FileSystemScanner.java

/*
 * Copyright 2013 eXo Platform SAS
 *
 * Licensed 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 juzu.impl.fs;

import juzu.impl.common.Resource;
import juzu.impl.fs.spi.ReadFileSystem;
import juzu.impl.common.Tools;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;

/** @author <a href="mailto:julien.viet@exoplatform.com">Julien Viet</a> */
public abstract class FileSystemScanner<P> implements Filter<P> {

  public static <P> FileSystemScanner<P> createTimestamped(ReadFileSystem<P> fs) {
    return new Timestamped<P>(fs);
  }

  public static <P> FileSystemScanner<P> createHashing(ReadFileSystem<P> fs) {
    return new Hash<P>(fs);
  }

  public static class Timestamped<P> extends FileSystemScanner<P> {
    public Timestamped(ReadFileSystem<P> fs) {
      super(fs);
    }

    @Override
    protected long stampOf(P file) throws IOException {
      return fs.getLastModified(file);
    }

    @Override
    protected boolean isModified(long snapshot, long current) {
      return snapshot < current;
    }
  }

  public static class Hash<P> extends FileSystemScanner<P> {
    public Hash(ReadFileSystem<P> fs) {
      super(fs);
    }

    @Override
    protected long stampOf(P file) throws IOException {
      juzu.impl.common.Timestamped<Resource> resource = fs.getResource(file);
      InputStream in = resource.getObject().getInputStream();
      byte[] bytes = Tools.bytes(in);
      return Tools.md5(bytes);
    }

    @Override
    protected boolean isModified(long snapshot, long current) {
      return snapshot != current;
    }
  }

  /** . */
  protected final ReadFileSystem<P> fs;

  /** . */
  final ArrayList<String> stack = new ArrayList<String>();

  private FileSystemScanner(ReadFileSystem<P> fs) {
    this.fs = fs;
  }

  public ReadFileSystem<P> getFileSystem() {
    return fs;
  }

  public Snapshot<P> take() {
    return new Snapshot<P>(this);
  }

  public boolean acceptDir(P dir, String name) throws IOException {
    return !name.startsWith(".");
  }

  public boolean acceptFile(P file, String name) throws IOException {
    return !name.startsWith(".");
  }

  protected abstract long stampOf(P file) throws IOException;

  protected abstract boolean isModified(long snapshot, long current);

}