@code getValue("HostName") == getValue("HOSTNAME")}.
		 *
		 * @param key
		 *            to get the values of
		 * @return a possibly empty list of values
		 */
		public List<String> getValues(String key) {
			List<String> values = listOptions != null ? listOptions.get(key)
					: null;
			if (values == null) {
				values = multiOptions != null ? multiOptions.get(key) : null;
			}
			if (values == null || values.isEmpty()) {
				return new ArrayList<>();
			}
			return new ArrayList<>(values);
		}

		
Sets the value of a single-valued key if it not set yet, or adds a value to a multi-valued key. If the value is null, the key is removed altogether, whether it is single-, list-, or multi-valued. 
Params:
key – 
           to modify
value – 
           to set or add/**
		 * Sets the value of a single-valued key if it not set yet, or adds a
		 * value to a multi-valued key. If the value is {@code null}, the key is
		 * removed altogether, whether it is single-, list-, or multi-valued.
		 *
		 * @param key
		 *            to modify
		 * @param value
		 *            to set or add
		 */
		public void setValue(String key, String value) {
			if (value == null) {
				if (multiOptions != null) {
					multiOptions.remove(key);
				}
				if (listOptions != null) {
					listOptions.remove(key);
				}
				if (options != null) {
					options.remove(key);
				}
				return;
			}
			if (MULTI_KEYS.contains(key)) {
				if (multiOptions == null) {
					multiOptions = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				List<String> values = multiOptions.get(key);
				if (values == null) {
					values = new ArrayList<>(4);
					multiOptions.put(key, values);
				}
				values.add(value);
			} else {
				if (options == null) {
					options = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				if (!options.containsKey(key)) {
					options.put(key, value);
				}
			}
		}

		
Sets the values of a multi- or list-valued key.
Params:
key – 
           to set
values – 
           a non-empty list of values/**
		 * Sets the values of a multi- or list-valued key.
		 *
		 * @param key
		 *            to set
		 * @param values
		 *            a non-empty list of values
		 */
		public void setValue(String key, List<String> values) {
			if (values.isEmpty()) {
				return;
			}
			// Check multi-valued keys first; because of the replacement
			// strategy, they must take precedence over list-valued keys
			// which always follow the "first occurrence wins" strategy.
			//
			// Note that SendEnv is a multi-valued list-valued key. (It's
			// rather immaterial for JGit, though.)
			if (MULTI_KEYS.contains(key)) {
				if (multiOptions == null) {
					multiOptions = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				List<String> items = multiOptions.get(key);
				if (items == null) {
					items = new ArrayList<>(values);
					multiOptions.put(key, items);
				} else {
					items.addAll(values);
				}
			} else {
				if (listOptions == null) {
					listOptions = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				if (!listOptions.containsKey(key)) {
					listOptions.put(key, values);
				}
			}
		}

		
Does the key take a whitespace-separated list of values?
Params:
key – 
           to check
Returns:
true if the key is a list-valued key./**
		 * Does the key take a whitespace-separated list of values?
		 *
		 * @param key
		 *            to check
		 * @return {@code true} if the key is a list-valued key.
		 */
		public static boolean isListKey(String key) {
			return LIST_KEYS.contains(key.toUpperCase(Locale.ROOT));
		}

		void merge(HostEntry entry) {
			if (entry == null) {
				// Can occur if we could not read the config file
				return;
			}
			if (entry.options != null) {
				if (options == null) {
					options = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				for (Map.Entry<String, String> item : entry.options
						.entrySet()) {
					if (!options.containsKey(item.getKey())) {
						options.put(item.getKey(), item.getValue());
					}
				}
			}
			if (entry.listOptions != null) {
				if (listOptions == null) {
					listOptions = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				for (Map.Entry<String, List<String>> item : entry.listOptions
						.entrySet()) {
					if (!listOptions.containsKey(item.getKey())) {
						listOptions.put(item.getKey(), item.getValue());
					}
				}

