/*
 * Copyright (C) 2011-2013, Chris Aniszczyk <caniszczyk@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.api;

import java.io.IOException;
import java.text.MessageFormat;
import java.util.Collection;
import java.util.LinkedList;

import org.eclipse.jgit.api.errors.CheckoutConflictException;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.api.errors.JGitInternalException;
import org.eclipse.jgit.dircache.DirCache;
import org.eclipse.jgit.dircache.DirCacheBuildIterator;
import org.eclipse.jgit.dircache.DirCacheBuilder;
import org.eclipse.jgit.dircache.DirCacheCheckout;
import org.eclipse.jgit.dircache.DirCacheEntry;
import org.eclipse.jgit.dircache.DirCacheIterator;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefUpdate;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.lib.RepositoryState;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.CanonicalTreeParser;
import org.eclipse.jgit.treewalk.EmptyTreeIterator;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.treewalk.filter.PathFilterGroup;

A class used to execute a Reset command. It has setters for all supported options and arguments of this command and a call() method to finally execute the command. Each instance of this class should only be used for one invocation of the command (means: one call to call()) 
See Also:
Git documentation about Reset/**
 * A class used to execute a {@code Reset} command. It has setters for all
 * supported options and arguments of this command and a {@link #call()} method
 * to finally execute the command. Each instance of this class should only be
 * used for one invocation of the command (means: one call to {@link #call()})
 *
 * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-reset.html"
 *      >Git documentation about Reset</a>
 */
public class ResetCommand extends GitCommand<Ref> {

	
Kind of reset
/**
	 * Kind of reset
	 */
	public enum ResetType {
		
Just change the ref, the index and workdir are not changed.
/**
		 * Just change the ref, the index and workdir are not changed.
		 */
		SOFT,

		
Change the ref and the index, the workdir is not changed.
/**
		 * Change the ref and the index, the workdir is not changed.
		 */
		MIXED,

		
Change the ref, the index and the workdir
/**
		 * Change the ref, the index and the workdir
		 */
		HARD,

		
Resets the index and updates the files in the working tree that are
different between respective commit and HEAD, but keeps those which
are different between the index and working tree
/**
		 * Resets the index and updates the files in the working tree that are
		 * different between respective commit and HEAD, but keeps those which
		 * are different between the index and working tree
		 */
		MERGE, // TODO not implemented yet

		
Change the ref, the index and the workdir that are different between
respective commit and HEAD
/**
		 * Change the ref, the index and the workdir that are different between
		 * respective commit and HEAD
		 */
		KEEP // TODO not implemented yet
	}

	// We need to be able to distinguish whether the caller set the ref
	// explicitly or not, so we apply the default (HEAD) only later.
	private String ref = null;

	private ResetType mode;

	private Collection<String> filepaths = new LinkedList<>();

	private boolean isReflogDisabled;

	private ProgressMonitor monitor = NullProgressMonitor.INSTANCE;

	

Constructor for ResetCommand.

Params:
repo –  the Repository/**
	 * <p>
	 * Constructor for ResetCommand.
	 * </p>
	 *
	 * @param repo
	 *            the {@link org.eclipse.jgit.lib.Repository}
	 */
	public ResetCommand(Repository repo) {
		super(repo);
	}

	
{@inheritDoc}
 Executes the Reset command. Each instance of this class should only be used for one invocation of the command. Don't call this method twice on an instance. /**
	 * {@inheritDoc}
	 * <p>
	 * Executes the {@code Reset} command. Each instance of this class should
	 * only be used for one invocation of the command. Don't call this method
	 * twice on an instance.
	 */
	@Override
	public Ref call() throws GitAPIException, CheckoutConflictException {
		checkCallable();

		try {
			RepositoryState state = repo.getRepositoryState();
			final boolean merging = state.equals(RepositoryState.MERGING)
					|| state.equals(RepositoryState.MERGING_RESOLVED);
			final boolean cherryPicking = state
					.equals(RepositoryState.CHERRY_PICKING)
					|| state.equals(RepositoryState.CHERRY_PICKING_RESOLVED);
			final boolean reverting = state.equals(RepositoryState.REVERTING)
					|| state.equals(RepositoryState.REVERTING_RESOLVED);

			final ObjectId commitId = resolveRefToCommitId();
			// When ref is explicitly specified, it has to resolve
			if (ref != null && commitId == null) {
				// @TODO throw an InvalidRefNameException. We can't do that
				// now because this would break the API
				throw new JGitInternalException(MessageFormat
						.format(JGitText.get().invalidRefName, ref));
			}

			final ObjectId commitTree;
			if (commitId != null)
				commitTree = parseCommit(commitId).getTree();
			else
				commitTree = null;

			if (!filepaths.isEmpty()) {
				// reset [commit] -- paths
				resetIndexForPaths(commitTree);
				setCallable(false);
				return repo.exactRef(Constants.HEAD);
			}

			final Ref result;
			if (commitId != null) {
				// write the ref
				final RefUpdate ru = repo.updateRef(Constants.HEAD);
				ru.setNewObjectId(commitId);

