/*
    * Copyright (C) 2008-2011, Google Inc.
    * Copyright (C) 2006-2008, 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.internal.storage.dfs;
  
  import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  import java.util.zip.DataFormatException;
  import java.util.zip.Inflater;
  
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.errors.StoredObjectRepresentationNotAvailableException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.file.BitmapIndexImpl;
  import org.eclipse.jgit.internal.storage.file.PackBitmapIndex;
  import org.eclipse.jgit.internal.storage.file.PackIndex;
  import org.eclipse.jgit.internal.storage.file.PackReverseIndex;
  import org.eclipse.jgit.internal.storage.pack.CachedPack;
  import org.eclipse.jgit.internal.storage.pack.ObjectReuseAsIs;
  import org.eclipse.jgit.internal.storage.pack.ObjectToPack;
  import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
  import org.eclipse.jgit.internal.storage.pack.PackWriter;
  import org.eclipse.jgit.lib.AbbreviatedObjectId;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.AsyncObjectLoaderQueue;
  import org.eclipse.jgit.lib.AsyncObjectSizeQueue;
  import org.eclipse.jgit.lib.BitmapIndex;
  import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
  import org.eclipse.jgit.lib.InflaterCache;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectLoader;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.util.BlockList;
  
  /**
   * Reader to access repository content through.
   * <p>
   * See the base {@link ObjectReader} documentation for details. Notably, a
   * reader is not thread safe.
   */
  public final class DfsReader extends ObjectReader implements ObjectReuseAsIs {
  	/** Temporary buffer large enough for at least one raw object id. */
  	final byte[] tempId = new byte[OBJECT_ID_LENGTH];
  
  	/** Database this reader loads objects from. */
  	final DfsObjDatabase db;
  
 	private Inflater inf;
 
 	private DfsBlock block;
 
 	private DeltaBaseCache baseCache;
 
 	private DfsPackFile last;
 
 	private boolean avoidUnreachable;
 
 	DfsReader(DfsObjDatabase db) {
 		this.db = db;
 	}
 
 	DfsReaderOptions getOptions() {
 		return db.getReaderOptions();
 	}
 
 	DeltaBaseCache getDeltaBaseCache() {
 		if (baseCache == null)
 			baseCache = new DeltaBaseCache(this);
 		return baseCache;
 	}
 
 	int getStreamFileThreshold() {
 		return getOptions().getStreamFileThreshold();
 	}
 
 	@Override
 	public ObjectReader newReader() {
 		return new DfsReader(db);
 	}
 
 	@Override
 	public void setAvoidUnreachableObjects(boolean avoid) {
 		avoidUnreachable = avoid;
 	}
 
 	@Override
 	public BitmapIndex getBitmapIndex() throws IOException {
 		for (DfsPackFile pack : db.getPacks()) {
 			PackBitmapIndex bitmapIndex = pack.getBitmapIndex(this);
 			if (bitmapIndex != null)
 				return new BitmapIndexImpl(bitmapIndex);
 		}
 		return null;
 	}
 
 	public Collection<CachedPack> getCachedPacksAndUpdate(
 		BitmapBuilder needBitmap) throws IOException {
 		for (DfsPackFile pack : db.getPacks()) {
 			PackBitmapIndex bitmapIndex = pack.getBitmapIndex(this);
 			if (needBitmap.removeAllOrNone(bitmapIndex))
 				return Collections.<CachedPack> singletonList(
 						new DfsCachedPack(pack));
 		}
 		return Collections.emptyList();
 	}
 
 	@Override
 	public Collection<ObjectId> resolve(AbbreviatedObjectId id)
 			throws IOException {
 		if (id.isComplete())
 			return Collections.singleton(id.toObjectId());
 		boolean noGarbage = avoidUnreachable;
 		HashSet<ObjectId> matches = new HashSet<ObjectId>(4);
 		for (DfsPackFile pack : db.getPacks()) {
 			if (noGarbage && pack.isGarbage())
 				continue;
 			pack.resolve(this, matches, id, 256);
 			if (256 <= matches.size())
 				break;
 		}
 		return matches;
 	}
 
 	@Override
 	public boolean has(AnyObjectId objectId) throws IOException {
 		if (last != null && last.hasObject(this, objectId))
 			return true;
 		boolean noGarbage = avoidUnreachable;
 		for (DfsPackFile pack : db.getPacks()) {
 			if (pack == last || (noGarbage && pack.isGarbage()))
 				continue;
 			if (pack.hasObject(this, objectId)) {
 				last = pack;
 				return true;
 			}
 		}
 		return false;
 	}
 
