/*
 *  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.myfaces.shared_tomahawk.util;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

/**
 * Various helpers to deal with exception
 * 
 * @author imario@apache.org
 */
public final class ExceptionUtils
{
    private ExceptionUtils()
    {
    }

    /**
     * <p>
     * returns a list of all throwables (including the one you passed in) wrapped by the given throwable.
     * In contrast to a simple call to <code>getClause()</code> on each throwable it will also check if the throwable class
     * contain a method <code>getRootCause()</code> (e.g. ServletException or JspException) and call it instead.
     * </p>
     * <p>
     * The first list element will your passed in exception, the last list element is the cause. 
     * </p>
     */
    public static List getExceptions(Throwable cause)
    {
        List exceptions = new ArrayList(10);
        exceptions.add(cause);
        
        do
        {
            Throwable nextCause;
            try
            {
                Method rootCause = cause.getClass().getMethod("getRootCause", new Class[]{});
                nextCause = (Throwable) rootCause.invoke(cause, new Object[]{});
            }
            catch(Exception e)
            {
                nextCause = cause.getCause();
            }
            if (cause == nextCause)
            {
                break;
            }
            
            if (nextCause != null)
            {
                exceptions.add(nextCause);
            }
            
            cause = nextCause;
        }
        while (cause != null);
        
        return exceptions;
    }

    /**
     * Find a throwable message starting with the last element.<br />
     * Returns the first throwable message where <code>throwable.getMessage() != null</code> 
     */
    public static String getExceptionMessage(List throwables)
    {
        if (throwables == null)
        {
            return null;
        }

        for (int i = throwables.size()-1; i>0; i--)
        {
            Throwable t = (Throwable) throwables.get(i);
            if (t.getMessage() != null)
            {
                return t.getMessage();
            }
        }
        
        return null;
    }
}
