/*
 * 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.flink.runtime.util;

import org.apache.flink.configuration.ConfigConstants;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.TokenIdentifier;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.util.Collection;

/**
 * Utility class for working with Hadoop-related classes. This should only be used if Hadoop
 * is on the classpath.
 */
public class HadoopUtils {

	private static final Logger LOG = LoggerFactory.getLogger(HadoopUtils.class);

	private static final Text HDFS_DELEGATION_TOKEN_KIND = new Text("HDFS_DELEGATION_TOKEN");

	public static Configuration getHadoopConfiguration(org.apache.flink.configuration.Configuration flinkConfiguration) {

		// Instantiate a HdfsConfiguration to load the hdfs-site.xml and hdfs-default.xml
		// from the classpath
		Configuration result = new HdfsConfiguration();
		boolean foundHadoopConfiguration = false;

		// We need to load both core-site.xml and hdfs-site.xml to determine the default fs path and
		// the hdfs configuration
		// Try to load HDFS configuration from Hadoop's own configuration files
		// 1. approach: Flink configuration
		final String hdfsDefaultPath =
			flinkConfiguration.getString(ConfigConstants.HDFS_DEFAULT_CONFIG, null);

		if (hdfsDefaultPath != null) {
			result.addResource(new org.apache.hadoop.fs.Path(hdfsDefaultPath));
			LOG.debug("Using hdfs-default configuration-file path form Flink config: {}", hdfsDefaultPath);
			foundHadoopConfiguration = true;
		} else {
			LOG.debug("Cannot find hdfs-default configuration-file path in Flink config.");
		}

		final String hdfsSitePath = flinkConfiguration.getString(ConfigConstants.HDFS_SITE_CONFIG, null);
		if (hdfsSitePath != null) {
			result.addResource(new org.apache.hadoop.fs.Path(hdfsSitePath));
			LOG.debug("Using hdfs-site configuration-file path form Flink config: {}", hdfsSitePath);
			foundHadoopConfiguration = true;
		} else {
			LOG.debug("Cannot find hdfs-site configuration-file path in Flink config.");
		}

		// 2. Approach environment variables
		String[] possibleHadoopConfPaths = new String[4];
		possibleHadoopConfPaths[0] = flinkConfiguration.getString(ConfigConstants.PATH_HADOOP_CONFIG, null);
		possibleHadoopConfPaths[1] = System.getenv("HADOOP_CONF_DIR");

		final String hadoopHome = System.getenv("HADOOP_HOME");
		if (hadoopHome != null) {
			possibleHadoopConfPaths[2] = hadoopHome + "/conf";
			possibleHadoopConfPaths[3] = hadoopHome + "/etc/hadoop"; // hadoop 2.2
		}

		for (String possibleHadoopConfPath : possibleHadoopConfPaths) {
			if (possibleHadoopConfPath != null) {
				if (new File(possibleHadoopConfPath).exists()) {
					if (new File(possibleHadoopConfPath + "/core-site.xml").exists()) {
						result.addResource(new org.apache.hadoop.fs.Path(possibleHadoopConfPath + "/core-site.xml"));
						LOG.debug("Adding " + possibleHadoopConfPath + "/core-site.xml to hadoop configuration");
						foundHadoopConfiguration = true;
					}
					if (new File(possibleHadoopConfPath + "/hdfs-site.xml").exists()) {
						result.addResource(new org.apache.hadoop.fs.Path(possibleHadoopConfPath + "/hdfs-site.xml"));
						LOG.debug("Adding " + possibleHadoopConfPath + "/hdfs-site.xml to hadoop configuration");
						foundHadoopConfiguration = true;
					}
				}
			}
		}

		if (!foundHadoopConfiguration) {
			LOG.debug("Could not find Hadoop configuration via any of the supported methods " +
				"(Flink configuration, environment variables).");
		}

		return result;
	}

	/**
	 * Indicates whether the current user has an HDFS delegation token.
	 */
	public static boolean hasHDFSDelegationToken() throws Exception {
		UserGroupInformation loginUser = UserGroupInformation.getCurrentUser();
		Collection<Token<? extends TokenIdentifier>> usrTok = loginUser.getTokens();
		for (Token<? extends TokenIdentifier> token : usrTok) {
			if (token.getKind().equals(HDFS_DELEGATION_TOKEN_KIND)) {
				return true;
			}
		}
		return false;
	}
}