/*
    * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
    *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above
   *   copyright notice, this list of conditions and the following
   *   disclaimer in the documentation and/or other materials provided
   *   with the distribution.
   *
   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
   *   products derived from this software without specific prior
   *   written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  package org.eclipse.jgit.internal.storage.file;
  
  import static org.eclipse.jgit.internal.storage.pack.PackWriter.NONE;
  import static org.eclipse.jgit.lib.Constants.INFO_ALTERNATES;
  import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.File;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.text.ParseException;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.internal.storage.file.PackIndex.MutableEntry;
  import org.eclipse.jgit.internal.storage.pack.PackWriter;
  import org.eclipse.jgit.junit.JGitTestUtil;
  import org.eclipse.jgit.junit.TestRepository;
  import org.eclipse.jgit.junit.TestRepository.BranchBuilder;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdSet;
  import org.eclipse.jgit.lib.ObjectInserter;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.Sets;
  import org.eclipse.jgit.revwalk.DepthWalk;
  import org.eclipse.jgit.revwalk.ObjectWalk;
  import org.eclipse.jgit.revwalk.RevBlob;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevObject;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.storage.pack.PackConfig;
  import org.eclipse.jgit.storage.pack.PackStatistics;
  import org.eclipse.jgit.test.resources.SampleDataRepositoryTestCase;
  import org.eclipse.jgit.transport.PackParser;
  import org.junit.After;
  import org.junit.Before;
  import org.junit.Test;
  
  public class PackWriterTest extends SampleDataRepositoryTestCase {
  
  	private static final List<RevObject> EMPTY_LIST_REVS = Collections
  			.<RevObject> emptyList();
  
  	private static final Set<ObjectIdSet> EMPTY_ID_SET = Collections
 			.<ObjectIdSet> emptySet();
 
 	private PackConfig config;
 
 	private PackWriter writer;
 
 	private ByteArrayOutputStream os;
 
 	private PackFile pack;
 
 	private ObjectInserter inserter;
 
 	private FileRepository dst;
 
 	private RevBlob contentA;
 
 	private RevBlob contentB;
 
 	private RevBlob contentC;
 
 	private RevBlob contentD;
 
 	private RevBlob contentE;
 
 	private RevCommit c1;
 
 	private RevCommit c2;
 
 	private RevCommit c3;
 
 	private RevCommit c4;
 
 	private RevCommit c5;
 
 	@Override
 	@Before
 	public void setUp() throws Exception {
 		super.setUp();
 		os = new ByteArrayOutputStream();
 		config = new PackConfig(db);
 
 		dst = createBareRepository();
 		File alt = new File(dst.getObjectDatabase().getDirectory(), INFO_ALTERNATES);
 		alt.getParentFile().mkdirs();
 		write(alt, db.getObjectDatabase().getDirectory().getAbsolutePath() + "\n");
 	}
 
 	@Override
 	@After
 	public void tearDown() throws Exception {
 		if (writer != null) {
 			writer.close();
 			writer = null;
 		}
 		if (inserter != null) {
 			inserter.close();
 			inserter = null;
 		}
 		super.tearDown();
 	}
 
 	/**
 	 * Test constructor for exceptions, default settings, initialization.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testContructor() throws IOException {
 		writer = new PackWriter(config, db.newObjectReader());
 		assertFalse(writer.isDeltaBaseAsOffset());
 		assertTrue(config.isReuseDeltas());
 		assertTrue(config.isReuseObjects());
 		assertEquals(0, writer.getObjectCount());
 	}
 
 	/**
 	 * Change default settings and verify them.
 	 */
 	@Test
 	public void testModifySettings() {
 		config.setReuseDeltas(false);
 		config.setReuseObjects(false);
 		config.setDeltaBaseAsOffset(false);
 		assertFalse(config.isReuseDeltas());
 		assertFalse(config.isReuseObjects());
 		assertFalse(config.isDeltaBaseAsOffset());
 
 		writer = new PackWriter(config, db.newObjectReader());
 		writer.setDeltaBaseAsOffset(true);
 		assertTrue(writer.isDeltaBaseAsOffset());
 		assertFalse(config.isDeltaBaseAsOffset());
 	}
 
