/*
    * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.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.internal.storage.file;
  
  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.Assume.assumeFalse;
  import static org.junit.Assume.assumeTrue;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.Writer;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.nio.file.StandardCopyOption;
  import java.nio.file.StandardOpenOption;
  //import java.nio.file.attribute.BasicFileAttributes;
  import java.text.ParseException;
  import java.time.Instant;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Random;
  import java.util.zip.Deflater;
  
  import org.eclipse.jgit.api.GarbageCollectCommand;
  import org.eclipse.jgit.api.Git;
  import org.eclipse.jgit.api.errors.AbortedByHookException;
  import org.eclipse.jgit.api.errors.ConcurrentRefUpdateException;
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.NoFilepatternException;
  import org.eclipse.jgit.api.errors.NoHeadException;
  import org.eclipse.jgit.api.errors.NoMessageException;
  import org.eclipse.jgit.api.errors.UnmergedPathsException;
  import org.eclipse.jgit.api.errors.WrongRepositoryStateException;
  import org.eclipse.jgit.junit.RepositoryTestCase;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.ConfigConstants;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.storage.file.FileBasedConfig;
  import org.eclipse.jgit.storage.pack.PackConfig;
  import org.eclipse.jgit.util.FS;
  import org.junit.Test;
  
  public class PackFileSnapshotTest extends RepositoryTestCase {
  
  	private static ObjectId unknownID = ObjectId
  			.fromString("1234567890123456789012345678901234567890");
  
  	@Test
  	public void testSamePackDifferentCompressionDetectChecksumChanged()
  			throws Exception {
  		Git git = Git.wrap(db);
  		File f = writeTrashFile("file", "foobar ");
  		for (int i = 0; i < 10; i++) {
  			appendRandomLine(f);
  			git.add().addFilepattern("file").call();
  			git.commit().setMessage("message" + i).call();
  		}
  
  		FileBasedConfig c = db.getConfig();
  		c.setInt(ConfigConstants.CONFIG_GC_SECTION, null,
  				ConfigConstants.CONFIG_KEY_AUTOPACKLIMIT, 1);
  		c.save();
  		Collection<Pack> packs = gc(Deflater.NO_COMPRESSION);
  		assertEquals("expected 1 packfile after gc", 1, packs.size());
  		Pack p1 = packs.iterator().next();
  		PackFileSnapshot snapshot = p1.getFileSnapshot();
  
  		packs = gc(Deflater.BEST_COMPRESSION);
  		assertEquals("expected 1 packfile after gc", 1, packs.size());
  		Pack p2 = packs.iterator().next();
  		File pf = p2.getPackFile();
  
  		// changing compression level with aggressive gc may change size,
  		// fileKey (on *nix) and checksum. Hence FileSnapshot.isModified can
  		// return true already based on size or fileKey.
  		// So the only thing we can test here is that we ensure that checksum
  		// also changed when we read it here in this test
  		assertTrue("expected snapshot to detect modified pack",
  				snapshot.isModified(pf));
  		assertTrue("expected checksum changed", snapshot.isChecksumChanged(pf));
  	}
  
  	private void appendRandomLine(File f, int length, Random r)
  			throws IOException {
  		try (Writer w = Files.newBufferedWriter(f.toPath(),
  				StandardOpenOption.APPEND)) {
  			appendRandomLine(w, length, r);
 		}
 	}
 
 	private void appendRandomLine(File f) throws IOException {
 		appendRandomLine(f, 5, new Random());
 	}
 
 	private void appendRandomLine(Writer w, int len, Random r)
 			throws IOException {
 		final int c1 = 32; // ' '
 		int c2 = 126; // '~'
 		for (int i = 0; i < len; i++) {
 			w.append((char) (c1 + r.nextInt(1 + c2 - c1)));
 		}
 	}
 
 	private ObjectId createTestRepo(int testDataSeed, int testDataLength)
 			throws IOException, GitAPIException, NoFilepatternException,
 			NoHeadException, NoMessageException, UnmergedPathsException,
 			ConcurrentRefUpdateException, WrongRepositoryStateException,
 			AbortedByHookException {
 		// Create a repo with two commits and one file. Each commit adds
 		// testDataLength number of bytes. Data are random bytes. Since the
 		// seed for the random number generator is specified we will get
 		// the same set of bytes for every run and for every platform
 		Random r = new Random(testDataSeed);
 		Git git = Git.wrap(db);
 		File f = writeTrashFile("file", "foobar ");
 		appendRandomLine(f, testDataLength, r);
 		git.add().addFilepattern("file").call();
 		git.commit().setMessage("message1").call();
 		appendRandomLine(f, testDataLength, r);
 		git.add().addFilepattern("file").call();
 		return git.commit().setMessage("message2").call().getId();
 	}
 