			}
			if (entry.multiOptions != null) {
				if (multiOptions == null) {
					multiOptions = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
				}
				for (Map.Entry<String, List<String>> item : entry.multiOptions
						.entrySet()) {
					List<String> values = multiOptions.get(item.getKey());
					if (values == null) {
						values = new ArrayList<>(item.getValue());
						multiOptions.put(item.getKey(), values);
					} else {
						values.addAll(item.getValue());
					}
				}
			}
		}

		private List<String> substitute(List<String> values, String allowed,
				Replacer r) {
			List<String> result = new ArrayList<>(values.size());
			for (String value : values) {
				result.add(r.substitute(value, allowed));
			}
			return result;
		}

		private List<String> replaceTilde(List<String> values, File home) {
			List<String> result = new ArrayList<>(values.size());
			for (String value : values) {
				result.add(toFile(value, home).getPath());
			}
			return result;
		}

		void substitute(String originalHostName, int port, String userName,
				String localUserName, File home) {
			int p = port >= 0 ? port : positive(getValue(SshConstants.PORT));
			if (p < 0) {
				p = SshConstants.SSH_DEFAULT_PORT;
			}
			String u = userName != null && !userName.isEmpty() ? userName
					: getValue(SshConstants.USER);
			if (u == null || u.isEmpty()) {
				u = localUserName;
			}
			Replacer r = new Replacer(originalHostName, p, u, localUserName,
					home);
			if (options != null) {
				// HOSTNAME first
				String hostName = options.get(SshConstants.HOST_NAME);
				if (hostName == null || hostName.isEmpty()) {
					options.put(SshConstants.HOST_NAME, originalHostName);
				} else {
					hostName = r.substitute(hostName, "h"); //$NON-NLS-1$
					options.put(SshConstants.HOST_NAME, hostName);
					r.update('h', hostName);
				}
			}
			if (multiOptions != null) {
				List<String> values = multiOptions
						.get(SshConstants.IDENTITY_FILE);
				if (values != null) {
					values = substitute(values, "dhlru", r); //$NON-NLS-1$
					values = replaceTilde(values, home);
					multiOptions.put(SshConstants.IDENTITY_FILE, values);
				}
				values = multiOptions.get(SshConstants.CERTIFICATE_FILE);
				if (values != null) {
					values = substitute(values, "dhlru", r); //$NON-NLS-1$
					values = replaceTilde(values, home);
					multiOptions.put(SshConstants.CERTIFICATE_FILE, values);
				}
			}
			if (listOptions != null) {
				List<String> values = listOptions
						.get(SshConstants.USER_KNOWN_HOSTS_FILE);
				if (values != null) {
					values = replaceTilde(values, home);
					listOptions.put(SshConstants.USER_KNOWN_HOSTS_FILE, values);
				}
			}
			if (options != null) {
				// HOSTNAME already done above
				String value = options.get(SshConstants.IDENTITY_AGENT);
				if (value != null) {
					value = r.substitute(value, "dhlru"); //$NON-NLS-1$
					value = toFile(value, home).getPath();
					options.put(SshConstants.IDENTITY_AGENT, value);
				}
				value = options.get(SshConstants.CONTROL_PATH);
				if (value != null) {
					value = r.substitute(value, "ChLlnpru"); //$NON-NLS-1$
					value = toFile(value, home).getPath();
					options.put(SshConstants.CONTROL_PATH, value);
				}
				value = options.get(SshConstants.LOCAL_COMMAND);
				if (value != null) {
					value = r.substitute(value, "CdhlnprTu"); //$NON-NLS-1$
					options.put(SshConstants.LOCAL_COMMAND, value);
				}
				value = options.get(SshConstants.REMOTE_COMMAND);
				if (value != null) {
					value = r.substitute(value, "Cdhlnpru"); //$NON-NLS-1$
					options.put(SshConstants.REMOTE_COMMAND, value);
				}
				value = options.get(SshConstants.PROXY_COMMAND);
				if (value != null) {
					value = r.substitute(value, "hpr"); //$NON-NLS-1$
					options.put(SshConstants.PROXY_COMMAND, value);
				}
			}
			// Match is not implemented and would need to be done elsewhere
			// anyway.
		}

