001/**
002 * Copyright 2015 DuraSpace, Inc.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.fcrepo.client;
017
018import java.net.URI;
019
020/**
021 * A class representing the value of an HTTP Link header
022 *
023 * @author Aaron Coburn
024 */
025public class FcrepoLink {
026
027    private static final String LINK_DELIM = ";";
028
029    private static final String META_REL = "rel";
030
031    private URI uri;
032
033    private String rel;
034
035    /**
036     * Create a representation of a Link header.
037     *
038     * @param link the value for a Link header
039     */
040    public FcrepoLink(final String link) {
041        parse(link);
042    }
043
044    /**
045     * Retrieve the URI of the link
046     *
047     * @return the URI portion of a Link header
048     */
049    public URI getUri() {
050        return uri;
051    }
052
053    /**
054     * Retrieve the REL portion of the link
055     *
056     * @return the "rel" portion of a Link header
057     */
058    public String getRel() {
059        return rel;
060    }
061
062    /**
063     * Parse the value of a link header
064     */
065    private void parse(final String link) {
066        if (link != null) {
067            final String[] segments = link.split(LINK_DELIM);
068            if (segments.length == 2) {
069                uri = getLinkPart(segments[0]);
070                if (uri != null) {
071                    rel = getRelPart(segments[1]);
072                }
073            }
074        }
075    }
076
077    /**
078     * Extract the rel="..." part of the link header
079     */
080    private static String getRelPart(final String relPart) {
081        final String[] segments = relPart.trim().split("=");
082        if (segments.length != 2 || !META_REL.equals(segments[0])) {
083            return null;
084        }
085        final String relValue = segments[1];
086        if (relValue.startsWith("\"") && relValue.endsWith("\"")) {
087            return relValue.substring(1, relValue.length() - 1);
088        } else {
089            return relValue;
090        }
091    }
092
093    /**
094     * Extract the URI part of the link header
095     */
096    private static URI getLinkPart(final String uriPart) {
097        final String linkPart = uriPart.trim();
098        if (!linkPart.startsWith("<") || !linkPart.endsWith(">")) {
099            return null;
100        } else {
101            return URI.create(linkPart.substring(1, linkPart.length() - 1));
102        }
103    }
104}