/*
 * Copyright (C) 2008-2009, Google Inc.
 * Copyright (C) 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;
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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package org.eclipse.jgit.dircache;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.IOException;
import java.io.InputStream;
import java.util.Collections;

import org.eclipse.jgit.attributes.AttributesNode;
import org.eclipse.jgit.attributes.AttributesRule;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectLoader;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.EmptyTreeIterator;
import org.eclipse.jgit.util.RawParseUtils;

Iterate a DirCache as part of a TreeWalk.

This is an iterator to adapt a loaded DirCache instance (such as
read from an existing .git/index file) to the tree structure
used by a TreeWalk, making it possible for applications to walk
over any combination of tree objects already in the object database, index
files, or working directories.
See Also:
TreeWalk/**
 * Iterate a {@link org.eclipse.jgit.dircache.DirCache} as part of a
 * <code>TreeWalk</code>.
 * <p>
 * This is an iterator to adapt a loaded <code>DirCache</code> instance (such as
 * read from an existing <code>.git/index</code> file) to the tree structure
 * used by a <code>TreeWalk</code>, making it possible for applications to walk
 * over any combination of tree objects already in the object database, index
 * files, or working directories.
 *
 * @see org.eclipse.jgit.treewalk.TreeWalk
 */
public class DirCacheIterator extends AbstractTreeIterator {
	
Byte array holding ".gitattributes" string /** Byte array holding ".gitattributes" string */
	private static final byte[] DOT_GIT_ATTRIBUTES_BYTES = Constants.DOT_GIT_ATTRIBUTES
			.getBytes(UTF_8);

	
The cache this iterator was created to walk. /** The cache this iterator was created to walk. */
	protected final DirCache cache;

	
The tree this iterator is walking. /** The tree this iterator is walking. */
	private final DirCacheTree tree;

	
First position in this tree. /** First position in this tree. */
	private final int treeStart;

	
Last position in this tree. /** Last position in this tree. */
	private final int treeEnd;

	
Special buffer to hold the ObjectId of currentSubtree. /** Special buffer to hold the ObjectId of {@link #currentSubtree}. */
	private final byte[] subtreeId;

	
Index of entry within cache. /** Index of entry within {@link #cache}. */
	protected int ptr;

	
Next subtree to consider within tree. /** Next subtree to consider within {@link #tree}. */
	private int nextSubtreePos;

	
The current file entry from cache. /** The current file entry from {@link #cache}. */
	protected DirCacheEntry currentEntry;

	
The subtree containing currentEntry if this is first entry. /** The subtree containing {@link #currentEntry} if this is first entry. */
	protected DirCacheTree currentSubtree;

	
Create a new iterator for an already loaded DirCache instance.

The iterator implementation may copy part of the cache's data during
construction, so the cache must be read in prior to creating the
iterator.
Params:
dc – 
           the cache to walk. It must be already loaded into memory./**
	 * Create a new iterator for an already loaded DirCache instance.
	 * <p>
	 * The iterator implementation may copy part of the cache's data during
	 * construction, so the cache must be read in prior to creating the
	 * iterator.
	 *
	 * @param dc
	 *            the cache to walk. It must be already loaded into memory.
	 */
	public DirCacheIterator(DirCache dc) {
		cache = dc;
		tree = dc.getCacheTree(true);
		treeStart = 0;
		treeEnd = tree.getEntrySpan();
		subtreeId = new byte[Constants.OBJECT_ID_LENGTH];
		if (!eof())
			parseEntry();
	}

	DirCacheIterator(DirCacheIterator p, DirCacheTree dct) {
		super(p, p.path, p.pathLen + 1);
		cache = p.cache;
		tree = dct;
		treeStart = p.ptr;
		treeEnd = treeStart + tree.getEntrySpan();
		subtreeId = p.subtreeId;
		ptr = p.ptr;
		parseEntry();
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public AbstractTreeIterator createSubtreeIterator(ObjectReader reader)
			throws IncorrectObjectTypeException, IOException {
		if (currentSubtree == null)
			throw new IncorrectObjectTypeException(getEntryObjectId(),
					Constants.TYPE_TREE);
		return new DirCacheIterator(this, currentSubtree);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public EmptyTreeIterator createEmptyTreeIterator() {
		final byte[] n = new byte[Math.max(pathLen + 1, DEFAULT_PATH_SIZE)];
		System.arraycopy(path, 0, n, 0, pathLen);
		n[pathLen] = '/';
		return new EmptyTreeIterator(this, n, pathLen + 1);
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public boolean hasId() {
		if (currentSubtree != null)
			return currentSubtree.isValid();
		return currentEntry != null;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public byte[] idBuffer() {
		if (currentSubtree != null)
			return currentSubtree.isValid() ? subtreeId : zeroid;
		if (currentEntry != null)
			return currentEntry.idBuffer();
		return zeroid;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public int idOffset() {
		if (currentSubtree != null)
			return 0;
		if (currentEntry != null)
			return currentEntry.idOffset();
		return 0;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void reset() {
		if (!first()) {
			ptr = treeStart;
			nextSubtreePos = 0;
			currentEntry = null;
			currentSubtree = null;
			if (!eof())
				parseEntry();
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public boolean first() {
		return ptr == treeStart;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public boolean eof() {
		return ptr == treeEnd;
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void next(int delta) {
		while (--delta >= 0) {
			if (currentSubtree != null)
				ptr += currentSubtree.getEntrySpan();
			else
				ptr++;
			if (eof())
				break;
			parseEntry();
		}
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public void back(int delta) {
		while (--delta >= 0) {
			if (currentSubtree != null)
				nextSubtreePos--;
			ptr--;
			parseEntry(false);
			if (currentSubtree != null)
				ptr -= currentSubtree.getEntrySpan() - 1;
		}
	}

