/**
 * 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.hadoop.lib.service.hadoop;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.lib.server.BaseService;
import org.apache.hadoop.lib.server.ServiceException;
import org.apache.hadoop.lib.service.FileSystemAccess;
import org.apache.hadoop.lib.service.FileSystemAccessException;
import org.apache.hadoop.lib.service.Instrumentation;
import org.apache.hadoop.lib.util.Check;
import org.apache.hadoop.lib.util.ConfigurationUtils;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.util.VersionInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.URI;
import java.security.PrivilegedExceptionAction;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

public class FileSystemAccessService extends BaseService implements FileSystemAccess {
  private static final Logger LOG = LoggerFactory.getLogger(FileSystemAccessService.class);

  public static final String PREFIX = "hadoop";

  private static final String INSTRUMENTATION_GROUP = "hadoop";

  public static final String AUTHENTICATION_TYPE = "authentication.type";
  public static final String KERBEROS_KEYTAB = "authentication.kerberos.keytab";
  public static final String KERBEROS_PRINCIPAL = "authentication.kerberos.principal";

  public static final String NAME_NODE_WHITELIST = "name.node.whitelist";

  private static final String HADOOP_CONF_PREFIX = "conf:";

  private static final String NAME_NODE_PROPERTY = "fs.default.name";

  public FileSystemAccessService() {
    super(PREFIX);
  }

  private Collection<String> nameNodeWhitelist;

  Configuration serviceHadoopConf;

  private AtomicInteger unmanagedFileSystems = new AtomicInteger();

  @Override
  protected void init() throws ServiceException {
    LOG.info("Using FileSystemAccess JARs version [{}]", VersionInfo.getVersion());
    String security = getServiceConfig().get(AUTHENTICATION_TYPE, "simple").trim();
    if (security.equals("kerberos")) {
      String defaultName = getServer().getName();
      String keytab = System.getProperty("user.home") + "/" + defaultName + ".keytab";
      keytab = getServiceConfig().get(KERBEROS_KEYTAB, keytab).trim();
      if (keytab.length() == 0) {
        throw new ServiceException(FileSystemAccessException.ERROR.H01, KERBEROS_KEYTAB);
      }
      String principal = defaultName + "/localhost@LOCALHOST";
      principal = getServiceConfig().get(KERBEROS_PRINCIPAL, principal).trim();
      if (principal.length() == 0) {
        throw new ServiceException(FileSystemAccessException.ERROR.H01, KERBEROS_PRINCIPAL);
      }
      Configuration conf = new Configuration();
      conf.set("hadoop.security.authentication", "kerberos");
      UserGroupInformation.setConfiguration(conf);
      try {
        UserGroupInformation.loginUserFromKeytab(principal, keytab);
      } catch (IOException ex) {
        throw new ServiceException(FileSystemAccessException.ERROR.H02, ex.getMessage(), ex);
      }
      LOG.info("Using FileSystemAccess Kerberos authentication, principal [{}] keytab [{}]", principal, keytab);
    } else if (security.equals("simple")) {
      Configuration conf = new Configuration();
      conf.set("hadoop.security.authentication", "simple");
      UserGroupInformation.setConfiguration(conf);
      LOG.info("Using FileSystemAccess simple/pseudo authentication, principal [{}]", System.getProperty("user.name"));
    } else {
      throw new ServiceException(FileSystemAccessException.ERROR.H09, security);
    }

    serviceHadoopConf = new Configuration(false);
    for (Map.Entry entry : getServiceConfig()) {
      String name = (String) entry.getKey();
      if (name.startsWith(HADOOP_CONF_PREFIX)) {
        name = name.substring(HADOOP_CONF_PREFIX.length());
        String value = (String) entry.getValue();
        serviceHadoopConf.set(name, value);

      }
    }
    setRequiredServiceHadoopConf(serviceHadoopConf);

    LOG.debug("FileSystemAccess default configuration:");
    for (Map.Entry entry : serviceHadoopConf) {
      LOG.debug("  {} = {}", entry.getKey(), entry.getValue());
    }

    nameNodeWhitelist = toLowerCase(getServiceConfig().getTrimmedStringCollection(NAME_NODE_WHITELIST));
  }

  @Override
  public void postInit() throws ServiceException {
    super.postInit();
    Instrumentation instrumentation = getServer().get(Instrumentation.class);
    instrumentation.addVariable(INSTRUMENTATION_GROUP, "unmanaged.fs", new Instrumentation.Variable<Integer>() {
      @Override
      public Integer getValue() {
        return unmanagedFileSystems.get();
      }
    });
    instrumentation.addSampler(INSTRUMENTATION_GROUP, "unmanaged.fs", 60, new Instrumentation.Variable<Long>() {
      @Override
      public Long getValue() {
        return (long) unmanagedFileSystems.get();
      }
    });
  }

  private Set<String> toLowerCase(Collection<String> collection) {
    Set<String> set = new HashSet<String>();
    for (String value : collection) {
      set.add(value.toLowerCase());
    }
    return set;
  }

