/*
 * Copyright (C) 2008-2010, Google Inc.
 * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
 * 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.pack;

import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.transport.PackedObjectInfo;

Per-object state used by PackWriter. 
 PackWriter uses this class to track the things it needs to include in the newly generated pack file, and how to efficiently obtain the raw data for each object as they are written to the output stream. /**
 * Per-object state used by
 * {@link org.eclipse.jgit.internal.storage.pack.PackWriter}.
 * <p>
 * {@code PackWriter} uses this class to track the things it needs to include in
 * the newly generated pack file, and how to efficiently obtain the raw data for
 * each object as they are written to the output stream.
 */
public class ObjectToPack extends PackedObjectInfo {
	private static final int REUSE_AS_IS = 1 << 0;
	private static final int DELTA_ATTEMPTED = 1 << 1;
	private static final int DO_NOT_DELTA = 1 << 2;
	private static final int EDGE = 1 << 3;
	private static final int ATTEMPT_DELTA_MASK = REUSE_AS_IS | DELTA_ATTEMPTED;
	private static final int TYPE_SHIFT = 5;
	private static final int EXT_SHIFT = 8;
	private static final int EXT_MASK = 0xf;
	private static final int DELTA_SHIFT = 12;
	private static final int NON_EXT_MASK = ~(EXT_MASK << EXT_SHIFT);
	private static final int NON_DELTA_MASK = 0xfff;

	
Other object being packed that this will delta against. /** Other object being packed that this will delta against. */
	private ObjectId deltaBase;

	
Bit field, from bit 0 to bit 31:

1 bit: canReuseAsIs
1 bit: deltaAttempted
1 bit: doNotDelta
1 bit: edgeObject
1 bit: unused
3 bits: type
4 bits: subclass flags (if any)
--
20 bits: deltaDepth

/**
	 * Bit field, from bit 0 to bit 31:
	 * <ul>
	 * <li>1 bit: canReuseAsIs</li>
	 * <li>1 bit: deltaAttempted</li>
	 * <li>1 bit: doNotDelta</li>
	 * <li>1 bit: edgeObject</li>
	 * <li>1 bit: unused</li>
	 * <li>3 bits: type</li>
	 * <li>4 bits: subclass flags (if any)</li>
	 * <li>--</li>
	 * <li>20 bits: deltaDepth</li>
	 * </ul>
	 */
	private int flags;

	
Hash of the object's tree path. /** Hash of the object's tree path. */
	private int pathHash;

	
If present, deflated delta instruction stream for this object. /** If present, deflated delta instruction stream for this object. */
	private DeltaCache.Ref cachedDelta;

	
Construct for the specified object id.
Params:
src – 
           object id of object for packing
type – 
           real type code of the object, not its in-pack type./**
	 * Construct for the specified object id.
	 *
	 * @param src
	 *            object id of object for packing
	 * @param type
	 *            real type code of the object, not its in-pack type.
	 */
	public ObjectToPack(AnyObjectId src, int type) {
		super(src);
		flags = type << TYPE_SHIFT;
	}

	
Get delta base object id if object is going to be packed in delta
representation
Returns:
delta base object id if object is going to be packed in delta
        representation; null otherwise - if going to be packed as a whole
        object./**
	 * Get delta base object id if object is going to be packed in delta
	 * representation
	 *
	 * @return delta base object id if object is going to be packed in delta
	 *         representation; null otherwise - if going to be packed as a whole
	 *         object.
	 */
	public final ObjectId getDeltaBaseId() {
		return deltaBase;
	}

	
Get delta base object to pack if object is going to be packed in delta
representation and delta is specified as object to pack
Returns:
delta base object to pack if object is going to be packed in
        delta representation and delta is specified as object to pack;
        null otherwise - if going to be packed as a whole object or delta
        base is specified only as id./**
	 * Get delta base object to pack if object is going to be packed in delta
	 * representation and delta is specified as object to pack
	 *
	 * @return delta base object to pack if object is going to be packed in
	 *         delta representation and delta is specified as object to pack;
	 *         null otherwise - if going to be packed as a whole object or delta
	 *         base is specified only as id.
	 */
	public final ObjectToPack getDeltaBase() {
		if (deltaBase instanceof ObjectToPack)
			return (ObjectToPack) deltaBase;
		return null;
	}

