/*
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * 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.revwalk;

import java.io.IOException;
import java.util.List;

import org.eclipse.jgit.diff.DiffConfig;
import org.eclipse.jgit.diff.DiffEntry;
import org.eclipse.jgit.diff.DiffEntry.ChangeType;
import org.eclipse.jgit.diff.RenameDetector;
import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.errors.StopWalkException;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.revwalk.filter.RevFilter;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.treewalk.filter.TreeFilter;

Filter applying a TreeFilter against changed paths in each commit. 
 Each commit is differenced concurrently against all of its parents to look for tree entries that are interesting to the TreeFilter. 
Since:
3.5/**
 * Filter applying a {@link org.eclipse.jgit.treewalk.filter.TreeFilter} against
 * changed paths in each commit.
 * <p>
 * Each commit is differenced concurrently against all of its parents to look
 * for tree entries that are interesting to the
 * {@link org.eclipse.jgit.treewalk.filter.TreeFilter}.
 *
 * @since 3.5
 */
public class TreeRevFilter extends RevFilter {
	private static final int PARSED = RevWalk.PARSED;

	private static final int UNINTERESTING = RevWalk.UNINTERESTING;

	private final int rewriteFlag;
	private final TreeWalk pathFilter;

	
Create a RevFilter from a TreeFilter. 
Params:
walker – 
           walker used for reading trees.
t –  filter to compare against any changed paths in each commit. If a FollowFilter, will be replaced with a new filter following new paths after a rename.
Since:
3.5/**
	 * Create a {@link org.eclipse.jgit.revwalk.filter.RevFilter} from a
	 * {@link org.eclipse.jgit.treewalk.filter.TreeFilter}.
	 *
	 * @param walker
	 *            walker used for reading trees.
	 * @param t
	 *            filter to compare against any changed paths in each commit. If
	 *            a {@link org.eclipse.jgit.revwalk.FollowFilter}, will be
	 *            replaced with a new filter following new paths after a rename.
	 * @since 3.5
	 */
	public TreeRevFilter(RevWalk walker, TreeFilter t) {
		this(walker, t, 0);
	}


	
Create a filter for the first phase of a parent-rewriting limited revision
walk.
 This filter is ANDed to evaluate before all other filters and ties the configured TreeFilter into the revision walking process. 
 If no interesting tree entries are found the commit is colored with rewriteFlag, allowing a later pass implemented by RewriteGenerator to remove those colored commits from the DAG. 
Params:
walker – 
           walker used for reading trees.
t –  filter to compare against any changed paths in each commit. If a FollowFilter, will be replaced with a new filter following new paths after a rename.
rewriteFlag – 
           flag to color commits to be removed from the simplified DAT.
See Also:
RewriteGenerator/**
	 * Create a filter for the first phase of a parent-rewriting limited revision
	 * walk.
	 * <p>
	 * This filter is ANDed to evaluate before all other filters and ties the
	 * configured {@link TreeFilter} into the revision walking process.
	 * <p>
	 * If no interesting tree entries are found the commit is colored with
	 * {@code rewriteFlag}, allowing a later pass implemented by
	 * {@link RewriteGenerator} to remove those colored commits from the DAG.
	 *
	 * @see RewriteGenerator
	 *
	 * @param walker
	 *            walker used for reading trees.
	 * @param t
	 *            filter to compare against any changed paths in each commit. If a
	 *            {@link FollowFilter}, will be replaced with a new filter
	 *            following new paths after a rename.
	 * @param rewriteFlag
	 *            flag to color commits to be removed from the simplified DAT.
	 */
	TreeRevFilter(RevWalk walker, TreeFilter t, int rewriteFlag) {
		pathFilter = new TreeWalk(walker.reader);
		pathFilter.setFilter(t);
		pathFilter.setRecursive(t.shouldBeRecursive());
		this.rewriteFlag = rewriteFlag;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public RevFilter clone() {
		throw new UnsupportedOperationException();
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public boolean include(RevWalk walker, RevCommit c)
			throws StopWalkException, MissingObjectException,
			IncorrectObjectTypeException, IOException {
		// Reset the tree filter to scan this commit and parents.
		//
		RevCommit[] pList = c.parents;
		int nParents = pList.length;
		TreeWalk tw = pathFilter;
		ObjectId[] trees = new ObjectId[nParents + 1];
		for (int i = 0; i < nParents; i++) {
			RevCommit p = c.parents[i];
			if ((p.flags & PARSED) == 0) {
				p.parseHeaders(walker);
			}
			trees[i] = p.getTree();
		}
		trees[nParents] = c.getTree();
		tw.reset(trees);

