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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.css.compiler.ast.*;

/**
 * Compiler pass that removes declaration nodes that have all the property
 * values marked as default.
 *
 * @author [email protected] (Oana Florescu)
 */
public class RemoveDefaultDeclarations extends DefaultTreeVisitor
        implements CssCompilerPass {

    private final MutatingVisitController visitController;

    private boolean canRemoveDefaultValue = false;

    public RemoveDefaultDeclarations(MutatingVisitController visitController) {
        this.visitController = visitController;
    }

    @Override
    public boolean enterCompositeValueNode(CssCompositeValueNode node) {
        removeDefault(node);
        return true;
    }

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

    private void removeDefault(CssValueNode node) {
        if (canRemoveDefaultValue && node.getIsDefault()) {
            visitController.removeCurrentNode();
        }
    }

    @Override
    public boolean enterDeclaration(CssDeclarationNode node) {
        boolean removeDeclaration = true;
        canRemoveDefaultValue =
                !node.getPropertyName().getProperty().hasPositionalParameters();
        // If any of the DeclarationNode's values is a priority node (marked with
        // "!important" in the css) then none of the values should be
        // removed. Otherwise remove the default values.
        for (CssValueNode value : node.getPropertyValue().childIterable()) {
            if (value instanceof CssPriorityNode) {
                removeDeclaration = false;
                canRemoveDefaultValue = false;
                break;
            }
            if (!value.getIsDefault()) {
                removeDeclaration = false;
            }
        }
        if (removeDeclaration) {
            visitController.removeCurrentNode();
        }
        return true;
    }

    @Override
    public void leaveDeclaration(CssDeclarationNode node) {
        canRemoveDefaultValue = false;
    }

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