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Solver subproject in the Theta model checking framework
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/*
 *  Copyright 2024 Budapest University of Technology and Economics
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package hu.bme.mit.theta.solver.utils;

import static com.google.common.base.Preconditions.checkNotNull;
import static hu.bme.mit.theta.core.type.booltype.BoolExprs.Not;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Function;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import hu.bme.mit.theta.core.model.Valuation;
import hu.bme.mit.theta.core.type.Expr;
import hu.bme.mit.theta.core.type.booltype.BoolType;
import hu.bme.mit.theta.solver.Solver;
import hu.bme.mit.theta.solver.SolverFactory;

public final class SolverUtils {

    private SolverUtils() {
    }

    public static boolean entails(final Solver solver, final Expr antecedent,
                                  final Expr consequent) {
        checkNotNull(solver);
        checkNotNull(antecedent);
        checkNotNull(consequent);
        try (WithPushPop wpp = new WithPushPop(solver)) {
            solver.add(antecedent);
            solver.add(Not(consequent));
            return solver.check().isUnsat();
        }
    }

    public static boolean entails(final Solver solver,
                                  final Iterable> antecedents,
                                  final Iterable> consequents) {
        checkNotNull(solver);
        checkNotNull(antecedents);
        checkNotNull(consequents);
        try (WithPushPop wpp = new WithPushPop(solver)) {
            antecedents.forEach(antecedent -> solver.add(antecedent));
            consequents.forEach(consequent -> solver.add(Not(consequent)));
            return solver.check().isUnsat();
        }
    }

    public static Stream models(final SolverFactory factory, final Expr expr) {
        return models(factory, expr, m -> Not(m.toExpr()));
    }

    public static Stream models(final SolverFactory factory, final Expr expr,
                                           final Function> feedback) {
        final Iterable iterable = () -> new ModelIterator(factory, expr, feedback);
        return StreamSupport.stream(iterable.spliterator(), false);
    }

    private static final class ModelIterator implements Iterator {

        private final Solver solver;
        private final Function> feedback;

        private ModelIterator(final SolverFactory factory, final Expr expr,
                              final Function> feedback) {
            checkNotNull(expr);
            checkNotNull(factory);
            this.feedback = checkNotNull(feedback);

            solver = factory.createSolver();
            solver.add(expr);
        }

        @Override
        public boolean hasNext() {
            return solver.check().isSat();
        }

        @Override
        public Valuation next() {
            if (!hasNext()) {
                throw new NoSuchElementException("Formula is UNSAT");
            }
            final Valuation model = solver.getModel();
            solver.add(feedback.apply(model));
            return model;
        }
    }

}