--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hg4j/src/main/java/org/tmatesoft/hg/internal/ChangelogHelper.java	Tue May 10 10:52:53 2011 +0200
@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2011 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import java.util.TreeMap;
+
+import org.tmatesoft.hg.repo.HgChangelog.RawChangeset;
+import org.tmatesoft.hg.repo.HgDataFile;
+import org.tmatesoft.hg.repo.HgInternals;
+import org.tmatesoft.hg.repo.HgRepository;
+import org.tmatesoft.hg.util.Path;
+
+/**
+ *
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class ChangelogHelper {
+	private final int leftBoundary;
+	private final HgRepository repo;
+	private final TreeMap<Integer, RawChangeset> cache = new TreeMap<Integer, RawChangeset>();
+	private String nextCommitAuthor;
+
+	/**
+	 * @param hgRepo
+	 * @param leftBoundaryRevision walker never visits revisions with local numbers less than specified,
+	 * IOW only revisions [leftBoundaryRevision..TIP] are considered.
+	 */
+	public ChangelogHelper(HgRepository hgRepo, int leftBoundaryRevision) {
+		repo = hgRepo;
+		leftBoundary = leftBoundaryRevision;
+	}
+	
+	/**
+	 * @return the repo
+	 */
+	public HgRepository getRepo() {
+		return repo;
+	}
+
+	/**
+	 * Walks changelog in reverse order
+	 * @param file
+	 * @return changeset where specified file is mentioned among affected files, or 
+	 * <code>null</code> if none found up to leftBoundary 
+	 */
+	public RawChangeset findLatestChangeWith(Path file) {
+		HgDataFile df = repo.getFileNode(file);
+		int changelogRev = df.getChangesetLocalRevision(HgRepository.TIP);
+		if (changelogRev >= leftBoundary) {
+			// the method is likely to be invoked for different files, 
+			// while changesets might be the same. Cache 'em not to read too much. 
+			RawChangeset cs = cache.get(changelogRev);
+			if (cs == null) {
+				cs = repo.getChangelog().range(changelogRev, changelogRev).get(0);
+				cache.put(changelogRev, cs);
+			}
+			return cs;
+		}
+		return null;
+	}
+
+	public String getNextCommitUsername() {
+		if (nextCommitAuthor == null) {
+			nextCommitAuthor = new HgInternals(repo).getNextCommitUsername();
+		}
+		return nextCommitAuthor;
+	}
+}