/*
 * Copyright (C) 2017 Matthias Heizmann (heizmann@informatik.uni-freiburg.de)
 * Copyright (C) 2017 University of Freiburg
 *
 * This file is part of the ULTIMATE ModelCheckerUtils Library.
 *
 * The ULTIMATE ModelCheckerUtils 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 3 of the License, or
 * (at your option) any later version.
 *
 * The ULTIMATE ModelCheckerUtils 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 the ULTIMATE ModelCheckerUtils Library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7:
 * If you modify the ULTIMATE ModelCheckerUtils Library, or any covered work, by linking
 * or combining it with Eclipse RCP (or a modified version of Eclipse RCP),
 * containing parts covered by the terms of the Eclipse Public License, the
 * licensors of the ULTIMATE ModelCheckerUtils Library grant you additional permission
 * to convey the resulting work.
 */
package de.uni_freiburg.informatik.ultimate.lib.modelcheckerutils.smt;

import de.uni_freiburg.informatik.ultimate.core.model.services.IUltimateServiceProvider;
import de.uni_freiburg.informatik.ultimate.lib.modelcheckerutils.smt.predicates.IPredicate;
import de.uni_freiburg.informatik.ultimate.lib.smtlibutils.IncrementalPlicationChecker;
import de.uni_freiburg.informatik.ultimate.lib.smtlibutils.ManagedScript;
import de.uni_freiburg.informatik.ultimate.lib.smtlibutils.ManagedScript.ILockHolderWithVoluntaryLockRelease;
import de.uni_freiburg.informatik.ultimate.lib.smtlibutils.SmtUtils;
import de.uni_freiburg.informatik.ultimate.lib.smtlibutils.IncrementalPlicationChecker.Validity;
import de.uni_freiburg.informatik.ultimate.logic.Script.LBool;

/**
 * Check implication between two formulas that each represent a set of
 * program states.
 * @author Matthias Heizmann (heizmann@informatik.uni-freiburg.de)
 *
 */
public class IncrementalImplicationChecker implements ILockHolderWithVoluntaryLockRelease {

	private final IUltimateServiceProvider mServices;
	private final ManagedScript mManagedScript;

	private IPredicate mSuccedent;

	public IncrementalImplicationChecker(final IUltimateServiceProvider services, final ManagedScript managedScript) {
		super();
		mServices = services;
		mManagedScript = managedScript;
	}


	/**
	 * Check if implication  antecedent ==> succedent  is valid.
	 */
	public Validity checkImplication(final IPredicate antecedent, final IPredicate succedent) {
		if (mSuccedent != null && mSuccedent != succedent) {
			unAssertSuccedent();
		}
		if (mSuccedent == null) {
			assertSuccedent(succedent);
		}
		return doCheckWithAntecedent(antecedent);
	}

	private void assertSuccedent(final IPredicate succedent) {
		if (mManagedScript.isLocked()) {
			mManagedScript.requestLockRelease();
		}
		mManagedScript.lock(this);
		mManagedScript.push(this, 1);
		assert (mSuccedent == null) : "already succedent asserted";
		mSuccedent = succedent;
		mManagedScript.assertTerm(this, SmtUtils.not(mManagedScript.getScript(), mSuccedent.getClosedFormula()));
	}

	private void unAssertSuccedent() {
		assert (mSuccedent != null) : "no succedent asserted";
		mSuccedent = null;
		mManagedScript.pop(this, 1);
		mManagedScript.unlock(this);
	}

	private Validity doCheckWithAntecedent(final IPredicate antecedent) {
		assert (mSuccedent != null) : "no succedent asserted";
		mManagedScript.push(this, 1);
		mManagedScript.assertTerm(this, antecedent.getClosedFormula());
		final LBool lbool = mManagedScript.checkSat(this);
		mManagedScript.pop(this, 1);
		return IncrementalPlicationChecker.convertLBool2Validity(lbool);
	}

	@Override
	public void releaseLock() {
		if (mSuccedent != null) {
			unAssertSuccedent();
		} else {
			// lock is not held by this object
		}
	}

}