/** Copyright (C) 2017 by Bundesanstalt für Gewässerkunde
 * Software engineering by
 *  Björnsen Beratende Ingenieure GmbH
 *  Dr. Schumacher Ingenieurbüro für Wasser und Umwelt
 *
 * This file is Free Software under the GNU AGPL (>=v3)
 * and comes with ABSOLUTELY NO WARRANTY! Check out the
 * documentation coming with Dive4Elements River for details.
 */
package org.dive4elements.river.artifacts.datacage.templating;

import java.util.List;
import java.util.UUID;

import javax.xml.xpath.XPathFunction;
import javax.xml.xpath.XPathFunctionException;

import org.dive4elements.artifactdatabase.data.StateData;
import org.dive4elements.artifacts.CallContext;
import org.dive4elements.river.artifacts.D4EArtifact;
import org.dive4elements.river.utils.RiverUtils;

/**
 * Very specialized function that gets state data from an artifact
 *
 * @author Gernot Belger
 */
public class DataFromArtifactXPathFunction implements XPathFunction {

    public static final String ID = "data_from_artifact";

    public static final int ARITY = 2;

    private final CallContext context;

    public DataFromArtifactXPathFunction(final CallContext context) {
        this.context = context;
    }

    @Override
    public Object evaluate(final List args) throws XPathFunctionException {

        final UUID uuid = (UUID) args.get(0);
        if (uuid == null)
            return null;

        final D4EArtifact artifact = RiverUtils.getArtifact(uuid.toString(), this.context);
        if (!(args.get(1) instanceof String))
            return null;

        final StateData data = artifact.getData(args.get(1).toString());
        final Object value = data.getValue();
        if (value == null)
            return null;

        return value;
    }
}