/*
    * Copyright (C) 2017, Markus Duft <markus.duft@ssi-schaefer.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.lfs;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.attribute.BasicFileAttributes;
  
  import org.eclipse.jgit.errors.LargeObjectException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.ObjectLoader;
  import org.eclipse.jgit.lib.ObjectStream;
  import org.eclipse.jgit.storage.pack.PackConfig;
  import org.eclipse.jgit.util.IO;
  
  /**
   * An {@link ObjectLoader} implementation that reads a media file from the LFS
   * storage.
   *
   * @since 4.11
   */
  public class LfsBlobLoader extends ObjectLoader {
  
  	private Path mediaFile;
  
  	private BasicFileAttributes attributes;
  
  	private byte[] cached;
  
  	/**
  	 * Create a loader for the LFS media file at the given path.
  	 *
  	 * @param mediaFile
  	 *            path to the file
  	 * @throws IOException
  	 *             in case of an error reading attributes
  	 */
  	public LfsBlobLoader(Path mediaFile) throws IOException {
  		this.mediaFile = mediaFile;
  		this.attributes = Files.readAttributes(mediaFile,
  				BasicFileAttributes.class);
  	}
  
  	@Override
  	public int getType() {
  		return Constants.OBJ_BLOB;
  	}
  
  	@Override
  	public long getSize() {
  		return attributes.size();
  	}
  
  	@Override
  	public byte[] getCachedBytes() throws LargeObjectException {
  		if (getSize() > PackConfig.DEFAULT_BIG_FILE_THRESHOLD) {
  			throw new LargeObjectException();
  		}
  
  		if (cached == null) {
  			try {
  				cached = IO.readFully(mediaFile.toFile());
  			} catch (IOException ioe) {
  				throw new LargeObjectException(ioe);
  			}
  		}
  		return cached;
  	}
  
  	@Override
  	public ObjectStream openStream()
  			throws MissingObjectException, IOException {
  		return new ObjectStream.Filter(getType(), getSize(),
  				Files.newInputStream(mediaFile));
  	}
  
  }