/*
    * Copyright (C) 2015, 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.internal.storage.pack;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.io.IOException;
  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.internal.storage.file.GcTestCase;
  import org.eclipse.jgit.internal.storage.file.PackBitmapIndexBuilder;
  import org.eclipse.jgit.junit.TestRepository.BranchBuilder;
  import org.eclipse.jgit.junit.TestRepository.CommitBuilder;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.storage.pack.PackConfig;
  import org.junit.Test;
  
  public class GcCommitSelectionTest extends GcTestCase {
  
  	@Test
  	public void testBitmapSpansNoMerges() throws Exception {
  		testBitmapSpansNoMerges(false);
  	}
  
  	@Test
  	public void testBitmapSpansNoMergesWithTags() throws Exception {
  		testBitmapSpansNoMerges(true);
  	}
  
  	private void testBitmapSpansNoMerges(boolean withTags) throws Exception {
  		/*
  		 * Commit counts -> expected bitmap counts for history without merges.
  		 * The top 100 contiguous commits should always have bitmaps, and the
  		 * "recent" bitmaps beyond that are spaced out every 100-200 commits.
  		 * (Starting at 100, the next 100 commits are searched for a merge
  		 * commit. Since one is not found, the spacing between commits is 200.
  		 */
  		int[][] bitmapCounts = { //
  				{ 1, 1 }, { 50, 50 }, { 99, 99 }, { 100, 100 }, { 101, 100 },
  				{ 200, 100 }, { 201, 100 }, { 299, 100 }, { 300, 101 },
  				{ 301, 101 }, { 401, 101 }, { 499, 101 }, { 500, 102 }, };
  		int currentCommits = 0;
  		BranchBuilder bb = tr.branch("refs/heads/main");
  
  		for (int[] counts : bitmapCounts) {
  			int nextCommitCount = counts[0];
  			int expectedBitmapCount = counts[1];
  			assertTrue(nextCommitCount > currentCommits); // programming error
  			for (int i = currentCommits; i < nextCommitCount; i++) {
  				String str = "A" + i;
  				RevCommit rc = bb.commit().message(str).add(str, str).create();
  				if (withTags) {
  					tr.lightweightTag(str, rc);
  				}
  			}
  			currentCommits = nextCommitCount;
  
  			gc.setPackExpireAgeMillis(0); // immediately delete old packs
  			gc.setExpireAgeMillis(0);
  			gc.gc().get();
  			assertEquals(currentCommits * 3, // commit/tree/object
  					gc.getStatistics().numberOfPackedObjects);
  			assertEquals(currentCommits + " commits: ", expectedBitmapCount,
  					gc.getStatistics().numberOfBitmaps);
  		}
  	}
  
  	@Test
  	public void testBitmapSpansWithMerges() throws Exception {
  		/*
  		 * Commits that are merged. Since 55 is in the oldest history it is
  		 * never considered. Searching goes from oldest to newest so 115 is the
  		 * first merge commit found. After that the range 116-216 is ignored so
  		 * 175 is never considered.
  		 */
  		List<Integer> merges = Arrays.asList(Integer.valueOf(55),
  				Integer.valueOf(115), Integer.valueOf(175),
  				Integer.valueOf(235));
  		/*
  		 * Commit counts -> expected bitmap counts for history with merges. The
  		 * top 100 contiguous commits should always have bitmaps, and the
  		 * "recent" bitmaps beyond that are spaced out every 100-200 commits.
 		 * Merges in the < 100 range have no effect and merges in the > 100
 		 * range will only be considered for commit counts > 200.
 		 */
 		int[][] bitmapCounts = { //
 				{ 1, 1 }, { 55, 55 }, { 56, 57 }, // +1 bitmap from branch A55
 				{ 99, 100 }, // still +1 branch @55
 				{ 100, 100 }, // 101 commits, only 100 newest
 				{ 116, 100 }, // @55 still in 100 newest bitmaps
 				{ 176, 101 }, // @55 branch tip is not in 100 newest
 				{ 213, 101 }, // 216 commits, @115&@175 in 100 newest
 				{ 214, 102 }, // @55 branch tip, merge @115, @177 in newest
 				{ 236, 102 }, // all 4 merge points in history
 				{ 273, 102 }, // 277 commits, @175&@235 in newest
 				{ 274, 103 }, // @55, @115, merge @175, @235 in newest
 				{ 334, 103 }, // @55,@115,@175, @235 in newest
 				{ 335, 104 }, // @55,@115,@175, merge @235
 				{ 435, 104 }, // @55,@115,@175,@235 tips
 				{ 436, 104 }, // force @236
 		};
 
 		int currentCommits = 0;
 		BranchBuilder bb = tr.branch("refs/heads/main");
 
