/*
    * Copyright (C) 2011-2013, Chris Aniszczyk <caniszczyk@gmail.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.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 {@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
  	 */
  	public enum ResetType {
  		/**
  		 * Just change the ref, the index and workdir are not changed.
  		 */
  		SOFT,
  
  		/**
  		 * Change the ref and the index, the workdir is not changed.
  		 */
  		MIXED,
  
  		/**
  		 * 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
  		 */
  		MERGE, // TODO not implemented yet
  
  		/**
  		 * 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;
  
  	/**
 	 * <p>
 	 * Constructor for ResetCommand.
 	 * </p>
 	 *
 	 * @param repo
 	 *            the {@link org.eclipse.jgit.lib.Repository}
 	 */
 	public ResetCommand(Repository repo) {
 		super(repo);
 	}
 
 	/**
 	 * {@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 <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
 	 *
 	 * @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
 	 *
 	 * @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
 	 *
 	 * @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
 	 *
 	 * @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;
 		}
 		return Constants.HEAD;
 	}
 
 	/**
 	 * 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} */
 	@SuppressWarnings("nls")
 	@Override
 	public String toString() {
 		return "ResetCommand [repo=" + repo + ", ref=" + ref + ", mode=" + mode
 				+ ", isReflogDisabled=" + isReflogDisabled + ", filepaths="
 				+ filepaths + "]";
 	}
 
 }