 	@Override
 	public ObjectLoader open(AnyObjectId objectId, int typeHint)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
 		if (last != null) {
 			ObjectLoader ldr = last.get(this, objectId);
 			if (ldr != null)
 				return ldr;
 		}
 
 		boolean noGarbage = avoidUnreachable;
 		for (DfsPackFile pack : db.getPacks()) {
 			if (pack == last || (noGarbage && pack.isGarbage()))
 				continue;
 			ObjectLoader ldr = pack.get(this, objectId);
 			if (ldr != null) {
 				last = pack;
 				return ldr;
 			}
 		}
 
 		if (typeHint == OBJ_ANY)
 			throw new MissingObjectException(objectId.copy(),
 					JGitText.get().unknownObjectType2);
 		throw new MissingObjectException(objectId.copy(), typeHint);
 	}
 
 	@Override
 	public Set<ObjectId> getShallowCommits() {
 		return Collections.emptySet();
 	}
 
 	private static final Comparator<FoundObject<?>> FOUND_OBJECT_SORT = new Comparator<FoundObject<?>>() {
 		public int compare(FoundObject<?> a, FoundObject<?> b) {
 			int cmp = a.packIndex - b.packIndex;
 			if (cmp == 0)
 				cmp = Long.signum(a.offset - b.offset);
 			return cmp;
 		}
 	};
 
 	private static class FoundObject<T extends ObjectId> {
 		final T id;
 		final DfsPackFile pack;
 		final long offset;
 		final int packIndex;
 
 		FoundObject(T objectId, int packIdx, DfsPackFile pack, long offset) {
 			this.id = objectId;
 			this.pack = pack;
 			this.offset = offset;
 			this.packIndex = packIdx;
 		}
 
 		FoundObject(T objectId) {
 			this.id = objectId;
 			this.pack = null;
 			this.offset = 0;
 			this.packIndex = 0;
 		}
 	}
 
 	private <T extends ObjectId> Iterable<FoundObject<T>> findAll(
 			Iterable<T> objectIds) throws IOException {
 		ArrayList<FoundObject<T>> r = new ArrayList<FoundObject<T>>();
 		DfsPackFile[] packList = db.getPacks();
 		if (packList.length == 0) {
 			for (T t : objectIds)
 				r.add(new FoundObject<T>(t));
 			return r;
 		}
 
 		int lastIdx = 0;
 		DfsPackFile lastPack = packList[lastIdx];
 		boolean noGarbage = avoidUnreachable;
 
 		OBJECT_SCAN: for (T t : objectIds) {
 			try {
 				long p = lastPack.findOffset(this, t);
 				if (0 < p) {
 					r.add(new FoundObject<T>(t, lastIdx, lastPack, p));
 					continue;
 				}
 			} catch (IOException e) {
 				// Fall though and try to examine other packs.
 			}
 
 			for (int i = 0; i < packList.length; i++) {
 				if (i == lastIdx)
 					continue;
 				DfsPackFile pack = packList[i];
 				if (noGarbage && pack.isGarbage())
 					continue;
 				try {
 					long p = pack.findOffset(this, t);
 					if (0 < p) {
 						r.add(new FoundObject<T>(t, i, pack, p));
 						lastIdx = i;
 						lastPack = pack;
 						continue OBJECT_SCAN;
 					}
 				} catch (IOException e) {
 					// Examine other packs.
 				}
 			}
 
 			r.add(new FoundObject<T>(t));
 		}
 
 		Collections.sort(r, FOUND_OBJECT_SORT);
 		last = lastPack;
 		return r;
 	}
 
 	@Override
 	public <T extends ObjectId> AsyncObjectLoaderQueue<T> open(
 			Iterable<T> objectIds, final boolean reportMissing) {
 		Iterable<FoundObject<T>> order;
 		IOException error = null;
 		try {
 			order = findAll(objectIds);
 		} catch (IOException e) {
 			order = Collections.emptyList();
 			error = e;
 		}
 
 		final Iterator<FoundObject<T>> idItr = order.iterator();
 		final IOException findAllError = error;
 		return new AsyncObjectLoaderQueue<T>() {
 			private FoundObject<T> cur;
 
 			public boolean next() throws MissingObjectException, IOException {
 				if (idItr.hasNext()) {
 					cur = idItr.next();
 					return true;
 				} else if (findAllError != null) {
 					throw findAllError;
 				} else {
 					return false;
 				}
 			}
 
 			public T getCurrent() {
 				return cur.id;
 			}
 
 			public ObjectId getObjectId() {
 				return cur.id;
 			}
 
 			public ObjectLoader open() throws IOException {
 				if (cur.pack == null)
 					throw new MissingObjectException(cur.id,
 							JGitText.get().unknownObjectType2);
 				return cur.pack.load(DfsReader.this, cur.offset);
 			}
 
