/*
    * 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;
   * 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.revwalk;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.io.IOException;
  import java.nio.charset.Charset;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.MutableObjectId;
  import org.eclipse.jgit.lib.ObjectInserter;
  import org.eclipse.jgit.lib.ObjectReader;
  import org.eclipse.jgit.lib.PersonIdent;
  import org.eclipse.jgit.util.RawParseUtils;
  import org.eclipse.jgit.util.StringUtils;
  
  /** A commit reference to a commit in the DAG. */
  public class RevCommit extends RevObject {
  	private static final int STACK_DEPTH = 500;
  
  	/**
  	 * Parse a commit from its canonical format.
  	 *
  	 * This method constructs a temporary revision pool, parses the commit as
  	 * supplied, and returns it to the caller. Since the commit was built inside
  	 * of a private revision pool its parent pointers will be initialized, but
  	 * will not have their headers loaded.
  	 *
  	 * Applications are discouraged from using this API. Callers usually need
  	 * more than one commit. Use {@link RevWalk#parseCommit(AnyObjectId)} to
  	 * obtain a RevCommit from an existing repository.
  	 *
  	 * @param raw
  	 *            the canonical formatted commit to be parsed.
  	 * @return the parsed commit, in an isolated revision pool that is not
  	 *         available to the caller.
  	 */
  	public static RevCommit parse(byte[] raw) {
  		try {
  			return parse(new RevWalk((ObjectReader) null), raw);
  		} catch (IOException ex) {
  			throw new RuntimeException(ex);
  		}
  	}
  
  	/**
  	 * Parse a commit from its canonical format.
 	 * <p>
 	 * This method inserts the commit directly into the caller supplied revision
 	 * pool, making it appear as though the commit exists in the repository,
 	 * even if it doesn't. The repository under the pool is not affected.
 	 * <p>
 	 * The body of the commit (message, author, committer) is always retained in
 	 * the returned {@code RevCommit}, even if the supplied {@code RevWalk} has
 	 * been configured with {@code setRetainBody(false)}.
 	 *
 	 * @param rw
 	 *            the revision pool to allocate the commit within. The commit's
 	 *            tree and parent pointers will be obtained from this pool.
 	 * @param raw
 	 *            the canonical formatted commit to be parsed. This buffer will
 	 *            be retained by the returned {@code RevCommit} and must not be
 	 *            modified by the caller.
 	 * @return the parsed commit, in an isolated revision pool that is not
 	 *         available to the caller.
 	 * @throws IOException
 	 *             in case of RevWalk initialization fails
 	 */
 	public static RevCommit parse(RevWalk rw, byte[] raw) throws IOException {
 		try (ObjectInserter.Formatter fmt = new ObjectInserter.Formatter()) {
 			RevCommit r = rw.lookupCommit(fmt.idFor(Constants.OBJ_COMMIT, raw));
 			r.parseCanonical(rw, raw);
 			r.buffer = raw;
 			return r;
 		}
 	}
 
 	static final RevCommit[] NO_PARENTS = {};
 
 	private RevTree tree;
 
 	RevCommit[] parents;
 
 	int commitTime; // An int here for performance, overflows in 2038
 
 	int inDegree;
 
 	private byte[] buffer;
 
 	/**
 	 * Create a new commit reference.
 	 *
 	 * @param id
 	 *            object name for the commit.
 	 */
 	protected RevCommit(final AnyObjectId id) {
 		super(id);
 	}
 
 	@Override
 	void parseHeaders(final RevWalk walk) throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		parseCanonical(walk, walk.getCachedBytes(this));
 	}
 
 	@Override
 	void parseBody(final RevWalk walk) throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		if (buffer == null) {
 			buffer = walk.getCachedBytes(this);
 			if ((flags & PARSED) == 0)
 				parseCanonical(walk, buffer);
 		}
 	}
 
 	void parseCanonical(final RevWalk walk, final byte[] raw)
 			throws IOException {
 		if (!walk.shallowCommitsInitialized)
 			walk.initializeShallowCommits();
 
 		final MutableObjectId idBuffer = walk.idBuffer;
 		idBuffer.fromString(raw, 5);
 		tree = walk.lookupTree(idBuffer);
 
