ProverCache.java

package org.ggp.base.util.prover.aima.cache;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import org.ggp.base.util.gdl.grammar.GdlSentence;
import org.ggp.base.util.prover.aima.substituter.Substituter;
import org.ggp.base.util.prover.aima.substitution.Substitution;
import org.ggp.base.util.prover.aima.unifier.Unifier;


public final class ProverCache
{

    private final Map<GdlSentence, Set<GdlSentence>> contents;

    private ProverCache(Map<GdlSentence, Set<GdlSentence>> mapForContents) {
        this.contents = mapForContents;
    }

    public static ProverCache createSingleThreadedCache() {
        return new ProverCache(new HashMap<GdlSentence, Set<GdlSentence>>());
    }

    public static ProverCache createMultiThreadedCache() {
        return new ProverCache(new ConcurrentHashMap<GdlSentence, Set<GdlSentence>>());
    }

    /**
     * NOTE: The given sentence must have been renamed with a VariableRenamer.
     */
    public boolean contains(GdlSentence renamedSentence)
    {
        return contents.containsKey(renamedSentence);
    }

    public List<Substitution> get(GdlSentence sentence, GdlSentence varRenamedSentence)
    {
        Set<GdlSentence> cacheContents = contents.get(varRenamedSentence);
        if (cacheContents == null) {
            return null;
        }
        Set<Substitution> results = new HashSet<Substitution>();
        for (GdlSentence answer : cacheContents)
        {
            results.add(Unifier.unify(sentence, answer));
        }

        return new ArrayList<Substitution>(results);
    }

    public void put(GdlSentence sentence, GdlSentence renamedSentence,
            Set<Substitution> answers)
    {
        Set<GdlSentence> results = new HashSet<GdlSentence>();
        for (Substitution answer : answers)
        {
            results.add(Substituter.substitute(sentence, answer));
        }

        contents.put(renamedSentence, results);
    }

}