 	/**
 	 * Write empty pack by providing empty sets of interesting/uninteresting
 	 * objects and check for correct format.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWriteEmptyPack1() throws IOException {
 		createVerifyOpenPack(NONE, NONE, false, false);
 
 		assertEquals(0, writer.getObjectCount());
 		assertEquals(0, pack.getObjectCount());
 		assertEquals("da39a3ee5e6b4b0d3255bfef95601890afd80709", writer
 				.computeName().name());
 	}
 
 	/**
 	 * Write empty pack by providing empty iterator of objects to write and
 	 * check for correct format.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWriteEmptyPack2() throws IOException {
 		createVerifyOpenPack(EMPTY_LIST_REVS);
 
 		assertEquals(0, writer.getObjectCount());
 		assertEquals(0, pack.getObjectCount());
 	}
 
 	/**
 	 * Try to pass non-existing object as uninteresting, with non-ignoring
 	 * setting.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testNotIgnoreNonExistingObjects() throws IOException {
 		final ObjectId nonExisting = ObjectId
 				.fromString("0000000000000000000000000000000000000001");
 		try {
 			createVerifyOpenPack(NONE, haves(nonExisting), false, false);
 			fail("Should have thrown MissingObjectException");
 		} catch (MissingObjectException x) {
 			// expected
 		}
 	}
 
 	/**
 	 * Try to pass non-existing object as uninteresting, with ignoring setting.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testIgnoreNonExistingObjects() throws IOException {
 		final ObjectId nonExisting = ObjectId
 				.fromString("0000000000000000000000000000000000000001");
 		createVerifyOpenPack(NONE, haves(nonExisting), false, true);
 		// shouldn't throw anything
 	}
 
 	/**
 	 * Try to pass non-existing object as uninteresting, with ignoring setting.
 	 * Use a repo with bitmap indexes because then PackWriter will use
 	 * PackWriterBitmapWalker which had problems with this situation.
 	 *
 	 * @throws IOException
 	 * @throws ParseException
 	 */
 	@Test
 	public void testIgnoreNonExistingObjectsWithBitmaps() throws IOException,
 			ParseException {
 		final ObjectId nonExisting = ObjectId
 				.fromString("0000000000000000000000000000000000000001");
 		new GC(db).gc();
 		createVerifyOpenPack(NONE, haves(nonExisting), false, true, true);
 		// shouldn't throw anything
 	}
 
 	/**
 	 * Create pack basing on only interesting objects, then precisely verify
 	 * content. No delta reuse here.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack1() throws IOException {
 		config.setReuseDeltas(false);
 		writeVerifyPack1();
 	}
 
 	/**
 	 * Test writing pack without object reuse. Pack content/preparation as in
 	 * {@link #testWritePack1()}.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack1NoObjectReuse() throws IOException {
 		config.setReuseDeltas(false);
 		config.setReuseObjects(false);
 		writeVerifyPack1();
 	}
 
 	/**
 	 * Create pack basing on both interesting and uninteresting objects, then
 	 * precisely verify content. No delta reuse here.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack2() throws IOException {
 		writeVerifyPack2(false);
 	}
 
 	/**
 	 * Test pack writing with deltas reuse, delta-base first rule. Pack
 	 * content/preparation as in {@link #testWritePack2()}.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack2DeltasReuseRefs() throws IOException {
 		writeVerifyPack2(true);
 	}
 
 	/**
 	 * Test pack writing with delta reuse. Delta bases referred as offsets. Pack
 	 * configuration as in {@link #testWritePack2DeltasReuseRefs()}.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack2DeltasReuseOffsets() throws IOException {
 		config.setDeltaBaseAsOffset(true);
 		writeVerifyPack2(true);
 	}
 