 		int ptr = 46;
 		if (parents == null) {
 			RevCommit[] pList = new RevCommit[1];
 			int nParents = 0;
 			for (;;) {
 				if (raw[ptr] != 'p')
 					break;
 				idBuffer.fromString(raw, ptr + 7);
 				final RevCommit p = walk.lookupCommit(idBuffer);
 				if (nParents == 0)
 					pList[nParents++] = p;
 				else if (nParents == 1) {
 					pList = new RevCommit[] { pList[0], p };
 					nParents = 2;
 				} else {
 					if (pList.length <= nParents) {
 						RevCommit[] old = pList;
 						pList = new RevCommit[pList.length + 32];
 						System.arraycopy(old, 0, pList, 0, nParents);
 					}
 					pList[nParents++] = p;
 				}
 				ptr += 48;
 			}
 			if (nParents != pList.length) {
 				RevCommit[] old = pList;
 				pList = new RevCommit[nParents];
 				System.arraycopy(old, 0, pList, 0, nParents);
 			}
 			parents = pList;
 		}
 
 		// extract time from "committer "
 		ptr = RawParseUtils.committer(raw, ptr);
 		if (ptr > 0) {
 			ptr = RawParseUtils.nextLF(raw, ptr, '>');
 
 			// In 2038 commitTime will overflow unless it is changed to long.
 			commitTime = RawParseUtils.parseBase10(raw, ptr, null);
 		}
 
 		if (walk.isRetainBody())
 			buffer = raw;
 		flags |= PARSED;
 	}
 
 	@Override
 	public final int getType() {
 		return Constants.OBJ_COMMIT;
 	}
 
 	static void carryFlags(RevCommit c, int carry) {
 		FIFORevQueue q = carryFlags1(c, carry, 0);
 		if (q != null)
 			slowCarryFlags(q, carry);
 	}
 
 	private static FIFORevQueue carryFlags1(RevCommit c, int carry, int depth) {
 		for(;;) {
 			RevCommit[] pList = c.parents;
 			if (pList == null || pList.length == 0)
 				return null;
 			if (pList.length != 1) {
 				if (depth == STACK_DEPTH)
 					return defer(c);
 				for (int i = 1; i < pList.length; i++) {
 					RevCommit p = pList[i];
 					if ((p.flags & carry) == carry)
 						continue;
 					p.flags |= carry;
 					FIFORevQueue q = carryFlags1(p, carry, depth + 1);
 					if (q != null)
 						return defer(q, carry, pList, i + 1);
 				}
 			}
 
 			c = pList[0];
 			if ((c.flags & carry) == carry)
 				return null;
 			c.flags |= carry;
 		}
 	}
 
 	private static FIFORevQueue defer(RevCommit c) {
 		FIFORevQueue q = new FIFORevQueue();
 		q.add(c);
 		return q;
 	}
 
 	private static FIFORevQueue defer(FIFORevQueue q, int carry,
 			RevCommit[] pList, int i) {
 		// In normal case the caller will run pList[0] in a tail recursive
 		// fashion by updating the variable. However the caller is unwinding
 		// the stack and will skip that pList[0] execution step.
 		carryOneStep(q, carry, pList[0]);
 
 		// Remaining parents (if any) need to have flags checked and be
 		// enqueued if they have ancestors.
 		for (; i < pList.length; i++)
 			carryOneStep(q, carry, pList[i]);
 		return q;
 	}
 
 	private static void slowCarryFlags(FIFORevQueue q, int carry) {
 		// Commits in q have non-null parent arrays and have set all
 		// flags in carry. This loop finishes copying over the graph.
 		for (RevCommit c; (c = q.next()) != null;) {
 			for (RevCommit p : c.parents)
 				carryOneStep(q, carry, p);
 		}
 	}
 
 	private static void carryOneStep(FIFORevQueue q, int carry, RevCommit c) {
 		if ((c.flags & carry) != carry) {
 			c.flags |= carry;
 			if (c.parents != null)
 				q.add(c);
 		}
 	}
 
 	/**
 	 * Carry a RevFlag set on this commit to its parents.
 	 * <p>
 	 * If this commit is parsed, has parents, and has the supplied flag set on
 	 * it we automatically add it to the parents, grand-parents, and so on until
 	 * an unparsed commit or a commit with no parents is discovered. This
 	 * permits applications to force a flag through the history chain when
 	 * necessary.
 	 *
 	 * @param flag
 	 *            the single flag value to carry back onto parents.
 	 */
 	public void carry(final RevFlag flag) {
 		final int carry = flags & flag.mask;
 		if (carry != 0)
 			carryFlags(this, carry);
 	}
 
