/*
 * 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.
 */

// Contributors: Christopher Williams
//               Mathias Bogaert

package org.apache.log4j;

import org.apache.log4j.helpers.DateLayout;
import org.apache.log4j.spi.LoggingEvent;

/**
 * TTCC layout format consists of time, thread, category and nested diagnostic
 * context information, hence the name.
 * 
 * <p>
 * Each of the four fields can be individually enabled or disabled. The time
 * format depends on the <code>DateFormat</code> used.
 * 
 * <p>
 * Here is an example TTCCLayout output with the
 * {@link org.apache.log4j.helpers.RelativeTimeDateFormat}.
 * 
 * <pre>
176 [main] INFO  org.apache.log4j.examples.Sort - Populating an array of 2 elements in reverse order.
225 [main] INFO  org.apache.log4j.examples.SortAlgo - Entered the sort method.
262 [main] DEBUG org.apache.log4j.examples.SortAlgo.OUTER i=1 - Outer loop.
276 [main] DEBUG org.apache.log4j.examples.SortAlgo.SWAP i=1 j=0 - Swapping intArray[0] = 1 and intArray[1] = 0
290 [main] DEBUG org.apache.log4j.examples.SortAlgo.OUTER i=0 - Outer loop.
304 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Dump of interger array:
317 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Element [0] = 0
331 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Element [1] = 1
343 [main] INFO  org.apache.log4j.examples.Sort - The next log statement should be an error message.
346 [main] ERROR org.apache.log4j.examples.SortAlgo.DUMP - Tried to dump an uninitialized array.
        at org.apache.log4j.examples.SortAlgo.dump(SortAlgo.java:58)
        at org.apache.log4j.examples.Sort.main(Sort.java:64)
467 [main] INFO  org.apache.log4j.examples.Sort - Exiting main method.
 * </pre>
 * 
 * <p>
 * The first field is the number of milliseconds elapsed since the start of the
 * program. The second field is the thread outputting the log statement. The
 * third field is the level, the fourth field is the category to which the
 * statement belongs.
 * 
 * <p>
 * The fifth field (just before the '-') is the nested diagnostic context. Note
 * the nested diagnostic context may be empty as in the first two statements.
 * The text after the '-' is the message of the statement.
 * 
 * <p>
 * <b>WARNING</b> Do not use the same TTCCLayout instance from within different
 * appenders. The TTCCLayout is not thread safe when used in his way. However,
 * it is perfectly safe to use a TTCCLayout instance from just one appender.
 * 
 * <p>
 * {@link PatternLayout} offers a much more flexible alternative.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author <A HREF="mailto:heinz.richter@ecmwf.int">Heinz Richter</a>
 * 
 */
public class TTCCLayout extends DateLayout {

    // Internal representation of options
    private boolean threadPrinting = true;
    private boolean categoryPrefixing = true;
    private boolean contextPrinting = true;

    protected final StringBuffer buf = new StringBuffer(256);

    /**
     * Instantiate a TTCCLayout object with
     * {@link org.apache.log4j.helpers.RelativeTimeDateFormat} as the date formatter
     * in the local time zone.
     * 
     * @since 0.7.5
     */
    public TTCCLayout() {
	this.setDateFormat(RELATIVE_TIME_DATE_FORMAT, null);
    }

    /**
     * Instantiate a TTCCLayout object using the local time zone. The DateFormat
     * used will depend on the <code>dateFormatType</code>.
     * 
     * <p>
     * This constructor just calls the {@link DateLayout#setDateFormat} method.
     * 
     */
    public TTCCLayout(String dateFormatType) {
	this.setDateFormat(dateFormatType);
    }

    /**
     * The <b>ThreadPrinting</b> option specifies whether the name of the current
     * thread is part of log output or not. This is true by default.
     */
    public void setThreadPrinting(boolean threadPrinting) {
	this.threadPrinting = threadPrinting;
    }

    /**
     * Returns value of the <b>ThreadPrinting</b> option.
     */
    public boolean getThreadPrinting() {
	return threadPrinting;
    }

    /**
     * The <b>CategoryPrefixing</b> option specifies whether {@link Category} name
     * is part of log output or not. This is true by default.
     */
    public void setCategoryPrefixing(boolean categoryPrefixing) {
	this.categoryPrefixing = categoryPrefixing;
    }

    /**
     * Returns value of the <b>CategoryPrefixing</b> option.
     */
    public boolean getCategoryPrefixing() {
	return categoryPrefixing;
    }

    /**
     * The <b>ContextPrinting</b> option specifies log output will include the
     * nested context information belonging to the current thread. This is true by
     * default.
     */
    public void setContextPrinting(boolean contextPrinting) {
	this.contextPrinting = contextPrinting;
    }

    /**
     * Returns value of the <b>ContextPrinting</b> option.
     */
    public boolean getContextPrinting() {
	return contextPrinting;
    }

    /**
     * In addition to the level of the statement and message, the returned byte
     * array includes time, thread, category and {@link NDC} information.
     * 
     * <p>
     * Time, thread, category and diagnostic context are printed depending on
     * options.
     * 
     * @param event The event to format
     * 
     */
    public String format(LoggingEvent event) {

	// Reset buf
	buf.setLength(0);

	dateFormat(buf, event);

	if (this.threadPrinting) {
	    buf.append('[');
	    buf.append(event.getThreadName());
	    buf.append("] ");
	}
	buf.append(event.getLevel().toString());
	buf.append(' ');

	if (this.categoryPrefixing) {
	    buf.append(event.getLoggerName());
	    buf.append(' ');
	}

	if (this.contextPrinting) {
	    String ndc = event.getNDC();

	    if (ndc != null) {
		buf.append(ndc);
		buf.append(' ');
	    }
	}
	buf.append("- ");
	buf.append(event.getRenderedMessage());
	buf.append(LINE_SEP);
	return buf.toString();
    }

    /**
     * The TTCCLayout does not handle the throwable contained within
     * {@link LoggingEvent LoggingEvents}. Thus, it returns <code>true</code>.
     * 
     * @since version 0.8.4
     */
    public boolean ignoresThrowable() {
	return true;
    }
}
