/*
    * 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.chukwa.extraction.engine.datasource;
  
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import org.apache.hadoop.chukwa.inputtools.mdl.DataConfig;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FileStatus;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  
  public class DsDirectory {
    private static Object lock = new Object();
    private static DsDirectory dsDirectory = null;
    private static final String[] emptyArray = new String[0];
  
    private String rootFolder = null;
    private DataConfig dataConfig = null;
  
    private static FileSystem fs = null;
    private static Configuration conf = null;
  
    private DsDirectory() {
      dataConfig = new DataConfig();
      conf = new Configuration();
      try {
        fs = FileSystem.get(conf);
      } catch (IOException e) {
        e.printStackTrace();
      }
      rootFolder = dataConfig.get("chukwa.engine.dsDirectory.rootFolder");
      if (!rootFolder.endsWith("/")) {
        rootFolder += "/";
      }
    }
  
    public static DsDirectory getInstance() {
      synchronized (lock) {
        if (dsDirectory == null) {
          dsDirectory = new DsDirectory();
        }
      }
      return dsDirectory;
    }
  
    public String[] list(String cluster) throws DataSourceException {
      List<String> datasources = new ArrayList<String>();
      try {
        FileStatus[] fileStat = fs.listStatus(new Path(rootFolder + cluster));
  
        for (FileStatus fstat : fileStat) {
          if (fstat.isDir()) {
            datasources.add(fstat.getPath().getName());
          }
        }
      } catch (IOException e) {
        e.printStackTrace();
        throw new DataSourceException(e);
      }
      return datasources.toArray(emptyArray);
    }
  
    public static void main(String[] args) throws DataSourceException {
      DsDirectory dsd = DsDirectory.getInstance();
      String[] dss = dsd.list("unknown");
      for (String d : dss) {
        System.out.println(d);
      }
    }
  }