package de.intevation.flys.artifacts.services;

import java.math.BigDecimal;
import java.util.Iterator;

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;

import de.intevation.flys.artifacts.cache.CacheFactory;

import net.sf.ehcache.Cache;

/**
 * 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);

    public static final String CACHE_NAME = "service-distanceinfo";

    public static final String RIVER_XPATH = "/art:river/text()";


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


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

        String river = XMLUtils.xpathString(
            data, RIVER_XPATH, ArtifactNamespaceContext.INSTANCE);

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

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

        Cache cache = CacheFactory.getCache(CACHE_NAME);

        if (cache == null) {
            logger.debug("no cache configured for distance info");
            return getUncached(river);
        }

        net.sf.ehcache.Element element = cache.get(river);

        if (element != null) {
            logger.debug("distance info found in cache");
            return (Document)element.getValue();
        }

        Document result = getUncached(river);

        element = new net.sf.ehcache.Element(river, result);

        logger.debug("store distance info found into cache");

        cache.put(element);

        return result;
    }

    protected Document getUncached(String river) {

        Document result = XMLUtils.newDocument();

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

        Session session = SessionHolder.acquire();

        try {
            Iterator<Annotation> iter =
                AnnotationsFactory.getAnnotationsIterator(river);

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

            while (iter.hasNext()) {
                Annotation a = iter.next();
                Element distance = buildDistanceNode(ec, a);
                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 static 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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