/*

 * 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();

    }

}