				String refName = Repository.shortenRefName(getRefOrHEAD());
				if (isReflogDisabled) {
					ru.disableRefLog();
				} else {
					String message = refName + ": updating " + Constants.HEAD; //$NON-NLS-1$
					ru.setRefLogMessage(message, false);
				}
				if (ru.forceUpdate() == RefUpdate.Result.LOCK_FAILURE)
					throw new JGitInternalException(MessageFormat.format(
							JGitText.get().cannotLock, ru.getName()));

				ObjectId origHead = ru.getOldObjectId();
				if (origHead != null)
					repo.writeOrigHead(origHead);
			}
			result = repo.exactRef(Constants.HEAD);

			if (mode == null)
				mode = ResetType.MIXED;

			switch (mode) {
				case HARD:
					checkoutIndex(commitTree);
					break;
				case MIXED:
					resetIndex(commitTree);
					break;
				case SOFT: // do nothing, only the ref was changed
					break;
				case KEEP: // TODO
				case MERGE: // TODO
					throw new UnsupportedOperationException();

			}

			if (mode != ResetType.SOFT) {
				if (merging)
					resetMerge();
				else if (cherryPicking)
					resetCherryPick();
				else if (reverting)
					resetRevert();
				else if (repo.readSquashCommitMsg() != null)
					repo.writeSquashCommitMsg(null /* delete */);
			}

			setCallable(false);
			return result;
		} catch (IOException e) {
			throw new JGitInternalException(MessageFormat.format(
					JGitText.get().exceptionCaughtDuringExecutionOfResetCommand,
					e.getMessage()), e);
		}
	}

	private RevCommit parseCommit(ObjectId commitId) {
		try (RevWalk rw = new RevWalk(repo)) {
			return rw.parseCommit(commitId);
		} catch (IOException e) {
			throw new JGitInternalException(MessageFormat.format(
					JGitText.get().cannotReadCommit, commitId.toString()), e);
		}
	}

	private ObjectId resolveRefToCommitId() {
		try {
			return repo.resolve(getRefOrHEAD() + "^{commit}"); //$NON-NLS-1$
		} catch (IOException e) {
			throw new JGitInternalException(
					MessageFormat.format(JGitText.get().cannotRead, getRefOrHEAD()),
					e);
		}
	}

	
Set the name of the Ref to reset to
Params:
ref – 
           the ref to reset to, defaults to HEAD if not specified
Returns:
this instance/**
	 * Set the name of the <code>Ref</code> to reset to
	 *
	 * @param ref
	 *            the ref to reset to, defaults to HEAD if not specified
	 * @return this instance
	 */
	public ResetCommand setRef(String ref) {
		this.ref = ref;
		return this;
	}

	
Set the reset mode
Params:
mode – 
           the mode of the reset command
Returns:
this instance/**
	 * Set the reset mode
	 *
	 * @param mode
	 *            the mode of the reset command
	 * @return this instance
	 */
	public ResetCommand setMode(ResetType mode) {
		if (!filepaths.isEmpty())
			throw new JGitInternalException(MessageFormat.format(
					JGitText.get().illegalCombinationOfArguments,
					"[--mixed | --soft | --hard]", "<paths>...")); //$NON-NLS-1$ //$NON-NLS-2$
		this.mode = mode;
		return this;
	}

	
Repository relative path of file or directory to reset
Params:
path – 
           repository-relative path of file/directory to reset (with
           / as separator)
Returns:
this instance/**
	 * Repository relative path of file or directory to reset
	 *
	 * @param path
	 *            repository-relative path of file/directory to reset (with
	 *            <code>/</code> as separator)
	 * @return this instance
	 */
	public ResetCommand addPath(String path) {
		if (mode != null)
			throw new JGitInternalException(MessageFormat.format(
					JGitText.get().illegalCombinationOfArguments, "<paths>...", //$NON-NLS-1$
					"[--mixed | --soft | --hard]")); //$NON-NLS-1$
		filepaths.add(path);
		return this;
	}

	
Whether to disable reflog
Params:
disable –  if true disables writing a reflog entry for this reset command
Returns:
this instance
Since:
4.5/**
	 * Whether to disable reflog
	 *
	 * @param disable
	 *            if {@code true} disables writing a reflog entry for this reset
	 *            command
	 * @return this instance
	 * @since 4.5
	 */
	public ResetCommand disableRefLog(boolean disable) {
		this.isReflogDisabled = disable;
		return this;
	}

