001/*-
002 * #%L
003 * HAPI FHIR - Server Framework
004 * %%
005 * Copyright (C) 2014 - 2024 Smile CDR, Inc.
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 *      http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package ca.uhn.fhir.rest.server.method;
021
022import ca.uhn.fhir.rest.api.Constants;
023import ca.uhn.fhir.rest.api.server.IBundleProvider;
024import ca.uhn.fhir.rest.api.server.RequestDetails;
025import ca.uhn.fhir.rest.server.RestfulServerUtils;
026
027public class OffsetCalculator {
028        /**
029         * Calculate the offset into the list of resources that should be used to create the returned bundle.
030         * @param theRequest
031         * @param theBundleProvider
032         * @return
033         */
034        public static int calculateOffset(RequestDetails theRequest, IBundleProvider theBundleProvider) {
035                Integer offset = RestfulServerUtils.tryToExtractNamedParameter(theRequest, Constants.PARAM_PAGINGOFFSET);
036                if (offset == null || offset < 0) {
037                        offset = 0;
038                }
039
040                Integer resultSize = theBundleProvider.size();
041                int retval = offset;
042                if (resultSize != null) {
043                        retval = Math.max(0, Math.min(offset, resultSize));
044                }
045                return retval;
046        }
047}