 	/**
 	 * Time from the "committer " line of the buffer.
 	 *
 	 * @return time, expressed as seconds since the epoch.
 	 */
 	public final int getCommitTime() {
 		return commitTime;
 	}
 
 	/**
 	 * Get a reference to this commit's tree.
 	 *
 	 * @return tree of this commit.
 	 */
 	public final RevTree getTree() {
 		return tree;
 	}
 
 	/**
 	 * Get the number of parent commits listed in this commit.
 	 *
 	 * @return number of parents; always a positive value but can be 0.
 	 */
 	public final int getParentCount() {
 		return parents.length;
 	}
 
 	/**
 	 * Get the nth parent from this commit's parent list.
 	 *
 	 * @param nth
 	 *            parent index to obtain. Must be in the range 0 through
 	 *            {@link #getParentCount()}-1.
 	 * @return the specified parent.
 	 * @throws ArrayIndexOutOfBoundsException
 	 *             an invalid parent index was specified.
 	 */
 	public final RevCommit getParent(final int nth) {
 		return parents[nth];
 	}
 
 	/**
 	 * Obtain an array of all parents (<b>NOTE - THIS IS NOT A COPY</b>).
 	 * <p>
 	 * This method is exposed only to provide very fast, efficient access to
 	 * this commit's parent list. Applications relying on this list should be
 	 * very careful to ensure they do not modify its contents during their use
 	 * of it.
 	 *
 	 * @return the array of parents.
 	 */
 	public final RevCommit[] getParents() {
 		return parents;
 	}
 
 	/**
 	 * Obtain the raw unparsed commit body (<b>NOTE - THIS IS NOT A COPY</b>).
 	 * <p>
 	 * This method is exposed only to provide very fast, efficient access to
 	 * this commit's message buffer within a RevFilter. Applications relying on
 	 * this buffer should be very careful to ensure they do not modify its
 	 * contents during their use of it.
 	 *
 	 * @return the raw unparsed commit body. This is <b>NOT A COPY</b>.
 	 *         Altering the contents of this buffer may alter the walker's
 	 *         knowledge of this commit, and the results it produces.
 	 */
 	public final byte[] getRawBuffer() {
 		return buffer;
 	}
 
 	/**
 	 * Parse the author identity from the raw buffer.
 	 * <p>
 	 * This method parses and returns the content of the author line, after
 	 * taking the commit's character set into account and decoding the author
 	 * name and email address. This method is fairly expensive and produces a
 	 * new PersonIdent instance on each invocation. Callers should invoke this
 	 * method only if they are certain they will be outputting the result, and
 	 * should cache the return value for as long as necessary to use all
 	 * information from it.
 	 * <p>
 	 * RevFilter implementations should try to use {@link RawParseUtils} to scan
 	 * the {@link #getRawBuffer()} instead, as this will allow faster evaluation
 	 * of commits.
 	 *
 	 * @return identity of the author (name, email) and the time the commit was
 	 *         made by the author; null if no author line was found.
 	 */
 	public final PersonIdent getAuthorIdent() {
 		final byte[] raw = buffer;
 		final int nameB = RawParseUtils.author(raw, 0);
 		if (nameB < 0)
 			return null;
 		return RawParseUtils.parsePersonIdent(raw, nameB);
 	}
 
 	/**
 	 * Parse the committer identity from the raw buffer.
 	 * <p>
 	 * This method parses and returns the content of the committer line, after
 	 * taking the commit's character set into account and decoding the committer
 	 * name and email address. This method is fairly expensive and produces a
 	 * new PersonIdent instance on each invocation. Callers should invoke this
 	 * method only if they are certain they will be outputting the result, and
 	 * should cache the return value for as long as necessary to use all
 	 * information from it.
 	 * <p>
 	 * RevFilter implementations should try to use {@link RawParseUtils} to scan
 	 * the {@link #getRawBuffer()} instead, as this will allow faster evaluation
 	 * of commits.
 	 *
 	 * @return identity of the committer (name, email) and the time the commit
 	 *         was made by the committer; null if no committer line was found.
 	 */
 	public final PersonIdent getCommitterIdent() {
 		final byte[] raw = buffer;
 		final int nameB = RawParseUtils.committer(raw, 0);
 		if (nameB < 0)
 			return null;
 		return RawParseUtils.parsePersonIdent(raw, nameB);
 	}
 
