/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.openmeetings.web.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import org.wicketstuff.select2.ChoiceProvider;

public abstract class RestrictiveChoiceProvider<T> extends ChoiceProvider<T> {
	private static final long serialVersionUID = 1L;
	private final Set<String> ids = new HashSet<>();

	public abstract String toId(T e);
	public abstract T fromId(String id);

	@Override
	public final String getIdValue(T e) {
		String id = toId(e);
		ids.add(id);
		return id;
	}

	@Override
	public final Collection<T> toChoices(Collection<String> inIds) {
		Collection<T> c = new ArrayList<>();
		for (String id : inIds) {
			if (ids.contains(id)) {
				T e = fromId(id);
				if (e != null) {
					c.add(e);
				}
			}
		}
		return c;
	}
}