	
Set delta base for the object. Delta base set by this method is used by PackWriter to write object - determines its representation in a created pack. 
Params:
deltaBase – 
           delta base object or null if object should be packed as a
           whole object./**
	 * Set delta base for the object. Delta base set by this method is used
	 * by {@link PackWriter} to write object - determines its representation
	 * in a created pack.
	 *
	 * @param deltaBase
	 *            delta base object or null if object should be packed as a
	 *            whole object.
	 *
	 */
	final void setDeltaBase(ObjectId deltaBase) {
		this.deltaBase = deltaBase;
	}

	final void setCachedDelta(DeltaCache.Ref data) {
		cachedDelta = data;
	}

	final DeltaCache.Ref popCachedDelta() {
		DeltaCache.Ref r = cachedDelta;
		if (r != null)
			cachedDelta = null;
		return r;
	}

	final void clearDeltaBase() {
		this.deltaBase = null;

		if (cachedDelta != null) {
			cachedDelta.clear();
			cachedDelta.enqueue();
			cachedDelta = null;
		}
	}

	
Whether object is going to be written as delta
Returns:
true if object is going to be written as delta; false otherwise./**
	 * Whether object is going to be written as delta
	 *
	 * @return true if object is going to be written as delta; false otherwise.
	 */
	public final boolean isDeltaRepresentation() {
		return deltaBase != null;
	}

	
Check if object is already written in a pack. This information is
used to achieve delta-base precedence in a pack file.
Returns:
true if object is already written; false otherwise./**
	 * Check if object is already written in a pack. This information is
	 * used to achieve delta-base precedence in a pack file.
	 *
	 * @return true if object is already written; false otherwise.
	 */
	public final boolean isWritten() {
		return 1 < getOffset(); // markWantWrite sets 1.
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public final int getType() {
		return (flags >> TYPE_SHIFT) & 0x7;
	}

	final int getDeltaDepth() {
		return flags >>> DELTA_SHIFT;
	}

	final void setDeltaDepth(int d) {
		flags = (d << DELTA_SHIFT) | (flags & NON_DELTA_MASK);
	}

	final int getChainLength() {
		return getDeltaDepth();
	}

	final void setChainLength(int len) {
		setDeltaDepth(len);
	}

	final void clearChainLength() {
		flags &= NON_DELTA_MASK;
	}

	final boolean wantWrite() {
		return getOffset() == 1;
	}

	final void markWantWrite() {
		setOffset(1);
	}

	
Whether an existing representation was selected to be reused as-is into
the pack stream.
Returns:
true if an existing representation was selected to be reused
        as-is into the pack stream./**
	 * Whether an existing representation was selected to be reused as-is into
	 * the pack stream.
	 *
	 * @return true if an existing representation was selected to be reused
	 *         as-is into the pack stream.
	 */
	public final boolean isReuseAsIs() {
		return (flags & REUSE_AS_IS) != 0;
	}

	final void setReuseAsIs() {
		flags |= REUSE_AS_IS;
	}

	
Forget the reuse information previously stored.
 Implementations may subclass this method, but they must also invoke the super version with super.clearReuseAsIs() to ensure the flag is properly cleared for the writer. /**
	 * Forget the reuse information previously stored.
	 * <p>
	 * Implementations may subclass this method, but they must also invoke the
	 * super version with {@code super.clearReuseAsIs()} to ensure the flag is
	 * properly cleared for the writer.
	 */
	protected void clearReuseAsIs() {
		flags &= ~REUSE_AS_IS;
	}

	final boolean isDoNotDelta() {
		return (flags & DO_NOT_DELTA) != 0;
	}

	final void setDoNotDelta() {
		flags |= DO_NOT_DELTA;
	}

	final boolean isEdge() {
		return (flags & EDGE) != 0;
	}

	final void setEdge() {
		flags |= EDGE;
	}

	final boolean doNotAttemptDelta() {
		// Do not attempt if delta attempted and object reuse.
		return (flags & ATTEMPT_DELTA_MASK) == ATTEMPT_DELTA_MASK;
	}

	final void setDeltaAttempted(boolean deltaAttempted) {
		if (deltaAttempted)
			flags |= DELTA_ATTEMPTED;
		else
			flags &= ~DELTA_ATTEMPTED;
	}

	
Get the extended flags on this object, in the range [0x0, 0xf].
Returns:
the extended flags on this object, in the range [0x0, 0xf]./**
	 * Get the extended flags on this object, in the range [0x0, 0xf].
	 *
	 * @return the extended flags on this object, in the range [0x0, 0xf].
	 */
	protected final int getExtendedFlags() {
		return (flags >>> EXT_SHIFT) & EXT_MASK;
	}

	
Determine if a particular extended flag bit has been set. This implementation may be faster than calling getExtendedFlags() and testing the result. 
Params:
flag – 
           the flag mask to test, must be between 0x0 and 0xf.
Returns:
true if any of the bits matching the mask are non-zero./**
	 * Determine if a particular extended flag bit has been set.
	 *
	 * This implementation may be faster than calling
	 * {@link #getExtendedFlags()} and testing the result.
	 *
	 * @param flag
	 *            the flag mask to test, must be between 0x0 and 0xf.
	 * @return true if any of the bits matching the mask are non-zero.
	 */
	protected final boolean isExtendedFlag(int flag) {
		return (flags & (flag << EXT_SHIFT)) != 0;
	}

