/*
    * Copyright (C) 2008, 2014, Google Inc.
    * 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
    *
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   * without modification, are permitted provided that the following
   * conditions are met:
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   *   notice, this list of conditions and the following disclaimer.
   *
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   *   with the distribution.
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   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
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  package org.eclipse.jgit.transport;
  
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.eclipse.jgit.errors.InvalidPatternException;
  import org.eclipse.jgit.fnmatch.FileNameMatcher;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.util.FS;
  import org.eclipse.jgit.util.StringUtils;
  
  /**
   * Simple configuration parser for the OpenSSH ~/.ssh/config file.
   * <p>
   * Since JSch does not (currently) have the ability to parse an OpenSSH
   * configuration file this is a simple parser to read that file and make the
   * critical options available to {@link SshSessionFactory}.
   */
  public class OpenSshConfig {
  	/** IANA assigned port number for SSH. */
  	static final int SSH_PORT = 22;
  
  	/**
  	 * Obtain the user's configuration data.
  	 * <p>
  	 * The configuration file is always returned to the caller, even if no file
  	 * exists in the user's home directory at the time the call was made. Lookup
  	 * requests are cached and are automatically updated if the user modifies
  	 * the configuration file since the last time it was cached.
  	 *
  	 * @param fs
  	 *            the file system abstraction which will be necessary to
  	 *            perform certain file system operations.
  	 * @return a caching reader of the user's configuration file.
  	 */
  	public static OpenSshConfig get(FS fs) {
  		File home = fs.userHome();
  		if (home == null)
  			home = new File(".").getAbsoluteFile(); //$NON-NLS-1$
  
  		final File config = new File(new File(home, ".ssh"), Constants.CONFIG); //$NON-NLS-1$
  		final OpenSshConfig osc = new OpenSshConfig(home, config);
  		osc.refresh();
  		return osc;
 	}
 
 	/** 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. */
 	private final File configFile;
 
 	/** Modification time of {@link #configFile} when {@link #hosts} loaded. */
 	private long lastModified;
 
 	/** Cached entries read out of the configuration file. */
 	private Map<String, Host> hosts;
 
 	OpenSshConfig(final File h, final File cfg) {
 		home = h;
 		configFile = cfg;
 		hosts = Collections.emptyMap();
 	}
 
 	/**
 	 * 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.
 	 * @return r configuration for the requested name. Never null.
 	 */
 	public Host lookup(final String hostName) {
 		final Map<String, Host> cache = refresh();
 		Host h = cache.get(hostName);
 		if (h == null)
 			h = new Host();
 		if (h.patternsApplied)
 			return h;
 
 		for (final Map.Entry<String, Host> e : cache.entrySet()) {
 			if (!isHostPattern(e.getKey()))
 				continue;
 			if (!isHostMatch(e.getKey(), hostName))
 				continue;
 			h.copyFrom(e.getValue());
 		}
 
 		if (h.hostName == null)
 			h.hostName = hostName;
 		if (h.user == null)
 			h.user = OpenSshConfig.userName();
 		if (h.port == 0)
 			h.port = OpenSshConfig.SSH_PORT;
 		if (h.connectionAttempts == 0)
 			h.connectionAttempts = 1;
 		h.patternsApplied = true;
 		return h;
 	}
 
 	private synchronized Map<String, Host> refresh() {
 		final long mtime = configFile.lastModified();
 		if (mtime != lastModified) {
 			try {
 				final FileInputStream in = new FileInputStream(configFile);
 				try {
 					hosts = parse(in);
 				} finally {
 					in.close();
 				}
 			} catch (FileNotFoundException none) {
 				hosts = Collections.emptyMap();
 			} catch (IOException err) {
 				hosts = Collections.emptyMap();
 			}
 			lastModified = mtime;
 		}
 		return hosts;
 	}
 
