Aggregation.java

package mil.nga.giat.geowave.core.store.query.aggregate;

import mil.nga.giat.geowave.core.index.Mergeable;
import mil.nga.giat.geowave.core.index.Persistable;

public interface Aggregation<P extends Persistable, R extends Mergeable, T>
{
	/**
	 * Returns a persistable object for any parameters that must be persisted to
	 * properly compute the aggregation
	 * 
	 * @return A persistable object for any parameters that must be persisted to
	 *         properly compute the aggregation
	 */
	public P getParameters();

	/**
	 * Sets the parameters based on what has been persisted
	 * 
	 * @param parameters
	 *            the persisted parameters for this aggregation function
	 */
	public void setParameters(
			P parameters );

	/**
	 * Get the current result of the aggregation. This must be mergeable and it
	 * is the responsibility of the caller to merge separate results if desired.
	 * It is the responsibility of the aggregation to start with a new instance
	 * of the result at the beginning of any aggregation.
	 * 
	 * @return the current result of the aggregation
	 */
	public R getResult();

	/**
	 * this will be called if the result should be reset to its default value
	 * 
	 */
	public void clearResult();

	/**
	 * Update the aggregation result using the new entry provided
	 * 
	 * @param entry
	 *            the new entry to compute an updated aggregation result on
	 */
	public void aggregate(
			T entry );
}