--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/core/HgChangesetFileSneaker.java	Thu Mar 22 20:14:06 2012 +0100
@@ -0,0 +1,219 @@
+/*
+ * Copyright (c) 2011-2012 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.core;
+
+import org.tmatesoft.hg.internal.ManifestRevision;
+import org.tmatesoft.hg.repo.HgDataFile;
+import org.tmatesoft.hg.repo.HgManifest;
+import org.tmatesoft.hg.repo.HgRepository;
+import org.tmatesoft.hg.util.Path;
+import org.tmatesoft.hg.util.Status;
+
+/**
+ * Primary purpose is to provide information about file revisions at specific changeset. Multiple {@link #check(Path)} calls 
+ * are possible once {@link #changeset(Nodeid)} (and optionally, {@link #followRenames(boolean)}) were set.
+ * 
+ * <p>Sample:
+ * <pre><code>
+ *   HgChangesetFileSneaker i = new HgChangesetFileSneaker(hgRepo).changeset(Nodeid.fromString("<40 digits>")).followRenames(true);
+ *   if (i.check(file)) {
+ *   	HgCatCommand catCmd = new HgCatCommand(hgRepo).revision(i.getFileRevision());
+ *   	catCmd.execute(...);
+ *   	...
+ *   }
+ * </pre></code>
+ *
+ * TODO may add #manifest(Nodeid) to select manifest according to its revision (not only changeset revision as it's now)
+ * 
+ * <p>Unlike {@link HgManifest#getFileRevision(int, Path)}, this class is useful when few files from the same changeset have to be inspected
+ * 
+ * @see HgManifest#getFileRevision(int, Path)
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+public class HgChangesetFileSneaker {// TODO mark final once HgFileInformer gone
+
+	private final HgRepository repo;
+	private boolean followRenames;
+	private Nodeid cset;
+	private ManifestRevision cachedManifest;
+	private HgFileRevision fileRevision;
+	private boolean renamed;
+	private Status checkResult;
+
+	public HgChangesetFileSneaker(HgRepository hgRepo) {
+		repo = hgRepo;
+	}
+
+	/**
+	 * Select specific changelog revision
+	 * 
+	 * @param nid changeset identifier
+	 * @return <code>this</code> for convenience
+	 */
+	public HgChangesetFileSneaker changeset(Nodeid nid) {
+		if (nid == null || nid.isNull()) {
+			throw new IllegalArgumentException(); 
+		}
+		cset = nid;
+		cachedManifest = null;
+		fileRevision = null;
+		return this;
+	}
+
+	/**
+	 * Whether to check file origins, default is false (look up only the name supplied)
+	 *
+	 * @param follow <code>true</code> to check copy/rename origin of the file if it is a copy.
+	 * @return <code>this</code> for convenience
+	 */
+	public HgChangesetFileSneaker followRenames(boolean follow) {
+		followRenames = follow;
+		fileRevision = null;
+		return this;
+	}
+
+	/**
+	 * Shortcut to perform {@link #check(Path)} and {@link #exists()}. Result of the check may be accessed via {@link #getCheckStatus()}.
+	 * 
+	 * @param file name of the file in question
+	 * @return <code>true</code> if file is known at the selected changeset.
+	 * @throws IllegalArgumentException if {@link #changeset(Nodeid)} not specified or file argument is bad.
+	 * @throws HgInvalidControlFileException if access to revlog index/data entry failed
+	 */
+	public boolean checkExists(Path file) throws HgInvalidControlFileException {
+		check(file);
+		if (!checkResult.isOk() && checkResult.getException() instanceof HgInvalidControlFileException) {
+			throw (HgInvalidControlFileException) checkResult.getException();
+		}
+		return checkResult.isOk() && exists();
+	}
+
+	/**
+	 * Find file (or its origin, if {@link #followRenames(boolean)} was set to <code>true</code>) among files known at specified {@link #changeset(Nodeid)}.