 	private Map<String, Host> parse(final InputStream in) throws IOException {
 		final Map<String, Host> m = new LinkedHashMap<String, Host>();
 		final BufferedReader br = new BufferedReader(new InputStreamReader(in));
 		final List<Host> current = new ArrayList<Host>(4);
 		String line;
 
 		while ((line = br.readLine()) != null) {
 			line = line.trim();
 			if (line.length() == 0 || line.startsWith("#")) //$NON-NLS-1$
 				continue;
 
 			final String[] parts = line.split("[ \t]*[= \t]", 2); //$NON-NLS-1$
 			final String keyword = parts[0].trim();
 			final String argValue = parts[1].trim();
 
 			if (StringUtils.equalsIgnoreCase("Host", keyword)) { //$NON-NLS-1$
 				current.clear();
 				for (final String pattern : argValue.split("[ \t]")) { //$NON-NLS-1$
 					final String name = dequote(pattern);
 					Host c = m.get(name);
 					if (c == null) {
 						c = new Host();
 						m.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 (StringUtils.equalsIgnoreCase("HostName", keyword)) { //$NON-NLS-1$
 				for (final Host c : current)
 					if (c.hostName == null)
 						c.hostName = dequote(argValue);
 			} else if (StringUtils.equalsIgnoreCase("User", keyword)) { //$NON-NLS-1$
 				for (final Host c : current)
 					if (c.user == null)
 						c.user = dequote(argValue);
 			} else if (StringUtils.equalsIgnoreCase("Port", keyword)) { //$NON-NLS-1$
 				try {
 					final int port = Integer.parseInt(dequote(argValue));
 					for (final Host c : current)
 						if (c.port == 0)
 							c.port = port;
 				} catch (NumberFormatException nfe) {
 					// Bad port number. Don't set it.
 				}
 			} else if (StringUtils.equalsIgnoreCase("IdentityFile", keyword)) { //$NON-NLS-1$
 				for (final Host c : current)
 					if (c.identityFile == null)
 						c.identityFile = toFile(dequote(argValue));
 			} else if (StringUtils.equalsIgnoreCase(
 					"PreferredAuthentications", keyword)) { //$NON-NLS-1$
 				for (final Host c : current)
 					if (c.preferredAuthentications == null)
 						c.preferredAuthentications = nows(dequote(argValue));
 			} else if (StringUtils.equalsIgnoreCase("BatchMode", keyword)) { //$NON-NLS-1$
 				for (final Host c : current)
 					if (c.batchMode == null)
 						c.batchMode = yesno(dequote(argValue));
 			} else if (StringUtils.equalsIgnoreCase(
 					"StrictHostKeyChecking", keyword)) { //$NON-NLS-1$
 				String value = dequote(argValue);
 				for (final Host c : current)
 					if (c.strictHostKeyChecking == null)
 						c.strictHostKeyChecking = value;
 			} else if (StringUtils.equalsIgnoreCase(
 					"ConnectionAttempts", keyword)) { //$NON-NLS-1$
 				try {
 					final int connectionAttempts = Integer.parseInt(dequote(argValue));
 					if (connectionAttempts > 0) {
 						for (final Host c : current)
 							if (c.connectionAttempts == 0)
 								c.connectionAttempts = connectionAttempts;
 					}
 				} catch (NumberFormatException nfe) {
 					// ignore bad values
 				}
 			}
 		}
 
 		return m;
 	}
 
 	private static boolean isHostPattern(final String s) {
 		return s.indexOf('*') >= 0 || s.indexOf('?') >= 0;
 	}
 
 	private static boolean isHostMatch(final String pattern, final String name) {
 		final FileNameMatcher fn;
 		try {
 			fn = new FileNameMatcher(pattern, null);
 		} catch (InvalidPatternException e) {
 			return false;
 		}
 		fn.append(name);
 		return fn.isMatch();
 	}
 
 	private static String dequote(final String value) {
 		if (value.startsWith("\"") && value.endsWith("\"")) //$NON-NLS-1$ //$NON-NLS-2$
 			return value.substring(1, value.length() - 1);
 		return value;
 	}
 
