001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.discovery.resource.names;
018
019import org.apache.commons.discovery.ResourceNameDiscover;
020import org.apache.commons.discovery.ResourceNameIterator;
021
022/**
023 * Helper class for methods implementing the ResourceNameDiscover interface.
024 */
025public abstract class ResourceNameDiscoverImpl implements ResourceNameDiscover {
026
027    /**
028     * Locate names of resources that are bound to {@code resourceName}.
029     *
030     * @param resourceName The resource name to locate
031     * @return A new {@link ResourceNameIterator}
032     */
033    public abstract ResourceNameIterator findResourceNames(String resourceName);
034
035    /**
036     * Locate names of resources that are bound to {@code inputNames}.
037     *
038     * @param inputNames The resource names to locate
039     * @return A new {@link ResourceNameIterator}
040     */
041    public ResourceNameIterator findResourceNames(final ResourceNameIterator inputNames) {
042        return new ResourceNameIterator() {
043
044            private ResourceNameIterator resourceNames = null;
045
046            private String resourceName = null;
047
048            public boolean hasNext() {
049                if (resourceName == null) {
050                    resourceName = getNextResourceName();
051                }
052                return resourceName != null;
053            }
054
055            public String nextResourceName() {
056                String name = resourceName;
057                resourceName = null;
058                return name;
059            }
060
061            private String getNextResourceName() {
062                while (inputNames.hasNext() && (resourceNames == null  ||  !resourceNames.hasNext())) {
063                    resourceNames =
064                        findResourceNames(inputNames.nextResourceName());
065                }
066
067                return (resourceNames != null  &&  resourceNames.hasNext())
068                       ? resourceNames.nextResourceName()
069                       : null;
070            }
071        };
072    }
073
074}