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Closure Stylesheets is an extension to CSS that adds variables, functions, conditionals, and mixins to standard CSS. The tool also supports minification, linting, RTL flipping, and CSS class renaming.

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/*
 * 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.common.css.compiler.passes;

import com.google.common.collect.Lists;
import com.google.common.css.compiler.ast.*;

import java.util.List;

/**
 * A compiler pass that transforms each well-formed {@code @def}
 * {@link CssUnknownAtRuleNode} to a {@link CssDefinitionNode}.
 */
public class CreateDefinitionNodes extends DefaultTreeVisitor
        implements CssCompilerPass {

    private static final String DEF_NAME =
            CssAtRuleNode.Type.DEF.getCanonicalName();
    private final MutatingVisitController visitController;
    private final ErrorManager errorManager;

    public CreateDefinitionNodes(
            MutatingVisitController visitController, ErrorManager errorManager) {
        this.visitController = visitController;
        this.errorManager = errorManager;
    }

    @Override
    public boolean enterUnknownAtRule(CssUnknownAtRuleNode node) {
        if (node.getName().getValue().equals(DEF_NAME)) {
            if (node.getType().hasBlock()) {
                reportError("@" + DEF_NAME + " with block", node);
                return false;
            }
            List params = node.getParameters();
            if (params.isEmpty()) {
                reportError("@" + DEF_NAME + " without name", node);
                return false;
            }
            CssNode nameNode = params.get(0);
            if (!(nameNode instanceof CssLiteralNode)) {
                reportError("@" + DEF_NAME + " without a valid literal as name", node);
                return false;
            }

            CssLiteralNode defNameNode = (CssLiteralNode) nameNode;
            String defName = defNameNode.getValue();
            if (!CssConstantReferenceNode.isDefinitionReference(defName)) {
                errorManager.reportWarning(new GssError(
                        String.format(
                                "WARNING for invalid @def name %s. We will ignore this.",
                                defName),
                        defNameNode.getSourceCodeLocation()));

                // Create a definition node anyway, so that the compiler doesn't crash.
            }
            CssDefinitionNode def = new CssDefinitionNode(
                    params.subList(1, params.size()),
                    (CssLiteralNode) nameNode,
                    node.getComments(),
                    node.getSourceCodeLocation());
            visitController.replaceCurrentBlockChildWith(
                    Lists.newArrayList((CssNode) def), false);
            return false;
        }
        return true;
    }

    private void reportError(String message, CssNode node) {
        errorManager.report(new GssError(message, node.getSourceCodeLocation()));
        visitController.removeCurrentNode();
    }

    @Override
    public void runPass() {
        visitController.startVisit(this);
    }
}