/**
 * 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.fs.http.server;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.fs.ContentSummary;
import org.apache.hadoop.fs.FileChecksum;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.GlobFilter;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.PathFilter;
import org.apache.hadoop.fs.XAttrCodec;
import org.apache.hadoop.fs.XAttrSetFlag;
import org.apache.hadoop.fs.http.client.HttpFSFileSystem;
import org.apache.hadoop.fs.permission.AclEntry;
import org.apache.hadoop.fs.permission.AclStatus;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.hdfs.protocol.AclException;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.lib.service.FileSystemAccess;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.EnumSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

/**
 * FileSystem operation executors used by {@link HttpFSServer}.
 */
@InterfaceAudience.Private
public class FSOperations {

  /**
   * This class is used to group a FileStatus and an AclStatus together.
   * It's needed for the GETFILESTATUS and LISTSTATUS calls, which take
   * most info from the FileStatus and a wee bit from the AclStatus.
   */
  private static class StatusPair {
    private FileStatus fileStatus;
    private AclStatus aclStatus;

    /**
     * Simple constructor
     * @param fileStatus Existing FileStatus object
     * @param aclStatus Existing AclStatus object
     */
    public StatusPair(FileStatus fileStatus, AclStatus aclStatus) {
      this.fileStatus = fileStatus;
      this.aclStatus = aclStatus;
    }

    /**
     * Create one StatusPair by performing the underlying calls to
     * fs.getFileStatus and fs.getAclStatus
     * @param fs The FileSystem where 'path' lives
     * @param path The file/directory to query
     * @throws IOException
     */
    public StatusPair(FileSystem fs, Path path) throws IOException {
      fileStatus = fs.getFileStatus(path);
      aclStatus = null;
      try {
        aclStatus = fs.getAclStatus(path);
      } catch (AclException e) {
        /*
         * The cause is almost certainly an "ACLS aren't enabled"
         * exception, so leave aclStatus at null and carry on.
         */
      } catch (UnsupportedOperationException e) {
        /* Ditto above - this is the case for a local file system */
      }
    }

    /**
     * Return a Map suitable for conversion into JSON format
     * @return The JSONish Map
     */
    public Map<String,Object> toJson() {
      Map<String,Object> json = new LinkedHashMap<String,Object>();
      json.put(HttpFSFileSystem.FILE_STATUS_JSON, toJsonInner(true));
      return json;
    }

    /**
     * Return in inner part of the JSON for the status - used by both the
     * GETFILESTATUS and LISTSTATUS calls.
     * @param emptyPathSuffix Whether or not to include PATH_SUFFIX_JSON
     * @return The JSONish Map
     */
    public Map<String,Object> toJsonInner(boolean emptyPathSuffix) {
      Map<String,Object> json = new LinkedHashMap<String,Object>();
      json.put(HttpFSFileSystem.PATH_SUFFIX_JSON,
              (emptyPathSuffix) ? "" : fileStatus.getPath().getName());
      json.put(HttpFSFileSystem.TYPE_JSON,
              HttpFSFileSystem.FILE_TYPE.getType(fileStatus).toString());
      json.put(HttpFSFileSystem.LENGTH_JSON, fileStatus.getLen());
      json.put(HttpFSFileSystem.OWNER_JSON, fileStatus.getOwner());
      json.put(HttpFSFileSystem.GROUP_JSON, fileStatus.getGroup());
      json.put(HttpFSFileSystem.PERMISSION_JSON,
              HttpFSFileSystem.permissionToString(fileStatus.getPermission()));
      json.put(HttpFSFileSystem.ACCESS_TIME_JSON, fileStatus.getAccessTime());
      json.put(HttpFSFileSystem.MODIFICATION_TIME_JSON,
              fileStatus.getModificationTime());
      json.put(HttpFSFileSystem.BLOCK_SIZE_JSON, fileStatus.getBlockSize());
      json.put(HttpFSFileSystem.REPLICATION_JSON, fileStatus.getReplication());
      if ( (aclStatus != null) && !(aclStatus.getEntries().isEmpty()) ) {
        json.put(HttpFSFileSystem.ACL_BIT_JSON,true);
      }
      return json;
    }
  }