 	/**
 	 * Test pack writing with delta reuse. Raw-data copy (reuse) is made on a
 	 * pack with CRC32 index. Pack configuration as in
 	 * {@link #testWritePack2DeltasReuseRefs()}.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack2DeltasCRC32Copy() throws IOException {
 		final File packDir = db.getObjectDatabase().getPackDirectory();
 		final File crc32Pack = new File(packDir,
 				"pack-34be9032ac282b11fa9babdc2b2a93ca996c9c2f.pack");
 		final File crc32Idx = new File(packDir,
 				"pack-34be9032ac282b11fa9babdc2b2a93ca996c9c2f.idx");
 		copyFile(JGitTestUtil.getTestResourceFile(
 				"pack-34be9032ac282b11fa9babdc2b2a93ca996c9c2f.idxV2"),
 				crc32Idx);
 		db.openPack(crc32Pack);
 
 		writeVerifyPack2(true);
 	}
 
 	/**
 	 * Create pack basing on fixed objects list, then precisely verify content.
 	 * No delta reuse here.
 	 *
 	 * @throws IOException
 	 * @throws MissingObjectException
 	 *
 	 */
 	@Test
 	public void testWritePack3() throws MissingObjectException, IOException {
 		config.setReuseDeltas(false);
 		final ObjectId forcedOrder[] = new ObjectId[] {
 				ObjectId.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"),
 				ObjectId.fromString("c59759f143fb1fe21c197981df75a7ee00290799"),
 				ObjectId.fromString("aabf2ffaec9b497f0950352b3e582d73035c2035"),
 				ObjectId.fromString("902d5476fa249b7abc9d84c611577a81381f0327"),
 				ObjectId.fromString("6ff87c4664981e4397625791c8ea3bbb5f2279a3") ,
 				ObjectId.fromString("5b6e7c66c276e7610d4a73c70ec1a1f7c1003259") };
 		try (RevWalk parser = new RevWalk(db)) {
 			final RevObject forcedOrderRevs[] = new RevObject[forcedOrder.length];
 			for (int i = 0; i < forcedOrder.length; i++)
 				forcedOrderRevs[i] = parser.parseAny(forcedOrder[i]);
 
 			createVerifyOpenPack(Arrays.asList(forcedOrderRevs));
 		}
 
 		assertEquals(forcedOrder.length, writer.getObjectCount());
 		verifyObjectsOrder(forcedOrder);
 		assertEquals("ed3f96b8327c7c66b0f8f70056129f0769323d86", writer
 				.computeName().name());
 	}
 
 	/**
 	 * Another pack creation: basing on both interesting and uninteresting
 	 * objects. No delta reuse possible here, as this is a specific case when we
 	 * write only 1 commit, associated with 1 tree, 1 blob.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack4() throws IOException {
 		writeVerifyPack4(false);
 	}
 
 	/**
 	 * Test thin pack writing: 1 blob delta base is on objects edge. Pack
 	 * configuration as in {@link #testWritePack4()}.
 	 *
 	 * @throws IOException
 	 */
 	@Test
 	public void testWritePack4ThinPack() throws IOException {
 		writeVerifyPack4(true);
 	}
 
 	/**
 	 * Compare sizes of packs created using {@link #testWritePack2()} and
 	 * {@link #testWritePack2DeltasReuseRefs()}. The pack using deltas should
 	 * be smaller.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testWritePack2SizeDeltasVsNoDeltas() throws Exception {
 		config.setReuseDeltas(false);
 		config.setDeltaCompress(false);
 		testWritePack2();
 		final long sizePack2NoDeltas = os.size();
 		tearDown();
 		setUp();
 		testWritePack2DeltasReuseRefs();
 		final long sizePack2DeltasRefs = os.size();
 
 		assertTrue(sizePack2NoDeltas > sizePack2DeltasRefs);
 	}
 
 	/**
 	 * Compare sizes of packs created using
 	 * {@link #testWritePack2DeltasReuseRefs()} and
 	 * {@link #testWritePack2DeltasReuseOffsets()}. The pack with delta bases
 	 * written as offsets should be smaller.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testWritePack2SizeOffsetsVsRefs() throws Exception {
 		testWritePack2DeltasReuseRefs();
 		final long sizePack2DeltasRefs = os.size();
 		tearDown();
 		setUp();
 		testWritePack2DeltasReuseOffsets();
 		final long sizePack2DeltasOffsets = os.size();
 
