/*
    * Copyright (C) 2010, 2013 Google Inc. 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.util.io;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  
  /**
   * Input stream that copies data read to another output stream.
   *
   * This stream is primarily useful with a
   * {@link org.eclipse.jgit.util.TemporaryBuffer}, where any data read or skipped
   * by the caller is also duplicated into the temporary buffer. Later the
   * temporary buffer can then be used instead of the original source stream.
   *
   * During close this stream copies any remaining data from the source stream
   * into the destination stream.
   */
  public class TeeInputStream extends InputStream {
  	private byte[] skipBuffer;
  
  	private InputStream src;
  
  	private OutputStream dst;
  
  	/**
  	 * Initialize a tee input stream.
  	 *
  	 * @param src
  	 *            source stream to consume.
  	 * @param dst
  	 *            destination to copy the source to as it is consumed. Typically
  	 *            this is a {@link org.eclipse.jgit.util.TemporaryBuffer}.
  	 */
  	public TeeInputStream(InputStream src, OutputStream dst) {
  		this.src = src;
  		this.dst = dst;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public int read() throws IOException {
  		byte[] b = skipBuffer();
  		int n = read(b, 0, 1);
  		return n == 1 ? b[0] & 0xff : -1;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public long skip(long count) throws IOException {
  		long skipped = 0;
  		long cnt = count;
  		final byte[] b = skipBuffer();
  		while (0 < cnt) {
  			final int n = src.read(b, 0, (int) Math.min(b.length, cnt));
  			if (n <= 0)
  				break;
  			dst.write(b, 0, n);
  			skipped += n;
  			cnt -= n;
  		}
  		return skipped;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public int read(byte[] b, int off, int len) throws IOException {
  		if (len == 0)
  			return 0;
  
  		int n = src.read(b, off, len);
  		if (0 < n)
  			dst.write(b, off, n);
  		return n;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public void close() throws IOException {
  		byte[] b = skipBuffer();
  		for (;;) {
  			int n = src.read(b);
  			if (n <= 0)
  				break;
  			dst.write(b, 0, n);
  		}
  		dst.close();
  		src.close();
  	}
  
 	private byte[] skipBuffer() {
 		if (skipBuffer == null)
 			skipBuffer = new byte[2048];
 		return skipBuffer;
 	}
 }