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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 2015 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.ImmutableList;
import com.google.common.css.compiler.ast.*;

import javax.annotation.Nullable;
import java.util.Map;

/**
 * Evaluates integer constants provided typically through command line. These constants were
 * introduced to specify for loop range, but they can also be used as value nodes.
 */
public class EvaluateCompileConstants extends DefaultTreeVisitor implements CssCompilerPass {

    private final MutatingVisitController visitController;
    private final Map compileConstants;

    public EvaluateCompileConstants(
            MutatingVisitController visitController, Map compileConstants) {
        this.visitController = visitController;
        this.compileConstants = compileConstants;
    }

    @Override
    public boolean enterValueNode(CssValueNode node) {
        CssNumericNode newNode = updateValueNode(node);
        if (newNode != null) {
            visitController.replaceCurrentBlockChildWith(ImmutableList.of(newNode), false);
        }
        return true;
    }

    @Override
    public boolean enterArgumentNode(CssValueNode node) {
        return enterValueNode(node);
    }

    @Override
    public boolean enterForLoop(CssForLoopRuleNode node) {
        CssNumericNode from = updateValueNode(node.getFrom());
        if (from != null) {
            node.setFrom(from);
        }
        CssNumericNode to = updateValueNode(node.getTo());
        if (to != null) {
            node.setTo(to);
        }
        CssNumericNode step = updateValueNode(node.getStep());
        if (step != null) {
            node.setStep(step);
        }
        return true;
    }

    /**
     * Check if the value node refers to a compile constant and if so returns a numeric node with the
     * replaced value.
     */
    @Nullable
    private CssNumericNode updateValueNode(CssValueNode node) {
        Integer value = compileConstants.get(node.getValue());
        if (value != null) {
            return new CssNumericNode(
                    String.valueOf(value), CssNumericNode.NO_UNITS, node.getSourceCodeLocation());
        }
        return null;
    }

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