 		assertTrue(sizePack2DeltasRefs > sizePack2DeltasOffsets);
 	}
 
 	/**
 	 * Compare sizes of packs created using {@link #testWritePack4()} and
 	 * {@link #testWritePack4ThinPack()}. Obviously, the thin pack should be
 	 * smaller.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testWritePack4SizeThinVsNoThin() throws Exception {
 		testWritePack4();
 		final long sizePack4 = os.size();
 		tearDown();
 		setUp();
 		testWritePack4ThinPack();
 		final long sizePack4Thin = os.size();
 
 		assertTrue(sizePack4 > sizePack4Thin);
 	}
 
 	@Test
 	public void testDeltaStatistics() throws Exception {
 		config.setDeltaCompress(true);
 		// TestRepository will close repo
 		FileRepository repo = createBareRepository();
 		ArrayList<RevObject> blobs = new ArrayList<>();
 		try (TestRepository<FileRepository> testRepo = new TestRepository<>(
 				repo)) {
 			blobs.add(testRepo.blob(genDeltableData(1000)));
 			blobs.add(testRepo.blob(genDeltableData(1005)));
 			try (PackWriter pw = new PackWriter(repo)) {
 				NullProgressMonitor m = NullProgressMonitor.INSTANCE;
 				pw.preparePack(blobs.iterator());
 				pw.writePack(m, m, os);
 				PackStatistics stats = pw.getStatistics();
 				assertEquals(1, stats.getTotalDeltas());
 				assertTrue("Delta bytes not set.",
 						stats.byObjectType(OBJ_BLOB).getDeltaBytes() > 0);
 			}
 		}
 	}
 
 	// Generate consistent junk data for building files that delta well
 	private String genDeltableData(int length) {
 		assertTrue("Generated data must have a length > 0", length > 0);
 		char[] data = {'a', 'b', 'c', '\n'};
 		StringBuilder builder = new StringBuilder(length);
 		for (int i = 0; i < length; i++) {
 			builder.append(data[i % 4]);
 		}
 		return builder.toString();
 	}
 
 
 	@Test
 	public void testWriteIndex() throws Exception {
 		config.setIndexVersion(2);
 		writeVerifyPack4(false);
 
 		File packFile = pack.getPackFile();
 		String name = packFile.getName();
 		String base = name.substring(0, name.lastIndexOf('.'));
 		File indexFile = new File(packFile.getParentFile(), base + ".idx");
 
 		// Validate that IndexPack came up with the right CRC32 value.
 		final PackIndex idx1 = PackIndex.open(indexFile);
 		assertTrue(idx1 instanceof PackIndexV2);
 		assertEquals(0x4743F1E4L, idx1.findCRC32(ObjectId
 				.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7")));
 
 		// Validate that an index written by PackWriter is the same.
 		final File idx2File = new File(indexFile.getAbsolutePath() + ".2");
 		try (FileOutputStream is = new FileOutputStream(idx2File)) {
 			writer.writeIndex(is);
 		}
 		final PackIndex idx2 = PackIndex.open(idx2File);
 		assertTrue(idx2 instanceof PackIndexV2);
 		assertEquals(idx1.getObjectCount(), idx2.getObjectCount());
 		assertEquals(idx1.getOffset64Count(), idx2.getOffset64Count());
 
 		for (int i = 0; i < idx1.getObjectCount(); i++) {
 			final ObjectId id = idx1.getObjectId(i);
 			assertEquals(id, idx2.getObjectId(i));
 			assertEquals(idx1.findOffset(id), idx2.findOffset(id));
 			assertEquals(idx1.findCRC32(id), idx2.findCRC32(id));
 		}
 	}
 
