javaparser-core/src/main/java/com/github/javaparser/printer/lexicalpreservation/PhantomNodeLogic.java

/*
 * Copyright (C) 2007-2010 Júlio Vilmar Gesser.
 * Copyright (C) 2011, 2013-2016 The JavaParser Team.
 *
 * This file is part of JavaParser.
 *
 * JavaParser can be used either under the terms of
 * a) the GNU Lesser General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 * b) the terms of the Apache License
 *
 * You should have received a copy of both licenses in LICENCE.LGPL and
 * LICENCE.APACHE. Please refer to those files for details.
 *
 * JavaParser is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 */

package com.github.javaparser.printer.lexicalpreservation;

import com.github.javaparser.ast.Node;
import com.github.javaparser.ast.observer.AstObserver;
import com.github.javaparser.ast.observer.AstObserverAdapter;
import com.github.javaparser.ast.type.UnknownType;

import java.util.IdentityHashMap;
import java.util.Map;

import static java.util.Collections.synchronizedMap;

/**
 * We want to recognize and ignore "phantom" nodes, like the fake type of variable in FieldDeclaration
 */
class PhantomNodeLogic {

    private static final int LEVELS_TO_EXPLORE = 3;

    private static final Map<Node, Boolean> isPhantomNodeCache = synchronizedMap(new IdentityHashMap<>());

    private static final AstObserver cacheCleaner = new AstObserverAdapter() {
        @Override
        public void parentChange(Node observedNode, Node previousParent, Node newParent) {
            isPhantomNodeCache.remove(observedNode);
        }
    };

    static boolean isPhantomNode(Node node) {
        if (isPhantomNodeCache.containsKey(node)) {
            return isPhantomNodeCache.get(node);
        } else {
            if (node instanceof UnknownType) {
                return true;
            }
            boolean res = (node.getParentNode().isPresent() &&
                    !node.getParentNode().get().getRange().get().contains(node.getRange().get())
                    || inPhantomNode(node, LEVELS_TO_EXPLORE));
            isPhantomNodeCache.put(node, res);
            node.register(cacheCleaner);
            return res;
        }
    }

    /**
     * A node contained in a phantom node is also a phantom node. We limit how many levels up we check just for performance reasons.
     */
    private static boolean inPhantomNode(Node node, int levels) {
        return node.getParentNode().isPresent() &&
                (isPhantomNode(node.getParentNode().get())
                        || inPhantomNode(node.getParentNode().get(), levels - 1));
    }
}