  /**
   * Simple class used to contain and operate upon a list of StatusPair
   * objects.  Used by LISTSTATUS.
   */
  private static class StatusPairs {
    private StatusPair[] statusPairs;

    /**
     * Construct a list of StatusPair objects
     * @param fs The FileSystem where 'path' lives
     * @param path The directory to query
     * @param filter A possible filter for entries in the directory
     * @throws IOException
     */
    public StatusPairs(FileSystem fs, Path path, PathFilter filter)
            throws IOException {
      /* Grab all the file statuses at once in an array */
      FileStatus[] fileStatuses = fs.listStatus(path, filter);

      /* We'll have an array of StatusPairs of the same length */
      AclStatus aclStatus = null;
      statusPairs = new StatusPair[fileStatuses.length];

      /*
       * For each FileStatus, attempt to acquire an AclStatus.  If the
       * getAclStatus throws an exception, we assume that ACLs are turned
       * off entirely and abandon the attempt.
       */
      boolean useAcls = true;   // Assume ACLs work until proven otherwise
      for (int i = 0; i < fileStatuses.length; i++) {
        if (useAcls) {
          try {
            aclStatus = fs.getAclStatus(fileStatuses[i].getPath());
          } catch (AclException e) {
            /* Almost certainly due to an "ACLs not enabled" exception */
            aclStatus = null;
            useAcls = false;
          } catch (UnsupportedOperationException e) {
            /* Ditto above - this is the case for a local file system */
            aclStatus = null;
            useAcls = false;
          }
        }
        statusPairs[i] = new StatusPair(fileStatuses[i], aclStatus);
      }
    }

    /**
     * Return a Map suitable for conversion into JSON.
     * @return A JSONish Map
     */
    @SuppressWarnings({"unchecked"})
    public Map<String,Object> toJson() {
      Map<String,Object> json = new LinkedHashMap<String,Object>();
      Map<String,Object> inner = new LinkedHashMap<String,Object>();
      JSONArray statuses = new JSONArray();
      for (StatusPair s : statusPairs) {
        statuses.add(s.toJsonInner(false));
      }
      inner.put(HttpFSFileSystem.FILE_STATUS_JSON, statuses);
      json.put(HttpFSFileSystem.FILE_STATUSES_JSON, inner);
      return json;
    }
  }

  /** Converts an <code>AclStatus</code> object into a JSON object.
   *
   * @param aclStatus AclStatus object
   *
   * @return The JSON representation of the ACLs for the file
   */
  @SuppressWarnings({"unchecked"})
  private static Map<String,Object> aclStatusToJSON(AclStatus aclStatus) {
    Map<String,Object> json = new LinkedHashMap<String,Object>();
    Map<String,Object> inner = new LinkedHashMap<String,Object>();
    JSONArray entriesArray = new JSONArray();
    inner.put(HttpFSFileSystem.OWNER_JSON, aclStatus.getOwner());
    inner.put(HttpFSFileSystem.GROUP_JSON, aclStatus.getGroup());
    inner.put(HttpFSFileSystem.ACL_STICKY_BIT_JSON, aclStatus.isStickyBit());
    for ( AclEntry e : aclStatus.getEntries() ) {
      entriesArray.add(e.toString());
    }
    inner.put(HttpFSFileSystem.ACL_ENTRIES_JSON, entriesArray);
    json.put(HttpFSFileSystem.ACL_STATUS_JSON, inner);
    return json;
  }