  @Override
  public Class getInterface() {
    return FileSystemAccess.class;
  }

  @Override
  public Class[] getServiceDependencies() {
    return new Class[]{Instrumentation.class};
  }

  protected UserGroupInformation getUGI(String user) throws IOException {
    return UserGroupInformation.createProxyUser(user, UserGroupInformation.getLoginUser());
  }

  protected void setRequiredServiceHadoopConf(Configuration conf) {
    conf.set("fs.hdfs.impl.disable.cache", "true");
  }

  protected Configuration createHadoopConf(Configuration conf) {
    Configuration hadoopConf = new Configuration();
    ConfigurationUtils.copy(serviceHadoopConf, hadoopConf);
    ConfigurationUtils.copy(conf, hadoopConf);
    return hadoopConf;
  }

  protected Configuration createNameNodeConf(Configuration conf) {
    return createHadoopConf(conf);
  }

  protected FileSystem createFileSystem(Configuration namenodeConf) throws IOException {
    return FileSystem.get(namenodeConf);
  }

  protected void closeFileSystem(FileSystem fs) throws IOException {
    fs.close();
  }

  protected void validateNamenode(String namenode) throws FileSystemAccessException {
    if (nameNodeWhitelist.size() > 0 && !nameNodeWhitelist.contains("*")) {
      if (!nameNodeWhitelist.contains(namenode.toLowerCase())) {
        throw new FileSystemAccessException(FileSystemAccessException.ERROR.H05, namenode, "not in whitelist");
      }
    }
  }

  protected void checkNameNodeHealth(FileSystem fileSystem) throws FileSystemAccessException {
  }

  @Override
  public <T> T execute(String user, final Configuration conf, final FileSystemExecutor<T> executor)
    throws FileSystemAccessException {
    Check.notEmpty(user, "user");
    Check.notNull(conf, "conf");
    Check.notNull(executor, "executor");
    if (conf.get(NAME_NODE_PROPERTY) == null || conf.getTrimmed(NAME_NODE_PROPERTY).length() == 0) {
      throw new FileSystemAccessException(FileSystemAccessException.ERROR.H06, NAME_NODE_PROPERTY);
    }
    try {
      validateNamenode(new URI(conf.get(NAME_NODE_PROPERTY)).getAuthority());
      UserGroupInformation ugi = getUGI(user);
      return ugi.doAs(new PrivilegedExceptionAction<T>() {
        public T run() throws Exception {
          Configuration namenodeConf = createNameNodeConf(conf);
          FileSystem fs = createFileSystem(namenodeConf);
          Instrumentation instrumentation = getServer().get(Instrumentation.class);
          Instrumentation.Cron cron = instrumentation.createCron();
          try {
            checkNameNodeHealth(fs);
            cron.start();
            return executor.execute(fs);
          } finally {
            cron.stop();
            instrumentation.addCron(INSTRUMENTATION_GROUP, executor.getClass().getSimpleName(), cron);
            closeFileSystem(fs);
          }
        }
      });
    } catch (FileSystemAccessException ex) {
      throw ex;
    } catch (Exception ex) {
      throw new FileSystemAccessException(FileSystemAccessException.ERROR.H03, ex);
    }
  }

  public FileSystem createFileSystemInternal(String user, final Configuration conf)
    throws IOException, FileSystemAccessException {
    Check.notEmpty(user, "user");
    Check.notNull(conf, "conf");
    try {
      validateNamenode(new URI(conf.get(NAME_NODE_PROPERTY)).getAuthority());
      UserGroupInformation ugi = getUGI(user);
      return ugi.doAs(new PrivilegedExceptionAction<FileSystem>() {
        public FileSystem run() throws Exception {
          Configuration namenodeConf = createNameNodeConf(conf);
          return createFileSystem(namenodeConf);
        }
      });
    } catch (IOException ex) {
      throw ex;
    } catch (FileSystemAccessException ex) {
      throw ex;
    } catch (Exception ex) {
      throw new FileSystemAccessException(FileSystemAccessException.ERROR.H08, ex.getMessage(), ex);
    }
  }

  @Override
  public FileSystem createFileSystem(String user, final Configuration conf) throws IOException,
    FileSystemAccessException {
    unmanagedFileSystems.incrementAndGet();
    return createFileSystemInternal(user, conf);
  }

  @Override
  public void releaseFileSystem(FileSystem fs) throws IOException {
    unmanagedFileSystems.decrementAndGet();
    closeFileSystem(fs);
  }


  @Override
  public Configuration getDefaultConfiguration() {
    Configuration conf = new Configuration(false);
    ConfigurationUtils.copy(serviceHadoopConf, conf);
    return conf;
  }

}