/*
 * Copyright (C) 2013, Google Inc.
 * 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.internal.storage.file;

import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;

import org.eclipse.jgit.internal.storage.file.BasePackBitmapIndex.StoredBitmap;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.BitmapIndex;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectIdOwnerMap;

import com.googlecode.javaewah.EWAHCompressedBitmap;
import com.googlecode.javaewah.IntIterator;

A PackBitmapIndex that remaps the bitmaps in the previous index to the
positions in the new pack index. Note, unlike typical PackBitmapIndex
implementations this implementation is not thread safe, as it is intended to
be used with a PackBitmapIndexBuilder, which is also not thread safe.
/**
 * A PackBitmapIndex that remaps the bitmaps in the previous index to the
 * positions in the new pack index. Note, unlike typical PackBitmapIndex
 * implementations this implementation is not thread safe, as it is intended to
 * be used with a PackBitmapIndexBuilder, which is also not thread safe.
 */
public class PackBitmapIndexRemapper extends PackBitmapIndex
		implements Iterable<PackBitmapIndexRemapper.Entry> {

	private final BasePackBitmapIndex oldPackIndex;
	final PackBitmapIndex newPackIndex;
	private final ObjectIdOwnerMap<StoredBitmap> convertedBitmaps;
	private final BitSet inflated;
	private final int[] prevToNewMapping;

	
A PackBitmapIndex that maps the positions in the prevBitmapIndex to the
ones in the newIndex.
Params:
prevBitmapIndex – 
           the bitmap index with the old mapping.
newIndex – 
           the bitmap index with the new mapping.
Returns:
a bitmap index that attempts to do the mapping between the two./**
	 * A PackBitmapIndex that maps the positions in the prevBitmapIndex to the
	 * ones in the newIndex.
	 *
	 * @param prevBitmapIndex
	 *            the bitmap index with the old mapping.
	 * @param newIndex
	 *            the bitmap index with the new mapping.
	 * @return a bitmap index that attempts to do the mapping between the two.
	 */
	public static PackBitmapIndexRemapper newPackBitmapIndex(
			BitmapIndex prevBitmapIndex, PackBitmapIndex newIndex) {
		if (!(prevBitmapIndex instanceof BitmapIndexImpl))
			return new PackBitmapIndexRemapper(newIndex);

		PackBitmapIndex prevIndex = ((BitmapIndexImpl) prevBitmapIndex)
				.getPackBitmapIndex();
		if (!(prevIndex instanceof BasePackBitmapIndex))
			return new PackBitmapIndexRemapper(newIndex);

		return new PackBitmapIndexRemapper(
				(BasePackBitmapIndex) prevIndex, newIndex);
	}

	private PackBitmapIndexRemapper(PackBitmapIndex newPackIndex) {
		this.oldPackIndex = null;
		this.newPackIndex = newPackIndex;
		this.convertedBitmaps = null;
		this.inflated = null;
		this.prevToNewMapping = null;
	}

	private PackBitmapIndexRemapper(
			BasePackBitmapIndex oldPackIndex, PackBitmapIndex newPackIndex) {
		this.oldPackIndex = oldPackIndex;
		this.newPackIndex = newPackIndex;
		convertedBitmaps = new ObjectIdOwnerMap<>();
		inflated = new BitSet(newPackIndex.getObjectCount());

		prevToNewMapping = new int[oldPackIndex.getObjectCount()];
		for (int pos = 0; pos < prevToNewMapping.length; pos++)
			prevToNewMapping[pos] = newPackIndex.findPosition(
					oldPackIndex.getObject(pos));
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public int findPosition(AnyObjectId objectId) {
		return newPackIndex.findPosition(objectId);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public ObjectId getObject(int position) throws IllegalArgumentException {
		return newPackIndex.getObject(position);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public int getObjectCount() {
		return newPackIndex.getObjectCount();
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public EWAHCompressedBitmap ofObjectType(
			EWAHCompressedBitmap bitmap, int type) {
		return newPackIndex.ofObjectType(bitmap, type);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public Iterator<Entry> iterator() {
		if (oldPackIndex == null)
			return Collections.<Entry> emptyList().iterator();

		final Iterator<StoredBitmap> it = oldPackIndex.getBitmaps().iterator();
		return new Iterator<Entry>() {
			private Entry entry;

			@Override
			public boolean hasNext() {
				while (entry == null && it.hasNext()) {
					StoredBitmap sb = it.next();
					if (newPackIndex.findPosition(sb) != -1)
						entry = new Entry(sb, sb.getFlags());
				}
				return entry != null;
			}

			@Override
			public Entry next() {
				if (!hasNext())
					throw new NoSuchElementException();

				Entry res = entry;
				entry = null;
				return res;
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}
		};
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public EWAHCompressedBitmap getBitmap(AnyObjectId objectId) {
		EWAHCompressedBitmap bitmap = newPackIndex.getBitmap(objectId);
		if (bitmap != null || oldPackIndex == null)
			return bitmap;

		StoredBitmap stored = convertedBitmaps.get(objectId);
		if (stored != null)
			return stored.getBitmap();

		StoredBitmap oldBitmap = oldPackIndex.getBitmaps().get(objectId);
		if (oldBitmap == null)
			return null;

		if (newPackIndex.findPosition(objectId) == -1)
			return null;

		inflated.clear();
		for (IntIterator i = oldBitmap.getBitmap().intIterator(); i.hasNext();)
			inflated.set(prevToNewMapping[i.next()]);
		bitmap = inflated.toEWAHCompressedBitmap();
		bitmap.trim();
		convertedBitmaps.add(
				new StoredBitmap(objectId, bitmap, null, oldBitmap.getFlags()));
		return bitmap;
	}

	
An entry in the old PackBitmapIndex. /** An entry in the old PackBitmapIndex. */
	public static final class Entry extends ObjectId {
		private final int flags;

		Entry(AnyObjectId src, int flags) {
			super(src);
			this.flags = flags;
		}

		
Returns:
the flags associated with the bitmap./** @return the flags associated with the bitmap. */
		public int getFlags() {
			return flags;
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public int getBitmapCount() {
		// The count is only useful for the end index, not the remapper.
		return 0;
	}
}