  /**
   * Converts a <code>FileChecksum</code> object into a JSON array
   * object.
   *
   * @param checksum file checksum.
   *
   * @return The JSON representation of the file checksum.
   */
  @SuppressWarnings({"unchecked"})
  private static Map fileChecksumToJSON(FileChecksum checksum) {
    Map json = new LinkedHashMap();
    json.put(HttpFSFileSystem.CHECKSUM_ALGORITHM_JSON, checksum.getAlgorithmName());
    json.put(HttpFSFileSystem.CHECKSUM_BYTES_JSON,
             org.apache.hadoop.util.StringUtils.byteToHexString(checksum.getBytes()));
    json.put(HttpFSFileSystem.CHECKSUM_LENGTH_JSON, checksum.getLength());
    Map response = new LinkedHashMap();
    response.put(HttpFSFileSystem.FILE_CHECKSUM_JSON, json);
    return response;
  }

  /**
   * Converts xAttrs to a JSON object.
   *
   * @param xAttrs file xAttrs.
   * @param encoding format of xattr values.
   *
   * @return The JSON representation of the xAttrs.
   * @throws IOException 
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  private static Map xAttrsToJSON(Map<String, byte[]> xAttrs, 
      XAttrCodec encoding) throws IOException {
    Map jsonMap = new LinkedHashMap();
    JSONArray jsonArray = new JSONArray();
    if (xAttrs != null) {
      for (Entry<String, byte[]> e : xAttrs.entrySet()) {
        Map json = new LinkedHashMap();
        json.put(HttpFSFileSystem.XATTR_NAME_JSON, e.getKey());
        if (e.getValue() != null) {
          json.put(HttpFSFileSystem.XATTR_VALUE_JSON, 
              XAttrCodec.encodeValue(e.getValue(), encoding));
        }
        jsonArray.add(json);
      }
    }
    jsonMap.put(HttpFSFileSystem.XATTRS_JSON, jsonArray);
    return jsonMap;
  }

  /**
   * Converts xAttr names to a JSON object.
   *
   * @param names file xAttr names.
   *
   * @return The JSON representation of the xAttr names.
   * @throws IOException 
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  private static Map xAttrNamesToJSON(List<String> names) throws IOException {
    Map jsonMap = new LinkedHashMap();
    jsonMap.put(HttpFSFileSystem.XATTRNAMES_JSON, JSONArray.toJSONString(names));
    return jsonMap;
  }

  /**
   * Converts a <code>ContentSummary</code> object into a JSON array
   * object.
   *
   * @param contentSummary the content summary
   *
   * @return The JSON representation of the content summary.
   */
  @SuppressWarnings({"unchecked"})
  private static Map contentSummaryToJSON(ContentSummary contentSummary) {
    Map json = new LinkedHashMap();
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_DIRECTORY_COUNT_JSON, contentSummary.getDirectoryCount());
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_FILE_COUNT_JSON, contentSummary.getFileCount());
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_LENGTH_JSON, contentSummary.getLength());
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_QUOTA_JSON, contentSummary.getQuota());
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_SPACE_CONSUMED_JSON, contentSummary.getSpaceConsumed());
    json.put(HttpFSFileSystem.CONTENT_SUMMARY_SPACE_QUOTA_JSON, contentSummary.getSpaceQuota());
    Map response = new LinkedHashMap();
    response.put(HttpFSFileSystem.CONTENT_SUMMARY_JSON, json);
    return response;
  }

  /**
   * Converts an object into a Json Map with with one key-value entry.
   * <p/>
   * It assumes the given value is either a JSON primitive type or a
   * <code>JsonAware</code> instance.
   *
   * @param name name for the key of the entry.
   * @param value for the value of the entry.
   *
   * @return the JSON representation of the key-value pair.
   */
  @SuppressWarnings("unchecked")
  private static JSONObject toJSON(String name, Object value) {
    JSONObject json = new JSONObject();
    json.put(name, value);
    return json;
  }

  /**
   * Executor that performs an append FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSAppend implements FileSystemAccess.FileSystemExecutor<Void> {
    private InputStream is;
    private Path path;

