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/*
 * Copyright (C) 2008-2018, Robin Rosenberg 
 * Copyright (C) 2008, Shawn O. Pearce  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.openrewrite.jgit.revplot;

import static org.openrewrite.jgit.lib.Constants.R_HEADS;
import static org.openrewrite.jgit.lib.Constants.R_REMOTES;
import static org.openrewrite.jgit.lib.Constants.R_TAGS;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.openrewrite.jgit.errors.IncorrectObjectTypeException;
import org.openrewrite.jgit.errors.MissingObjectException;
import org.openrewrite.jgit.internal.JGitText;
import org.openrewrite.jgit.lib.AnyObjectId;
import org.openrewrite.jgit.lib.PersonIdent;
import org.openrewrite.jgit.lib.Ref;
import org.openrewrite.jgit.lib.Repository;
import org.openrewrite.jgit.revwalk.RevCommit;
import org.openrewrite.jgit.revwalk.RevObject;
import org.openrewrite.jgit.revwalk.RevSort;
import org.openrewrite.jgit.revwalk.RevTag;
import org.openrewrite.jgit.revwalk.RevWalk;

/**
 * Specialized RevWalk for visualization of a commit graph.
 */
public class PlotWalk extends RevWalk {

	private Map> additionalRefMap;

	private Map> reverseRefMap;

	private Repository repository;

	/** {@inheritDoc} */
	@Override
	public void dispose() {
		super.dispose();
		if (reverseRefMap != null) {
			reverseRefMap.clear();
			reverseRefMap = null;
		}
		if (additionalRefMap != null) {
			additionalRefMap.clear();
			additionalRefMap = null;
		}
		repository = null;
	}

	/**
	 * Create a new revision walker for a given repository.
	 *
	 * @param repo
	 *            the repository the walker will obtain data from.
	 */
	public PlotWalk(Repository repo) {
		super(repo);
		super.sort(RevSort.TOPO, true);
		additionalRefMap = new HashMap<>();
		repository = repo;
	}

	/**
	 * Add additional refs to the walk
	 *
	 * @param refs
	 *            additional refs
	 * @throws java.io.IOException
	 */
	public void addAdditionalRefs(Iterable refs) throws IOException {
		for (Ref ref : refs) {
			Set set = additionalRefMap.get(ref.getObjectId());
			if (set == null)
				set = Collections.singleton(ref);
			else {
				set = new HashSet<>(set);
				set.add(ref);
			}
			additionalRefMap.put(ref.getObjectId(), set);
		}
	}

	/** {@inheritDoc} */
	@Override
	public void sort(RevSort s, boolean use) {
		if (s == RevSort.TOPO && !use)
			throw new IllegalArgumentException(JGitText.get().topologicalSortRequired);
		super.sort(s, use);
	}

	/** {@inheritDoc} */
	@Override
	protected RevCommit createCommit(AnyObjectId id) {
		return new PlotCommit(id);
	}

	/** {@inheritDoc} */
	@Override
	public RevCommit next() throws MissingObjectException,
			IncorrectObjectTypeException, IOException {
		PlotCommit pc = (PlotCommit) super.next();
		if (pc != null)
			pc.refs = getRefs(pc);
		return pc;
	}

	private Ref[] getRefs(AnyObjectId commitId) {
		if (reverseRefMap == null) {
			reverseRefMap = repository.getAllRefsByPeeledObjectId();
			for (Map.Entry> entry : additionalRefMap
					.entrySet()) {
				Set set = reverseRefMap.get(entry.getKey());
				Set additional = entry.getValue();
				if (set != null) {
					if (additional.size() == 1) {
						// It's an unmodifiable singleton set...
						additional = new HashSet<>(additional);
					}
					additional.addAll(set);
				}
				reverseRefMap.put(entry.getKey(), additional);
			}
			additionalRefMap.clear();
			additionalRefMap = null;
		}
		Collection list = reverseRefMap.get(commitId);
		if (list == null) {
			return PlotCommit.NO_REFS;
		}
		Ref[] tags = list.toArray(new Ref[0]);
		Arrays.sort(tags, new PlotRefComparator());
		return tags;
	}

	class PlotRefComparator implements Comparator {
		@Override
		public int compare(Ref o1, Ref o2) {
			try {
				RevObject obj1 = parseAny(o1.getObjectId());
				RevObject obj2 = parseAny(o2.getObjectId());
				long t1 = timeof(obj1);
				long t2 = timeof(obj2);
				if (t1 > t2)
					return -1;
				if (t1 < t2)
					return 1;
			} catch (IOException e) {
				// ignore
			}

			int cmp = kind(o1) - kind(o2);
			if (cmp == 0)
				cmp = o1.getName().compareTo(o2.getName());
			return cmp;
		}

		long timeof(RevObject o) {
			if (o instanceof RevCommit)
				return ((RevCommit) o).getCommitTime();
			if (o instanceof RevTag) {
				RevTag tag = (RevTag) o;
				try {
					parseBody(tag);
				} catch (IOException e) {
					return 0;
				}
				PersonIdent who = tag.getTaggerIdent();
				return who != null ? who.getWhen().getTime() : 0;
			}
			return 0;
		}

		int kind(Ref r) {
			if (r.getName().startsWith(R_TAGS))
				return 0;
			if (r.getName().startsWith(R_HEADS))
				return 1;
			if (r.getName().startsWith(R_REMOTES))
				return 2;
			return 3;
		}
	}
}