/*
 * 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.samoa.streams.fs;

import java.io.IOException;
import java.io.InputStream;
import java.nio.file.FileSystems;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;

/**
 * Source for FileStream for HDFS files
 * 
 * @author Casey
 */
public class HDFSFileStreamSource implements FileStreamSource {

  /**
   *
   */
  private static final long serialVersionUID = -3887354805787167400L;

  private transient InputStream fileStream;
  private transient Configuration config;
  private List<String> filePaths;
  private int currentIndex;

  public HDFSFileStreamSource() {
    this.currentIndex = -1;
  }

  public void init(String path, String ext) {
    this.init(this.getDefaultConfig(), path, ext);
  }

  public void init(Configuration config, String path, String ext) {
    this.config = config;
    config.set("fs.hdfs.impl",
        org.apache.hadoop.hdfs.DistributedFileSystem.class.getName());
    config.set("fs.file.impl",
        org.apache.hadoop.fs.LocalFileSystem.class.getName());
    this.filePaths = new ArrayList<>();
    Path hdfsPath = new Path(path);
    FileSystem fs;
    try {
      fs = FileSystem.get(config);
      FileStatus fileStat = fs.getFileStatus(hdfsPath);
      if (fileStat.isDirectory()) {
        Path filterPath = hdfsPath;
        if (ext != null) {
          filterPath = new Path(path, "*." + ext);
        } else {
          filterPath = new Path(path, "*");
        }
        FileStatus[] filesInDir = fs.globStatus(filterPath);
        for (FileStatus aFilesInDir : filesInDir) {
          if (aFilesInDir.isFile()) {
            filePaths.add(aFilesInDir.getPath().toString());
          }
        }
      } else {
        this.filePaths.add(path);
      }
    } catch (IOException ioe) {
      throw new RuntimeException("Failed getting list of files at:" + path, ioe);
    }

    this.currentIndex = -1;
  }

  private Configuration getDefaultConfig() {
    String hadoopHome = System.getenv("HADOOP_HOME");
    Configuration conf = new Configuration();
    if (hadoopHome != null) {
      java.nio.file.Path coreSitePath = FileSystems.getDefault().getPath(hadoopHome, "etc/hadoop/core-site.xml");
      java.nio.file.Path hdfsSitePath = FileSystems.getDefault().getPath(hadoopHome, "etc/hadoop/hdfs-site.xml");
      conf.addResource(new Path(coreSitePath.toAbsolutePath().toString()));
      conf.addResource(new Path(hdfsSitePath.toAbsolutePath().toString()));
    }
    return conf;
  }

  public void reset() throws IOException {
    this.currentIndex = -1;
    this.closeFileStream();
  }

  private void closeFileStream() {
    IOUtils.closeStream(fileStream);
  }

  public InputStream getNextInputStream() {
    this.closeFileStream();
    if (this.currentIndex >= (this.filePaths.size() - 1))
      return null;

    this.currentIndex++;
    String filePath = this.filePaths.get(currentIndex);

    Path hdfsPath = new Path(filePath);
    FileSystem fs;
    try {
      fs = FileSystem.get(config);
      fileStream = fs.open(hdfsPath);
    } catch (IOException ioe) {
      this.closeFileStream();
      throw new RuntimeException("Failed opening file:" + filePath, ioe);
    }

    return fileStream;
  }

  public InputStream getCurrentInputStream() {
    return fileStream;
  }

  protected int getFilePathListSize() {
    if (filePaths != null)
      return filePaths.size();
    return 0;
  }

  protected String getFilePathAt(int index) {
    if (filePaths != null && filePaths.size() > index)
      return filePaths.get(index);
    return null;
  }
}