/*
    * 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.commons.vfs2.provider.sftp;
  
  import java.io.File;
  import java.io.IOException;
  import java.time.Duration;
  import java.util.Objects;
  import java.util.Properties;
  
  import org.apache.commons.lang3.SystemProperties;
  import org.apache.commons.lang3.SystemUtils;
  import org.apache.commons.lang3.time.DurationUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.vfs2.FileSystemException;
  import org.apache.commons.vfs2.FileSystemOptions;
  
  import com.jcraft.jsch.ConfigRepository;
  import com.jcraft.jsch.JSch;
  import com.jcraft.jsch.JSchException;
  import com.jcraft.jsch.Logger;
  import com.jcraft.jsch.OpenSSHConfig;
  import com.jcraft.jsch.Proxy;
  import com.jcraft.jsch.ProxyHTTP;
  import com.jcraft.jsch.ProxySOCKS5;
  import com.jcraft.jsch.Session;
  import com.jcraft.jsch.UserInfo;
  
  /**
   * Create a JSch Session instance.
   */
  public final class SftpClientFactory {
  
      /** Interface JSchLogger with JCL. */
      private static final class JSchLogger implements Logger {
          @Override
          public boolean isEnabled(final int level) {
              switch (level) {
              case FATAL:
                  return LOG.isFatalEnabled();
              case ERROR:
                  return LOG.isErrorEnabled();
              case WARN:
                  return LOG.isDebugEnabled();
              case DEBUG:
                  return LOG.isDebugEnabled();
              case INFO:
                  return LOG.isInfoEnabled();
              default:
                  return LOG.isDebugEnabled();
              }
          }
  
          @Override
          public void log(final int level, final String msg) {
              switch (level) {
              case FATAL:
                  LOG.fatal(msg);
                  break;
              case ERROR:
                  LOG.error(msg);
                  break;
              case WARN:
                  LOG.warn(msg);
                  break;
              case DEBUG:
                  LOG.debug(msg);
                  break;
              case INFO:
                  LOG.info(msg);
                  break;
              default:
                  LOG.debug(msg);
              }
          }
      }
      private static final String KEY_COMPRESSION_C2S = "compression.c2s";
      private static final String KEY_COMPRESSION_S2C = "compression.s2c";
      private static final String KEY_PREFERRED_AUTHENTICATIONS = "PreferredAuthentications";
  
      private static final String KEY_STRICT_HOST_KEY_CHECKING = "StrictHostKeyChecking";
  
      private static final String SSH_DIR_NAME = ".ssh";
      private static final String OPENSSH_CONFIG_NAME = "config";
     private static final Log LOG = LogFactory.getLog(SftpClientFactory.class);
 
     static {
         JSch.setLogger(new JSchLogger());
     }
 
     private static void addIdentities(final JSch jsch, final File sshDir, final IdentityProvider[] identities)
             throws FileSystemException {
         if (identities != null) {
             for (final IdentityProvider info : identities) {
                 addIdentity(jsch, info);
             }
         } else {
             // Load the private key (rsa-key only)
             final File privateKeyFile = new File(sshDir, "id_rsa");
             if (privateKeyFile.isFile() && privateKeyFile.canRead()) {
                 addIdentity(jsch, new IdentityInfo(privateKeyFile));
             }
         }
     }
 
     private static void addIdentity(final JSch jsch, final IdentityProvider identity) throws FileSystemException {
         try {
             identity.addIdentity(jsch);
         } catch (final JSchException e) {
             throw new FileSystemException("vfs.provider.sftp/load-private-key.error", identity, e);
         }
     }
 
     /**
      * Creates a new connection to the server.
      *
      * @param hostname The name of the host to connect to.
      * @param port The port to use.
      * @param username The user's id.
      * @param password The user's password.
      * @param fileSystemOptions The FileSystem options.
      * @return A Session, never null.
      * @throws FileSystemException if an error occurs.
      */
     public static Session createConnection(final String hostname, final int port, final char[] username,
         final char[] password, final FileSystemOptions fileSystemOptions) throws FileSystemException {
         Objects.requireNonNull(username, "username");
         final JSch jsch = new JSch();
 
