/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.rocketmq.remoting.internal;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

public class ExceptionUtils {

    private static final String LINE_SEPARATOR = System.getProperty("line.separator");

    /**
     * <p>Produces a <code>List</code> of stack frames - the message
     * is not included. Only the trace of the specified exception is
     * returned, any caused by trace is stripped.</p>
     *
     * <p>This works in most cases - it will only fail if the exception
     * message contains a line that starts with:
     * <code>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
     *
     * @param t is any throwable
     * @return List of stack frames
     */
    static List<String> getStackFrameList(final Throwable t) {
        final String stackTrace = getStackTrace(t);
        final String linebreak = LINE_SEPARATOR;
        final StringTokenizer frames = new StringTokenizer(stackTrace, linebreak);
        final List<String> list = new ArrayList<String>();
        boolean traceStarted = false;
        while (frames.hasMoreTokens()) {
            final String token = frames.nextToken();
            // Determine if the line starts with <whitespace>at
            final int at = token.indexOf("at");
            if (at != -1 && token.substring(0, at).trim().isEmpty()) {
                traceStarted = true;
                list.add(token);
            } else if (traceStarted) {
                break;
            }
        }
        return list;
    }

    /**
     * <p>Gets the stack trace from a Throwable as a String.</p>
     *
     * <p>The result of this method vary by JDK version as this method
     * uses {@link Throwable#printStackTrace(java.io.PrintWriter)}.
     * On JDK1.3 and earlier, the cause exception will not be shown
     * unless the specified throwable alters printStackTrace.</p>
     *
     * @param throwable the <code>Throwable</code> to be examined
     * @return the stack trace as generated by the exception's
     * <code>printStackTrace(PrintWriter)</code> method
     */
    public static String getStackTrace(final Throwable throwable) {
        final StringWriter sw = new StringWriter();
        final PrintWriter pw = new PrintWriter(sw, true);
        throwable.printStackTrace(pw);
        return sw.getBuffer().toString();
    }
}