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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 2011 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.*;

import java.util.Set;

/**
 * Base class for compiler passes enforcing a specific CSS level.
 *
 * @author [email protected] (Florian Benz)
 */
public abstract class StrictCssBase extends DefaultTreeVisitor
        implements CssCompilerPass {
    private static final String SUPPORTED_LIST_PREFIX = "\nsupported names: ";
    private static final String SUPPORTED_LIST_SUFFIX = "\n";

    static final String INVALID_UNIT_PREFIX = "Invalid unit: ";

    protected final VisitController visitController;
    protected final ErrorManager errorManager;

    public StrictCssBase(VisitController visitController,
                         ErrorManager errorManager) {
        this.visitController = visitController;
        this.errorManager = errorManager;
    }

    abstract Set getValidCssUnits();

    /**
     * Checks numeric nodes for valid units.
     */
    @Override
    public boolean enterValueNode(CssValueNode node) {
        if (node instanceof CssNumericNode) {
            // NOTE(nicksantos): At some point, we should attach type information
            // to the AST so that we can validate by the type of unit.
            String unit = ((CssNumericNode) node).getUnit();
            if (!getValidCssUnits().contains(unit)) {
                errorManager.report(
                        new GssError(INVALID_UNIT_PREFIX + unit,
                                node.getSourceCodeLocation()));
                return false;
            }
        }
        return true;
    }

    /**
     * Adds a list of supported names to the error message and then reports
     * the error.
     */
    protected void reportUnsupported(CssNode node, String message,
                                     Set supportedNames) {
        StringBuilder sb = new StringBuilder();
        sb.append(message);
        sb.append(SUPPORTED_LIST_PREFIX);
        for (String name : supportedNames) {
            sb.append(name);
            sb.append(", ");
        }
        sb.append(SUPPORTED_LIST_SUFFIX);
        errorManager.report(new GssError(sb.toString(),
                node.getSourceCodeLocation()));
    }

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