 	private static String nows(final 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 Boolean yesno(final String value) {
 		if (StringUtils.equalsIgnoreCase("yes", value)) //$NON-NLS-1$
 			return Boolean.TRUE;
 		return Boolean.FALSE;
 	}
 
 	private File toFile(final String path) {
 		if (path.startsWith("~/")) //$NON-NLS-1$
 			return new File(home, path.substring(2));
 		File ret = new File(path);
 		if (ret.isAbsolute())
 			return ret;
 		return new File(home, path);
 	}
 
 	static String userName() {
 		return AccessController.doPrivileged(new PrivilegedAction<String>() {
 			public String run() {
 				return System.getProperty("user.name"); //$NON-NLS-1$
 			}
 		});
 	}
 
 	/**
 	 * Configuration of one "Host" block in the configuration file.
 	 * <p>
 	 * If returned from {@link OpenSshConfig#lookup(String)} some or all of the
 	 * properties may not be populated. The properties which are not populated
 	 * should be defaulted by the caller.
 	 * <p>
 	 * When returned from {@link OpenSshConfig#lookup(String)} any wildcard
 	 * entries which appear later in the configuration file will have been
 	 * already merged into this block.
 	 */
 	public static class Host {
 		boolean patternsApplied;
 
 		String hostName;
 
 		int port;
 
 		File identityFile;
 
 		String user;
 
 		String preferredAuthentications;
 
 		Boolean batchMode;
 
 		String strictHostKeyChecking;
 
 		int connectionAttempts;
 
 		void copyFrom(final Host src) {
 			if (hostName == null)
 				hostName = src.hostName;
 			if (port == 0)
 				port = src.port;
 			if (identityFile == null)
 				identityFile = src.identityFile;
 			if (user == null)
 				user = src.user;
 			if (preferredAuthentications == null)
 				preferredAuthentications = src.preferredAuthentications;
 			if (batchMode == null)
 				batchMode = src.batchMode;
 			if (strictHostKeyChecking == null)
 				strictHostKeyChecking = src.strictHostKeyChecking;
 			if (connectionAttempts == 0)
 				connectionAttempts = src.connectionAttempts;
 		}
 
 		/**
 		 * @return the value StrictHostKeyChecking property, the valid values
 		 *         are "yes" (unknown hosts are not accepted), "no" (unknown
 		 *         hosts are always accepted), and "ask" (user should be asked
 		 *         before accepting the host)
 		 */
 		public String getStrictHostKeyChecking() {
 			return strictHostKeyChecking;
 		}
 
 		/**
 		 * @return the real IP address or host name to connect to; never null.
 		 */
 		public String getHostName() {
 			return hostName;
 		}
 
 		/**
 		 * @return the real port number to connect to; never 0.
 		 */
 		public int getPort() {
 			return port;
 		}
 
 		/**
 		 * @return path of the private key file to use for authentication; null
 		 *         if the caller should use default authentication strategies.
 		 */
 		public File getIdentityFile() {
 			return identityFile;
 		}
 
 		/**
 		 * @return the real user name to connect as; never null.
 		 */
 		public String getUser() {
 			return user;
 		}
 
 		/**
 		 * @return the preferred authentication methods, separated by commas if
 		 *         more than one authentication method is preferred.
 		 */
 		public String getPreferredAuthentications() {
 			return preferredAuthentications;
 		}
 
 		/**
 		 * @return true if batch (non-interactive) mode is preferred for this
 		 *         host connection.
 		 */
 		public boolean isBatchMode() {
 			return batchMode != null && batchMode.booleanValue();
 		}
 
 		/**
 		 * @return the number of tries (one per second) to connect before
 		 *         exiting. The argument must be an integer. This may be useful
 		 *         in scripts if the connection sometimes fails. The default is
 		 *         1.
 		 * @since 3.4
 		 */
 		public int getConnectionAttempts() {
 			return connectionAttempts;
 		}
 	}
 }