	
Set an extended flag bit.
This implementation is more efficient than getting the extended flags,
adding the bit, and setting them all back.
Params:
flag – 
           the bits to set, must be between 0x0 and 0xf./**
	 * Set an extended flag bit.
	 *
	 * This implementation is more efficient than getting the extended flags,
	 * adding the bit, and setting them all back.
	 *
	 * @param flag
	 *            the bits to set, must be between 0x0 and 0xf.
	 */
	protected final void setExtendedFlag(int flag) {
		flags |= (flag & EXT_MASK) << EXT_SHIFT;
	}

	
Clear an extended flag bit.
This implementation is more efficient than getting the extended flags,
removing the bit, and setting them all back.
Params:
flag – 
           the bits to clear, must be between 0x0 and 0xf./**
	 * Clear an extended flag bit.
	 *
	 * This implementation is more efficient than getting the extended flags,
	 * removing the bit, and setting them all back.
	 *
	 * @param flag
	 *            the bits to clear, must be between 0x0 and 0xf.
	 */
	protected final void clearExtendedFlag(int flag) {
		flags &= ~((flag & EXT_MASK) << EXT_SHIFT);
	}

	
Set the extended flags used by the subclass.
Subclass implementations may store up to 4 bits of information inside of
the internal flags field already used by the base ObjectToPack instance.
Params:
extFlags – 
           additional flag bits to store in the flags field. Due to space
           constraints only values [0x0, 0xf] are permitted./**
	 * Set the extended flags used by the subclass.
	 *
	 * Subclass implementations may store up to 4 bits of information inside of
	 * the internal flags field already used by the base ObjectToPack instance.
	 *
	 * @param extFlags
	 *            additional flag bits to store in the flags field. Due to space
	 *            constraints only values [0x0, 0xf] are permitted.
	 */
	protected final void setExtendedFlags(int extFlags) {
		flags = ((extFlags & EXT_MASK) << EXT_SHIFT) | (flags & NON_EXT_MASK);
	}

	final int getFormat() {
		if (isReuseAsIs()) {
			if (isDeltaRepresentation())
				return StoredObjectRepresentation.PACK_DELTA;
			return StoredObjectRepresentation.PACK_WHOLE;
		}
		return StoredObjectRepresentation.FORMAT_OTHER;
	}

	// Overload weight into CRC since we don't need them at the same time.
	final int getWeight() {
		return getCRC();
	}

	final void setWeight(int weight) {
		setCRC(weight);
	}

	final int getPathHash() {
		return pathHash;
	}

	final void setPathHash(int hc) {
		pathHash = hc;
	}

	final int getCachedSize() {
		return pathHash;
	}

	final void setCachedSize(int sz) {
		pathHash = sz;
	}

	
Remember a specific representation for reuse at a later time.
 Implementers should remember the representation chosen, so it can be reused at a later time. PackWriter may invoke this method multiple times for the same object, each time saving the current best representation found. 
Params:
ref – 
           the object representation./**
	 * Remember a specific representation for reuse at a later time.
	 * <p>
	 * Implementers should remember the representation chosen, so it can be
	 * reused at a later time.
	 * {@link org.eclipse.jgit.internal.storage.pack.PackWriter} may invoke this
	 * method multiple times for the same object, each time saving the current
	 * best representation found.
	 *
	 * @param ref
	 *            the object representation.
	 */
	public void select(StoredObjectRepresentation ref) {
		// Empty by default.
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@SuppressWarnings("nls")
	@Override
	public String toString() {
		StringBuilder buf = new StringBuilder();
		buf.append("ObjectToPack[");
		buf.append(Constants.typeString(getType()));
		buf.append(" ");
		buf.append(name());
		if (wantWrite())
			buf.append(" wantWrite");
		if (isReuseAsIs())
			buf.append(" reuseAsIs");
		if (isDoNotDelta())
			buf.append(" doNotDelta");
		if (isEdge())
			buf.append(" edge");
		if (getDeltaDepth() > 0)
			buf.append(" depth=").append(getDeltaDepth());
		if (isDeltaRepresentation()) {
			if (getDeltaBase() != null)
				buf.append(" base=inpack:").append(getDeltaBase().name());
			else
				buf.append(" base=edge:").append(getDeltaBaseId().name());
		}
		if (isWritten())
			buf.append(" offset=").append(getOffset());
		buf.append("]");
		return buf.toString();
	}
}