 		for (int[] counts : bitmapCounts) {
 			int nextCommitCount = counts[0];
 			int expectedBitmapCount = counts[1];
 			assertTrue(nextCommitCount > currentCommits); // programming error
 			for (int i = currentCommits; i < nextCommitCount; i++) {
 				String str = "A" + i;
 				if (!merges.contains(Integer.valueOf(i))) {
 					bb.commit().message(str).add(str, str).create();
 				} else {
 					BranchBuilder bbN = tr.branch("refs/heads/A" + i);
 					bb.commit().message(str).add(str, str)
 							.parent(bbN.commit().create()).create();
 				}
 			}
 			currentCommits = nextCommitCount;
 
 			gc.setPackExpireAgeMillis(0); // immediately delete old packs
 			gc.setExpireAgeMillis(0);
 			gc.gc().get();
 			assertEquals(currentCommits + " commits: ", expectedBitmapCount,
 					gc.getStatistics().numberOfBitmaps);
 		}
 	}
 
 	@Test
 	public void testBitmapsForExcessiveBranches() throws Exception {
 		int oneDayInSeconds = 60 * 60 * 24;
 
 		// All of branch A is committed on day1
 		BranchBuilder bbA = tr.branch("refs/heads/A");
 		for (int i = 0; i < 1001; i++) {
 			String msg = "A" + i;
 			bbA.commit().message(msg).add(msg, msg).create();
 		}
 		// All of in branch B is committed on day91
 		tr.tick(oneDayInSeconds * 90);
 		BranchBuilder bbB = tr.branch("refs/heads/B");
 		for (int i = 0; i < 1001; i++) {
 			String msg = "B" + i;
 			bbB.commit().message(msg).add(msg, msg).create();
 		}
 		// Create 100 other branches with a single commit
 		for (int i = 0; i < 100; i++) {
 			BranchBuilder bb = tr.branch("refs/heads/N" + i);
 			String msg = "singlecommit" + i;
 			bb.commit().message(msg).add(msg, msg).create();
 		}
 		// now is day92
 		tr.tick(oneDayInSeconds);
 
 		// Since there are no merges, commits in recent history are selected
 		// every 200 commits.
 		final int commitsForSparseBranch = 1 + (1001 / 200);
 		final int commitsForFullBranch = 100 + (901 / 200);
 		final int commitsForShallowBranches = 100;
 
 		// Excessive branch history pruning, one old branch.
 		gc.setPackExpireAgeMillis(0); // immediately delete old packs
 		gc.setExpireAgeMillis(0);
 		gc.gc().get();
 		assertEquals(
 				commitsForSparseBranch + commitsForFullBranch
 						+ commitsForShallowBranches,
 				gc.getStatistics().numberOfBitmaps);
 	}
 
 	@Test
 	public void testSelectionOrderingWithChains() throws Exception {
 		/*-
 		 * Create a history like this, where 'N' is the number of seconds from
 		 * the first commit in the branch:
 		 *
 		 *      ---o---o---o        commits b3,b5,b7
 		 *     /            \
 		 * o--o--o---o---o---o--o   commits m0,m1,m2,m4,m6,m8,m9
 		 */
 		BranchBuilder bb = tr.branch("refs/heads/main");
 		RevCommit m0 = addCommit(bb, "m0");
 		RevCommit m1 = addCommit(bb, "m1", m0);
 		RevCommit m2 = addCommit(bb, "m2", m1);
 		RevCommit b3 = addCommit(bb, "b3", m1);
 		RevCommit m4 = addCommit(bb, "m4", m2);
 		RevCommit b5 = addCommit(bb, "m5", b3);
 		RevCommit m6 = addCommit(bb, "m6", m4);
 		RevCommit b7 = addCommit(bb, "m7", b5);
 		RevCommit m8 = addCommit(bb, "m8", m6, b7);
 		RevCommit m9 = addCommit(bb, "m9", m8);
 
 		List<RevCommit> commits = Arrays.asList(m0, m1, m2, b3, m4, b5, m6, b7,
 				m8, m9);
 		PackWriterBitmapPreparer preparer = newPreparer(
 				Collections.singleton(m9), commits, new PackConfig());
 		List<BitmapCommit> selection = new ArrayList<>(
 				preparer.selectCommits(commits.size(), PackWriter.NONE));
 
 		// Verify that the output is ordered by the separate "chains"
 		String[] expected = { m0.name(), m1.name(), m2.name(), m4.name(),
 				m6.name(), m8.name(), m9.name(), b3.name(), b5.name(),
 				b7.name() };
 		assertEquals(expected.length, selection.size());
 		for (int i = 0; i < expected.length; i++) {
 			assertEquals("Entry " + i, expected[i], selection.get(i).getName());
 		}
 	}
 
 	private RevCommit addCommit(BranchBuilder bb, String msg,
 			RevCommit... parents) throws Exception {
 		CommitBuilder commit = bb.commit().message(msg).add(msg, msg).tick(1)
 				.noParents();
 		for (RevCommit parent : parents) {
 			commit.parent(parent);
 		}
 		return commit.create();
 	}
 
