/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2005, University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.ba.heap;

import java.util.HashSet;
import java.util.Set;

import edu.umd.cs.findbugs.ba.XField;

/**
 * @author David Hovemeyer
 */
public class FieldSet {
	private boolean isTop, isBottom;
	private Set<XField> fieldSet;

	public FieldSet() {
		fieldSet = new HashSet<XField>();
	}

	public void setTop() {
		clear();
		isTop = true;
	}

	public boolean isTop() {
		return isTop;
	}

	public void setBottom() {
		clear();
		isBottom = true;
	}

	public boolean isBottom() {
		return isBottom;
	}

	public boolean isValid() {
		return !isTop && !isBottom;
	}

	public boolean isEmpty() {
		return !isTop && !isBottom && fieldSet.isEmpty();
	}

	public void clear() {
		isTop = isBottom = false;
		fieldSet.clear();
	}

	public void addField(XField field) {
		if (!isValid())
			throw new IllegalStateException();
		fieldSet.add(field);
	}

	public boolean contains(XField field) {
		return fieldSet.contains(field);
	}

	public void mergeWith(FieldSet other) {
		if (other.isTop() || this.isBottom())
			return;

		if (other.isBottom() || this.isTop()) {
			this.copyFrom(other);
			return;
		}

		fieldSet.addAll(other.fieldSet);
	}

	public boolean sameAs(FieldSet other) {
		return this.isTop == other.isTop
			&& this.isBottom == other.isBottom
			&& this.fieldSet.equals(other.fieldSet);
	}

	public void copyFrom(FieldSet other) {
		this.isTop = other.isTop;
		this.isBottom = other.isBottom;
		this.fieldSet.clear();
		this.fieldSet.addAll(other.fieldSet);
	}

	public boolean isIntersectionNonEmpty(FieldSet other) {
		for (XField field : fieldSet) {
			if (other.fieldSet.contains(field))
				return true;
		}
		return false;
	}

	@Override
		 public String toString() {
		if (isTop)
			return "TOP";
		else if (isBottom)
			return "BOTTOM";
		else
			return fieldSet.toString();
	}
}