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//               The Next Generation Logic Library                       //
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//  Copyright 2015-20xx Christoph Zengler                                //
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package org.logicng.handlers;

import org.logicng.datastructures.Assignment;

/**
 * Interface for a handler for MaxSAT solvers.
 * @version 2.1.0
 * @since 1.0
 */
public interface MaxSATHandler extends Handler {

    /**
     * Returns a SAT handler which can be used to cancel internal SAT calls of the MaxSAT solver.
     * @return a SAT handler
     */
    SATHandler satHandler();

    @Override
    default boolean aborted() {
        return satHandler() != null && satHandler().aborted();
    }

    /**
     * This method is called when the MaxSAT solver found a new lower bound for a solution.
     * @param lowerBound the cost of the lower bound
     * @param model      the model of the lower bound, may be null if not applicable
     * @return {@code true} if the solving process should be continued, otherwise {@code false}
     */
    boolean foundLowerBound(final int lowerBound, final Assignment model);

    /**
     * This method is called when the MaxSAT solver found a new upper bound for a solution.
     * @param upperBound the cost of the upper bound
     * @param model      the model of the upper bound, may be null if not applicable
     * @return {@code true} if the solving process should be continued, otherwise {@code false}
     */
    boolean foundUpperBound(final int upperBound, final Assignment model);

    /**
     * This method is called when the MaxSAT solver finished solving.
     */
    default void finishedSolving() {

    }

    /**
     * Returns the last approximation of the result or -1 if there is no approximation for the lower bound.
     * If the handler does not cancel the solving process, it is not guaranteed that this
     * method will return the optimal result. Use the respective method of the MaxSAT solver instead.
     * @return the last approximation of the result or -1 if no approximation is known
     */
    int lowerBoundApproximation();

    /**
     * Returns the last approximation of the result or -1 if there is no approximation for the lower bound.
     * If the handler does not cancel the solving process, it is not guaranteed that this
     * method will return the optimal result. Use the respective method of the MaxSAT solver instead.
     * @return the last approximation of the result or -1 if no approximation is known
     */
    int upperBoundApproximation();
}