/*
    * Copyright (C) 2008, 2018, Google Inc. 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;
  
  import static org.eclipse.jgit.internal.transport.ssh.OpenSshConfigFile.positive;
  
  import java.io.File;
  import java.util.List;
  import java.util.Map;
  import java.util.TreeMap;
  
  import org.eclipse.jgit.internal.transport.ssh.OpenSshConfigFile;
  import org.eclipse.jgit.internal.transport.ssh.OpenSshConfigFile.HostEntry;
  import org.eclipse.jgit.util.FS;
  
  import com.jcraft.jsch.ConfigRepository;
  
  /**
   * Fairly complete configuration parser for the OpenSSH ~/.ssh/config file.
   * <p>
   * JSch does have its own config file parser
   * {@link com.jcraft.jsch.OpenSSHConfig} since version 0.1.50, but it has a
   * number of problems:
   * <ul>
   * <li>it splits lines of the format "keyword = value" wrongly: you'd end up
   * with the value "= value".
   * <li>its "Host" keyword is not case insensitive.
   * <li>it doesn't handle quoted values.
   * <li>JSch's OpenSSHConfig doesn't monitor for config file changes.
   * </ul>
   * <p>
   * This parser makes the critical options available to
   * {@link org.eclipse.jgit.transport.SshSessionFactory} via
   * {@link org.eclipse.jgit.transport.OpenSshConfig.Host} objects returned by
   * {@link #lookup(String)}, and implements a fully conforming
   * {@link com.jcraft.jsch.ConfigRepository} providing
   * {@link com.jcraft.jsch.ConfigRepository.Config}s via
   * {@link #getConfig(String)}.
   * </p>
   *
   * @see OpenSshConfigFile
   */
  public class OpenSshConfig implements ConfigRepository {
  
  	/**
  	 * 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, SshConstants.SSH_DIR),
  				SshConstants.CONFIG);
  		return new OpenSshConfig(home, config);
  	}
  
  	/** The base file. */
  	private OpenSshConfigFile configFile;
  
  	OpenSshConfig(File h, File cfg) {
  		configFile = new OpenSshConfigFile(h, cfg,
  				SshSessionFactory.getLocalUserName());
  	}
  
  	/**
  	 * 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(String hostName) {
  		HostEntry entry = configFile.lookup(hostName, -1, null);
  		return new Host(entry, hostName, configFile.getLocalUserName());
  	}
  
  	/**
  	 * 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 {
 		String hostName;
 
 		int port;
 
 		File identityFile;
 
 		String user;
 
 		String preferredAuthentications;
 
 		Boolean batchMode;
 
 		String strictHostKeyChecking;
 
 		int connectionAttempts;
 
 		private HostEntry entry;
 
 		private Config config;
 
 		// See com.jcraft.jsch.OpenSSHConfig. Translates some command-line keys
 		// to ssh-config keys.
 		private static final Map<String, String> KEY_MAP = new TreeMap<>(
 				String.CASE_INSENSITIVE_ORDER);
 
 		static {
 			KEY_MAP.put("kex", SshConstants.KEX_ALGORITHMS); //$NON-NLS-1$
 			KEY_MAP.put("server_host_key", SshConstants.HOST_KEY_ALGORITHMS); //$NON-NLS-1$
 			KEY_MAP.put("cipher.c2s", SshConstants.CIPHERS); //$NON-NLS-1$
 			KEY_MAP.put("cipher.s2c", SshConstants.CIPHERS); //$NON-NLS-1$
 			KEY_MAP.put("mac.c2s", SshConstants.MACS); //$NON-NLS-1$
 			KEY_MAP.put("mac.s2c", SshConstants.MACS); //$NON-NLS-1$
 			KEY_MAP.put("compression.s2c", SshConstants.COMPRESSION); //$NON-NLS-1$
 			KEY_MAP.put("compression.c2s", SshConstants.COMPRESSION); //$NON-NLS-1$
 			KEY_MAP.put("compression_level", "CompressionLevel"); //$NON-NLS-1$ //$NON-NLS-2$
 			KEY_MAP.put("MaxAuthTries", //$NON-NLS-1$
 					SshConstants.NUMBER_OF_PASSWORD_PROMPTS);
 		}
 
 		private static String mapKey(String key) {
 			String k = KEY_MAP.get(key);
 			return k != null ? k : key;
 		}
 
