/*
    * Copyright (C) 2008, 2014 Shawn O. Pearce <spearce@spearce.org> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.revplot;
  
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.revwalk.RevCommit;
  
  /**
   * A commit reference to a commit in the DAG.
   *
   * @param <L>
   *            type of lane being used by the plotter.
   * @see PlotCommitList
   */
  public class PlotCommit<L extends PlotLane> extends RevCommit {
  	static final PlotCommit[] NO_CHILDREN = {};
  
  	static final PlotLane[] NO_LANES = {};
  
  	static final Ref[] NO_REFS = {};
  
  	PlotLane[] forkingOffLanes;
  
  	PlotLane[] passingLanes;
  
  	PlotLane[] mergingLanes;
  
  	PlotLane lane;
  
  	PlotCommit[] children;
  
  	Ref[] refs;
  
  	/**
  	 * Create a new commit.
  	 *
  	 * @param id
  	 *            the identity of this commit.
  	 */
  	protected PlotCommit(AnyObjectId id) {
  		super(id);
  		forkingOffLanes = NO_LANES;
  		passingLanes = NO_LANES;
  		mergingLanes = NO_LANES;
  		children = NO_CHILDREN;
  		refs = NO_REFS;
  	}
  
  	void addForkingOffLane(PlotLane f) {
  		forkingOffLanes = addLane(f, forkingOffLanes);
  	}
  
  	void addPassingLane(PlotLane c) {
  		passingLanes = addLane(c, passingLanes);
  	}
  
  	void addMergingLane(PlotLane m) {
  		mergingLanes = addLane(m, mergingLanes);
  	}
  
  	private static PlotLane[] addLane(PlotLane l, PlotLane[] lanes) {
  		final int cnt = lanes.length;
  		switch (cnt) {
  		case 0:
  			lanes = new PlotLane[] { l };
  			break;
  		case 1:
  			lanes = new PlotLane[] { lanes[0], l };
  			break;
  		default:
  			final PlotLane[] n = new PlotLane[cnt + 1];
  			System.arraycopy(lanes, 0, n, 0, cnt);
  			n[cnt] = l;
  			lanes = n;
  			break;
  		}
  		return lanes;
  	}
  
  	void addChild(PlotCommit c) {
  		final int cnt = children.length;
  		switch (cnt) {
  		case 0:
  			children = new PlotCommit[] { c };
  			break;
  		case 1:
  			if (!c.getId().equals(children[0].getId()))
  				children = new PlotCommit[] { children[0], c };
  			break;
  		default:
 			for (PlotCommit pc : children)
 				if (c.getId().equals(pc.getId()))
 					return;
 			final PlotCommit[] n = new PlotCommit[cnt + 1];
 			System.arraycopy(children, 0, n, 0, cnt);
 			n[cnt] = c;
 			children = n;
 			break;
 		}
 	}
 
 	/**
 	 * Get the number of child commits listed in this commit.
 	 *
 	 * @return number of children; always a positive value but can be 0.
 	 */
 	public final int getChildCount() {
 		return children.length;
 	}
 
 	/**
 	 * Get the nth child from this commit's child list.
 	 *
 	 * @param nth
 	 *            child index to obtain. Must be in the range 0 through
 	 *            {@link #getChildCount()}-1.
 	 * @return the specified child.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             an invalid child index was specified.
 	 */
 	public final PlotCommit getChild(int nth) {
 		return children[nth];
 	}
 
 	/**
 	 * Determine if the given commit is a child (descendant) of this commit.
 	 *
 	 * @param c
 	 *            the commit to test.
 	 * @return true if the given commit built on top of this commit.
 	 */
 	@SuppressWarnings("ReferenceEquality")
 	public final boolean isChild(PlotCommit c) {
 		for (PlotCommit a : children)
 			if (a == c)
 				return true;
 		return false;
 	}
 
 	/**
 	 * Get the number of refs for this commit.
 	 *
 	 * @return number of refs; always a positive value but can be 0.
 	 */
 	public final int getRefCount() {
 		return refs.length;
 	}
 
 	/**
 	 * Get the nth Ref from this commit's ref list.
 	 *
 	 * @param nth
 	 *            ref index to obtain. Must be in the range 0 through
 	 *            {@link #getRefCount()}-1.
 	 * @return the specified ref.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             an invalid ref index was specified.
 	 */
 	public final Ref getRef(int nth) {
 		return refs[nth];
 	}
 
 	/**
 	 * Obtain the lane this commit has been plotted into.
 	 *
 	 * @return the assigned lane for this commit.
 	 */
 	@SuppressWarnings("unchecked")
 	public final L getLane() {
 		return (L) lane;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void reset() {
 		forkingOffLanes = NO_LANES;
 		passingLanes = NO_LANES;
 		mergingLanes = NO_LANES;
 		children = NO_CHILDREN;
 		lane = null;
 		super.reset();
 	}
 }