 	// Try repacking so fast that you get two new packs which differ only in
 	// content/chksum but have same name, size and lastmodified.
 	// Since this is done with standard gc (which creates new tmp files and
 	// renames them) the filekeys of the new packfiles differ helping jgit
 	// to detect the fast modification
 	@Test
 	public void testDetectModificationAlthoughSameSizeAndModificationtime()
 			throws Exception {
 		int testDataSeed = 1;
 		int testDataLength = 100;
 		FileBasedConfig config = db.getConfig();
 		// don't use mtime of the parent folder to detect pack file
 		// modification.
 		config.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_KEY_TRUSTFOLDERSTAT, false);
 		config.save();
 
 		createTestRepo(testDataSeed, testDataLength);
 
 		// repack to create initial packfile
 		Pack p = repackAndCheck(5, null, null, null);
 		Path packFilePath = p.getPackFile().toPath();
 		AnyObjectId chk1 = p.getPackChecksum();
 		String name = p.getPackName();
 		Long length = Long.valueOf(p.getPackFile().length());
 		FS fs = db.getFS();
 		Instant m1 = fs.lastModifiedInstant(packFilePath);
 
 		// Wait for a filesystem timer tick to enhance probability the rest of
 		// this test is done before the filesystem timer ticks again.
 		fsTick(packFilePath.toFile());
 
 		// Repack to create packfile with same name, length. Lastmodified and
 		// content and checksum are different since compression level differs
 		AnyObjectId chk2 = repackAndCheck(6, name, length, chk1)
 				.getPackChecksum();
 		Instant m2 = fs.lastModifiedInstant(packFilePath);
 		assumeFalse(m2.equals(m1));
 
 		// Repack to create packfile with same name, length. Lastmodified is
 		// equal to the previous one because we are in the same filesystem timer
 		// slot. Content and its checksum are different
 		AnyObjectId chk3 = repackAndCheck(7, name, length, chk2)
 				.getPackChecksum();
 		Instant m3 = fs.lastModifiedInstant(packFilePath);
 
 		// ask for an unknown git object to force jgit to rescan the list of
 		// available packs. If we would ask for a known objectid then JGit would
 		// skip searching for new/modified packfiles
 		db.getObjectDatabase().has(unknownID);
 		assertEquals(chk3, getSinglePack(db.getObjectDatabase().getPacks())
 				.getPackChecksum());
 		assumeTrue(m3.equals(m2));
 	}
 
 	// Try repacking so fast that we get two new packs which differ only in
 	// content and checksum but have same name, size and lastmodified.
 	// To avoid that JGit detects modification by checking the filekey create
 	// two new packfiles upfront and create copies of them. Then modify the
 	// packfiles in-place by opening them for write and then copying the
 	// content.
 	@Test
 	public void testDetectModificationAlthoughSameSizeAndModificationtimeAndFileKey()
 			throws Exception {
 		int testDataSeed = 1;
 		int testDataLength = 100;
 		FileBasedConfig config = db.getConfig();
 		config.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_KEY_TRUSTFOLDERSTAT, false);
 		config.save();
 
 		createTestRepo(testDataSeed, testDataLength);
 
 		// Repack to create initial packfile. Make a copy of it
 		Pack p = repackAndCheck(5, null, null, null);
 		Path packFilePath = p.getPackFile().toPath();
 		Path fn = packFilePath.getFileName();
 		assertNotNull(fn);
 		String packFileName = fn.toString();
 		Path packFileBasePath = packFilePath
 				.resolveSibling(packFileName.replaceAll(".pack", ""));
 		AnyObjectId chk1 = p.getPackChecksum();
 		String name = p.getPackName();
 		Long length = Long.valueOf(p.getPackFile().length());
 		copyPack(packFileBasePath, "", ".copy1");
 
 		// Repack to create second packfile. Make a copy of it
 		AnyObjectId chk2 = repackAndCheck(6, name, length, chk1)
 				.getPackChecksum();
 		copyPack(packFileBasePath, "", ".copy2");
 