	private void parseEntry() {
		parseEntry(true);
	}

	private void parseEntry(boolean forward) {
		currentEntry = cache.getEntry(ptr);
		final byte[] cep = currentEntry.path;

		if (!forward) {
			if (nextSubtreePos > 0) {
				final DirCacheTree p = tree.getChild(nextSubtreePos - 1);
				if (p.contains(cep, pathOffset, cep.length)) {
					nextSubtreePos--;
					currentSubtree = p;
				}
			}
		}
		if (nextSubtreePos != tree.getChildCount()) {
			final DirCacheTree s = tree.getChild(nextSubtreePos);
			if (s.contains(cep, pathOffset, cep.length)) {
				// The current position is the first file of this subtree.
				// Use the subtree instead as the current position.
				//
				currentSubtree = s;
				nextSubtreePos++;

				if (s.isValid())
					s.getObjectId().copyRawTo(subtreeId, 0);
				mode = FileMode.TREE.getBits();
				path = cep;
				pathLen = pathOffset + s.nameLength();
				return;
			}
		}

		// The current position is a file/symlink/gitlink so we
		// do not have a subtree located here.
		//
		mode = currentEntry.getRawMode();
		path = cep;
		pathLen = cep.length;
		currentSubtree = null;
		// Checks if this entry is a .gitattributes file
		if (RawParseUtils.match(path, pathOffset, DOT_GIT_ATTRIBUTES_BYTES) == path.length)
			attributesNode = new LazyLoadingAttributesNode(
					currentEntry.getObjectId());
	}

	
Get the DirCacheEntry for the current file.
Returns:
the current cache entry, if this iterator is positioned on a
        non-tree./**
	 * Get the DirCacheEntry for the current file.
	 *
	 * @return the current cache entry, if this iterator is positioned on a
	 *         non-tree.
	 */
	public DirCacheEntry getDirCacheEntry() {
		return currentSubtree == null ? currentEntry : null;
	}

	
Retrieves the AttributesNode for the current entry. 
Params:
reader –  ObjectReader used to parse the .gitattributes entry.
Throws:
IOException – 
Returns:
AttributesNode for the current entry.
Since:
3.7/**
	 * Retrieves the {@link org.eclipse.jgit.attributes.AttributesNode} for the
	 * current entry.
	 *
	 * @param reader
	 *            {@link org.eclipse.jgit.lib.ObjectReader} used to parse the
	 *            .gitattributes entry.
	 * @return {@link org.eclipse.jgit.attributes.AttributesNode} for the
	 *         current entry.
	 * @throws java.io.IOException
	 * @since 3.7
	 */
	public AttributesNode getEntryAttributesNode(ObjectReader reader)
			throws IOException {
		if (attributesNode instanceof LazyLoadingAttributesNode)
			attributesNode = ((LazyLoadingAttributesNode) attributesNode)
					.load(reader);
		return attributesNode;
	}

	
AttributesNode implementation that provides lazy loading facilities. /**
	 * {@link AttributesNode} implementation that provides lazy loading
	 * facilities.
	 */
	private static class LazyLoadingAttributesNode extends AttributesNode {
		final ObjectId objectId;

		LazyLoadingAttributesNode(ObjectId objectId) {
			super(Collections.<AttributesRule> emptyList());
			this.objectId = objectId;

		}

		AttributesNode load(ObjectReader reader) throws IOException {
			AttributesNode r = new AttributesNode();
			ObjectLoader loader = reader.open(objectId);
			if (loader != null) {
				try (InputStream in = loader.openStream()) {
					r.parse(in);
				}
			}
			return r.getRules().isEmpty() ? null : r;
		}
	}

}