/*
 * 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.axiom.om.impl.stream.xop;

import org.apache.axiom.util.UIDGenerator;

/**
 * Content ID generator interface. Implementations of this interface are used by {@link
 * XOPEncodingFilterHandler} to generate content IDs for use in {@code xop:Include} elements.
 */
public interface ContentIDGenerator {
    /** Default content ID generator that preserves any existing content ID. */
    ContentIDGenerator DEFAULT =
            new ContentIDGenerator() {
                @Override
                public String generateContentID(String existingContentID) {
                    if (existingContentID == null) {
                        return UIDGenerator.generateContentId();
                    } else {
                        return existingContentID;
                    }
                }
            };

    /**
     * Generate a content ID.
     *
     * @param existingContentID An existing content ID for the {@link javax.activation.DataHandler}
     *     being processed, as returned by {@link
     *     org.apache.axiom.ext.stax.BlobReader#getContentID()}, or <code>null
     *     </code> if no existing content ID is known. The implementation is free to use this
     *     information or not.
     * @return the content ID; may not be <code>null</code>
     */
    String generateContentID(String existingContentID);
}