 	/**
 	 * Parse the complete commit message and decode it to a string.
 	 * <p>
 	 * This method parses and returns the message portion of the commit buffer,
 	 * after taking the commit's character set into account and decoding the
 	 * buffer using that character set. This method is a fairly expensive
 	 * operation and produces a new string on each invocation.
 	 *
 	 * @return decoded commit message as a string. Never null.
 	 */
 	public final String getFullMessage() {
 		byte[] raw = buffer;
 		int msgB = RawParseUtils.commitMessage(raw, 0);
 		if (msgB < 0) {
 			return ""; //$NON-NLS-1$
 		}
 		return RawParseUtils.decode(guessEncoding(), raw, msgB, raw.length);
 	}
 
 	/**
 	 * Parse the commit message and return the first "line" of it.
 	 * <p>
 	 * The first line is everything up to the first pair of LFs. This is the
 	 * "oneline" format, suitable for output in a single line display.
 	 * <p>
 	 * This method parses and returns the message portion of the commit buffer,
 	 * after taking the commit's character set into account and decoding the
 	 * buffer using that character set. This method is a fairly expensive
 	 * operation and produces a new string on each invocation.
 	 *
 	 * @return decoded commit message as a string. Never null. The returned
 	 *         string does not contain any LFs, even if the first paragraph
 	 *         spanned multiple lines. Embedded LFs are converted to spaces.
 	 */
 	public final String getShortMessage() {
 		byte[] raw = buffer;
 		int msgB = RawParseUtils.commitMessage(raw, 0);
 		if (msgB < 0) {
 			return ""; //$NON-NLS-1$
 		}
 
 		int msgE = RawParseUtils.endOfParagraph(raw, msgB);
 		String str = RawParseUtils.decode(guessEncoding(), raw, msgB, msgE);
 		if (hasLF(raw, msgB, msgE)) {
 			str = StringUtils.replaceLineBreaksWithSpace(str);
 		}
 		return str;
 	}
 
 	static boolean hasLF(final byte[] r, int b, final int e) {
 		while (b < e)
 			if (r[b++] == '\n')
 				return true;
 		return false;
 	}
 
 	/**
 	 * Determine the encoding of the commit message buffer.
 	 * <p>
 	 * Locates the "encoding" header (if present) and returns its value. Due to
 	 * corruption in the wild this may be an invalid encoding name that is not
 	 * recognized by any character encoding library.
 	 * <p>
 	 * If no encoding header is present, null.
 	 *
 	 * @return the preferred encoding of {@link #getRawBuffer()}; or null.
 	 * @since 4.2
 	 */
 	@Nullable
 	public final String getEncodingName() {
 		return RawParseUtils.parseEncodingName(buffer);
 	}
 
 	/**
 	 * Determine the encoding of the commit message buffer.
 	 * <p>
 	 * Locates the "encoding" header (if present) and then returns the proper
 	 * character set to apply to this buffer to evaluate its contents as
 	 * character data.
 	 * <p>
 	 * If no encoding header is present {@code UTF-8} is assumed.
 	 *
 	 * @return the preferred encoding of {@link #getRawBuffer()}.
 	 * @throws IllegalCharsetNameException
 	 *             if the character set requested by the encoding header is
 	 *             malformed and unsupportable.
 	 * @throws UnsupportedCharsetException
 	 *             if the JRE does not support the character set requested by
 	 *             the encoding header.
 	 */
 	public final Charset getEncoding() {
 		return RawParseUtils.parseEncoding(buffer);
 	}
 
 	private Charset guessEncoding() {
 		try {
 			return getEncoding();
 		} catch (IllegalCharsetNameException | UnsupportedCharsetException e) {
 			return UTF_8;
 		}
 	}
 
 	/**
 	 * Parse the footer lines (e.g. "Signed-off-by") for machine processing.
 	 * <p>
 	 * This method splits all of the footer lines out of the last paragraph of
 	 * the commit message, providing each line as a key-value pair, ordered by
 	 * the order of the line's appearance in the commit message itself.
 	 * <p>
 	 * A footer line's key must match the pattern {@code ^[A-Za-z0-9-]+:}, while
 	 * the value is free-form, but must not contain an LF. Very common keys seen
 	 * in the wild are:
 	 * <ul>
 	 * <li>{@code Signed-off-by} (agrees to Developer Certificate of Origin)
 	 * <li>{@code Acked-by} (thinks change looks sane in context)
 	 * <li>{@code Reported-by} (originally found the issue this change fixes)
 	 * <li>{@code Tested-by} (validated change fixes the issue for them)
 	 * <li>{@code CC}, {@code Cc} (copy on all email related to this change)
 	 * <li>{@code Bug} (link to project's bug tracking system)
 	 * </ul>
 	 *
 	 * @return ordered list of footer lines; empty list if no footers found.
 	 */
 	public final List<FooterLine> getFooterLines() {
 		final byte[] raw = buffer;
 		int ptr = raw.length - 1;
 		while (raw[ptr] == '\n') // trim any trailing LFs, not interesting
 			ptr--;
 