 	@Test
 	public void testExclude() throws Exception {
 		// TestRepository closes repo
 		FileRepository repo = createBareRepository();
 
 		try (TestRepository<FileRepository> testRepo = new TestRepository<>(
 				repo)) {
 			BranchBuilder bb = testRepo.branch("refs/heads/master");
 			contentA = testRepo.blob("A");
 			c1 = bb.commit().add("f", contentA).create();
 			testRepo.getRevWalk().parseHeaders(c1);
 			PackIndex pf1 = writePack(repo, wants(c1), EMPTY_ID_SET);
 			assertContent(pf1, Arrays.asList(c1.getId(), c1.getTree().getId(),
 					contentA.getId()));
 			contentB = testRepo.blob("B");
 			c2 = bb.commit().add("f", contentB).create();
 			testRepo.getRevWalk().parseHeaders(c2);
 			PackIndex pf2 = writePack(repo, wants(c2),
 					Sets.of((ObjectIdSet) pf1));
 			assertContent(pf2, Arrays.asList(c2.getId(), c2.getTree().getId(),
 					contentB.getId()));
 		}
 	}
 
 	private static void assertContent(PackIndex pi, List<ObjectId> expected) {
 		assertEquals("Pack index has wrong size.", expected.size(),
 				pi.getObjectCount());
 		for (int i = 0; i < pi.getObjectCount(); i++)
 			assertTrue(
 					"Pack index didn't contain the expected id "
 							+ pi.getObjectId(i),
 					expected.contains(pi.getObjectId(i)));
 	}
 
 	@Test
 	public void testShallowIsMinimalDepth1() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 1, wants(c2), NONE, NONE);
 			assertContent(idx, Arrays.asList(c2.getId(), c2.getTree().getId(),
 					contentA.getId(), contentB.getId()));
 
 			// Client already has blobs A and B, verify those are not packed.
 			idx = writeShallowPack(repo, 1, wants(c5), haves(c2), shallows(c2));
 			assertContent(idx, Arrays.asList(c5.getId(), c5.getTree().getId(),
 					contentC.getId(), contentD.getId(), contentE.getId()));
 		}
 	}
 
 	@Test
 	public void testShallowIsMinimalDepth2() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 2, wants(c2), NONE, NONE);
 			assertContent(idx,
 					Arrays.asList(c1.getId(), c2.getId(), c1.getTree().getId(),
 							c2.getTree().getId(), contentA.getId(),
 							contentB.getId()));
 
 			// Client already has blobs A and B, verify those are not packed.
 			idx = writeShallowPack(repo, 2, wants(c5), haves(c1, c2),
 					shallows(c1));
 			assertContent(idx,
 					Arrays.asList(c4.getId(), c5.getId(), c4.getTree().getId(),
 							c5.getTree().getId(), contentC.getId(),
 							contentD.getId(), contentE.getId()));
 		}
 	}
 
 	@Test
 	public void testShallowFetchShallowParentDepth1() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 1, wants(c5), NONE, NONE);
 			assertContent(idx, Arrays.asList(c5.getId(), c5.getTree().getId(),
 					contentA.getId(), contentB.getId(), contentC.getId(),
 					contentD.getId(), contentE.getId()));
 
 			idx = writeShallowPack(repo, 1, wants(c4), haves(c5), shallows(c5));
 			assertContent(idx, Arrays.asList(c4.getId(), c4.getTree().getId()));
 		}
 	}
 
 	@Test
 	public void testShallowFetchShallowParentDepth2() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 2, wants(c5), NONE, NONE);
 			assertContent(idx,
 					Arrays.asList(c4.getId(), c5.getId(), c4.getTree().getId(),
 							c5.getTree().getId(), contentA.getId(),
 							contentB.getId(), contentC.getId(),
 							contentD.getId(), contentE.getId()));
 
 			idx = writeShallowPack(repo, 2, wants(c3), haves(c4, c5),
 					shallows(c4));
 			assertContent(idx, Arrays.asList(c2.getId(), c3.getId(),
 					c2.getTree().getId(), c3.getTree().getId()));
 		}
 	}
 
 	@Test
 	public void testShallowFetchShallowAncestorDepth1() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 1, wants(c5), NONE, NONE);
 			assertContent(idx, Arrays.asList(c5.getId(), c5.getTree().getId(),
 					contentA.getId(), contentB.getId(), contentC.getId(),
 					contentD.getId(), contentE.getId()));
 
 			idx = writeShallowPack(repo, 1, wants(c3), haves(c5), shallows(c5));
 			assertContent(idx, Arrays.asList(c3.getId(), c3.getTree().getId()));
 		}
 	}
 
