/*
* Copyright 2014 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.gss;
import com.google.gwt.resources.gss.ast.CssRuntimeConditionalRuleNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssAtRuleNode.Type;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssBooleanExpressionNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssCompilerPass;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssConditionalBlockNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.CssConditionalRuleNode;
import com.google.gwt.thirdparty.common.css.compiler.ast.MutatingVisitController;
import com.google.gwt.thirdparty.common.css.compiler.passes.BooleanExpressionEvaluator;
import com.google.gwt.thirdparty.common.css.compiler.passes.EliminateConditionalNodes;
import com.google.gwt.thirdparty.guava.common.collect.Lists;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
* A compiler pass that eliminates the conditional blocks for which the boolean
* expression does not evaluate to true.
* <p>This compiler pass does not deal with conditional nodes that need to be evaluated at runtime.
*/
public class ExtendedEliminateConditionalNodes extends EliminateConditionalNodes
implements CssCompilerPass {
private final MutatingVisitController visitController;
private final Set<String> trueConditions;
private final Set<CssConditionalBlockNode> runtimeConditionalNodes;
private final Set<CssConditionalBlockNode> alreadyTreatedNode =
new HashSet<CssConditionalBlockNode>();
public ExtendedEliminateConditionalNodes(MutatingVisitController visitController,
Set<String> trueConditions, Set<CssConditionalBlockNode> runtimeConditionalNodes) {
super(visitController, trueConditions);
this.visitController = visitController;
this.trueConditions = trueConditions;
this.runtimeConditionalNodes = runtimeConditionalNodes;
}
@Override
public boolean enterConditionalBlock(CssConditionalBlockNode block) {
if (alreadyTreatedNode.contains(block)) {
// don't visit this block again but visit its children
return true;
}
if (runtimeConditionalNodes.contains(block)) {
return enterRuntimeConditionalBlock(block);
} else {
// block without any runtime condition.
return super.enterConditionalBlock(block);
}
}
private boolean enterRuntimeConditionalBlock(CssConditionalBlockNode block) {
boolean runtimeEvaluationNodeFound = false;
List<CssConditionalRuleNode> newChildren =
new ArrayList<CssConditionalRuleNode>(block.numChildren());
for (CssConditionalRuleNode currentConditional : block.childIterable()) {
if (currentConditional.getType() == Type.ELSE) {
newChildren.add(currentConditional);
break;
}
if (currentConditional instanceof CssRuntimeConditionalRuleNode) {
runtimeEvaluationNodeFound = true;
newChildren.add(currentConditional);
continue;
}
// The node can be evaluated at compile time
BooleanExpressionEvaluator evaluator = new BooleanExpressionEvaluator(
currentConditional.getCondition(), trueConditions);
CssBooleanExpressionNode result = evaluator.evaluate();
boolean isTrue = CssBooleanExpressionNode.Type.TRUE_CONSTANT.equals(result.getValue());
if (!isTrue) {
// any node evaluated to false can be removed
} else if (!runtimeEvaluationNodeFound) {
// node evaluated to true before the runtime condition, replace the conditional block by the
// children of this current conditional node.
visitController.replaceCurrentBlockChildWith(currentConditional.getBlock().getChildren(),
true);
return true;
} else {
// node evaluated to true before the runtime condition, transform this node to an else node
CssConditionalRuleNode newNode = new CssConditionalRuleNode(Type.ELSE,
currentConditional.getName(), null, currentConditional.getBlock());
newChildren.add(newNode);
break;
}
}
CssConditionalBlockNode newNode = new CssConditionalBlockNode();
for (CssConditionalRuleNode child : newChildren) {
newNode.addChildToBack(child);
}
visitController.replaceCurrentBlockChildWith(Lists.newArrayList(newNode), true);
// mark this node as already visited.
alreadyTreatedNode.add(newNode);
return true;
}
@Override
public void runPass() {
alreadyTreatedNode.clear();
visitController.startVisit(this);
}
}