 		final int msgB = RawParseUtils.commitMessage(raw, 0);
 		final ArrayList<FooterLine> r = new ArrayList<>(4);
 		final Charset enc = guessEncoding();
 		for (;;) {
 			ptr = RawParseUtils.prevLF(raw, ptr);
 			if (ptr <= msgB)
 				break; // Don't parse commit headers as footer lines.
 
 			final int keyStart = ptr + 2;
 			if (raw[keyStart] == '\n')
 				break; // Stop at first paragraph break, no footers above it.
 
 			final int keyEnd = RawParseUtils.endOfFooterLineKey(raw, keyStart);
 			if (keyEnd < 0)
 				continue; // Not a well formed footer line, skip it.
 
 			// Skip over the ': *' at the end of the key before the value.
 			//
 			int valStart = keyEnd + 1;
 			while (valStart < raw.length && raw[valStart] == ' ')
 				valStart++;
 
 			// Value ends at the LF, and does not include it.
 			//
 			int valEnd = RawParseUtils.nextLF(raw, valStart);
 			if (raw[valEnd - 1] == '\n')
 				valEnd--;
 
 			r.add(new FooterLine(raw, enc, keyStart, keyEnd, valStart, valEnd));
 		}
 		Collections.reverse(r);
 		return r;
 	}
 
 	/**
 	 * Get the values of all footer lines with the given key.
 	 *
 	 * @param keyName
 	 *            footer key to find values of, case insensitive.
 	 * @return values of footers with key of {@code keyName}, ordered by their
 	 *         order of appearance. Duplicates may be returned if the same
 	 *         footer appeared more than once. Empty list if no footers appear
 	 *         with the specified key, or there are no footers at all.
 	 * @see #getFooterLines()
 	 */
 	public final List<String> getFooterLines(final String keyName) {
 		return getFooterLines(new FooterKey(keyName));
 	}
 
 	/**
 	 * Get the values of all footer lines with the given key.
 	 *
 	 * @param keyName
 	 *            footer key to find values of, case insensitive.
 	 * @return values of footers with key of {@code keyName}, ordered by their
 	 *         order of appearance. Duplicates may be returned if the same
 	 *         footer appeared more than once. Empty list if no footers appear
 	 *         with the specified key, or there are no footers at all.
 	 * @see #getFooterLines()
 	 */
 	public final List<String> getFooterLines(final FooterKey keyName) {
 		final List<FooterLine> src = getFooterLines();
 		if (src.isEmpty())
 			return Collections.emptyList();
 		final ArrayList<String> r = new ArrayList<>(src.size());
 		for (final FooterLine f : src) {
 			if (f.matches(keyName))
 				r.add(f.getValue());
 		}
 		return r;
 	}
 
 	/**
 	 * Reset this commit to allow another RevWalk with the same instances.
 	 * <p>
 	 * Subclasses <b>must</b> call <code>super.reset()</code> to ensure the
 	 * basic information can be correctly cleared out.
 	 */
 	public void reset() {
 		inDegree = 0;
 	}
 
 	/**
 	 * Discard the message buffer to reduce memory usage.
 	 * <p>
 	 * After discarding the memory usage of the {@code RevCommit} is reduced to
 	 * only the {@link #getTree()} and {@link #getParents()} pointers and the
 	 * time in {@link #getCommitTime()}. Accessing other properties such as
 	 * {@link #getAuthorIdent()}, {@link #getCommitterIdent()} or either message
 	 * function requires reloading the buffer by invoking
 	 * {@link RevWalk#parseBody(RevObject)}.
 	 *
 	 * @since 4.0
 	 */
 	public final void disposeBody() {
 		buffer = null;
 	}
 
 	@Override
 	public String toString() {
 		final StringBuilder s = new StringBuilder();
 		s.append(Constants.typeString(getType()));
 		s.append(' ');
 		s.append(name());
 		s.append(' ');
 		s.append(commitTime);
 		s.append(' ');
 		appendCoreFlags(s);
 		return s.toString();
 	}
 }