    /**
     * Creates an Append executor.
     *
     * @param is input stream to append.
     * @param path path of the file to append.
     */
    public FSAppend(InputStream is, String path) {
      this.is = is;
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      int bufferSize = fs.getConf().getInt("httpfs.buffer.size", 4096);
      OutputStream os = fs.append(path, bufferSize);
      IOUtils.copyBytes(is, os, bufferSize, true);
      os.close();
      return null;
    }

  }

  /**
   * Executor that performs an append FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSConcat implements FileSystemAccess.FileSystemExecutor<Void> {
    private Path path;
    private Path[] sources;

    /**
     * Creates a Concat executor.
     *
     * @param path target path to concat to.
     * @param sources comma seperated absolute paths to use as sources.
     */
    public FSConcat(String path, String[] sources) {
      this.sources = new Path[sources.length];

      for(int i = 0; i < sources.length; i++) {
        this.sources[i] = new Path(sources[i]);
      }

      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.concat(path, sources);
      return null;
    }

  }

  /**
   * Executor that performs a content-summary FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSContentSummary implements FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;

    /**
     * Creates a content-summary executor.
     *
     * @param path the path to retrieve the content-summary.
     */
    public FSContentSummary(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return a Map object (JSON friendly) with the content-summary.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      ContentSummary contentSummary = fs.getContentSummary(path);
      return contentSummaryToJSON(contentSummary);
    }

  }

  /**
   * Executor that performs a create FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSCreate implements FileSystemAccess.FileSystemExecutor<Void> {
    private InputStream is;
    private Path path;
    private short permission;
    private boolean override;
    private short replication;
    private long blockSize;

    /**
     * Creates a Create executor.
     *
     * @param is input stream to for the file to create.
     * @param path path of the file to create.
     * @param perm permission for the file.
     * @param override if the file should be overriden if it already exist.
     * @param repl the replication factor for the file.
     * @param blockSize the block size for the file.
     */
    public FSCreate(InputStream is, String path, short perm, boolean override,
                    short repl, long blockSize) {
      this.is = is;
      this.path = new Path(path);
      this.permission = perm;
      this.override = override;
      this.replication = repl;
      this.blockSize = blockSize;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return The URI of the created file.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      if (replication == -1) {
        replication = fs.getDefaultReplication(path);
      }
      if (blockSize == -1) {
        blockSize = fs.getDefaultBlockSize(path);
      }
      FsPermission fsPermission = new FsPermission(permission);
      int bufferSize = fs.getConf().getInt("httpfs.buffer.size", 4096);
      OutputStream os = fs.create(path, fsPermission, override, bufferSize, replication, blockSize, null);
      IOUtils.copyBytes(is, os, bufferSize, true);
      os.close();
      return null;
    }

  }

  /**
   * Executor that performs a delete FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSDelete implements FileSystemAccess.FileSystemExecutor<JSONObject> {
    private Path path;
    private boolean recursive;

    /**
     * Creates a Delete executor.
     *
     * @param path path to delete.
     * @param recursive if the delete should be recursive or not.
     */
    public FSDelete(String path, boolean recursive) {
      this.path = new Path(path);
      this.recursive = recursive;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return <code>true</code> if the delete operation was successful,
     *         <code>false</code> otherwise.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public JSONObject execute(FileSystem fs) throws IOException {
      boolean deleted = fs.delete(path, recursive);
      return toJSON(HttpFSFileSystem.DELETE_JSON.toLowerCase(), deleted);
    }

  }

  /**
   * Executor that performs a file-checksum FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSFileChecksum implements FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;

    /**
     * Creates a file-checksum executor.
     *
     * @param path the path to retrieve the checksum.
     */
    public FSFileChecksum(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return a Map object (JSON friendly) with the file checksum.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      FileChecksum checksum = fs.getFileChecksum(path);
      return fileChecksumToJSON(checksum);
    }

  }

  /**
   * Executor that performs a file-status FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSFileStatus implements FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;

