/*
* 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.shindig.gadgets.parse.caja;
import org.apache.shindig.common.cache.Cache;
import org.apache.shindig.common.cache.CacheProvider;
import org.apache.shindig.common.util.HashUtil;
import org.apache.shindig.gadgets.GadgetException;
import org.apache.shindig.gadgets.http.HttpResponse;
import com.google.caja.lexer.CharProducer;
import com.google.caja.lexer.CssLexer;
import com.google.caja.lexer.CssTokenType;
import com.google.caja.lexer.InputSource;
import com.google.caja.lexer.ParseException;
import com.google.caja.lexer.Token;
import com.google.caja.lexer.TokenQueue;
import com.google.caja.lexer.TokenStream;
import com.google.caja.parser.css.CssParser;
import com.google.caja.parser.css.CssTree;
import com.google.caja.render.Concatenator;
import com.google.caja.render.CssPrettyPrinter;
import com.google.caja.reporting.MessageLevel;
import com.google.caja.reporting.MessageQueue;
import com.google.caja.reporting.RenderContext;
import com.google.caja.reporting.SimpleMessageQueue;
import com.google.caja.util.Criterion;
import com.google.inject.Inject;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.net.URI;
import java.util.Collections;
import java.util.logging.Logger;
/** A CSS DOM parser using Caja. */
public class CajaCssParser {
/**
* Dummy URI that is never read from. Needed to construct Caja parser
*/
private static final URI FAKE_SOURCE = URI.create("http://a.dummy.url");
// Switch to "parsedCss" once CajaCssLexerParser is removed. See ehCacheConfig
private static final String PARSED_CSS = "parsedCssDom";
private Cache<String, CssTree.StyleSheet> parsedCssCache;
@Inject
public void setCacheProvider(CacheProvider cacheProvider) {
parsedCssCache = cacheProvider.createCache(PARSED_CSS);
}
/**
* Parse CSS content into Caja's CSS DOM model
*
* @return A parsed stylesheet
*/
public CssTree.StyleSheet parseDom(String content) throws GadgetException {
CssTree.StyleSheet parsedCss = null;
boolean shouldCache = shouldCache();
String key = null;
if (shouldCache) {
// TODO - Consider using the source if its under a certain size
key = HashUtil.rawChecksum(content.getBytes());
parsedCss = parsedCssCache.getElement(key);
}
if (parsedCss == null) {
try {
parsedCss = parseImpl(content);
if (shouldCache) {
parsedCssCache.addElement(key, parsedCss);
}
} catch (ParseException pe) {
// Bad input; not server's fault.
throw new GadgetException(GadgetException.Code.CSS_PARSE_ERROR, pe,
HttpResponse.SC_BAD_REQUEST);
}
}
if (shouldCache) {
return (CssTree.StyleSheet)parsedCss.clone();
}
return parsedCss;
}
private CssTree.StyleSheet parseImpl(String css) throws ParseException {
InputSource inputSource = new InputSource(FAKE_SOURCE);
CharProducer producer = CharProducer.Factory.create(new StringReader(css),
inputSource);
TokenStream<CssTokenType> lexer = new CssLexer(producer);
TokenQueue<CssTokenType> queue = new TokenQueue<CssTokenType>(lexer, inputSource,
new Criterion<Token<CssTokenType>>() {
public boolean accept(Token<CssTokenType> t) {
return CssTokenType.SPACE != t.type
&& CssTokenType.COMMENT != t.type;
}
});
if (queue.isEmpty()) {
// Return empty stylesheet
return new CssTree.StyleSheet(null, Collections.<CssTree.CssStatement>emptyList());
}
MessageQueue mq = new SimpleMessageQueue();
CssParser parser = new CssParser(queue, mq, MessageLevel.WARNING);
return parser.parseStyleSheet();
}
/** Serialize a stylesheet to a String */
public String serialize(CssTree.StyleSheet styleSheet) {
StringWriter writer = new StringWriter();
serialize(styleSheet, writer);
return writer.toString();
}
/** Serialize a stylesheet to a Writer. */
public void serialize(CssTree.StyleSheet styleSheet, Writer writer) {
CssPrettyPrinter cssPrinter = new CssPrettyPrinter(new Concatenator(writer, null));
styleSheet.render(new RenderContext(cssPrinter));
cssPrinter.noMoreTokens();
}
private boolean shouldCache() {
return parsedCssCache != null && parsedCssCache.getCapacity() != 0;
}
}