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/*
 * 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.log4j.pattern;

import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.ThrowableInformation;

/**
 * Outputs the ThrowableInformation portion of the LoggingEvent. By default,
 * outputs the full stack trace. %throwable{none} or %throwable{0} suppresses
 * the stack trace. %throwable{short} or %throwable{1} outputs just the first
 * line. %throwable{n} will output n lines for a positive integer or drop the
 * last -n lines for a negative integer.
 *
 * @author Paul Smith
 *
 */
public class ThrowableInformationPatternConverter extends LoggingEventPatternConverter {

    /**
     * Maximum lines of stack trace to output.
     */
    private int maxLines = Integer.MAX_VALUE;

    /**
     * Private constructor.
     * 
     * @param options options, may be null.
     */
    private ThrowableInformationPatternConverter(final String[] options) {
	super("Throwable", "throwable");

	if ((options != null) && (options.length > 0)) {
	    if ("none".equals(options[0])) {
		maxLines = 0;
	    } else if ("short".equals(options[0])) {
		maxLines = 1;
	    } else {
		try {
		    maxLines = Integer.parseInt(options[0]);
		} catch (NumberFormatException ex) {
		}
	    }
	}
    }

    /**
     * Gets an instance of the class.
     * 
     * @param options pattern options, may be null. If first element is "short",
     *                only the first line of the throwable will be formatted.
     * @return instance of class.
     */
    public static ThrowableInformationPatternConverter newInstance(final String[] options) {
	return new ThrowableInformationPatternConverter(options);
    }

    /**
     * {@inheritDoc}
     */
    public void format(final LoggingEvent event, final StringBuffer toAppendTo) {
	if (maxLines != 0) {
	    ThrowableInformation information = event.getThrowableInformation();

	    if (information != null) {
		String[] stringRep = information.getThrowableStrRep();

		int length = stringRep.length;
		if (maxLines < 0) {
		    length += maxLines;
		} else if (length > maxLines) {
		    length = maxLines;
		}

		for (int i = 0; i < length; i++) {
		    String string = stringRep[i];
		    toAppendTo.append(string).append("\n");
		}
	    }
	}
    }

    /**
     * This converter obviously handles throwables.
     * 
     * @return true.
     */
    public boolean handlesThrowable() {
	return true;
    }
}