 			public boolean cancel(boolean mayInterruptIfRunning) {
 				return true;
 			}
 
 			public void release() {
 				// Nothing to clean up.
 			}
 		};
 	}
 
 	@Override
 	public <T extends ObjectId> AsyncObjectSizeQueue<T> getObjectSize(
 			Iterable<T> objectIds, final boolean reportMissing) {
 		Iterable<FoundObject<T>> order;
 		IOException error = null;
 		try {
 			order = findAll(objectIds);
 		} catch (IOException e) {
 			order = Collections.emptyList();
 			error = e;
 		}
 
 		final Iterator<FoundObject<T>> idItr = order.iterator();
 		final IOException findAllError = error;
 		return new AsyncObjectSizeQueue<T>() {
 			private FoundObject<T> cur;
 
 			private long sz;
 
 			public boolean next() throws MissingObjectException, IOException {
 				if (idItr.hasNext()) {
 					cur = idItr.next();
 					if (cur.pack == null)
 						throw new MissingObjectException(cur.id,
 								JGitText.get().unknownObjectType2);
 					sz = cur.pack.getObjectSize(DfsReader.this, cur.offset);
 					return true;
 				} else if (findAllError != null) {
 					throw findAllError;
 				} else {
 					return false;
 				}
 			}
 
 			public T getCurrent() {
 				return cur.id;
 			}
 
 			public ObjectId getObjectId() {
 				return cur.id;
 			}
 
 			public long getSize() {
 				return sz;
 			}
 
 			public boolean cancel(boolean mayInterruptIfRunning) {
 				return true;
 			}
 
 			public void release() {
 				// Nothing to clean up.
 			}
 		};
 	}
 
 	@Override
 	public long getObjectSize(AnyObjectId objectId, int typeHint)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
 		if (last != null) {
 			long sz = last.getObjectSize(this, objectId);
 			if (0 <= sz)
 				return sz;
 		}
 
 		for (DfsPackFile pack : db.getPacks()) {
 			if (pack == last)
 				continue;
 			long sz = pack.getObjectSize(this, objectId);
 			if (0 <= sz) {
 				last = pack;
 				return sz;
 			}
 		}
 
 		if (typeHint == OBJ_ANY)
 			throw new MissingObjectException(objectId.copy(),
 					JGitText.get().unknownObjectType2);
 		throw new MissingObjectException(objectId.copy(), typeHint);
 	}
 
 	public DfsObjectToPack newObjectToPack(AnyObjectId objectId, int type) {
 		return new DfsObjectToPack(objectId, type);
 	}
 
 	private static final Comparator<DfsObjectToPack> OFFSET_SORT = new Comparator<DfsObjectToPack>() {
 		public int compare(DfsObjectToPack a, DfsObjectToPack b) {
 			return Long.signum(a.getOffset() - b.getOffset());
 		}
 	};
 
 	public void selectObjectRepresentation(PackWriter packer,
 			ProgressMonitor monitor, Iterable<ObjectToPack> objects)
 			throws IOException, MissingObjectException {
 		for (DfsPackFile pack : db.getPacks()) {
 			List<DfsObjectToPack> tmp = findAllFromPack(pack, objects);
 			if (tmp.isEmpty())
 				continue;
 			Collections.sort(tmp, OFFSET_SORT);
 			PackReverseIndex rev = pack.getReverseIdx(this);
 			DfsObjectRepresentation rep = new DfsObjectRepresentation(pack);
 			for (DfsObjectToPack otp : tmp) {
 				pack.representation(rep, otp.getOffset(), this, rev);
 				otp.setOffset(0);
 				packer.select(otp, rep);
 				if (!otp.isFound()) {
 					otp.setFound();
 					monitor.update(1);
 				}
 			}
 		}
 	}
 
 	private List<DfsObjectToPack> findAllFromPack(DfsPackFile pack,
 			Iterable<ObjectToPack> objects) throws IOException {
 		List<DfsObjectToPack> tmp = new BlockList<DfsObjectToPack>();
 		PackIndex idx = pack.getPackIndex(this);
 		for (ObjectToPack otp : objects) {
 			long p = idx.findOffset(otp);
 			if (0 < p) {
 				otp.setOffset(p);
 				tmp.add((DfsObjectToPack) otp);
 			}
 		}
 		return tmp;
 	}
 
 	public void copyObjectAsIs(PackOutputStream out, ObjectToPack otp,
 			boolean validate) throws IOException,
 			StoredObjectRepresentationNotAvailableException {
 		DfsObjectToPack src = (DfsObjectToPack) otp;
 		src.pack.copyAsIs(out, src, validate, this);
 	}
 
 	public void writeObjects(PackOutputStream out, List<ObjectToPack> list)
 			throws IOException {
 		for (ObjectToPack otp : list)
 			out.writeObject(otp);
 	}
 
 	public void copyPackAsIs(PackOutputStream out, CachedPack pack)
 			throws IOException {
 		((DfsCachedPack) pack).copyAsIs(out, this);
 	}
 
