/*
    * Copyright (C) 2012, 2021 GitHub 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.api;
  
  import static org.eclipse.jgit.treewalk.TreeWalk.OperationType.CHECKOUT_OP;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.InvalidRefNameException;
  import org.eclipse.jgit.api.errors.JGitInternalException;
  import org.eclipse.jgit.api.errors.NoHeadException;
  import org.eclipse.jgit.api.errors.StashApplyFailureException;
  import org.eclipse.jgit.api.errors.WrongRepositoryStateException;
  import org.eclipse.jgit.dircache.DirCache;
  import org.eclipse.jgit.dircache.DirCacheBuilder;
  import org.eclipse.jgit.dircache.DirCacheCheckout;
  import org.eclipse.jgit.dircache.DirCacheCheckout.CheckoutMetadata;
  import org.eclipse.jgit.dircache.DirCacheEntry;
  import org.eclipse.jgit.dircache.DirCacheIterator;
  import org.eclipse.jgit.errors.CheckoutConflictException;
  import org.eclipse.jgit.events.WorkingTreeModifiedEvent;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.CoreConfig.EolStreamType;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.RepositoryState;
  import org.eclipse.jgit.merge.ContentMergeStrategy;
  import org.eclipse.jgit.merge.MergeStrategy;
  import org.eclipse.jgit.merge.Merger;
  import org.eclipse.jgit.merge.ResolveMerger;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevTree;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.treewalk.AbstractTreeIterator;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.treewalk.TreeWalk;
  
  /**
   * Command class to apply a stashed commit.
   *
   * This class behaves like <em>git stash apply --index</em>, i.e. it tries to
   * recover the stashed index state in addition to the working tree state.
   *
   * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-stash.html"
   *      >Git documentation about Stash</a>
   * @since 2.0
   */
  public class StashApplyCommand extends GitCommand<ObjectId> {
  
  	private static final String DEFAULT_REF = Constants.STASH + "@{0}"; //$NON-NLS-1$
  
  	private String stashRef;
  
  	private boolean restoreIndex = true;
  
  	private boolean restoreUntracked = true;
  
  	private boolean ignoreRepositoryState;
  
  	private MergeStrategy strategy = MergeStrategy.RECURSIVE;
  
  	private ContentMergeStrategy contentStrategy;
  
  	/**
  	 * Create command to apply the changes of a stashed commit
  	 *
  	 * @param repo
  	 *            the {@link org.eclipse.jgit.lib.Repository} to apply the stash
  	 *            to
  	 */
  	public StashApplyCommand(Repository repo) {
  		super(repo);
  	}
  
  	/**
  	 * Set the stash reference to apply
  	 * <p>
  	 * This will default to apply the latest stashed commit (stash@{0}) if
  	 * unspecified
  	 *
  	 * @param stashRef
  	 *            name of the stash {@code Ref} to apply
  	 * @return {@code this}
  	 */
  	public StashApplyCommand setStashRef(String stashRef) {
 		this.stashRef = stashRef;
 		return this;
 	}
 
 	/**
 	 * Whether to ignore the repository state when applying the stash
 	 *
 	 * @param willIgnoreRepositoryState
 	 *            whether to ignore the repository state when applying the stash
 	 * @return {@code this}
 	 * @since 3.2
 	 */
 	public StashApplyCommand ignoreRepositoryState(boolean willIgnoreRepositoryState) {
 		this.ignoreRepositoryState = willIgnoreRepositoryState;
 		return this;
 	}
 
 	private ObjectId getStashId() throws GitAPIException {
 		final String revision = stashRef != null ? stashRef : DEFAULT_REF;
 		final ObjectId stashId;
 		try {
 			stashId = repo.resolve(revision);
 		} catch (IOException e) {
 			throw new InvalidRefNameException(MessageFormat.format(
 					JGitText.get().stashResolveFailed, revision), e);
 		}
 		if (stashId == null)
 			throw new InvalidRefNameException(MessageFormat.format(
 					JGitText.get().stashResolveFailed, revision));
 		return stashId;
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Apply the changes in a stashed commit to the working directory and index
 	 */
 	@Override
 	public ObjectId call() throws GitAPIException,
 			WrongRepositoryStateException, NoHeadException,
 			StashApplyFailureException {
 		checkCallable();
 
 		if (!ignoreRepositoryState
 				&& repo.getRepositoryState() != RepositoryState.SAFE)
 			throw new WrongRepositoryStateException(MessageFormat.format(
 					JGitText.get().stashApplyOnUnsafeRepository,
 					repo.getRepositoryState()));
 
 		try (ObjectReader reader = repo.newObjectReader();
 				RevWalk revWalk = new RevWalk(reader)) {
 