    /**
     * Creates a file-status executor.
     *
     * @param path the path to retrieve the status.
     */
    public FSFileStatus(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem getFileStatus operation and returns the
     * result in a JSONish Map.
     *
     * @param fs filesystem instance to use.
     *
     * @return a Map object (JSON friendly) with the file status.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      StatusPair sp = new StatusPair(fs, path);
      return sp.toJson();
    }

  }

  /**
   * Executor that performs a home-dir FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSHomeDir implements FileSystemAccess.FileSystemExecutor<JSONObject> {

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return a JSON object with the user home directory.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    @SuppressWarnings("unchecked")
    public JSONObject execute(FileSystem fs) throws IOException {
      Path homeDir = fs.getHomeDirectory();
      JSONObject json = new JSONObject();
      json.put(HttpFSFileSystem.HOME_DIR_JSON, homeDir.toUri().getPath());
      return json;
    }

  }

  /**
   * Executor that performs a list-status FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSListStatus implements FileSystemAccess.FileSystemExecutor<Map>, PathFilter {
    private Path path;
    private PathFilter filter;

    /**
     * Creates a list-status executor.
     *
     * @param path the directory to retrieve the status of its contents.
     * @param filter glob filter to use.
     *
     * @throws IOException thrown if the filter expression is incorrect.
     */
    public FSListStatus(String path, String filter) throws IOException {
      this.path = new Path(path);
      this.filter = (filter == null) ? this : new GlobFilter(filter);
    }

    /**
     * Returns data for a JSON Map containing the information for
     * the set of files in 'path' that match 'filter'.
     *
     * @param fs filesystem instance to use.
     *
     * @return a Map with the file status of the directory
     *         contents that match the filter
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      StatusPairs sp = new StatusPairs(fs, path, filter);
      return sp.toJson();
    }

    @Override
    public boolean accept(Path path) {
      return true;
    }

  }

  /**
   * Executor that performs a mkdirs FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSMkdirs implements FileSystemAccess.FileSystemExecutor<JSONObject> {

    private Path path;
    private short permission;

    /**
     * Creates a mkdirs executor.
     *
     * @param path directory path to create.
     * @param permission permission to use.
     */
    public FSMkdirs(String path, short permission) {
      this.path = new Path(path);
      this.permission = permission;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return <code>true</code> if the mkdirs operation was successful,
     *         <code>false</code> otherwise.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public JSONObject execute(FileSystem fs) throws IOException {
      FsPermission fsPermission = new FsPermission(permission);
      boolean mkdirs = fs.mkdirs(path, fsPermission);
      return toJSON(HttpFSFileSystem.MKDIRS_JSON, mkdirs);
    }

  }

  /**
   * Executor that performs a open FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSOpen implements FileSystemAccess.FileSystemExecutor<InputStream> {
    private Path path;

    /**
     * Creates a open executor.
     *
     * @param path file to open.
     */
    public FSOpen(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return The inputstream of the file.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public InputStream execute(FileSystem fs) throws IOException {
      int bufferSize = HttpFSServerWebApp.get().getConfig().getInt("httpfs.buffer.size", 4096);
      return fs.open(path, bufferSize);
    }

  }

  /**
   * Executor that performs a rename FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSRename implements FileSystemAccess.FileSystemExecutor<JSONObject> {
    private Path path;
    private Path toPath;

    /**
     * Creates a rename executor.
     *
     * @param path path to rename.
     * @param toPath new name.
     */
    public FSRename(String path, String toPath) {
      this.path = new Path(path);
      this.toPath = new Path(toPath);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return <code>true</code> if the rename operation was successful,
     *         <code>false</code> otherwise.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public JSONObject execute(FileSystem fs) throws IOException {
      boolean renamed = fs.rename(path, toPath);
      return toJSON(HttpFSFileSystem.RENAME_JSON, renamed);
    }

  }

  /**
   * Executor that performs a set-owner FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSSetOwner implements FileSystemAccess.FileSystemExecutor<Void> {
    private Path path;
    private String owner;
    private String group;

