/*
* Copyright 2008 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.common.css.compiler.passes;
import com.google.common.css.compiler.ast.CssAtRuleNode.Type;
import com.google.common.css.compiler.ast.CssBooleanExpressionNode;
import com.google.common.css.compiler.ast.CssCompilerPass;
import com.google.common.css.compiler.ast.CssConditionalBlockNode;
import com.google.common.css.compiler.ast.CssConditionalRuleNode;
import com.google.common.css.compiler.ast.DefaultTreeVisitor;
import com.google.common.css.compiler.ast.MutatingVisitController;
import java.util.Set;
/**
* A compiler pass that eliminates the conditional blocks for which the boolean
* expression does not evaluate to true.
*
*/
public class EliminateConditionalNodes extends DefaultTreeVisitor
implements CssCompilerPass {
private final MutatingVisitController visitController;
private Set<String> trueConditions;
public EliminateConditionalNodes(MutatingVisitController visitController,
Set<String> trueConditions) {
this.visitController = visitController;
this.trueConditions = trueConditions;
}
@Override
public boolean enterConditionalBlock(CssConditionalBlockNode block) {
int i = 0;
for (CssConditionalRuleNode currentCondtional : block.childIterable()) {
if (currentCondtional.getType() == Type.ELSE) {
// assert i == block.numChildren() - 1;
// TODO(dgajda): Optimize by using immutable children list or an
// iterable.
visitController.replaceCurrentBlockChildWith(
currentCondtional.getBlock().getChildren(), true);
return true;
}
BooleanExpressionEvaluator evaluator = new BooleanExpressionEvaluator(
currentCondtional.getCondition(), trueConditions);
CssBooleanExpressionNode result = evaluator.evaluate();
if (CssBooleanExpressionNode.Type.TRUE_CONSTANT.equals(
result.getValue())) {
visitController.replaceCurrentBlockChildWith(
currentCondtional.getBlock().getChildren(), true);
return true;
}
i++;
}
// No ELSE was encountered and nothing was true.
visitController.removeCurrentNode();
return true;
}
@Override
public void runPass() {
visitController.startVisit(this);
}
}