+	 * 
+	 * @param file name of the file in question
+	 * @return status object that describes outcome, {@link Status#isOk() Ok} status indicates successful completion of the operation, but doesn't imply
+	 * file existence, use {@link #exists()} for that purpose. Message of the status may provide further hints on what exactly had happened. 
+	 * @throws IllegalArgumentException if {@link #changeset(Nodeid)} not specified or file argument is bad.
+	 */
+	public Status check(Path file) {
+		fileRevision = null;
+		checkResult = null;
+		renamed = false;
+		if (cset == null || file == null || file.isDirectory()) {
+			throw new IllegalArgumentException();
+		}
+		HgDataFile dataFile = repo.getFileNode(file);
+		if (!dataFile.exists()) {
+			checkResult = new Status(Status.Kind.OK, String.format("File named %s is not known in the repository", file));
+			return checkResult;
+		}
+		Nodeid toExtract = null;
+		HgManifest.Flags extractRevFlags = null;
+		String phaseMsg = "Extract manifest revision failed";
+		try {
+			if (cachedManifest == null) {
+				int csetRev = repo.getChangelog().getRevisionIndex(cset);
+				cachedManifest = new ManifestRevision(null, null); // XXX how about context and cached manifest revisions
+				repo.getManifest().walk(csetRev, csetRev, cachedManifest);
+				// cachedManifest shall be meaningful - changelog.getRevisionIndex() above ensures we've got version that exists.
+			}
+			toExtract = cachedManifest.nodeid(file);
+			extractRevFlags = cachedManifest.flags(file);
+			phaseMsg = "Follow copy/rename failed";
+			if (toExtract == null && followRenames) {
+				while (toExtract == null && dataFile.isCopy()) {
+					renamed = true;
+					file = dataFile.getCopySourceName();
+					dataFile = repo.getFileNode(file);
+					toExtract = cachedManifest.nodeid(file);
+					extractRevFlags = cachedManifest.flags(file);
+				}
+			}
+		} catch (HgException ex) {
+			checkResult = new Status(Status.Kind.ERROR, phaseMsg, ex);
+			return checkResult;
+		}
+		if (toExtract != null) {
+			fileRevision = new HgFileRevision(repo, toExtract, extractRevFlags, dataFile.getPath());
+			checkResult = new Status(Status.Kind.OK, String.format("File %s, revision %s found at changeset %s", dataFile.getPath(), toExtract.shortNotation(), cset.shortNotation()));
+			return checkResult;
+		} 
+		checkResult = new Status(Status.Kind.OK, String.format("File %s nor its origins were known at repository %s revision", file, cset.shortNotation()));
+		return checkResult;
+	}
+	
+	/**
+	 * Re-get latest check status object
+	 */
+	public Status getCheckStatus() {
+		assertCheckRan();
+		return checkResult;
+	}
+	
+	/**
+	 * @return result of the last {@link #check(Path)} call.
+	 */
+	public boolean exists() {
+		assertCheckRan();
+		return fileRevision != null;
+	}
+	
+	/**
+	 * @return <code>true</code> if checked file was known by another name at the time of specified changeset.
+	 */
+	public boolean hasAnotherName() {
+		assertCheckRan();
+		return renamed;
+	}
+
+	/**
+	 * @return holder for file revision information
+	 */
+	public HgFileRevision getFileRevision() {
+		assertCheckRan();
+		return fileRevision;
+	}
+
+	/**
+	 * Name of the checked file as it was known at the time of the specified changeset.
+	 * 
+	 * @return handy shortcut for <code>getFileRevision().getPath()</code>
+	 */
+	public Path filename() {
+		assertCheckRan();
+		return fileRevision.getPath();
+	}
+	
+	/**
+	 * Revision of the checked file
+	 * 
+	 * @return handy shortcut for <code>getFileRevision().getRevision()</code>
+	 */
+	public Nodeid revision() {
+		assertCheckRan();
+		return fileRevision.getRevision();
+	}
+
+	private void assertCheckRan() {
+		if (checkResult == null) {
+			throw new HgBadStateException("Shall invoke #check(Path) first");
+		}
+	}
+
+}