/*
 * Copyright (C) 2009, Robin Rosenberg
 * Copyright (C) 2009, Robin Rosenberg <robin.rosenberg@dewire.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.lib;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.eclipse.jgit.util.IO;
import org.eclipse.jgit.util.RawParseUtils;

/**
 * Utility for reading reflog entries
 */
public class ReflogReader {
	/**
	 * Parsed reflog entry
	 */
	static public class Entry {
		private ObjectId oldId;

		private ObjectId newId;

		private PersonIdent who;

		private String comment;

		Entry(byte[] raw, int pos) {
			oldId = ObjectId.fromString(raw, pos);
			pos += Constants.OBJECT_ID_STRING_LENGTH;
			if (raw[pos++] != ' ')
				throw new IllegalArgumentException(
						"Raw log message does not parse as log entry");
			newId = ObjectId.fromString(raw, pos);
			pos += Constants.OBJECT_ID_STRING_LENGTH;
			if (raw[pos++] != ' ') {
				throw new IllegalArgumentException(
						"Raw log message does not parse as log entry");
			}
			who = RawParseUtils.parsePersonIdentOnly(raw, pos);
			int p0 = RawParseUtils.next(raw, pos, '\t'); // personident has no
															// \t
			if (p0 == -1) {
				throw new IllegalArgumentException(
						"Raw log message does not parse as log entry");
			}
			int p1 = RawParseUtils.nextLF(raw, p0);
			if (p1 == -1) {
				throw new IllegalArgumentException(
						"Raw log message does not parse as log entry");
			}
			comment = RawParseUtils.decode(raw, p0, p1 - 1);
		}

		/**
		 * @return the commit id before the change
		 */
		public ObjectId getOldId() {
			return oldId;
		}

		/**
		 * @return the commit id after the change
		 */
		public ObjectId getNewId() {
			return newId;
		}

		/**
		 * @return user performin the change
		 */
		public PersonIdent getWho() {
			return who;
		}

		/**
		 * @return textual description of the change
		 */
		public String getComment() {
			return comment;
		}

		@Override
		public String toString() {
			return "Entry[" + oldId.name() + ", " + newId.name() + ", " + getWho() + ", "
					+ getComment() + "]";
		}
	}

	private File logName;

	ReflogReader(Repository db, String refname) {
		logName = new File(db.getDirectory(), "logs/" + refname);
	}

	/**
	 * Get the last entry in the reflog
	 *
	 * @return the latest reflog entry, or null if no log
	 * @throws IOException
	 */
	public Entry getLastEntry() throws IOException {
		List<Entry> entries = getReverseEntries(1);
		return entries.size() > 0 ? entries.get(0) : null;
	}

	/**
	 * @return all reflog entries in reverse order
	 * @throws IOException
	 */
	public List<Entry> getReverseEntries() throws IOException {
		return getReverseEntries(Integer.MAX_VALUE);
	}

	/**
	 * @param max
	 *            max numer of entries to read
	 * @return all reflog entries in reverse order
	 * @throws IOException
	 */
	public List<Entry> getReverseEntries(int max) throws IOException {
		final byte[] log;
		try {
			log = IO.readFully(logName);
		} catch (FileNotFoundException e) {
			return Collections.emptyList();
		}

		int rs = RawParseUtils.prevLF(log, log.length);
		List<Entry> ret = new ArrayList<Entry>();
		while (rs >= 0 && max-- > 0) {
			rs = RawParseUtils.prevLF(log, rs);
			Entry entry = new Entry(log, rs < 0 ? 0 : rs + 2);
			ret.add(entry);
		}
		return ret;
	}
}