package org.simantics.db.common.recursive;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.Statement;
import org.simantics.db.exception.DatabaseException;
import org.simantics.layer0.Layer0;

public class FindParentsWithType extends FindRoots {
    private final ReadGraph graph;
    private final Resource rootType;
    private final Layer0 L0;
    
    public FindParentsWithType(ReadGraph graph, Resource rootType) {
        this.graph = graph;
        this.rootType = rootType;
        this.L0 = Layer0.getInstance(graph);
    }

    @Override
    protected boolean isRoot(Resource resource) throws DatabaseException {
        return graph.isInstanceOf(resource, rootType);
    }

    @Override
    protected Collection<Resource> children(Resource resource) throws DatabaseException {
        Resource parent = graph.getPossibleObject(resource, L0.PartOf);
        if(parent != null)
            return Collections.singletonList(parent);
        
        ArrayList<Resource> result = new ArrayList<Resource>(4); 
        for(Statement s : graph.getStatements(resource, L0.IsWeaklyRelatedTo)) {
            if(!s.getSubject().equals(resource))
                continue;
            Resource inverse = graph.getPossibleInverse(s.getPredicate());
            if(inverse != null && graph.isSubrelationOf(inverse, L0.IsRelatedTo))
                result.add(s.getObject());
        }
        return result;
    }

    /**
     * Makes a query for just one resource. If you want to make multiple queries with the same type, 
     * instantiate this class and call the {@code get} method.
     */
    public static List<Resource> findParentsWithType(ReadGraph graph, Resource r, Resource type) throws DatabaseException {
        Set<Resource> set = new FindParentsWithType(graph, type).get(r);
        if(set == null)
            return Collections.emptyList();
        else
            return new ArrayList<Resource>(set);
    }
}