/*
* Copyright 2009 Google Inc.
*
* Licensed 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 com.google.gwt.resources.css;
import com.google.gwt.resources.css.ast.Context;
import com.google.gwt.resources.css.ast.CssIf;
import com.google.gwt.resources.css.ast.CssMediaRule;
import com.google.gwt.resources.css.ast.CssModVisitor;
import com.google.gwt.resources.css.ast.CssNode;
import com.google.gwt.resources.css.ast.CssProperty;
import com.google.gwt.resources.css.ast.CssRule;
import com.google.gwt.resources.rg.CssResourceGenerator;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* Merges rules that have identical content.
*/
public class MergeRulesByContentVisitor extends CssModVisitor {
private Map<String, CssRule> rulesByContents = new HashMap<String, CssRule>();
private final List<CssRule> rulesInOrder = new ArrayList<CssRule>();
@Override
public boolean visit(CssIf x, Context ctx) {
visitInNewContext(x.getNodes());
visitInNewContext(x.getElseNodes());
return false;
}
@Override
public boolean visit(CssMediaRule x, Context ctx) {
visitInNewContext(x.getNodes());
return false;
}
@Override
public boolean visit(CssRule x, Context ctx) {
StringBuilder b = new StringBuilder();
for (CssProperty p : x.getProperties()) {
b.append(p.getName()).append(":").append(p.getValues().getExpression());
}
String content = b.toString();
CssRule canonical = rulesByContents.get(content);
// Check everything between the canonical rule and this rule for common
// properties. If there are common properties, it would be unsafe to
// promote the rule.
if (canonical != null) {
boolean hasCommon = false;
int index = rulesInOrder.indexOf(canonical) + 1;
assert index != 0;
for (Iterator<CssRule> i = rulesInOrder.listIterator(index); i.hasNext()
&& !hasCommon;) {
hasCommon = CssResourceGenerator.haveCommonProperties(i.next(), x);
}
if (!hasCommon) {
canonical.getSelectors().addAll(x.getSelectors());
ctx.removeMe();
return false;
}
}
rulesByContents.put(content, x);
rulesInOrder.add(x);
return false;
}
private void visitInNewContext(List<CssNode> nodes) {
MergeRulesByContentVisitor v = new MergeRulesByContentVisitor();
v.acceptWithInsertRemove(nodes);
rulesInOrder.addAll(v.rulesInOrder);
}
}