/*
    * 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 java.io.IOException;
  
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  
  /**
   * A queue of commits in FIFO order.
   */
  public class FIFORevQueue extends BlockRevQueue {
  	private Block head;
  
  	private Block tail;
  
  	/**
  	 * Create an empty FIFO queue.
  	 */
  	public FIFORevQueue() {
  		super();
  	}
  
  	FIFORevQueue(Generator s) throws MissingObjectException,
  			IncorrectObjectTypeException, IOException {
  		super(s);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public void add(RevCommit c) {
  		Block b = tail;
  		if (b == null) {
  			b = free.newBlock();
  			b.add(c);
  			head = b;
  			tail = b;
  			return;
  		} else if (b.isFull()) {
  			b = free.newBlock();
  			tail.next = b;
  			tail = b;
  		}
  		b.add(c);
  	}
  
  	/**
  	 * Insert the commit pointer at the front of the queue.
  	 *
  	 * @param c
  	 *            the commit to insert into the queue.
  	 */
  	public void unpop(RevCommit c) {
  		Block b = head;
  		if (b == null) {
  			b = free.newBlock();
  			b.resetToMiddle();
 			b.add(c);
 			head = b;
 			tail = b;
 			return;
 		} else if (b.canUnpop()) {
 			b.unpop(c);
 			return;
 		}
 
 		b = free.newBlock();
 		b.resetToEnd();
 		b.unpop(c);
 		b.next = head;
 		head = b;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public RevCommit next() {
 		final Block b = head;
 		if (b == null)
 			return null;
 
 		final RevCommit c = b.pop();
 		if (b.isEmpty()) {
 			head = b.next;
 			if (head == null)
 				tail = null;
 			free.freeBlock(b);
 		}
 		return c;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void clear() {
 		head = null;
 		tail = null;
 		free.clear();
 	}
 
 	@Override
 	boolean everbodyHasFlag(int f) {
 		for (Block b = head; b != null; b = b.next) {
 			for (int i = b.headIndex; i < b.tailIndex; i++)
 				if ((b.commits[i].flags & f) == 0)
 					return false;
 		}
 		return true;
 	}
 
 	@Override
 	boolean anybodyHasFlag(int f) {
 		for (Block b = head; b != null; b = b.next) {
 			for (int i = b.headIndex; i < b.tailIndex; i++)
 				if ((b.commits[i].flags & f) != 0)
 					return true;
 		}
 		return false;
 	}
 
 	void removeFlag(int f) {
 		final int not_f = ~f;
 		for (Block b = head; b != null; b = b.next) {
 			for (int i = b.headIndex; i < b.tailIndex; i++)
 				b.commits[i].flags &= not_f;
 		}
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		final StringBuilder s = new StringBuilder();
 		for (Block q = head; q != null; q = q.next) {
 			for (int i = q.headIndex; i < q.tailIndex; i++)
 				describe(s, q.commits[i]);
 		}
 		return s.toString();
 	}
 }