    /**
     * Creates a set-owner executor.
     *
     * @param path the path to set the owner.
     * @param owner owner to set.
     * @param group group to set.
     */
    public FSSetOwner(String path, String owner, String group) {
      this.path = new Path(path);
      this.owner = owner;
      this.group = group;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.setOwner(path, owner, group);
      return null;
    }

  }

  /**
   * Executor that performs a set-permission FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSSetPermission implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private short permission;

    /**
     * Creates a set-permission executor.
     *
     * @param path path to set the permission.
     * @param permission permission to set.
     */
    public FSSetPermission(String path, short permission) {
      this.path = new Path(path);
      this.permission = permission;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      FsPermission fsPermission = new FsPermission(permission);
      fs.setPermission(path, fsPermission);
      return null;
    }

  }

  /**
   * Executor that sets the acl for a file in a FileSystem
   */
  @InterfaceAudience.Private
  public static class FSSetAcl implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private List<AclEntry> aclEntries;

    /**
     * Creates a set-acl executor.
     *
     * @param path path to set the acl.
     * @param aclSpec acl to set.
     */
    public FSSetAcl(String path, String aclSpec) {
      this.path = new Path(path);
      this.aclEntries = AclEntry.parseAclSpec(aclSpec, true);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.setAcl(path, aclEntries);
      return null;
    }

  }

  /**
   * Executor that removes all acls from a file in a FileSystem
   */
  @InterfaceAudience.Private
  public static class FSRemoveAcl implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;

    /**
     * Creates a remove-acl executor.
     *
     * @param path path from which to remove the acl.
     */
    public FSRemoveAcl(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.removeAcl(path);
      return null;
    }

  }

  /**
   * Executor that modifies acl entries for a file in a FileSystem
   */
  @InterfaceAudience.Private
  public static class FSModifyAclEntries implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private List<AclEntry> aclEntries;

    /**
     * Creates a modify-acl executor.
     *
     * @param path path to set the acl.
     * @param aclSpec acl to set.
     */
    public FSModifyAclEntries(String path, String aclSpec) {
      this.path = new Path(path);
      this.aclEntries = AclEntry.parseAclSpec(aclSpec, true);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.modifyAclEntries(path, aclEntries);
      return null;
    }

  }

  /**
   * Executor that removes acl entries from a file in a FileSystem
   */
  @InterfaceAudience.Private
  public static class FSRemoveAclEntries implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private List<AclEntry> aclEntries;

    /**
     * Creates a remove acl entry executor.
     *
     * @param path path to set the acl.
     * @param aclSpec acl parts to remove.
     */
    public FSRemoveAclEntries(String path, String aclSpec) {
      this.path = new Path(path);
      this.aclEntries = AclEntry.parseAclSpec(aclSpec, true);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.removeAclEntries(path, aclEntries);
      return null;
    }

  }

  /**
   * Executor that removes the default acl from a directory in a FileSystem
   */
  @InterfaceAudience.Private
  public static class FSRemoveDefaultAcl implements FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;

    /**
     * Creates an executor for removing the default acl.
     *
     * @param path path to set the acl.
     */
    public FSRemoveDefaultAcl(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.removeDefaultAcl(path);
      return null;
    }

  }

  /**
   * Executor that gets the ACL information for a given file.
   */
  @InterfaceAudience.Private
  public static class FSAclStatus implements FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;

    /**
     * Creates an executor for getting the ACLs for a file.
     *
     * @param path the path to retrieve the ACLs.
     */
    public FSAclStatus(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return a Map object (JSON friendly) with the file status.
     *
     * @throws IOException thrown if an IO error occurred.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      AclStatus status = fs.getAclStatus(path);
      return aclStatusToJSON(status);
    }

  }

  /**
   * Executor that performs a set-replication FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSSetReplication implements FileSystemAccess.FileSystemExecutor<JSONObject> {
    private Path path;
    private short replication;