 	@Test
 	public void testDistributionOnMultipleBranches() throws Exception {
 		BranchBuilder[] branches = { tr.branch("refs/heads/main"),
 				tr.branch("refs/heads/a"), tr.branch("refs/heads/b"),
 				tr.branch("refs/heads/c") };
 		RevCommit[] tips = new RevCommit[branches.length];
 		List<RevCommit> commits = createHistory(branches, tips);
 		PackConfig config = new PackConfig();
 		config.setBitmapContiguousCommitCount(1);
 		config.setBitmapRecentCommitSpan(5);
 		config.setBitmapDistantCommitSpan(20);
 		config.setBitmapRecentCommitCount(100);
 		Set<RevCommit> wants = new HashSet<>(Arrays.asList(tips));
 		PackWriterBitmapPreparer preparer = newPreparer(wants, commits, config);
 		List<BitmapCommit> selection = new ArrayList<>(
 				preparer.selectCommits(commits.size(), PackWriter.NONE));
 		Set<ObjectId> selected = new HashSet<>();
 		for (BitmapCommit c : selection) {
 			selected.add(c.toObjectId());
 		}
 
 		// Verify that each branch has uniform bitmap selection coverage
 		for (RevCommit c : wants) {
 			assertTrue(selected.contains(c.toObjectId()));
 			int count = 1;
 			int selectedCount = 1;
 			RevCommit parent = c;
 			while (parent.getParentCount() != 0) {
 				parent = parent.getParent(0);
 				count++;
 				if (selected.contains(parent.toObjectId())) {
 					selectedCount++;
 				}
 			}
 			// The selection algorithm prefers merges and will look in the
 			// current range plus the recent commit span before selecting a
 			// commit. Since this history has no merges, we expect the recent
 			// span should have 100/10=10 and distant commit spans should have
 			// 100/25=4 per 100 commit range.
 			int expectedCount = 10 + (count - 100 - 24) / 25;
 			assertTrue(expectedCount <= selectedCount);
 		}
 	}
 
 	private List<RevCommit> createHistory(BranchBuilder[] branches,
 			RevCommit[] tips) throws Exception {
 		/*-
 		 * Create a history like this, where branches a, b and c branch off of the main branch
 		 * at commits 100, 200 and 300, and where commit times move forward alternating between
 		 * branches.
 		 *
 		 * o...o...o...o...o      commits root,m0,m1,...,m399
 		 *      \   \   \
 		 *       \   \   o...     commits branch_c,c300,c301,...,c399
 		 *        \   \
 		 *         \   o...o...   commits branch_b,b200,b201,...,b399
 		 *          \
 		 *           o...o...o... commits branch_a,b100,b101,...,a399
 		 */
 		List<RevCommit> commits = new ArrayList<>();
 		String[] prefixes = { "m", "a", "b", "c" };
 		int branchCount = branches.length;
 		tips[0] = addCommit(commits, branches[0], "root");
 		int counter = 0;
 
 		for (int b = 0; b < branchCount; b++) {
 			for (int i = 0; i < 100; i++, counter++) {
 				for (int j = 0; j <= b; j++) {
 					tips[j] = addCommit(commits, branches[j],
 							prefixes[j] + counter);
 				}
 			}
 			// Create a new branch from current value of the master branch
 			if (b < branchCount - 1) {
 				tips[b + 1] = addCommit(branches[b + 1],
 						"branch_" + prefixes[b + 1], tips[0]);
 			}
 		}
 		return commits;
 	}
 
 	private RevCommit addCommit(List<RevCommit> commits, BranchBuilder bb,
 			String msg, RevCommit... parents) throws Exception {
 		CommitBuilder commit = bb.commit().message(msg).add(msg, msg).tick(1);
 		if (parents.length > 0) {
 			commit.noParents();
 			for (RevCommit parent : parents) {
 				commit.parent(parent);
 			}
 		}
 		RevCommit c = commit.create();
 		commits.add(c);
 		return c;
 	}
 
 	private PackWriterBitmapPreparer newPreparer(Set<RevCommit> wants,
 			List<RevCommit> commits, PackConfig config) throws IOException {
 		List<ObjectToPack> objects = new ArrayList<>(commits.size());
 		for (RevCommit commit : commits) {
 			objects.add(new ObjectToPack(commit, Constants.OBJ_COMMIT));
 		}
 		PackBitmapIndexBuilder builder = new PackBitmapIndexBuilder(objects);
 		return new PackWriterBitmapPreparer(
 				tr.getRepository().newObjectReader(), builder,
 				NullProgressMonitor.INSTANCE, wants, config);
 	}
 }