TreePrinter.java

/*
 * Copyright (C) 2012 Facebook, 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.facebook.swift.parser;

import com.google.common.base.Strings;
import com.google.common.collect.ImmutableList;
import org.antlr.runtime.tree.Tree;

import java.util.List;

public class TreePrinter
{
    public static String treeToString(Tree tree)
    {
        return treeToString(tree, 1);
    }

    private static String treeToString(Tree tree, int depth)
    {
        if (tree.getChildCount() == 0) {
            return tree.toString();
        }
        StringBuilder sb = new StringBuilder();
        sb.append("(");
        sb.append(tree.toString());
        for (Tree t : children(tree)) {
            if (leafCount(tree) > 2) {
                sb.append("\n");
                sb.append(Strings.repeat("   ", depth));
            }
            else {
                sb.append(" ");
            }
            sb.append(treeToString(t, depth + 1));
        }
        sb.append(")");
        return sb.toString();
    }

    private static int leafCount(Tree tree)
    {
        if (tree.getChildCount() == 0) {
            return 1;
        }

        int n = 0;
        for (Tree t : children(tree)) {
            n += leafCount(t);
        }
        return n;
    }

    private static List<Tree> children(Tree tree)
    {
        ImmutableList.Builder<Tree> list = ImmutableList.builder();
        for (int i = 0; i < tree.getChildCount(); i++) {
            list.add(tree.getChild(i));
        }
        return list.build();
    }
}