/**
 * 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.mapred;

import java.util.HashMap;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.mapreduce.JobACL;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.authorize.AccessControlList;

@InterfaceAudience.Private
public abstract class JobACLsManager {

  static final Log LOG = LogFactory.getLog(JobACLsManager.class);

  public static final String UNAUTHORIZED_JOB_ACCESS_ERROR =
      " is not authorized for performing the operation ";
  protected abstract boolean isJobLevelAuthorizationEnabled();

  protected abstract boolean isSuperUserOrSuperGroup(
      UserGroupInformation callerUGI);

  /**
   * Construct the jobACLs from the configuration so that they can be kept in
   * the memory. If authorization is disabled on the JT, nothing is constructed
   * and an empty map is returned.
   * 
   * @return JobACL to AccessControlList map.
   */
  Map<JobACL, AccessControlList> constructJobACLs(JobConf conf) {

    Map<JobACL, AccessControlList> acls =
        new HashMap<JobACL, AccessControlList>();

    // Don't construct anything if authorization is disabled.
    if (!isJobLevelAuthorizationEnabled()) {
      return acls;
    }

    for (JobACL aclName : JobACL.values()) {
      String aclConfigName = aclName.getAclName();
      String aclConfigured = conf.get(aclConfigName);
      if (aclConfigured == null) {
        // If ACLs are not configured at all, we grant no access to anyone. So
        // jobOwner and superuser/supergroup _only_ can do 'stuff'
        aclConfigured = "";
      }
      acls.put(aclName, new AccessControlList(aclConfigured));
    }
    return acls;
  }

  /**
   * If authorization is enabled, checks whether the user (in the callerUGI) is
   * authorized to perform the operation specified by 'jobOperation' on the job.
   * <ul>
   * <li>The owner of the job can do any operation on the job</li>
   * <li>The superuser/supergroup is always permitted to do operations on any
   * job.</li>
   * <li>For all other users/groups job-acls are checked</li>
   * </ul>
   * 
   * @param jobStatus
   * @param callerUGI
   * @param jobOperation
   */
  void checkAccess(JobStatus jobStatus, UserGroupInformation callerUGI,
      JobACL jobOperation) throws AccessControlException {

    JobID jobId = jobStatus.getJobID();
    String jobOwner = jobStatus.getUsername();
    AccessControlList acl = jobStatus.getJobACLs().get(jobOperation);
    checkAccess(jobId, callerUGI, jobOperation, jobOwner, acl);
  }

  /**
   * If authorization is enabled, checks whether the user (in the callerUGI) is
   * authorized to perform the operation specified by 'jobOperation' on the job.
   * <ul>
   * <li>The owner of the job can do any operation on the job</li>
   * <li>The superuser/supergroup is always permitted to do operations on any
   * job.</li>
   * <li>For all other users/groups job-acls are checked</li>
   * </ul>
   * @param jobId
   * @param callerUGI
   * @param jobOperation
   * @param jobOwner
   * @param jobACL
   * @throws AccessControlException
   */
  void checkAccess(JobID jobId, UserGroupInformation callerUGI,
      JobACL jobOperation, String jobOwner, AccessControlList jobACL)
      throws AccessControlException {

    if (!isJobLevelAuthorizationEnabled()) {
      return;
    }

    // Check for superusers/supergroups
    if (isSuperUserOrSuperGroup(callerUGI)) {
      LOG.info("superuser/supergroupMember "
          + callerUGI.getShortUserName() + " trying to perform "
          + jobOperation.toString() + " on " + jobId);
      return;
    }

    // Job-owner is always part of all the ACLs
    if (callerUGI.getShortUserName().equals(jobOwner)) {
      LOG.info("Jobowner " + callerUGI.getShortUserName()
          + " trying to perform " + jobOperation.toString() + " on "
          + jobId);
      return;
    }

    
    if (jobACL.isUserAllowed(callerUGI)) {
      LOG.info("Normal user " + callerUGI.getShortUserName()
          + " trying to perform " + jobOperation.toString() + " on "
          + jobId);
      return;
    }

    throw new AccessControlException(callerUGI
        + UNAUTHORIZED_JOB_ACCESS_ERROR
        + jobOperation.toString() + " on " + jobId + ". "
        + jobOperation.toString()
        + " Access control list configured for this job : "
        + jobACL.toString());
  }
}