         // new style - user passed
         final SftpFileSystemConfigBuilder builder = SftpFileSystemConfigBuilder.getInstance();
         final File knownHostsFile = builder.getKnownHosts(fileSystemOptions);
         final IdentityProvider[] identities = builder.getIdentityProvider(fileSystemOptions);
         final IdentityRepositoryFactory repositoryFactory = builder.getIdentityRepositoryFactory(fileSystemOptions);
         final ConfigRepository configRepository = builder.getConfigRepository(fileSystemOptions);
         final boolean loadOpenSSHConfig = builder.isLoadOpenSSHConfig(fileSystemOptions);
 
         final File sshDir = findSshDir();
 
         setKnownHosts(jsch, sshDir, knownHostsFile);
 
         if (repositoryFactory != null) {
             jsch.setIdentityRepository(repositoryFactory.create(jsch));
         }
 
         addIdentities(jsch, sshDir, identities);
         setConfigRepository(jsch, sshDir, configRepository, loadOpenSSHConfig);
 
         final Session session;
         try {
             session = jsch.getSession(new String(username), hostname, port);
             if (password != null) {
                 session.setPassword(new String(password));
             }
 
             final Duration sessionTimeout = builder.getSessionTimeout(fileSystemOptions);
             if (sessionTimeout != null) {
                 session.setTimeout(DurationUtils.toMillisInt(sessionTimeout));
             }
 
             final UserInfo userInfo = builder.getUserInfo(fileSystemOptions);
             if (userInfo != null) {
                 session.setUserInfo(userInfo);
             }
 
             final Properties config = new Properties();
 
             // set StrictHostKeyChecking property
             final String strictHostKeyChecking = builder.getStrictHostKeyChecking(fileSystemOptions);
             if (strictHostKeyChecking != null) {
                 config.setProperty(KEY_STRICT_HOST_KEY_CHECKING, strictHostKeyChecking);
             }
             // set PreferredAuthentications property
             final String preferredAuthentications = builder.getPreferredAuthentications(fileSystemOptions);
             if (preferredAuthentications != null) {
                 config.setProperty(KEY_PREFERRED_AUTHENTICATIONS, preferredAuthentications);
             }
 
             // set compression property
             final String compression = builder.getCompression(fileSystemOptions);
             if (compression != null) {
                 config.setProperty(KEY_COMPRESSION_S2C, compression);
                 config.setProperty(KEY_COMPRESSION_C2S, compression);
             }
 
             final String keyExchangeAlgorithm = builder.getKeyExchangeAlgorithm(fileSystemOptions);
             if (keyExchangeAlgorithm != null) {
                 config.setProperty("kex", keyExchangeAlgorithm);
             }
 
             final String proxyHost = builder.getProxyHost(fileSystemOptions);
             if (proxyHost != null) {
                 final int proxyPort = builder.getProxyPort(fileSystemOptions);
                 final SftpFileSystemConfigBuilder.ProxyType proxyType = builder.getProxyType(fileSystemOptions);
                 final String proxyUser = builder.getProxyUser(fileSystemOptions);
                 final String proxyPassword = builder.getProxyPassword(fileSystemOptions);
                 Proxy proxy = null;
                 if (SftpFileSystemConfigBuilder.PROXY_HTTP.equals(proxyType)) {
                     proxy = createProxyHTTP(proxyHost, proxyPort);
                     ((ProxyHTTP) proxy).setUserPasswd(proxyUser, proxyPassword);
                 } else if (SftpFileSystemConfigBuilder.PROXY_SOCKS5.equals(proxyType)) {
                     proxy = createProxySOCKS5(proxyHost, proxyPort);
                     ((ProxySOCKS5) proxy).setUserPasswd(proxyUser, proxyPassword);
                 } else if (SftpFileSystemConfigBuilder.PROXY_STREAM.equals(proxyType)) {
                     proxy = createStreamProxy(proxyHost, proxyPort, fileSystemOptions, builder);
                 }
 
                 if (proxy != null) {
                     session.setProxy(proxy);
                 }
             }
 
             // set properties for the session
             if (!config.isEmpty()) {
                 session.setConfig(config);
             }
             session.setDaemonThread(true);
             session.connect();
         } catch (final Exception exc) {
             throw new FileSystemException("vfs.provider.sftp/connect.error", exc, hostname);
         }
 
         return session;
     }
 
     private static ProxyHTTP createProxyHTTP(final String proxyHost, final int proxyPort) {
         return proxyPort == 0 ? new ProxyHTTP(proxyHost) : new ProxyHTTP(proxyHost, proxyPort);
     }
 
     private static ProxySOCKS5 createProxySOCKS5(final String proxyHost, final int proxyPort) {
         return proxyPort == 0 ? new ProxySOCKS5(proxyHost) : new ProxySOCKS5(proxyHost, proxyPort);
     }
 
     private static Proxy createStreamProxy(final String proxyHost, final int proxyPort,
             final FileSystemOptions fileSystemOptions, final SftpFileSystemConfigBuilder builder) {
         // Use a stream proxy, i.e. it will use a remote host as a proxy
         // and run a command (e.g. netcat) that forwards input/output
         // to the target host.
 
