com.facebook.presto.sql.parser.TreePrinter.java Source code

Introduction

Here is the source code for com.facebook.presto.sql.parser.TreePrinter.java

Source

/*
 * 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.presto.sql.parser;

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

import java.util.List;

public final class TreePrinter {
    private TreePrinter() {
    }

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

    private static String treeToString(Tree tree, int depth) {
        if (tree.getChildCount() == 0) {
            return quotedString(tree.toString());
        }
        StringBuilder sb = new StringBuilder();
        sb.append("(");
        sb.append(tree.toString());
        for (Tree t : children(tree)) {
            if (hasSubtree(t) && (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 String quotedString(String s) {
        return s.contains(" ") ? ('"' + s + '"') : s;
    }

    private static boolean hasSubtree(Tree tree) {
        for (Tree t : children(tree)) {
            if (t.getChildCount() > 0) {
                return true;
            }
        }
        return false;
    }

    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();
    }
}