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.GlobalContext;

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

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.model.Edge;

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 {

    private static enum DistanceFilter {
        NONE, LOCATIONS, DISTANCES
    }

    /** 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()";

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


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


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

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

        String filter  = XMLUtils.xpathString(
            data, FILTER_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, filter);
        }


        String key = getCacheKey(river, filter);

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

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

        Document result = getUncached(river, filter);

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

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

        cache.put(element);

        return result;
    }


    protected String getCacheKey(String river, String filtertype) {
        return filtertype != null && filtertype.length() > 0
            ? river + "_" + filtertype
            : river;
    }


    protected Document getUncached(String river, String filtertype) {

        Document result = XMLUtils.newDocument();

        Session session = SessionHolder.acquire();

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

            Element all = result.createElement("distances");

            DistanceFilter filter = getDistanceFilter(filtertype);

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

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

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

        return result;
    }


    protected static DistanceFilter getDistanceFilter(String type) {
        if (type.equals("locations")) {
            logger.debug("Found 'location' filter.");
            return DistanceFilter.LOCATIONS;
        }
        else if (type.equals("distances")) {
            logger.debug("Found 'distances' filter.");
            return DistanceFilter.DISTANCES;
        }

        logger.debug("Do not use any filter at all.");

        return DistanceFilter.NONE;
    }


    /**
     * Builds an Element for a distance info.
     *
     * @param anno The Annotation that provides information about the distance.
     *
     * @return an Element that contains information about a distance.
     */
    protected static Element buildDistanceNode(
        Document       document,
        Annotation     anno,
        DistanceFilter filter
    ) {
        Position   pos   = anno.getPosition();
        Range      range = anno.getRange();
        Attribute  attr  = anno.getAttribute();
        Edge       edge  = anno.getEdge();
        BigDecimal a     = range.getA();
        BigDecimal b     = range.getB();

        if (b == null && filter == DistanceFilter.DISTANCES) {
            return null;
        }

        if (b != null && filter == DistanceFilter.LOCATIONS) {
            return null;
        }

        Element distance = document.createElement("distance");

        distance.setAttribute("description", pos.getValue());

        String riverSide = attr.getValue();

        if (riverSide != null && riverSide.length() > 0) {
            distance.setAttribute("riverside", riverSide);
        }

        if (a != null) {
            distance.setAttribute("from", a.toString());
        }
        if (b != null) {
            distance.setAttribute("to", b.toString());
        }
        if (edge != null) {
            BigDecimal bottom = edge.getBottom();
            BigDecimal top    = edge.getTop();
            if (bottom != null) {
                distance.setAttribute("bottom", bottom.toString());
            }
            if (top != null) {
                distance.setAttribute("top", top.toString());
            }
        }

        return distance;
    }
}
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