 		/**
 		 * Creates a new uninitialized {@link Host}.
 		 */
 		public Host() {
 			// For API backwards compatibility with pre-4.9 JGit
 		}
 
 		Host(HostEntry entry, String hostName, String localUserName) {
 			this.entry = entry;
 			complete(hostName, localUserName);
 		}
 
 		/**
 		 * @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;
 		}
 
 
 		private void complete(String initialHostName, String localUserName) {
 			// Try to set values from the options.
 			hostName = entry.getValue(SshConstants.HOST_NAME);
 			user = entry.getValue(SshConstants.USER);
 			port = positive(entry.getValue(SshConstants.PORT));
 			connectionAttempts = positive(
 					entry.getValue(SshConstants.CONNECTION_ATTEMPTS));
 			strictHostKeyChecking = entry
 					.getValue(SshConstants.STRICT_HOST_KEY_CHECKING);
 			batchMode = Boolean.valueOf(OpenSshConfigFile
 					.flag(entry.getValue(SshConstants.BATCH_MODE)));
 			preferredAuthentications = entry
 					.getValue(SshConstants.PREFERRED_AUTHENTICATIONS);
 			// Fill in defaults if still not set
 			if (hostName == null || hostName.isEmpty()) {
 				hostName = initialHostName;
 			}
 			if (user == null || user.isEmpty()) {
 				user = localUserName;
 			}
 			if (port <= 0) {
 				port = SshConstants.SSH_DEFAULT_PORT;
 			}
 			if (connectionAttempts <= 0) {
 				connectionAttempts = 1;
 			}
 			List<String> identityFiles = entry
 					.getValues(SshConstants.IDENTITY_FILE);
 			if (identityFiles != null && !identityFiles.isEmpty()) {
 				identityFile = new File(identityFiles.get(0));
 			}
 		}
 
 		Config getConfig() {
 			if (config == null) {
 				config = new Config() {
 
 					@Override
 					public String getHostname() {
 						return Host.this.getHostName();
 					}
 
 					@Override
 					public String getUser() {
 						return Host.this.getUser();
 					}
 
 					@Override
 					public int getPort() {
 						return Host.this.getPort();
 					}
 
 					@Override
 					public String getValue(String key) {
 						// See com.jcraft.jsch.OpenSSHConfig.MyConfig.getValue()
 						// for this special case.
 						if (key.equals("compression.s2c") //$NON-NLS-1$
 								|| key.equals("compression.c2s")) { //$NON-NLS-1$
 							if (!OpenSshConfigFile.flag(
 									Host.this.entry.getValue(mapKey(key)))) {
 								return "none,zlib@openssh.com,zlib"; //$NON-NLS-1$
 							}
 							return "zlib@openssh.com,zlib,none"; //$NON-NLS-1$
 						}
 						return Host.this.entry.getValue(mapKey(key));
 					}
 
 					@Override
 					public String[] getValues(String key) {
 						List<String> values = Host.this.entry
 								.getValues(mapKey(key));
 						if (values == null) {
 							return new String[0];
 						}
 						return values.toArray(new String[0]);
 					}
 				};
 			}
 			return config;
 		}
 
 		@Override
 		@SuppressWarnings("nls")
 		public String toString() {
 			return "Host [hostName=" + hostName + ", port=" + port
 					+ ", identityFile=" + identityFile + ", user=" + user
 					+ ", preferredAuthentications=" + preferredAuthentications
 					+ ", batchMode=" + batchMode + ", strictHostKeyChecking="
 					+ strictHostKeyChecking + ", connectionAttempts="
 					+ connectionAttempts + ", entry=" + entry + "]";
 		}
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Retrieves the full {@link com.jcraft.jsch.ConfigRepository.Config Config}
 	 * for the given host name. Should be called only by Jsch and tests.
 	 *
 	 * @since 4.9
 	 */
 	@Override
 	public Config getConfig(String hostName) {
 		Host host = lookup(hostName);
 		return host.getConfig();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		return "OpenSshConfig [configFile=" + configFile + ']'; //$NON-NLS-1$
 	}
 }