/*
    * Copyright (C) 2010, Garmin International
    * Copyright (C) 2010, Matt Fischer <matt.fischer@garmin.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,
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   */
  
  package org.eclipse.jgit.revwalk;
  
  import java.io.IOException;
  
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  
  /**
   * Only produce commits which are below a specified depth.
   *
   * @see DepthWalk
   */
  class DepthGenerator extends Generator {
  	private final FIFORevQueue pending;
  
  	private final int depth;
  
  	private final RevWalk walk;
  
  	/**
  	 * Commits which used to be shallow in the client, but which are
  	 * being extended as part of this fetch.  These commits should be
  	 * returned to the caller as UNINTERESTING so that their blobs/trees
  	 * can be marked appropriately in the pack writer.
  	 */
  	private final RevFlag UNSHALLOW;
  
  	/**
  	 * Commits which the normal framework has marked as UNINTERESTING,
  	 * but which we now care about again.  This happens if a client is
  	 * extending a shallow checkout to become deeper--the new commits at
  	 * the bottom of the graph need to be sent, even though they are
  	 * below other commits which the client already has.
  	 */
  	private final RevFlag REINTERESTING;
  
  	/**
  	 * @param w
  	 * @param s Parent generator
  	 * @throws MissingObjectException
  	 * @throws IncorrectObjectTypeException
  	 * @throws IOException
  	 */
  	DepthGenerator(DepthWalk w, Generator s) throws MissingObjectException,
  			IncorrectObjectTypeException, IOException {
  		pending = new FIFORevQueue();
  		walk = (RevWalk)w;
  
  		this.depth = w.getDepth();
  		this.UNSHALLOW = w.getUnshallowFlag();
  		this.REINTERESTING = w.getReinterestingFlag();
  
  		s.shareFreeList(pending);
  
  		// Begin by sucking out all of the source's commits, and
 		// adding them to the pending queue
 		for (;;) {
 			RevCommit c = s.next();
 			if (c == null)
 				break;
 			if (((DepthWalk.Commit) c).getDepth() == 0)
 				pending.add(c);
 		}
 	}
 
 	@Override
 	int outputType() {
 		return pending.outputType() | HAS_UNINTERESTING;
 	}
 
 	@Override
 	void shareFreeList(final BlockRevQueue q) {
 		pending.shareFreeList(q);
 	}
 
 	@Override
 	RevCommit next() throws MissingObjectException,
 			IncorrectObjectTypeException, IOException {
 		// Perform a breadth-first descent into the commit graph,
 		// marking depths as we go.  This means that if a commit is
 		// reachable by more than one route, we are guaranteed to
 		// arrive by the shortest route first.
 		for (;;) {
 			final DepthWalk.Commit c = (DepthWalk.Commit) pending.next();
 			if (c == null)
 				return null;
 
 			if ((c.flags & RevWalk.PARSED) == 0)
 				c.parseHeaders(walk);
 
 			int newDepth = c.depth + 1;
 
 			for (final RevCommit p : c.parents) {
 				DepthWalk.Commit dp = (DepthWalk.Commit) p;
 
 				// If no depth has been assigned to this commit, assign
 				// it now.  Since we arrive by the shortest route first,
 				// this depth is guaranteed to be the smallest value that
 				// any path could produce.
 				if (dp.depth == -1) {
 					dp.depth = newDepth;
 
 					// If the parent is not too deep, add it to the queue
 					// so that we can produce it later
 					if (newDepth <= depth)
 						pending.add(p);
 				}
 
 				// If the current commit has become unshallowed, everything
 				// below us is new to the client.  Mark its parent as
 				// re-interesting, and carry that flag downward to all
 				// of its ancestors.
 				if(c.has(UNSHALLOW) || c.has(REINTERESTING)) {
 					p.add(REINTERESTING);
 					p.flags &= ~RevWalk.UNINTERESTING;
 				}
 			}
 
 			// Produce all commits less than the depth cutoff
 			boolean produce = c.depth <= depth;
 
 			// Unshallow commits are uninteresting, but still need to be sent
 			// up to the PackWriter so that it will exclude objects correctly.
 			// All other uninteresting commits should be omitted.
 			if ((c.flags & RevWalk.UNINTERESTING) != 0 && !c.has(UNSHALLOW))
 				produce = false;
 
 			if (produce)
 				return c;
 		}
 	}
 }