 	@Test
 	public void testShallowFetchShallowAncestorDepth2() throws Exception {
 		try (FileRepository repo = setupRepoForShallowFetch()) {
 			PackIndex idx = writeShallowPack(repo, 2, wants(c5), NONE, NONE);
 			assertContent(idx,
 					Arrays.asList(c4.getId(), c5.getId(), c4.getTree().getId(),
 							c5.getTree().getId(), contentA.getId(),
 							contentB.getId(), contentC.getId(),
 							contentD.getId(), contentE.getId()));
 
 			idx = writeShallowPack(repo, 2, wants(c2), haves(c4, c5),
 					shallows(c4));
 			assertContent(idx, Arrays.asList(c1.getId(), c2.getId(),
 					c1.getTree().getId(), c2.getTree().getId()));
 		}
 	}
 
 	private FileRepository setupRepoForShallowFetch() throws Exception {
 		FileRepository repo = createBareRepository();
 		// TestRepository will close the repo, but we need to return an open
 		// one!
 		repo.incrementOpen();
 		try (TestRepository<Repository> r = new TestRepository<>(repo)) {
 			BranchBuilder bb = r.branch("refs/heads/master");
 			contentA = r.blob("A");
 			contentB = r.blob("B");
 			contentC = r.blob("C");
 			contentD = r.blob("D");
 			contentE = r.blob("E");
 			c1 = bb.commit().add("a", contentA).create();
 			c2 = bb.commit().add("b", contentB).create();
 			c3 = bb.commit().add("c", contentC).create();
 			c4 = bb.commit().add("d", contentD).create();
 			c5 = bb.commit().add("e", contentE).create();
 			r.getRevWalk().parseHeaders(c5); // fully initialize the tip RevCommit
 			return repo;
 		}
 	}
 
 	private static PackIndex writePack(FileRepository repo,
 			Set<? extends ObjectId> want, Set<ObjectIdSet> excludeObjects)
 					throws IOException {
 		try (RevWalk walk = new RevWalk(repo)) {
 			return writePack(repo, walk, 0, want, NONE, excludeObjects);
 		}
 	}
 
 	private static PackIndex writeShallowPack(FileRepository repo, int depth,
 			Set<? extends ObjectId> want, Set<? extends ObjectId> have,
 			Set<? extends ObjectId> shallow) throws IOException {
 		// During negotiation, UploadPack would have set up a DepthWalk and
 		// marked the client's "shallow" commits. Emulate that here.
 		try (DepthWalk.RevWalk walk = new DepthWalk.RevWalk(repo, depth - 1)) {
 			walk.assumeShallow(shallow);
 			return writePack(repo, walk, depth, want, have, EMPTY_ID_SET);
 		}
 	}
 
 	private static PackIndex writePack(FileRepository repo, RevWalk walk,
 			int depth, Set<? extends ObjectId> want,
 			Set<? extends ObjectId> have, Set<ObjectIdSet> excludeObjects)
 					throws IOException {
 		try (PackWriter pw = new PackWriter(repo)) {
 			pw.setDeltaBaseAsOffset(true);
 			pw.setReuseDeltaCommits(false);
 			for (ObjectIdSet idx : excludeObjects) {
 				pw.excludeObjects(idx);
 			}
 			if (depth > 0) {
 				pw.setShallowPack(depth, null);
 			}
 			// ow doesn't need to be closed; caller closes walk.
 			ObjectWalk ow = walk.toObjectWalkWithSameObjects();
 
 			pw.preparePack(NullProgressMonitor.INSTANCE, ow, want, have, NONE);
 			String id = pw.computeName().getName();
 			File packdir = repo.getObjectDatabase().getPackDirectory();
 			File packFile = new File(packdir, "pack-" + id + ".pack");
 			try (FileOutputStream packOS = new FileOutputStream(packFile)) {
 				pw.writePack(NullProgressMonitor.INSTANCE,
 						NullProgressMonitor.INSTANCE, packOS);
 			}
 			File idxFile = new File(packdir, "pack-" + id + ".idx");
 			try (FileOutputStream idxOS = new FileOutputStream(idxFile)) {
 				pw.writeIndex(idxOS);
 			}
 			return PackIndex.open(idxFile);
 		}
 	}
 