		if (nParents == 1) {
			// We have exactly one parent. This is a very common case.
			//
			int chgs = 0, adds = 0;
			while (tw.next()) {
				chgs++;
				if (tw.getRawMode(0) == 0 && tw.getRawMode(1) != 0) {
					adds++;
				} else {
					break; // no point in looking at this further.
				}
			}

			if (chgs == 0) {
				// No changes, so our tree is effectively the same as
				// our parent tree. We pass the buck to our parent.
				//
				c.flags |= rewriteFlag;
				return false;
			} else {
				// We have interesting items, but neither of the special
				// cases denoted above.
				//
				if (adds > 0 && tw.getFilter() instanceof FollowFilter) {
					// One of the paths we care about was added in this
					// commit. We need to update our filter to its older
					// name, if we can discover it. Find out what that is.
					//
					updateFollowFilter(trees, ((FollowFilter) tw.getFilter()).cfg);
				}
				return true;
			}
		} else if (nParents == 0) {
			// We have no parents to compare against. Consider us to be
			// REWRITE only if we have no paths matching our filter.
			//
			if (tw.next()) {
				return true;
			}
			c.flags |= rewriteFlag;
			return false;
		}

		// We are a merge commit. We can only be REWRITE if we are same
		// to _all_ parents. We may also be able to eliminate a parent if
		// it does not contribute changes to us. Such a parent may be an
		// uninteresting side branch.
		//
		int[] chgs = new int[nParents];
		int[] adds = new int[nParents];
		while (tw.next()) {
			int myMode = tw.getRawMode(nParents);
			for (int i = 0; i < nParents; i++) {
				int pMode = tw.getRawMode(i);
				if (myMode == pMode && tw.idEqual(i, nParents)) {
					continue;
				}
				chgs[i]++;
				if (pMode == 0 && myMode != 0) {
					adds[i]++;
				}
			}
		}

		boolean same = false;
		boolean diff = false;
		for (int i = 0; i < nParents; i++) {
			if (chgs[i] == 0) {
				// No changes, so our tree is effectively the same as
				// this parent tree. We pass the buck to only this one
				// parent commit.
				//

				RevCommit p = pList[i];
				if ((p.flags & UNINTERESTING) != 0) {
					// This parent was marked as not interesting by the
					// application. We should look for another parent
					// that is interesting.
					//
					same = true;
					continue;
				}

				c.flags |= rewriteFlag;
				c.parents = new RevCommit[] { p };
				return false;
			}

			if (chgs[i] == adds[i]) {
				// All of the differences from this parent were because we
				// added files that they did not have. This parent is our
				// "empty tree root" and thus their history is not relevant.
				// Cut our grandparents to be an empty list.
				//
				pList[i].parents = RevCommit.NO_PARENTS;
			}

			// We have an interesting difference relative to this parent.
			//
			diff = true;
		}

		if (diff && !same) {
			// We did not abort above, so we are different in at least one
			// way from all of our parents. We have to take the blame for
			// that difference.
			//
			return true;
		}

		// We are the same as all of our parents. We must keep them
		// as they are and allow those parents to flow into pending
		// for further scanning.
		//
		c.flags |= rewriteFlag;
		return false;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public boolean requiresCommitBody() {
		return false;
	}

	private void updateFollowFilter(ObjectId[] trees, DiffConfig cfg)
			throws MissingObjectException, IncorrectObjectTypeException,
			CorruptObjectException, IOException {
		TreeWalk tw = pathFilter;
		FollowFilter oldFilter = (FollowFilter) tw.getFilter();
		tw.setFilter(TreeFilter.ANY_DIFF);
		tw.reset(trees);

		List<DiffEntry> files = DiffEntry.scan(tw);
		RenameDetector rd = new RenameDetector(tw.getObjectReader(), cfg);
		rd.addAll(files);
		files = rd.compute();

		TreeFilter newFilter = oldFilter;
		for (DiffEntry ent : files) {
			if (isRename(ent) && ent.getNewPath().equals(oldFilter.getPath())) {
				newFilter = FollowFilter.create(ent.getOldPath(), cfg);
				RenameCallback callback = oldFilter.getRenameCallback();
				if (callback != null) {
					callback.renamed(ent);
					// forward the callback to the new follow filter
					((FollowFilter) newFilter).setRenameCallback(callback);
				}
				break;
			}
		}
		tw.setFilter(newFilter);
	}

	private static boolean isRename(DiffEntry ent) {
		return ent.getChangeType() == ChangeType.RENAME
				|| ent.getChangeType() == ChangeType.COPY;
	}
}