    /**
     * Creates a set-replication executor.
     *
     * @param path path to set the replication factor.
     * @param replication replication factor to set.
     */
    public FSSetReplication(String path, short replication) {
      this.path = new Path(path);
      this.replication = replication;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return <code>true</code> if the replication value was set,
     *         <code>false</code> otherwise.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    @SuppressWarnings("unchecked")
    public JSONObject execute(FileSystem fs) throws IOException {
      boolean ret = fs.setReplication(path, replication);
      JSONObject json = new JSONObject();
      json.put(HttpFSFileSystem.SET_REPLICATION_JSON, ret);
      return json;
    }

  }

  /**
   * Executor that performs a set-times FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSSetTimes implements FileSystemAccess.FileSystemExecutor<Void> {
    private Path path;
    private long mTime;
    private long aTime;

    /**
     * Creates a set-times executor.
     *
     * @param path path to set the times.
     * @param mTime modified time to set.
     * @param aTime access time to set.
     */
    public FSSetTimes(String path, long mTime, long aTime) {
      this.path = new Path(path);
      this.mTime = mTime;
      this.aTime = aTime;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return void.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.setTimes(path, mTime, aTime);
      return null;
    }

  }

  /**
   * Executor that performs a setxattr FileSystemAccess files system operation.
   */
  @InterfaceAudience.Private
  public static class FSSetXAttr implements 
      FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private String name;
    private byte[] value;
    private EnumSet<XAttrSetFlag> flag;

    public FSSetXAttr(String path, String name, String encodedValue, 
        EnumSet<XAttrSetFlag> flag) throws IOException {
      this.path = new Path(path);
      this.name = name;
      this.value = XAttrCodec.decodeValue(encodedValue);
      this.flag = flag;
    }

    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.setXAttr(path, name, value, flag);
      return null;
    }
  }

  /**
   * Executor that performs a removexattr FileSystemAccess files system 
   * operation.
   */
  @InterfaceAudience.Private
  public static class FSRemoveXAttr implements 
      FileSystemAccess.FileSystemExecutor<Void> {

    private Path path;
    private String name;

    public FSRemoveXAttr(String path, String name) {
      this.path = new Path(path);
      this.name = name;
    }

    @Override
    public Void execute(FileSystem fs) throws IOException {
      fs.removeXAttr(path, name);
      return null;
    }
  }

  /**
   * Executor that performs listing xattrs FileSystemAccess files system 
   * operation.
   */
  @SuppressWarnings("rawtypes")
  @InterfaceAudience.Private
  public static class FSListXAttrs implements 
      FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;

    /**
     * Creates listing xattrs executor.
     *
     * @param path the path to retrieve the xattrs.
     */
    public FSListXAttrs(String path) {
      this.path = new Path(path);
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return Map a map object (JSON friendly) with the xattr names.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      List<String> names = fs.listXAttrs(path);
      return xAttrNamesToJSON(names);
    }
  }

  /**
   * Executor that performs getting xattrs FileSystemAccess files system 
   * operation.
   */
  @SuppressWarnings("rawtypes")
  @InterfaceAudience.Private
  public static class FSGetXAttrs implements 
      FileSystemAccess.FileSystemExecutor<Map> {
    private Path path;
    private List<String> names;
    private XAttrCodec encoding;

    /**
     * Creates getting xattrs executor.
     *
     * @param path the path to retrieve the xattrs.
     */
    public FSGetXAttrs(String path, List<String> names, XAttrCodec encoding) {
      this.path = new Path(path);
      this.names = names;
      this.encoding = encoding;
    }

    /**
     * Executes the filesystem operation.
     *
     * @param fs filesystem instance to use.
     *
     * @return Map a map object (JSON friendly) with the xattrs.
     *
     * @throws IOException thrown if an IO error occured.
     */
    @Override
    public Map execute(FileSystem fs) throws IOException {
      Map<String, byte[]> xattrs = null;
      if (names != null && !names.isEmpty()) {
        xattrs = fs.getXAttrs(path, names);
      } else {
        xattrs = fs.getXAttrs(path);
      }
      return xAttrsToJSON(xattrs, encoding);
    }
  }
}