/**
 * 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.hcatalog.templeton;

import java.io.File;
import java.io.IOException;
import java.security.PrivilegedExceptionAction;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hive.conf.HiveConf;
import org.apache.hadoop.hive.metastore.HiveMetaStoreClient;
import org.apache.hadoop.hive.metastore.api.MetaException;
import org.apache.hadoop.io.Text;
import org.apache.thrift.TException;
import org.apache.hadoop.security.Credentials;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;

/**
 * Helper class to run jobs using Kerberos security.  Always safe to
 * use these methods, it's a noop if security is not enabled.
 */
public class SecureProxySupport {
    private Path tokenPath;
    private final String HCAT_SERVICE = "hcat";
    private boolean isEnabled;
    private String user;

    public SecureProxySupport() {
        isEnabled = UserGroupInformation.isSecurityEnabled();
    }

    private static final Log LOG = LogFactory.getLog(SecureProxySupport.class);
    
    /**
     * The file where we store the auth token
     */
    public Path getTokenPath() { return( tokenPath ); }

    /**
     * The token to pass to hcat.
     */
    public String getHcatServiceStr() { return( HCAT_SERVICE ); }

    /**
     * Create the delegation token.
     */
    public Path open(String user, Configuration conf)
        throws IOException, InterruptedException
    {
        close();
        if (isEnabled) {
            this.user = user;
            File t = File.createTempFile("templeton", null);
            tokenPath = new Path(t.toURI());
            Token fsToken = getFSDelegationToken(user, conf);
            String hcatTokenStr;
            try {
                hcatTokenStr = buildHcatDelegationToken(user);
            } catch (Exception e) {
                throw new IOException(e);
            }
            Token<?> msToken = new Token();
            msToken.decodeFromUrlString(hcatTokenStr);
            msToken.setService(new Text(HCAT_SERVICE));
            writeProxyDelegationTokens(fsToken, msToken, conf, user, tokenPath);
            
        }
        return tokenPath;
    }

    /**
     * Cleanup
     */
    public void close() {
        if (tokenPath != null) {
            new File(tokenPath.toUri()).delete();
            tokenPath = null;
        }
    }

    /**
     * Add Hadoop env variables.
     */
    public void addEnv(Map<String, String> env) {
        if (isEnabled) {
            env.put(UserGroupInformation.HADOOP_TOKEN_FILE_LOCATION,
                    getTokenPath().toUri().getPath());
        }
    }

    /**
     * Add hcat args.
     */
    public void addArgs(List<String> args) {
        if (isEnabled) {
            args.add("-D");
            args.add("hive.metastore.token.signature=" + getHcatServiceStr());
            args.add("-D");
            args.add("proxy.user.name=" + user);            
        }
    }
    
    class TokenWrapper { 
        Token<?> token;
    }

    private Token<?> getFSDelegationToken(String user,
                                           final Configuration conf)
        throws IOException, InterruptedException
    {
        LOG.info("user: " + user + " loginUser: " + UserGroupInformation.getLoginUser().getUserName());
        final UserGroupInformation ugi = UgiFactory.getUgi(user);

       final TokenWrapper twrapper = new TokenWrapper();
       ugi.doAs(new PrivilegedExceptionAction<Object>() {
           public Object run() throws IOException {
               FileSystem fs = FileSystem.get(conf);
               twrapper.token =  fs.getDelegationToken(ugi.getShortUserName());
               return null;
           }
       });
       return twrapper.token;
       
    }

    private void writeProxyDelegationTokens(final Token<?> fsToken,
            final Token<?> msToken,
            final Configuration conf,
            String user,
            final Path tokenPath)
                    throws IOException, InterruptedException{
        
        
        LOG.info("user: " + user + " loginUser: " + UserGroupInformation.getLoginUser().getUserName());
        final UserGroupInformation ugi  =  UgiFactory.getUgi(user);

        
        ugi.doAs(new PrivilegedExceptionAction<Object>() {
                     public Object run() throws IOException {
                         Credentials cred = new Credentials();
                         cred.addToken(fsToken.getService(), fsToken);
                         cred.addToken(msToken.getService(), msToken);
                         cred.writeTokenStorageFile(tokenPath, conf);
                         return null;
                     }
                 });
        
    }
    
    private String buildHcatDelegationToken(String user)
        throws IOException, InterruptedException, MetaException, TException
    {
        HiveConf c = new HiveConf();
        final HiveMetaStoreClient client = new HiveMetaStoreClient(c);
        LOG.info("user: " + user + " loginUser: " + UserGroupInformation.getLoginUser().getUserName());
        final TokenWrapper twrapper = new TokenWrapper();
        final UserGroupInformation ugi = UgiFactory.getUgi(user);
        String s = ugi.doAs(new PrivilegedExceptionAction<String>() {
                                public String run()
                                    throws IOException, MetaException, TException
                                {
                                    String u = ugi.getUserName();
                                    return client.getDelegationToken(u);
                                }
                            });
        return s;
    }
}