package de.intevation.flys.artifacts.services;

import java.math.BigDecimal;
import java.util.List;

import org.apache.log4j.Logger;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

import de.intevation.artifacts.CallMeta;

import de.intevation.artifacts.common.ArtifactNamespaceContext;
import de.intevation.artifacts.common.utils.XMLUtils;
import de.intevation.artifacts.common.utils.XMLUtils.ElementCreator;

import de.intevation.artifactdatabase.DefaultService;

import de.intevation.flys.backend.SessionHolder;
import de.intevation.flys.model.Annotation;
import de.intevation.flys.model.Attribute;
import de.intevation.flys.model.Position;
import de.intevation.flys.model.Range;

import de.intevation.flys.artifacts.model.AnnotationsFactory;

import org.hibernate.Session;

/**
 * This service provides information about distances of a specified river.
 *
 * @author <a href="mailto:ingo.weinzierl@intevation.de">Ingo Weinzierl</a>
 */
public class DistanceInfoService extends DefaultService {

    /** The logger used in this service.*/
    private static Logger logger = Logger.getLogger(DistanceInfoService.class);


    /**
     * The default constructor.
     */
    public DistanceInfoService() {
    }


    public Document process(
        Document data,
        Object   globalContext,
        CallMeta callMeta)
    {
        logger.debug("DistanceInfoService.process");

        Document result = XMLUtils.newDocument();

        String river = XMLUtils.xpathString(
            data, "/art:river/text()", ArtifactNamespaceContext.INSTANCE);

        if (river == null || river.trim().length() == 0) {
            logger.warn("No river specified. Cannot return distance info!");
            return result;
        }

        logger.debug("Search distances for river: " + river);

        ElementCreator ec = new ElementCreator(
            result,
            ArtifactNamespaceContext.NAMESPACE_URI,
            ArtifactNamespaceContext.NAMESPACE_PREFIX);

        Session session = SessionHolder.acquire();
        try {
            List<Annotation> annotations = AnnotationsFactory.getAnnotations(river);

            if (annotations == null || annotations.size() == 0) {
                logger.warn("No information found for the specified river!");
                return result;
            }

            Element all = ec.create("distances");

            for (Annotation a: annotations) {
                Element distance = buildDistanceNode(ec, a);

                if (distance != null) {
                    all.appendChild(distance);
                }
            }

            result.appendChild(all);
        }
        finally {
            session.close();
            SessionHolder.release();
        }

        return result;
    }


    /**
     * This method build an Element for a distance info.
     *
     * @param ec The ElementCreator.
     * @param anno The Annotation that provides information about the distance.
     *
     * @return an Element that contains information about a distance.
     */
    protected Element buildDistanceNode(ElementCreator ec, Annotation anno) {
        Position  pos   = anno.getPosition();
        Range     range = anno.getRange();
        Attribute attr  = anno.getAttribute();

        BigDecimal a = range.getA();
        BigDecimal b = range.getB();

        Element distance = ec.create("distance");
        ec.addAttr(distance, "description", pos.getValue(), true);
        ec.addAttr(distance, "from", a != null ? a.toString() : "", true);
        ec.addAttr(distance, "to", b != null ? b.toString() : "", true);
        ec.addAttr(distance, "riverside", attr.getValue(), true);

        return distance;
    }
}
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