 			ObjectId headCommit = repo.resolve(Constants.HEAD);
 			if (headCommit == null)
 				throw new NoHeadException(JGitText.get().stashApplyWithoutHead);
 
 			final ObjectId stashId = getStashId();
 			RevCommit stashCommit = revWalk.parseCommit(stashId);
 			if (stashCommit.getParentCount() < 2
 					|| stashCommit.getParentCount() > 3)
 				throw new JGitInternalException(MessageFormat.format(
 						JGitText.get().stashCommitIncorrectNumberOfParents,
 						stashId.name(),
 						Integer.valueOf(stashCommit.getParentCount())));
 
 			ObjectId headTree = repo.resolve(Constants.HEAD + "^{tree}"); //$NON-NLS-1$
 			ObjectId stashIndexCommit = revWalk.parseCommit(stashCommit
 					.getParent(1));
 			ObjectId stashHeadCommit = stashCommit.getParent(0);
 			ObjectId untrackedCommit = null;
 			if (restoreUntracked && stashCommit.getParentCount() == 3)
 				untrackedCommit = revWalk.parseCommit(stashCommit.getParent(2));
 
 			Merger merger = strategy.newMerger(repo);
 			boolean mergeSucceeded;
 			if (merger instanceof ResolveMerger) {
 				ResolveMerger resolveMerger = (ResolveMerger) merger;
 				resolveMerger
 						.setCommitNames(new String[] { "stashed HEAD", "HEAD", //$NON-NLS-1$ //$NON-NLS-2$
 								"stash" }); //$NON-NLS-1$
 				resolveMerger.setBase(stashHeadCommit);
 				resolveMerger
 						.setWorkingTreeIterator(new FileTreeIterator(repo));
 				resolveMerger.setContentMergeStrategy(contentStrategy);
 				mergeSucceeded = resolveMerger.merge(headCommit, stashCommit);
 				List<String> modifiedByMerge = resolveMerger.getModifiedFiles();
 				if (!modifiedByMerge.isEmpty()) {
 					repo.fireEvent(new WorkingTreeModifiedEvent(modifiedByMerge,
 							null));
 				}
 			} else {
 				mergeSucceeded = merger.merge(headCommit, stashCommit);
 			}
 			if (mergeSucceeded) {
 				DirCache dc = repo.lockDirCache();
 				DirCacheCheckout dco = new DirCacheCheckout(repo, headTree,
 						dc, merger.getResultTreeId());
 				dco.setFailOnConflict(true);
 				dco.checkout(); // Ignoring failed deletes....
 				if (restoreIndex) {
 					Merger ixMerger = strategy.newMerger(repo, true);
 					if (ixMerger instanceof ResolveMerger) {
 						ResolveMerger resolveMerger = (ResolveMerger) ixMerger;
 						resolveMerger.setCommitNames(new String[] { "stashed HEAD", //$NON-NLS-1$
 								"HEAD", "stashed index" }); //$NON-NLS-1$//$NON-NLS-2$
 						resolveMerger.setBase(stashHeadCommit);
 						resolveMerger.setContentMergeStrategy(contentStrategy);
 					}
 					boolean ok = ixMerger.merge(headCommit, stashIndexCommit);
 					if (ok) {
 						resetIndex(revWalk
 								.parseTree(ixMerger.getResultTreeId()));
 					} else {
 						throw new StashApplyFailureException(
 								JGitText.get().stashApplyConflict);
 					}
 				}
 
 				if (untrackedCommit != null) {
 					Merger untrackedMerger = strategy.newMerger(repo, true);
 					if (untrackedMerger instanceof ResolveMerger) {
 						ResolveMerger resolveMerger = (ResolveMerger) untrackedMerger;
 						resolveMerger.setCommitNames(new String[] { "null", "HEAD", //$NON-NLS-1$//$NON-NLS-2$
 								"untracked files" }); //$NON-NLS-1$
 						// There is no common base for HEAD & untracked files
 						// because the commit for untracked files has no parent.
 						// If we use stashHeadCommit as common base (as in the
 						// other merges) we potentially report conflicts for
 						// files which are not even member of untracked files
 						// commit.
 						resolveMerger.setBase(null);
 						resolveMerger.setContentMergeStrategy(contentStrategy);
 					}
 					boolean ok = untrackedMerger.merge(headCommit,
 							untrackedCommit);
 					if (ok) {
 						try {
 							RevTree untrackedTree = revWalk
 									.parseTree(untrackedCommit);
 							resetUntracked(untrackedTree);
 						} catch (CheckoutConflictException e) {
 							throw new StashApplyFailureException(
 									JGitText.get().stashApplyConflict, e);
 						}
 					} else {
 						throw new StashApplyFailureException(
 								JGitText.get().stashApplyConflict);
 					}
 				}
 			} else {
 				throw new StashApplyFailureException(
 						JGitText.get().stashApplyConflict);
 			}
 			return stashId;
 
 		} catch (JGitInternalException e) {
 			throw e;
 		} catch (IOException e) {
 			throw new JGitInternalException(JGitText.get().stashApplyFailed, e);
 		}
 	}
 
