package de.intevation.flys.artifacts.model;

import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;

import org.apache.log4j.Logger;

import de.intevation.flys.model.Annotation;
import de.intevation.flys.model.Position;
import de.intevation.flys.model.Range;

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

import java.util.Map;
import java.util.TreeMap;
import java.util.Comparator;
import java.util.Iterator;

import java.io.Serializable;


public class LocationProvider {

    public static final double EPSILON = 1e-5;

    public static class KmComparator
    implements          Serializable, Comparator<Double>
    {
        @Override
        public int compare(Double a, Double b) {
            double diff = a - b;
            if (diff < -EPSILON) return -1;
            if (diff > +EPSILON) return +1;
            return 0;
        }
    } // class KmComparator

    public static final String CACHE_KEY = "location-provider";

    public static final String PREFIX = "lp-";


    private static final Logger logger =
        Logger.getLogger(LocationProvider.class);


    private LocationProvider() {
    }

    public static String getLocation(String river, double km) {

        Double KM = Double.valueOf(km);

        return getKmMap(river, KM).get(KM);
    }

    protected static Map<Double, String> getKmMap(String river, double km) {

        Cache cache = CacheFactory.getCache(CACHE_KEY);

        if (cache == null) {
            return uncachedKmMap(river, km);
        }

        String key = PREFIX + river;

        Element element = cache.get(key);

        if (element != null) {
            return (Map<Double, String>)element.getValue();
        }

        Map<Double, String> map = uncachedKmMap(river, null);

        cache.put(new Element(key, map));

        return map;
    }

    protected static Map<Double, String> uncachedKmMap(
        String river,
        Double queryKm
    ) {
        Map<Double, String> map =
            new TreeMap<Double, String>(new KmComparator());
        
        if (queryKm != null) {
            Annotation annotation =
                AnnotationsFactory.getAnnotation(river, queryKm);
            if (annotation != null) {
                map.put(queryKm, annotation.getPosition().getValue());
            }
            return map;
        }

        for (Iterator<Annotation> iter =
            AnnotationsFactory.getAnnotationsIterator(river);
            iter.hasNext();
        ) {
            Annotation annotation = iter.next();
            Position pos   = annotation.getPosition();
            Range    range = annotation.getRange();
            Double   km    = range.getA().doubleValue();
            map.put(km, pos.getValue());
        }

        return map;
    }
}
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