 	/**
 	 * Copy bytes from the window to a caller supplied buffer.
 	 *
 	 * @param pack
 	 *            the file the desired window is stored within.
 	 * @param position
 	 *            position within the file to read from.
 	 * @param dstbuf
 	 *            destination buffer to copy into.
 	 * @param dstoff
 	 *            offset within <code>dstbuf</code> to start copying into.
 	 * @param cnt
 	 *            number of bytes to copy. This value may exceed the number of
 	 *            bytes remaining in the window starting at offset
 	 *            <code>pos</code>.
 	 * @return number of bytes actually copied; this may be less than
 	 *         <code>cnt</code> if <code>cnt</code> exceeded the number of bytes
 	 *         available.
 	 * @throws IOException
 	 *             this cursor does not match the provider or id and the proper
 	 *             window could not be acquired through the provider's cache.
 	 */
 	int copy(DfsPackFile pack, long position, byte[] dstbuf, int dstoff, int cnt)
 			throws IOException {
 		if (cnt == 0)
 			return 0;
 
 		long length = pack.length;
 		if (0 <= length && length <= position)
 			return 0;
 
 		int need = cnt;
 		do {
 			pin(pack, position);
 			int r = block.copy(position, dstbuf, dstoff, need);
 			position += r;
 			dstoff += r;
 			need -= r;
 			if (length < 0)
 				length = pack.length;
 		} while (0 < need && position < length);
 		return cnt - need;
 	}
 
 	/**
 	 * Inflate a region of the pack starting at {@code position}.
 	 *
 	 * @param pack
 	 *            the file the desired window is stored within.
 	 * @param position
 	 *            position within the file to read from.
 	 * @param dstbuf
 	 *            destination buffer the inflater should output decompressed
 	 *            data to. Must be large enough to store the entire stream,
 	 *            unless headerOnly is true.
 	 * @param headerOnly
 	 *            if true the caller wants only {@code dstbuf.length} bytes.
 	 * @return number of bytes inflated into <code>dstbuf</code>.
 	 * @throws IOException
 	 *             this cursor does not match the provider or id and the proper
 	 *             window could not be acquired through the provider's cache.
 	 * @throws DataFormatException
 	 *             the inflater encountered an invalid chunk of data. Data
 	 *             stream corruption is likely.
 	 */
 	int inflate(DfsPackFile pack, long position, byte[] dstbuf,
 			boolean headerOnly) throws IOException, DataFormatException {
 		prepareInflater();
 		pin(pack, position);
 		position += block.setInput(position, inf);
 		for (int dstoff = 0;;) {
 			int n = inf.inflate(dstbuf, dstoff, dstbuf.length - dstoff);
 			dstoff += n;
 			if (inf.finished() || (headerOnly && dstoff == dstbuf.length))
 				return dstoff;
 			if (inf.needsInput()) {
 				pin(pack, position);
 				position += block.setInput(position, inf);
 			} else if (n == 0)
 				throw new DataFormatException();
 		}
 	}
 
 	DfsBlock quickCopy(DfsPackFile p, long pos, long cnt)
 			throws IOException {
 		pin(p, pos);
 		if (block.contains(p.key, pos + (cnt - 1)))
 			return block;
 		return null;
 	}
 
 	Inflater inflater() {
 		prepareInflater();
 		return inf;
 	}
 
 	private void prepareInflater() {
 		if (inf == null)
 			inf = InflaterCache.get();
 		else
 			inf.reset();
 	}
 
 	void pin(DfsPackFile pack, long position) throws IOException {
 		DfsBlock b = block;
 		if (b == null || !b.contains(pack.key, position)) {
 			// If memory is low, we may need what is in our window field to
 			// be cleaned up by the GC during the get for the next window.
 			// So we always clear it, even though we are just going to set
 			// it again.
 			block = null;
 			block = pack.getOrLoadBlock(position, this);
 		}
 	}
 
 	void unpin() {
 		block = null;
 	}
 
 	/** Release the current window cursor. */
 	@Override
 	public void close() {
 		last = null;
 		block = null;
 		baseCache = null;
 		try {
 			InflaterCache.release(inf);
 		} finally {
 			inf = null;
 		}
 	}
 }