 	/**
 	 * Whether to restore the index state
 	 *
 	 * @param applyIndex
 	 *            true (default) if the command should restore the index state
 	 * @deprecated use {@link #setRestoreIndex} instead
 	 */
 	@Deprecated
 	public void setApplyIndex(boolean applyIndex) {
 		this.restoreIndex = applyIndex;
 	}
 
 	/**
 	 * Whether to restore the index state
 	 *
 	 * @param restoreIndex
 	 *            true (default) if the command should restore the index state
 	 * @return {@code this}
 	 * @since 5.3
 	 */
 	public StashApplyCommand setRestoreIndex(boolean restoreIndex) {
 		this.restoreIndex = restoreIndex;
 		return this;
 	}
 
 	/**
 	 * Set the <code>MergeStrategy</code> to use.
 	 *
 	 * @param strategy
 	 *            The merge strategy to use in order to merge during this
 	 *            command execution.
 	 * @return {@code this}
 	 * @since 3.4
 	 */
 	public StashApplyCommand setStrategy(MergeStrategy strategy) {
 		this.strategy = strategy;
 		return this;
 	}
 
 	/**
 	 * Sets the content merge strategy to use if the
 	 * {@link #setStrategy(MergeStrategy) merge strategy} is "resolve" or
 	 * "recursive".
 	 *
 	 * @param strategy
 	 *            the {@link ContentMergeStrategy} to be used
 	 * @return {@code this}
 	 * @since 5.12
 	 */
 	public StashApplyCommand setContentMergeStrategy(
 			ContentMergeStrategy strategy) {
 		checkCallable();
 		this.contentStrategy = strategy;
 		return this;
 	}
 
 	/**
 	 * Whether the command should restore untracked files
 	 *
 	 * @param applyUntracked
 	 *            true (default) if the command should restore untracked files
 	 * @since 3.4
 	 * @deprecated use {@link #setRestoreUntracked} instead
 	 */
 	@Deprecated
 	public void setApplyUntracked(boolean applyUntracked) {
 		this.restoreUntracked = applyUntracked;
 	}
 
 	/**
 	 * Whether the command should restore untracked files
 	 *
 	 * @param restoreUntracked
 	 *            true (default) if the command should restore untracked files
 	 * @return {@code this}
 	 * @since 5.3
 	 */
 	public StashApplyCommand setRestoreUntracked(boolean restoreUntracked) {
 		this.restoreUntracked = restoreUntracked;
 		return this;
 	}
 
 	private void resetIndex(RevTree tree) throws IOException {
 		DirCache dc = repo.lockDirCache();
 		try (TreeWalk walk = new TreeWalk(repo)) {
 			DirCacheBuilder builder = dc.builder();
 
 			walk.addTree(tree);
 			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 resetUntracked(RevTree tree) throws CheckoutConflictException,
 			IOException {
 		Set<String> actuallyModifiedPaths = new HashSet<>();
 		// TODO maybe NameConflictTreeWalk ?
 		try (TreeWalk walk = new TreeWalk(repo)) {
 			walk.addTree(tree);
 			walk.addTree(new FileTreeIterator(repo));
 			walk.setRecursive(true);
 
 			final ObjectReader reader = walk.getObjectReader();
 
 			while (walk.next()) {
 				final AbstractTreeIterator cIter = walk.getTree(0,
 						AbstractTreeIterator.class);
 				if (cIter == null)
 					// Not in commit, don't create untracked
 					continue;
 
 				final EolStreamType eolStreamType = walk
 						.getEolStreamType(CHECKOUT_OP);
 				final DirCacheEntry entry = new DirCacheEntry(walk.getRawPath());
 				entry.setFileMode(cIter.getEntryFileMode());
 				entry.setObjectIdFromRaw(cIter.idBuffer(), cIter.idOffset());
 
 				FileTreeIterator fIter = walk
 						.getTree(1, FileTreeIterator.class);
 				if (fIter != null) {
 					if (fIter.isModified(entry, true, reader)) {
 						// file exists and is dirty
 						throw new CheckoutConflictException(
 								entry.getPathString());
 					}
 				}
 
 				checkoutPath(entry, reader,
 						new CheckoutMetadata(eolStreamType, null));
 				actuallyModifiedPaths.add(entry.getPathString());
 			}
 		} finally {
 			if (!actuallyModifiedPaths.isEmpty()) {
 				repo.fireEvent(new WorkingTreeModifiedEvent(
 						actuallyModifiedPaths, null));
 			}
 		}
 	}
 
 	private void checkoutPath(DirCacheEntry entry, ObjectReader reader,
 			CheckoutMetadata checkoutMetadata) {
 		try {
 			DirCacheCheckout.checkoutEntry(repo, entry, reader, true,
 					checkoutMetadata);
 		} catch (IOException e) {
 			throw new JGitInternalException(MessageFormat.format(
 					JGitText.get().checkoutConflictWithFile,
 					entry.getPathString()), e);
 		}
 	}
 }