 		// Repack to create third packfile
 		AnyObjectId chk3 = repackAndCheck(7, name, length, chk2)
 				.getPackChecksum();
 		FS fs = db.getFS();
 		Instant m3 = fs.lastModifiedInstant(packFilePath);
 		db.getObjectDatabase().has(unknownID);
 		assertEquals(chk3, getSinglePack(db.getObjectDatabase().getPacks())
 				.getPackChecksum());
 
 		// Wait for a filesystem timer tick to enhance probability the rest of
 		// this test is done before the filesystem timer ticks.
 		fsTick(packFilePath.toFile());
 
 		// Copy copy2 to packfile data to force modification of packfile without
 		// changing the packfile's filekey.
 		copyPack(packFileBasePath, ".copy2", "");
 		Instant m2 = fs.lastModifiedInstant(packFilePath);
 		assumeFalse(m3.equals(m2));
 
 		db.getObjectDatabase().has(unknownID);
 		assertEquals(chk2, getSinglePack(db.getObjectDatabase().getPacks())
 				.getPackChecksum());
 
 		// Copy copy2 to packfile data to force modification of packfile without
 		// changing the packfile's filekey.
 		copyPack(packFileBasePath, ".copy1", "");
 		Instant m1 = fs.lastModifiedInstant(packFilePath);
 		assumeTrue(m2.equals(m1));
 		db.getObjectDatabase().has(unknownID);
 		assertEquals(chk1, getSinglePack(db.getObjectDatabase().getPacks())
 				.getPackChecksum());
 	}
 
 	// Copy file from src to dst but avoid creating a new File (with new
 	// FileKey) if dst already exists
 	private Path copyFile(Path src, Path dst) throws IOException {
 		if (Files.exists(dst)) {
 			dst.toFile().setWritable(true);
 			try (OutputStream dstOut = Files.newOutputStream(dst)) {
 				Files.copy(src, dstOut);
 				return dst;
 			}
 		}
 		return Files.copy(src, dst, StandardCopyOption.REPLACE_EXISTING);
 	}
 
 	private Path copyPack(Path base, String srcSuffix, String dstSuffix)
 			throws IOException {
 		copyFile(Paths.get(base + ".idx" + srcSuffix),
 				Paths.get(base + ".idx" + dstSuffix));
 		copyFile(Paths.get(base + ".bitmap" + srcSuffix),
 				Paths.get(base + ".bitmap" + dstSuffix));
 		return copyFile(Paths.get(base + ".pack" + srcSuffix),
 				Paths.get(base + ".pack" + dstSuffix));
 	}
 
 	private Pack repackAndCheck(int compressionLevel, String oldName,
 			Long oldLength, AnyObjectId oldChkSum)
 			throws IOException, ParseException {
 		Pack p = getSinglePack(gc(compressionLevel));
 		File pf = p.getPackFile();
 		// The following two assumptions should not cause the test to fail. If
 		// on a certain platform we get packfiles (containing the same git
 		// objects) where the lengths differ or the checksums don't differ we
 		// just skip this test. A reason for that could be that compression
 		// works differently or random number generator works differently. Then
 		// we have to search for more consistent test data or checkin these
 		// packfiles as test resources
 		assumeTrue(oldLength == null || pf.length() == oldLength.longValue());
 		assumeTrue(oldChkSum == null || !p.getPackChecksum().equals(oldChkSum));
 		assertTrue(oldName == null || p.getPackName().equals(oldName));
 		return p;
 	}
 
 	private Pack getSinglePack(Collection<Pack> packs) {
 		Iterator<Pack> pIt = packs.iterator();
 		Pack p = pIt.next();
 		assertFalse(pIt.hasNext());
 		return p;
 	}
 
 	private Collection<Pack> gc(int compressionLevel)
 			throws IOException, ParseException {
 		GC gc = new GC(db);
 		PackConfig pc = new PackConfig(db.getConfig());
 		pc.setCompressionLevel(compressionLevel);
 
 		pc.setSinglePack(true);
 
 		// --aggressive
 		pc.setDeltaSearchWindowSize(
 				GarbageCollectCommand.DEFAULT_GC_AGGRESSIVE_WINDOW);
 		pc.setMaxDeltaDepth(GarbageCollectCommand.DEFAULT_GC_AGGRESSIVE_DEPTH);
 		pc.setReuseObjects(false);
 
 		gc.setPackConfig(pc);
 		gc.setExpireAgeMillis(0);
 		gc.setPackExpireAgeMillis(0);
 		return gc.gc();
 	}
 
 }