// Copyright 2009 Google Inc. All Rights Reserved.
package org.waveprotocol.wave.model.util;
/**
* A typeclass-style interface for manipulating mutable data
*
* @author danilatos@google.com (Daniel Danilatos)
*
* @param <T> The data type (e.g. StringSet)
* @param <R> A read-only version of the data type (e.g. ReadableStringSet).
* If none is available, then this may be the same as <T>.
*/
public interface DataDomain<R, T extends R> {
/**
* @return a new empty instance of the data
*/
T empty();
/**
* Updates {@code target} to be the result of combining {@code changes} onto
* {@code base}
*
* @param target
* @param changes
* @param base
*/
void compose(T target, R changes, R base);
/**
* @param modifiable
* @return optionally a read-only view of the modifiable data, to provide
* runtime readonly guarantees. Otherwise just return the parameter.
*/
R readOnlyView(T modifiable);
}