 	// TODO: testWritePackDeltasCycle()
 	// TODO: testWritePackDeltasDepth()
 
 	private void writeVerifyPack1() throws IOException {
 		final HashSet<ObjectId> interestings = new HashSet<>();
 		interestings.add(ObjectId
 				.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"));
 		createVerifyOpenPack(interestings, NONE, false, false);
 
 		final ObjectId expectedOrder[] = new ObjectId[] {
 				ObjectId.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"),
 				ObjectId.fromString("c59759f143fb1fe21c197981df75a7ee00290799"),
 				ObjectId.fromString("540a36d136cf413e4b064c2b0e0a4db60f77feab"),
 				ObjectId.fromString("aabf2ffaec9b497f0950352b3e582d73035c2035"),
 				ObjectId.fromString("902d5476fa249b7abc9d84c611577a81381f0327"),
 				ObjectId.fromString("4b825dc642cb6eb9a060e54bf8d69288fbee4904"),
 				ObjectId.fromString("6ff87c4664981e4397625791c8ea3bbb5f2279a3"),
 				ObjectId.fromString("5b6e7c66c276e7610d4a73c70ec1a1f7c1003259") };
 
 		assertEquals(expectedOrder.length, writer.getObjectCount());
 		verifyObjectsOrder(expectedOrder);
 		assertEquals("34be9032ac282b11fa9babdc2b2a93ca996c9c2f", writer
 				.computeName().name());
 	}
 
 	private void writeVerifyPack2(boolean deltaReuse) throws IOException {
 		config.setReuseDeltas(deltaReuse);
 		final HashSet<ObjectId> interestings = new HashSet<>();
 		interestings.add(ObjectId
 				.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"));
 		final HashSet<ObjectId> uninterestings = new HashSet<>();
 		uninterestings.add(ObjectId
 				.fromString("540a36d136cf413e4b064c2b0e0a4db60f77feab"));
 		createVerifyOpenPack(interestings, uninterestings, false, false);
 
 		final ObjectId expectedOrder[] = new ObjectId[] {
 				ObjectId.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"),
 				ObjectId.fromString("c59759f143fb1fe21c197981df75a7ee00290799"),
 				ObjectId.fromString("aabf2ffaec9b497f0950352b3e582d73035c2035"),
 				ObjectId.fromString("902d5476fa249b7abc9d84c611577a81381f0327"),
 				ObjectId.fromString("6ff87c4664981e4397625791c8ea3bbb5f2279a3") ,
 				ObjectId.fromString("5b6e7c66c276e7610d4a73c70ec1a1f7c1003259") };
 		if (!config.isReuseDeltas() && !config.isDeltaCompress()) {
 			// If no deltas are in the file the final two entries swap places.
 			swap(expectedOrder, 4, 5);
 		}
 		assertEquals(expectedOrder.length, writer.getObjectCount());
 		verifyObjectsOrder(expectedOrder);
 		assertEquals("ed3f96b8327c7c66b0f8f70056129f0769323d86", writer
 				.computeName().name());
 	}
 
 	private static void swap(ObjectId[] arr, int a, int b) {
 		ObjectId tmp = arr[a];
 		arr[a] = arr[b];
 		arr[b] = tmp;
 	}
 
 	private void writeVerifyPack4(final boolean thin) throws IOException {
 		final HashSet<ObjectId> interestings = new HashSet<>();
 		interestings.add(ObjectId
 				.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"));
 		final HashSet<ObjectId> uninterestings = new HashSet<>();
 		uninterestings.add(ObjectId
 				.fromString("c59759f143fb1fe21c197981df75a7ee00290799"));
 		createVerifyOpenPack(interestings, uninterestings, thin, false);
 
 		final ObjectId writtenObjects[] = new ObjectId[] {
 				ObjectId.fromString("82c6b885ff600be425b4ea96dee75dca255b69e7"),
 				ObjectId.fromString("aabf2ffaec9b497f0950352b3e582d73035c2035"),
 				ObjectId.fromString("5b6e7c66c276e7610d4a73c70ec1a1f7c1003259") };
 		assertEquals(writtenObjects.length, writer.getObjectCount());
 		ObjectId expectedObjects[];
 		if (thin) {
 			expectedObjects = new ObjectId[4];
 			System.arraycopy(writtenObjects, 0, expectedObjects, 0,
 					writtenObjects.length);
 			expectedObjects[3] = ObjectId
 					.fromString("6ff87c4664981e4397625791c8ea3bbb5f2279a3");
 
