/*

  * Created on 13.04.2003

  *

  * To change the template for this generated file go to

  * Window>Preferences>Java>Code Generation>Code and Comments

  */

 package de.laures.cewolf.taglib;

 import java.io.Serializable;

 import java.util.Date;

 import java.util.Map;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 import org.jfree.data.general.Dataset;

 import de.laures.cewolf.DatasetProduceException;

 import de.laures.cewolf.DatasetProducer;

 import de.laures.cewolf.taglib.util.DatasetProductionTimeStore;

 import de.laures.cewolf.taglib.util.KeyGenerator;

 import de.laures.cewolf.util.Assert;

 /**

  * @author guido

  *

  * To change the template for this generated type comment go to

  * Window>Preferences>Java>Code Generation>Code and Comments

  */

 public class DataContainer implements DataAware, Serializable {

     private static transient final Log log = LogFactory.getLog(ChartImageDefinition.class);

     private transient Dataset data;

     private transient DatasetProducer producer;

     private Map datasetProductionParams;

     private long datasetProduceTime;

     private boolean useCache = true;

     public void setDataProductionConfig(DatasetProducer dsp, Map params, boolean useCache) {

         log.debug("setDataProductionConfig");

         producer = dsp;

         datasetProductionParams = params;

         this.useCache = useCache;

         checkDataProductionNeed();

     }

     public Object getDataset() throws DatasetProduceException {

         Assert.check(producer != null, "you need to specifiy a producer for the data of the chart.");

         log.debug("getting data..");

         if (data == null) {

             log.debug("producing new dataset for " + producer.getProducerId());

             data = (Dataset) producer.produceDataset(datasetProductionParams);

             DatasetProductionTimeStore dataCache = DatasetProductionTimeStore.getInstance();

             dataCache.addEntry(producer.getProducerId(), datasetProductionParams, new Date(datasetProduceTime));

         }

         Assert.check(data != null, "your producer of type " + producer.getClass().getName() + " produced a null dataset.");

         return data;

     }

     /**

      * This method checks if there has been a dataset production 

      * for the same DatasetProvider and parameters. If so the DatasetProducer

      * is consulted to check the expiry of this data.

      * If the data has expired the retrieval of a cached image of this

      * ChartDefinition is avoided by setting the datasetProduceTime to the

      * actual time. After this the hash code of this object can not be

      * present in the image cache and so a new image with new data will

      * be rendered.

      * If the data did not expire the last dataset production time is stored

      * as a memeber to reach the same hash code for this object as the one

      * before if possible.

      * This method is called during serialization to ensure the same serialized

      * representation of this and a eventually formally stored object.

      */

     private void checkDataProductionNeed() {

         log.debug("checking data actuality..." + producer + ", " + datasetProductionParams);

         final String prodId = producer.getProducerId();

         log.debug(prodId + ", " + KeyGenerator.generateKey((Serializable)datasetProductionParams));

         log.debug("useCache = " + useCache);

         DatasetProductionTimeStore dataCache = DatasetProductionTimeStore.getInstance();

         if (useCache && dataCache.containsEntry(prodId, datasetProductionParams)) {

             Date produceTime = dataCache.getProductionTime(prodId, datasetProductionParams);

             log.debug("cached data available.");

             // cached data available

             if (!producer.hasExpired(datasetProductionParams, produceTime)) {

                 log.debug("cached data is still valid.");

                 this.datasetProduceTime = produceTime.getTime();

                 return;

             }

             dataCache.removeEntry(prodId, datasetProductionParams);

         }

         datasetProduceTime = System.currentTimeMillis();

     }

 }