language/unify/CHash.java

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/*
 * @cond LICENSE
 * ######################################################################################
 * # LGPL License                                                                       #
 * #                                                                                    #
 * # This file is part of the LightJason AgentSpeak(L++)                                #
 * # Copyright (c) 2015-19, LightJason (info@lightjason.org)                            #
 * # This program 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.                                    #
 * #                                                                                    #
 * # This program 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 program. If not, see http://www.gnu.org/licenses/                  #
 * ######################################################################################
 * @endcond
 */

package org.lightjason.agentspeak.language.unify;

import com.codepoetics.protonpack.StreamUtils;
import org.lightjason.agentspeak.language.ITerm;
import org.lightjason.agentspeak.language.variable.CRelocateMutexVariable;
import org.lightjason.agentspeak.language.variable.CRelocateVariable;
import org.lightjason.agentspeak.language.variable.IVariable;

import java.util.Set;
import java.util.stream.Stream;


public final class CHash implements IUnifier.IAlgorithm
{

    @Override
    public final <T extends ITerm> boolean unify( final Set<IVariable<?>> p_variables, final Stream<T> p_source, final Stream<T> p_target )
    {
        return StreamUtils.zip(
            p_source,
            p_target,
            ( s, t ) ->
            {
                // if s and t are variable create a realocated variable for backtracking
                if ( ( t instanceof IVariable<?> ) && ( s instanceof IVariable<?> ) )
                {
                    p_variables.add(
                        ( (IVariable<?>) t ).mutex()
                        ? new CRelocateMutexVariable<>( t.fqnfunctor(), s.term() )
                        : new CRelocateVariable<>( t.fqnfunctor(), s.term() )
                    );
                    return true;
                }

                // if target type is a variable set the value
                if ( t instanceof IVariable<?> )
                {
                    p_variables.add( t.<IVariable<Object>>term().set( s ) );
                    return true;
                }

                // otherwise check equality
                return s.equals( t );
            }
        ).allMatch( i -> i );
    }
}