 		} else {
 			expectedObjects = writtenObjects;
 		}
 		verifyObjectsOrder(expectedObjects);
 		assertEquals("cded4b74176b4456afa456768b2b5aafb41c44fc", writer
 				.computeName().name());
 	}
 
 	private void createVerifyOpenPack(final Set<ObjectId> interestings,
 			final Set<ObjectId> uninterestings, final boolean thin,
 			final boolean ignoreMissingUninteresting)
 			throws MissingObjectException, IOException {
 		createVerifyOpenPack(interestings, uninterestings, thin,
 				ignoreMissingUninteresting, false);
 	}
 
 	private void createVerifyOpenPack(final Set<ObjectId> interestings,
 			final Set<ObjectId> uninterestings, final boolean thin,
 			final boolean ignoreMissingUninteresting, boolean useBitmaps)
 			throws MissingObjectException, IOException {
 		NullProgressMonitor m = NullProgressMonitor.INSTANCE;
 		writer = new PackWriter(config, db.newObjectReader());
 		writer.setUseBitmaps(useBitmaps);
 		writer.setThin(thin);
 		writer.setIgnoreMissingUninteresting(ignoreMissingUninteresting);
 		writer.preparePack(m, interestings, uninterestings);
 		writer.writePack(m, m, os);
 		writer.close();
 		verifyOpenPack(thin);
 	}
 
 	private void createVerifyOpenPack(List<RevObject> objectSource)
 			throws MissingObjectException, IOException {
 		NullProgressMonitor m = NullProgressMonitor.INSTANCE;
 		writer = new PackWriter(config, db.newObjectReader());
 		writer.preparePack(objectSource.iterator());
 		assertEquals(objectSource.size(), writer.getObjectCount());
 		writer.writePack(m, m, os);
 		writer.close();
 		verifyOpenPack(false);
 	}
 
 	private void verifyOpenPack(boolean thin) throws IOException {
 		final byte[] packData = os.toByteArray();
 
 		if (thin) {
 			PackParser p = index(packData);
 			try {
 				p.parse(NullProgressMonitor.INSTANCE);
 				fail("indexer should grumble about missing object");
 			} catch (IOException x) {
 				// expected
 			}
 		}
 
 		ObjectDirectoryPackParser p = (ObjectDirectoryPackParser) index(packData);
 		p.setKeepEmpty(true);
 		p.setAllowThin(thin);
 		p.setIndexVersion(2);
 		p.parse(NullProgressMonitor.INSTANCE);
 		pack = p.getPackFile();
 		assertNotNull("have PackFile after parsing", pack);
 	}
 
 	private PackParser index(byte[] packData) throws IOException {
 		if (inserter == null)
 			inserter = dst.newObjectInserter();
 		return inserter.newPackParser(new ByteArrayInputStream(packData));
 	}
 
 	private void verifyObjectsOrder(ObjectId objectsOrder[]) {
 		final List<PackIndex.MutableEntry> entries = new ArrayList<>();
 
 		for (MutableEntry me : pack) {
 			entries.add(me.cloneEntry());
 		}
 		Collections.sort(entries, (MutableEntry o1, MutableEntry o2) -> Long
 				.signum(o1.getOffset() - o2.getOffset()));
 
 		int i = 0;
 		for (MutableEntry me : entries) {
 			assertEquals(objectsOrder[i++].toObjectId(), me.toObjectId());
 		}
 	}
 
 	private static Set<ObjectId> haves(ObjectId... objects) {
 		return Sets.of(objects);
 	}
 
 	private static Set<ObjectId> wants(ObjectId... objects) {
 		return Sets.of(objects);
 	}
 
 	private static Set<ObjectId> shallows(ObjectId... objects) {
 		return Sets.of(objects);
 	}
 }