/*
    * Copyright (C) 2012, Google 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.internal.storage.file;
  
  import java.text.MessageFormat;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.NoSuchElementException;
  
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.file.BitmapIndexImpl.CompressedBitmap;
  import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
  import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdOwnerMap;
  import org.eclipse.jgit.util.BlockList;
  
  import com.googlecode.javaewah.EWAHCompressedBitmap;
  
  /**
   * Helper for constructing
   * {@link org.eclipse.jgit.internal.storage.file.PackBitmapIndex}es.
   */
  public class PackBitmapIndexBuilder extends BasePackBitmapIndex {
  	private static final int MAX_XOR_OFFSET_SEARCH = 10;
  
  	private final EWAHCompressedBitmap commits;
  	private final EWAHCompressedBitmap trees;
  	private final EWAHCompressedBitmap blobs;
  	private final EWAHCompressedBitmap tags;
  	private final BlockList<PositionEntry> byOffset;
  	final BlockList<StoredBitmap>
  			byAddOrder = new BlockList<>();
  	final ObjectIdOwnerMap<PositionEntry>
  			positionEntries = new ObjectIdOwnerMap<>();
  
  	/**
  	 * Creates a PackBitmapIndex used for building the contents of an index
  	 * file.
  	 *
  	 * @param objects
  	 *            objects sorted by name. The list must be initially sorted by
  	 *            ObjectId (name); it will be resorted in place.
  	 */
  	public PackBitmapIndexBuilder(List<ObjectToPack> objects) {
  		super(new ObjectIdOwnerMap<StoredBitmap>());
  		byOffset = new BlockList<>(objects.size());
  		sortByOffsetAndIndex(byOffset, positionEntries, objects);
  
  		// 64 objects fit in a single long word (64 bits).
  		// On average a repository is 30% commits, 30% trees, 30% blobs.
  		// Initialize bitmap capacity for worst case to minimize growing.
  		int sizeInWords = Math.max(4, byOffset.size() / 64 / 3);
  		commits = new EWAHCompressedBitmap(sizeInWords);
  		trees = new EWAHCompressedBitmap(sizeInWords);
  		blobs = new EWAHCompressedBitmap(sizeInWords);
  		tags = new EWAHCompressedBitmap(sizeInWords);
  		for (int i = 0; i < objects.size(); i++) {
  			int type = objects.get(i).getType();
  			switch (type) {
  			case Constants.OBJ_COMMIT:
  				commits.set(i);
  				break;
  			case Constants.OBJ_TREE:
  				trees.set(i);
  				break;
  			case Constants.OBJ_BLOB:
  				blobs.set(i);
  				break;
  			case Constants.OBJ_TAG:
  				tags.set(i);
  				break;
  			default:
  				throw new IllegalArgumentException(MessageFormat.format(
  						JGitText.get().badObjectType, String.valueOf(type)));
  			}
  		}
  		commits.trim();
  		trees.trim();
  		blobs.trim();
  		tags.trim();
  	}
  
  	private static void sortByOffsetAndIndex(BlockList<PositionEntry> byOffset,
  			ObjectIdOwnerMap<PositionEntry> positionEntries,
  			List<ObjectToPack> entries) {
  		for (int i = 0; i < entries.size(); i++) {
 			positionEntries.add(new PositionEntry(entries.get(i), i));
 		}
 		Collections.sort(entries, (ObjectToPack"../../../../../../org/eclipse/jgit/internal/storage/pack/ObjectToPack.html#ObjectToPack">ObjectToPack a, ObjectToPack b) -> Long
 				.signum(a.getOffset() - b.getOffset()));
 		for (int i = 0; i < entries.size(); i++) {
 			PositionEntry e = positionEntries.get(entries.get(i));
 			e.offsetPosition = i;
 			byOffset.add(e);
 		}
 	}
 
 	/**
 	 * Get set of objects included in the pack.
 	 *
 	 * @return set of objects included in the pack.
 	 */
 	public ObjectIdOwnerMap<ObjectIdOwnerMap.Entry> getObjectSet() {
 		ObjectIdOwnerMap<ObjectIdOwnerMap.Entry> r = new ObjectIdOwnerMap<>();
 		for (PositionEntry e : byOffset) {
 			r.add(new ObjectIdOwnerMap.Entry(e) {
 				// A new entry that copies the ObjectId
 			});
 		}
 		return r;
 	}
 
 	/**
 	 * Stores the bitmap for the objectId.
 	 *
 	 * @param objectId
 	 *            the object id key for the bitmap.
 	 * @param bitmap
 	 *            the bitmap
 	 * @param flags
 	 *            the flags to be stored with the bitmap
 	 */
 	public void addBitmap(AnyObjectId objectId, Bitmap bitmap, int flags) {
 		if (bitmap instanceof BitmapBuilder)
 			bitmap = ((BitmapBuilder) bitmap).build();
 