	
Whether reflog is disabled
Returns:
true if writing reflog is disabled for this reset command
Since:
4.5/**
	 * Whether reflog is disabled
	 *
	 * @return {@code true} if writing reflog is disabled for this reset command
	 * @since 4.5
	 */
	public boolean isReflogDisabled() {
		return this.isReflogDisabled;
	}

	private String getRefOrHEAD() {
		if (ref != null)
			return ref;
		else
			return Constants.HEAD;
	}

	
The progress monitor associated with the reset operation. By default,
this is set to NullProgressMonitor
Params:
monitor –  a ProgressMonitor
See Also:
NullProgressMonitor
Returns:
this
Since:
4.11/**
	 * The progress monitor associated with the reset operation. By default,
	 * this is set to <code>NullProgressMonitor</code>
	 *
	 * @see NullProgressMonitor
	 * @param monitor
	 *            a {@link org.eclipse.jgit.lib.ProgressMonitor}
	 * @return {@code this}
	 * @since 4.11
	 */
	public ResetCommand setProgressMonitor(ProgressMonitor monitor) {
		if (monitor == null) {
			monitor = NullProgressMonitor.INSTANCE;
		}
		this.monitor = monitor;
		return this;
	}

	private void resetIndexForPaths(ObjectId commitTree) {
		DirCache dc = null;
		try (TreeWalk tw = new TreeWalk(repo)) {
			dc = repo.lockDirCache();
			DirCacheBuilder builder = dc.builder();

			tw.addTree(new DirCacheBuildIterator(builder));
			if (commitTree != null)
				tw.addTree(commitTree);
			else
				tw.addTree(new EmptyTreeIterator());
			tw.setFilter(PathFilterGroup.createFromStrings(filepaths));
			tw.setRecursive(true);

			while (tw.next()) {
				final CanonicalTreeParser tree = tw.getTree(1,
						CanonicalTreeParser.class);
				// only keep file in index if it's in the commit
				if (tree != null) {
				    // revert index to commit
					DirCacheEntry entry = new DirCacheEntry(tw.getRawPath());
					entry.setFileMode(tree.getEntryFileMode());
					entry.setObjectId(tree.getEntryObjectId());
					builder.add(entry);
				}
			}

			builder.commit();
		} catch (IOException e) {
			throw new RuntimeException(e);
		} finally {
			if (dc != null)
				dc.unlock();
		}
	}

	private void resetIndex(ObjectId commitTree) throws IOException {
		DirCache dc = repo.lockDirCache();
		try (TreeWalk walk = new TreeWalk(repo)) {
			DirCacheBuilder builder = dc.builder();

			if (commitTree != null)
				walk.addTree(commitTree);
			else
				walk.addTree(new EmptyTreeIterator());
			walk.addTree(new DirCacheIterator(dc));
			walk.setRecursive(true);

			while (walk.next()) {
				AbstractTreeIterator cIter = walk.getTree(0,
						AbstractTreeIterator.class);
				if (cIter == null) {
					// Not in commit, don't add to new index
					continue;
				}

				final DirCacheEntry entry = new DirCacheEntry(walk.getRawPath());
				entry.setFileMode(cIter.getEntryFileMode());
				entry.setObjectIdFromRaw(cIter.idBuffer(), cIter.idOffset());

				DirCacheIterator dcIter = walk.getTree(1,
						DirCacheIterator.class);
				if (dcIter != null && dcIter.idEqual(cIter)) {
					DirCacheEntry indexEntry = dcIter.getDirCacheEntry();
					entry.setLastModified(indexEntry.getLastModifiedInstant());
					entry.setLength(indexEntry.getLength());
				}

				builder.add(entry);
			}

			builder.commit();
		} finally {
			dc.unlock();
		}
	}

	private void checkoutIndex(ObjectId commitTree) throws IOException,
			GitAPIException {
		DirCache dc = repo.lockDirCache();
		try {
			DirCacheCheckout checkout = new DirCacheCheckout(repo, dc,
					commitTree);
			checkout.setFailOnConflict(false);
			checkout.setProgressMonitor(monitor);
			try {
				checkout.checkout();
			} catch (org.eclipse.jgit.errors.CheckoutConflictException cce) {
				throw new CheckoutConflictException(checkout.getConflicts(),
						cce);
			}
		} finally {
			dc.unlock();
		}
	}

	private void resetMerge() throws IOException {
		repo.writeMergeHeads(null);
		repo.writeMergeCommitMsg(null);
	}

	private void resetCherryPick() throws IOException {
		repo.writeCherryPickHead(null);
		repo.writeMergeCommitMsg(null);
	}

	private void resetRevert() throws IOException {
		repo.writeRevertHead(null);
		repo.writeMergeCommitMsg(null);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@SuppressWarnings("nls")
	@Override
	public String toString() {
		return "ResetCommand [repo=" + repo + ", ref=" + ref + ", mode=" + mode
				+ ", isReflogDisabled=" + isReflogDisabled + ", filepaths="
				+ filepaths + "]";
	}

}