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/*
 * 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.
 * 

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 trueConditions; private final Set runtimeConditionalNodes; private final Set alreadyTreatedNode = new HashSet(); public ExtendedEliminateConditionalNodes(MutatingVisitController visitController, Set trueConditions, Set 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 newChildren = new ArrayList(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); } }





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