/**
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.waveprotocol.wave.model.adt.docbased;
import org.waveprotocol.wave.model.util.CollectionUtils;
import org.waveprotocol.wave.model.util.Preconditions;
import java.util.Map;
/**
* Provides initialization for a document element.
*
* The document interfaces currently only support atomic initialization of
* attributes on a single element, not atomic initialization of a document
* subtree. Thus this interface only provides attribute map initialization.
*
* @author anorth@google.com (Alex North)
*/
public interface Initializer {
/**
* Initializes attributes in a map.
*
* @param target receives the initialization values
* @throws IllegalArgumentException if {@code target} already contains a key
* equal to one set by this initializer
*/
void initialize(Map<String, String> target);
/**
* Initializer utilities.
*/
final class Helper {
/**
* Builds an attribute map for an abstract initial state via a
* {@link Factory} which can build an {@link Initializer}.
*
* @param initialState abstract initial state
* @param initializerFactory translates initial state into an initializer
* @return an attribute map initialized with the initial state
*/
public static <I> Map<String, String> buildAttributes(I initialState,
Factory<?, ?, I> initializerFactory) {
Map<String, String> attrs = CollectionUtils.newHashMap();
initializerFactory.createInitializer(initialState).initialize(attrs);
return attrs;
}
/**
* Initializes an attribute, failing if the target map already contains an
* initialization for the same key.
*
* @throws IllegalArgumentException if the map already contains {@code key}
*/
public static void initialiseAttribute(Map<String, String> target, String key, String value) {
if (target.containsKey(key)) {
Preconditions.illegalArgument("Duplicate initialiser key '" + key + "' in initialiser");
}
target.put(key, value);
}
}
}