 		EWAHCompressedBitmap compressed;
 		if (bitmap instanceof CompressedBitmap)
 			compressed = ((CompressedBitmap) bitmap).getEwahCompressedBitmap();
 		else
 			throw new IllegalArgumentException(bitmap.getClass().toString());
 
 		addBitmap(objectId, compressed, flags);
 	}
 
 	/**
 	 * Stores the bitmap for the objectId.
 	 *
 	 * @param objectId
 	 *            the object id key for the bitmap.
 	 * @param bitmap
 	 *            the bitmap
 	 * @param flags
 	 *            the flags to be stored with the bitmap
 	 */
 	public void addBitmap(
 			AnyObjectId objectId, EWAHCompressedBitmap bitmap, int flags) {
 		bitmap.trim();
 		StoredBitmap result = new StoredBitmap(objectId, bitmap, null, flags);
 		getBitmaps().add(result);
 		byAddOrder.add(result);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public EWAHCompressedBitmap ofObjectType(
 			EWAHCompressedBitmap bitmap, int type) {
 		switch (type) {
 		case Constants.OBJ_BLOB:
 			return getBlobs().and(bitmap);
 		case Constants.OBJ_TREE:
 			return getTrees().and(bitmap);
 		case Constants.OBJ_COMMIT:
 			return getCommits().and(bitmap);
 		case Constants.OBJ_TAG:
 			return getTags().and(bitmap);
 		}
 		throw new IllegalArgumentException();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public int findPosition(AnyObjectId objectId) {
 		PositionEntry entry = positionEntries.get(objectId);
 		if (entry == null)
 			return -1;
 		return entry.offsetPosition;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public ObjectId getObject(int position) throws IllegalArgumentException {
 		ObjectId objectId = byOffset.get(position);
 		if (objectId == null)
 			throw new IllegalArgumentException();
 		return objectId;
 	}
 
 	/**
 	 * Get the commit object bitmap.
 	 *
 	 * @return the commit object bitmap.
 	 */
 	public EWAHCompressedBitmap getCommits() {
 		return commits;
 	}
 
 	/**
 	 * Get the tree object bitmap.
 	 *
 	 * @return the tree object bitmap.
 	 */
 	public EWAHCompressedBitmap getTrees() {
 		return trees;
 	}
 
 	/**
 	 * Get the blob object bitmap.
 	 *
 	 * @return the blob object bitmap.
 	 */
 	public EWAHCompressedBitmap getBlobs() {
 		return blobs;
 	}
 
 	/**
 	 * Get the tag object bitmap.
 	 *
 	 * @return the tag object bitmap.
 	 */
 	public EWAHCompressedBitmap getTags() {
 		return tags;
 	}
 
 	/**
 	 * Get the index storage options.
 	 *
 	 * @return the index storage options.
 	 */
 	public int getOptions() {
 		return PackBitmapIndexV1.OPT_FULL;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public int getBitmapCount() {
 		return getBitmaps().size();
 	}
 
 	/**
 	 * Remove all the bitmaps entries added.
 	 */
 	public void clearBitmaps() {
 		byAddOrder.clear();
 		getBitmaps().clear();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public int getObjectCount() {
 		return byOffset.size();
 	}
 
 	/**
 	 * Get an iterator over the xor compressed entries.
 	 *
 	 * @return an iterator over the xor compressed entries.
 	 */
 	public Iterable<StoredEntry> getCompressedBitmaps() {
 		// Add order is from oldest to newest. The reverse add order is the
 		// output order.
 		return () -> new Iterator<StoredEntry>() {
 
 			private int index = byAddOrder.size() - 1;
 
 			@Override
 			public boolean hasNext() {
 				return index >= 0;
 			}
 
 			@Override
 			public StoredEntry next() {
 				if (!hasNext()) {
 					throw new NoSuchElementException();
 				}
 				StoredBitmap item = byAddOrder.get(index);
 				int bestXorOffset = 0;
 				EWAHCompressedBitmap bestBitmap = item.getBitmap();
 
 				// Attempt to compress the bitmap with an XOR of the
 				// previously written entries.
 				for (int i = 1; i <= MAX_XOR_OFFSET_SEARCH; i++) {
 					int curr = i + index;
 					if (curr >= byAddOrder.size()) {
 						break;
 					}
 
 					StoredBitmap other = byAddOrder.get(curr);
 					EWAHCompressedBitmap bitmap = other.getBitmap()
 							.xor(item.getBitmap());
 
 					if (bitmap.sizeInBytes() < bestBitmap.sizeInBytes()) {
 						bestBitmap = bitmap;
 						bestXorOffset = i;
 					}
 				}
 				index--;
 
 				PositionEntry entry = positionEntries.get(item);
 				if (entry == null) {
 					throw new IllegalStateException();
 				}
 				bestBitmap.trim();
 				return new StoredEntry(entry.namePosition, bestBitmap,
 						bestXorOffset, item.getFlags());
 			}
 
 			@Override
 			public void remove() {
 				throw new UnsupportedOperationException();
 			}
 		};
 	}
 
 	/** Data object for the on disk representation of a bitmap entry. */
 	public static final class StoredEntry {
 		private final long objectId;
 		private final EWAHCompressedBitmap bitmap;
 		private final int xorOffset;
 		private final int flags;
 
 		StoredEntry(long objectId, EWAHCompressedBitmap bitmap,
 				int xorOffset, int flags) {
 			this.objectId = objectId;
 			this.bitmap = bitmap;
 			this.xorOffset = xorOffset;
 			this.flags = flags;
 		}
 
 		/** @return the bitmap */
 		public EWAHCompressedBitmap getBitmap() {
 			return bitmap;
 		}
 
 		/** @return the xorOffset */
 		public int getXorOffset() {
 			return xorOffset;
 		}
 
 		/** @return the flags */
 		public int getFlags() {
 			return flags;
 		}
 
 		/** @return the ObjectId */
 		public long getObjectId() {
 			return objectId;
 		}
 	}
 
 	private static final class PositionEntry extends ObjectIdOwnerMap.Entry {
 		final int namePosition;
 
 		int offsetPosition;
 
 		PositionEntry(AnyObjectId objectId, int namePosition) {
 			super(objectId);
 			this.namePosition = namePosition;
 		}
 	}
 }