/*
    * Copyright (C) 2021 Thomas Wolf <thomas.wolf@paranor.ch> 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 static org.junit.Assert.assertArrayEquals;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.io.ByteArrayOutputStream;
  import java.io.InputStream;
  import java.util.zip.InflaterInputStream;
  
  import org.junit.Test;
  
  /**
   * Crude tests for the {@link BinaryDeltaInputStream} using delta diffs
   * generated by C git.
   */
  public class BinaryDeltaInputStreamTest {
  
  	private InputStream getBinaryHunk(String name) {
  		return this.getClass().getResourceAsStream(name);
  	}
  
  	@Test
  	public void testBinaryDelta() throws Exception {
  		// Prepare our test data
  		byte[] data = new byte[8192];
  		for (int i = 0; i < data.length; i++) {
  			data[i] = (byte) (255 - (i % 256));
  		}
  		// Same, but with five 'x' inserted in the middle.
  		int middle = data.length / 2;
  		byte[] newData = new byte[data.length + 5];
  		System.arraycopy(data, 0, newData, 0, middle);
  		for (int i = 0; i < 5; i++) {
  			newData[middle + i] = 'x';
  		}
  		System.arraycopy(data, middle, newData, middle + 5, middle);
  		// delta1.forward has the instructions
  		// @formatter:off
  		// COPY 0 4096
  		// INSERT 5 xxxxx
  		// COPY 0 4096
  		// @formatter:on
  		// Note that the way we built newData could be expressed as
  		// @formatter:off
  		// COPY 0 4096
  		// INSERT 5 xxxxx
  		// COPY 4096 4096
  		// @formatter:on
  		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
  				BinaryDeltaInputStream input = new BinaryDeltaInputStream(data,
  						new InflaterInputStream(new BinaryHunkInputStream(
  								getBinaryHunk("delta1.forward"))))) {
  			byte[] buf = new byte[1024];
  			int n;
  			while ((n = input.read(buf)) >= 0) {
  				out.write(buf, 0, n);
  			}
  			assertArrayEquals(newData, out.toByteArray());
  			assertTrue(input.isFullyConsumed());
  		}
  		// delta1.reverse has the instructions
  		// @formatter:off
  		// COPY 0 4096
  		// COPY 256 3840
  		// COPY 256 256
  		// @formatter:on
  		// Note that there are alternatives, for instance
  		// @formatter:off
  		// COPY 0 4096
  		// COPY 4101 4096
  		// @formatter:on
  		// or
  		// @formatter:off
  		// COPY 0 4096
  		// COPY 0 4096
  		// @formatter:on
  		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
  				BinaryDeltaInputStream input = new BinaryDeltaInputStream(
  						newData,
  						new InflaterInputStream(new BinaryHunkInputStream(
  								getBinaryHunk("delta1.reverse"))))) {
  			long expectedSize = input.getExpectedResultSize();
  			assertEquals(data.length, expectedSize);
  			byte[] buf = new byte[1024];
  			int n;
  			while ((n = input.read(buf)) >= 0) {
  				out.write(buf, 0, n);
  			}
  			assertArrayEquals(data, out.toByteArray());
 			assertTrue(input.isFullyConsumed());
 		}
 	}
 }