/*
* 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.jackrabbit.webdav.util;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicHeaderValueParser;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Simple parser for HTTP Link header fields, as defined in RFC 5988.
*/
public class LinkHeaderFieldParser {
/**
* the default logger
*/
private static Logger log = LoggerFactory.getLogger(LinkHeaderFieldParser.class);
private final List<LinkRelation> relations;
public LinkHeaderFieldParser(List<String> fieldValues) {
List<LinkRelation> tmp = new ArrayList<LinkRelation>();
if (fieldValues != null) {
for (String value : fieldValues) {
addFields(tmp, value);
}
}
relations = Collections.unmodifiableList(tmp);
}
public LinkHeaderFieldParser(Enumeration<?> en) {
if (en != null && en.hasMoreElements()) {
List<LinkRelation> tmp = new ArrayList<LinkRelation>();
while (en.hasMoreElements()) {
addFields(tmp, en.nextElement().toString());
}
relations = Collections.unmodifiableList(tmp);
} else {
// optimize case of no Link headers
relations = Collections.emptyList();
}
}
public String getFirstTargetForRelation(String relationType) {
for (LinkRelation lr : relations) {
String relationNames = lr.getParameters().get("rel");
if (relationNames != null) {
// split rel value on whitespace
for (String rn : relationNames.toLowerCase(Locale.ENGLISH)
.split("\\s")) {
if (relationType.equals(rn)) {
return lr.getTarget();
}
}
}
}
return null;
}
// A single header field instance can contain multiple, comma-separated
// fields.
private void addFields(List<LinkRelation> l, String fieldValue) {
boolean insideAngleBrackets = false;
boolean insideDoubleQuotes = false;
for (int i = 0; i < fieldValue.length(); i++) {
char c = fieldValue.charAt(i);
if (insideAngleBrackets) {
insideAngleBrackets = c != '>';
} else if (insideDoubleQuotes) {
insideDoubleQuotes = c != '"';
if (c == '\\' && i < fieldValue.length() - 1) {
// skip over next character
c = fieldValue.charAt(++i);
}
} else {
insideAngleBrackets = c == '<';
insideDoubleQuotes = c == '"';
if (c == ',') {
String v = fieldValue.substring(0, i);
if (v.length() > 0) {
try {
l.add(new LinkRelation(v));
} catch (Exception ex) {
log.warn("parse error in Link Header field value",
ex);
}
}
addFields(l, fieldValue.substring(i + 1));
return;
}
}
}
if (fieldValue.length() > 0) {
try {
l.add(new LinkRelation(fieldValue));
} catch (Exception ex) {
log.warn("parse error in Link Header field value", ex);
}
}
}
private static class LinkRelation {
private static Pattern P = Pattern.compile("\\s*<(.*)>\\s*(.*)");
private String target;
private Map<String, String> parameters;
/**
* Parses a single link relation, consisting of <URI> and optional
* parameters.
*
* @param field
* field value
* @throws Exception
*/
public LinkRelation(String field) throws Exception {
// find the link target using a regexp
Matcher m = P.matcher(field);
if (!m.matches()) {
throw new Exception("illegal Link header field value:" + field);
}
target = m.group(1);
// pass the remainder to the generic parameter parser
NameValuePair[] params = BasicHeaderValueParser.parseParameters(m.group(2), null);
if (params.length == 0) {
parameters = Collections.emptyMap();
} else if (params.length == 1) {
NameValuePair nvp = params[0];
parameters = Collections.singletonMap(nvp.getName()
.toLowerCase(Locale.ENGLISH), nvp.getValue());
} else {
parameters = new HashMap<String, String>();
for (NameValuePair p : params) {
if (null != parameters.put(
p.getName().toLowerCase(Locale.ENGLISH),
p.getValue())) {
throw new Exception("duplicate parameter + "
+ p.getName() + " field ignored");
}
}
}
}
public String getTarget() {
return target;
}
public Map<String, String> getParameters() {
return parameters;
}
public String toString() {
return target + " " + parameters;
}
}
}