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This artifact provides various common utility operations for analyzing and manipulating automata and graphs, such as traversal, minimization and copying.

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/* Copyright (C) 2013 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 * 
 * AutomataLib is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 3.0 as published by the Free Software Foundation.
 * 
 * AutomataLib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with AutomataLib; if not, see
 * http://www.gnu.de/documents/lgpl.en.html.
 */
/**
 * 
 */
package net.automatalib.util.minimizer;

import java.util.BitSet;
import java.util.Collection;

import net.automatalib.commons.smartcollections.BasicLinkedListEntry;
import net.automatalib.commons.smartcollections.IntrusiveLinkedList;
import net.automatalib.commons.smartcollections.UnorderedCollection;


/**
 * Represents a transition label in the automaton model the minimizer
 * operates on. 
 * 
 * @author Malte Isberner 
 *
 * @param  state class.
 * @param  edge property class.
 */
final class TransitionLabel
		extends BasicLinkedListEntry,TransitionLabel> {
	// The original label
	private final EP originalLabel;
	// The list of states that have an outgoing transition
	// with this label, considered in the respective step.
	private final UnorderedCollection> list
		= new UnorderedCollection>();
	// Keeps track of the states that are contained in the above list.
	private final BitSet setContents = new BitSet();
	
	// The bucket, used for the weak sort of the algorithm.
	private final IntrusiveLinkedList> bucket
		= new IntrusiveLinkedList>();
	
	/**
	 * Constructor.
	 * 
	 * @param originalLabel the original transition label.
	 */
	public TransitionLabel(EP originalLabel) {
		this.originalLabel = originalLabel;
	}
	
	
	/**
	 * Retrieves the bucket.
	 * 
	 * @return the bucket.
	 */
	public IntrusiveLinkedList> getBucket() {
		return bucket;
	}
	
	/**
	 * Adds a state to this label's bucket.
	 * 
	 * @param state the state to be added to the bucket.
	 * @return true if this is the first state to be added
	 * to the bucket, false otherwise.
	 */
	public boolean addToBucket(State state) {
		boolean first = false;
		
		if(bucket.isEmpty())
			first = true;
		bucket.pushBack(state);
		
		return first;
	}
	
	/**
	 * Retrieves the original transition label.
	 * @return the original transition label.
	 */
	public EP getOriginalLabel() {
		return originalLabel;
	}
	
	/**
	 * Clears the state set associated with this label.
	 */
	public void clearSet() {
		setContents.clear();
		list.quickClear();
	}

	/**
	 * Adds a state to the associated state set. Note that a
	 * state can be in the sets of various transition labels.
	 * 
	 * @param state the state to be added. 
	 * @return true if this was the first state to be added
	 * to the set, false otherwise.
	 */
	public boolean addToSet(State state) {
		boolean first = list.isEmpty();
		if(first || !setContents.get(state.getId())) {
			list.add(state);
			setContents.set(state.getId());
		}
		return first;
	}

	/**
	 * Retrieves the state set associated with this transition label.
	 * Note that despite the fact that no {@link java.util.Set} is returned,
	 * each state is guaranteed to occur at most once.
	 * 
	 * @return the state set of this label.
	 */
	public Collection> getSet() {
		return list;
	}
	
	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return originalLabel.toString();
	}

	@Override
	public TransitionLabel getElement() {
		return this;
	}
}