         // Here we get the settings for connecting to the proxy:
         // user, password, options and a command
         final String proxyUser = builder.getProxyUser(fileSystemOptions);
         final String proxyPassword = builder.getProxyPassword(fileSystemOptions);
         final FileSystemOptions proxyOptions = builder.getProxyOptions(fileSystemOptions);
 
         final String proxyCommand = builder.getProxyCommand(fileSystemOptions);
 
         // Create the stream proxy
         return new SftpStreamProxy(proxyCommand, proxyUser, proxyHost, proxyPort, proxyPassword, proxyOptions);
     }
 
     /**
      * Finds the {@code .ssh} directory.
      * <p>
      * The lookup order is:
      * </p>
      * <ol>
      * <li>The system property {@code vfs.sftp.sshdir} (the override mechanism)</li>
      * <li>{@code user.home}/.ssh</li>
      * <li>On Windows only: {@code C:\cygwin\home[user.name]\.ssh}</li>
      * <li>The current directory, as a last resort.</li>
      * </ol>
      *
      * <h2>Windows Notes</h2>
      * <p>
      * The default installation directory for Cygwin is {@code C:\cygwin}. On my set up (Gary here), I have Cygwin in
      * {@code C:\bin\cygwin}, not the default. Also, my .ssh directory was created in the {@code user.home} directory.
      * </p>
      *
      * @return The {@code .ssh} directory
      */
     private static File findSshDir() {
         final String sshDirPath;
         sshDirPath = System.getProperty("vfs.sftp.sshdir");
         if (sshDirPath != null) {
             final File sshDir = new File(sshDirPath);
             if (sshDir.exists()) {
                 return sshDir;
             }
         }
 
         File sshDir = new File(SystemProperties.getUserHome(), SSH_DIR_NAME);
         if (sshDir.exists()) {
             return sshDir;
         }
 
         if (SystemUtils.IS_OS_WINDOWS) {
             // TODO - this may not be true
             final String userName = SystemProperties.getUserName();
             sshDir = new File("C:\\cygwin\\home\\" + userName + "\\" + SSH_DIR_NAME);
             if (sshDir.exists()) {
                 return sshDir;
             }
         }
         return new File("");
     }
 
     private static void setConfigRepository(final JSch jsch, final File sshDir, final ConfigRepository configRepository, final boolean loadOpenSSHConfig)
         throws FileSystemException {
         if (configRepository != null) {
             jsch.setConfigRepository(configRepository);
         } else if (loadOpenSSHConfig) {
             try {
                 // loading openssh config (~/.ssh/config)
                 final ConfigRepository openSSHConfig = OpenSSHConfig.parseFile(new File(sshDir, OPENSSH_CONFIG_NAME).getAbsolutePath());
                 jsch.setConfigRepository(openSSHConfig);
             } catch (final IOException e) {
                 throw new FileSystemException("vfs.provider.sftp/load-openssh-config.error", e);
             }
         }
     }
 
     private static void setKnownHosts(final JSch jsch, final File sshDir, File knownHostsFile)
             throws FileSystemException {
         try {
             if (knownHostsFile != null) {
                 jsch.setKnownHosts(knownHostsFile.getAbsolutePath());
             } else {
                 // Load the known hosts file
                 knownHostsFile = new File(sshDir, "known_hosts");
                 if (knownHostsFile.isFile() && knownHostsFile.canRead()) {
                     jsch.setKnownHosts(knownHostsFile.getAbsolutePath());
                 }
             }
         } catch (final JSchException e) {
             throw new FileSystemException("vfs.provider.sftp/known-hosts.error", knownHostsFile.getAbsolutePath(), e);
         }
 
     }
 
     private SftpClientFactory() {
     }
 }