		
Retrieves an unmodifiable map of all single-valued options, with
case-insensitive lookup by keys.
Returns:
all single-valued options/**
		 * Retrieves an unmodifiable map of all single-valued options, with
		 * case-insensitive lookup by keys.
		 *
		 * @return all single-valued options
		 */
		@NonNull
		public Map<String, String> getOptions() {
			if (options == null) {
				return Collections.emptyMap();
			}
			return Collections.unmodifiableMap(options);
		}

		
Retrieves an unmodifiable map of all multi-valued options, with
case-insensitive lookup by keys.
Returns:
all multi-valued options/**
		 * Retrieves an unmodifiable map of all multi-valued options, with
		 * case-insensitive lookup by keys.
		 *
		 * @return all multi-valued options
		 */
		@NonNull
		public Map<String, List<String>> getMultiValuedOptions() {
			if (listOptions == null && multiOptions == null) {
				return Collections.emptyMap();
			}
			Map<String, List<String>> allValues = new TreeMap<>(
					String.CASE_INSENSITIVE_ORDER);
			if (multiOptions != null) {
				allValues.putAll(multiOptions);
			}
			if (listOptions != null) {
				allValues.putAll(listOptions);
			}
			return Collections.unmodifiableMap(allValues);
		}

		@Override
		@SuppressWarnings("nls")
		public String toString() {
			return "HostEntry [options=" + options + ", multiOptions="
					+ multiOptions + ", listOptions=" + listOptions + "]";
		}
	}

	private static class Replacer {
		private final Map<Character, String> replacements = new HashMap<>();

		public Replacer(String host, int port, String user,
				String localUserName, File home) {
			replacements.put(Character.valueOf('%'), "%"); //$NON-NLS-1$
			replacements.put(Character.valueOf('d'), home.getPath());
			replacements.put(Character.valueOf('h'), host);
			String localhost = SystemReader.getInstance().getHostname();
			replacements.put(Character.valueOf('l'), localhost);
			int period = localhost.indexOf('.');
			if (period > 0) {
				localhost = localhost.substring(0, period);
			}
			replacements.put(Character.valueOf('L'), localhost);
			replacements.put(Character.valueOf('n'), host);
			replacements.put(Character.valueOf('p'), Integer.toString(port));
			replacements.put(Character.valueOf('r'), user == null ? "" : user); //$NON-NLS-1$
			replacements.put(Character.valueOf('u'), localUserName);
			replacements.put(Character.valueOf('C'),
					substitute("%l%h%p%r", "hlpr")); //$NON-NLS-1$ //$NON-NLS-2$
			replacements.put(Character.valueOf('T'), "NONE"); //$NON-NLS-1$
		}

		public void update(char key, String value) {
			replacements.put(Character.valueOf(key), value);
			if ("lhpr".indexOf(key) >= 0) { //$NON-NLS-1$
				replacements.put(Character.valueOf('C'),
						substitute("%l%h%p%r", "hlpr")); //$NON-NLS-1$ //$NON-NLS-2$
			}
		}

		public String substitute(String input, String allowed) {
			if (input == null || input.length() <= 1
					|| input.indexOf('%') < 0) {
				return input;
			}
			StringBuilder builder = new StringBuilder();
			int start = 0;
			int length = input.length();
			while (start < length) {
				int percent = input.indexOf('%', start);
				if (percent < 0 || percent + 1 >= length) {
					builder.append(input.substring(start));
					break;
				}
				String replacement = null;
				char ch = input.charAt(percent + 1);
				if (ch == '%' || allowed.indexOf(ch) >= 0) {
					replacement = replacements.get(Character.valueOf(ch));
				}
				if (replacement == null) {
					builder.append(input.substring(start, percent + 2));
				} else {
					builder.append(input.substring(start, percent))
							.append(replacement);
				}
				start = percent + 2;
			}
			return builder.toString();
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	@SuppressWarnings("nls")
	public String toString() {
		return "OpenSshConfig [home=" + home + ", configFile=" + configFile
				+ ", lastModified=" + lastModified + ", state=" + state + "]";
	}
}