FileDataProvider.java

package proj.zoie.impl.indexing;

/**
 * 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.
 */
import java.io.File;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Comparator;
import java.util.Stack;

import proj.zoie.api.DataConsumer.DataEvent;

public class FileDataProvider extends StreamDataProvider<File> {
  private final File _dir;
  private long _currentVersion = 0L;
  private Stack<Iterator<File>> _stack;
  private Iterator<File> _currentIterator;
  private boolean _looping;

  public FileDataProvider(File dir, Comparator<String> versionComparator) {
    super(versionComparator);
    if (!dir.exists()) throw new IllegalArgumentException("dir: " + dir + " does not exist.");
    _dir = dir;
    _stack = new Stack<Iterator<File>>();
    _looping = false;
    reset();
  }

  public File getDir() {
    return _dir;
  }

  public String getZoieVersion() {
    return Long.toString(_currentVersion);
  }

  public String getMinZoieVersion() {
    return Long.toString(0L);
  }

  public String nextZoieVersion() {
    return Long.toString(_currentVersion + 1L);
  }

  @Override
  public void reset() {
    _stack.clear();
    if (_dir.isFile()) {
      _currentIterator = Arrays.asList(new File[] { _dir }).iterator();
    } else {
      _currentIterator = Arrays.asList(_dir.listFiles()).iterator();
    }
  }

  public void setLooping(boolean looping) {
    _looping = looping;
  }

  @Override
  public DataEvent<File> next() {
    if (_currentIterator.hasNext()) {
      File next = _currentIterator.next();
      if (next.isFile()) {
        // ?? hao: how to implement version++
        // new DataEvent<File>(next, _currentVersion++);
        return new DataEvent<File>(next, nextZoieVersion());
      } else {
        _stack.push(_currentIterator);
        _currentIterator = Arrays.asList(next.listFiles()).iterator();
        return next();
      }
    } else {
      if (_stack.isEmpty()) {
        if (_looping) {
          reset();
          return next();
        } else {
          return null;
        }
      } else {
        _currentIterator = _stack.pop();
        return next();
      }
    }
  }

  @Override
  public void setStartingOffset(String version) {
    throw new UnsupportedOperationException("");
  }
}