/*
 * 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.helpers;

import org.apache.log4j.spi.LoggingEvent;

/**
 * 
 * <p>
 * PatternConverter is an abtract class that provides the formatting
 * functionality that derived classes need.
 * 
 * <p>
 * Conversion specifiers in a conversion patterns are parsed to individual
 * PatternConverters. Each of which is responsible for converting a logging
 * event in a converter specific manner.
 * 
 * @author <a href="mailto:cakalijp@Maritz.com">James P. Cakalic</a>
 * @author Ceki G&uuml;lc&uuml;
 * 
 * @since 0.8.2
 */
public abstract class PatternConverter {
    public PatternConverter next;
    int min = -1;
    int max = 0x7FFFFFFF;
    boolean leftAlign = false;

    protected PatternConverter() {
    }

    protected PatternConverter(FormattingInfo fi) {
	min = fi.min;
	max = fi.max;
	leftAlign = fi.leftAlign;
    }

    /**
     * Derived pattern converters must override this method in order to convert
     * conversion specifiers in the correct way.
     */
    abstract protected String convert(LoggingEvent event);

    /**
     * A template method for formatting in a converter specific way.
     */
    public void format(StringBuffer sbuf, LoggingEvent e) {
	String s = convert(e);

	if (s == null) {
	    if (0 < min)
		spacePad(sbuf, min);
	    return;
	}

	int len = s.length();

	if (len > max)
	    sbuf.append(s.substring(len - max));
	else if (len < min) {
	    if (leftAlign) {
		sbuf.append(s);
		spacePad(sbuf, min - len);
	    } else {
		spacePad(sbuf, min - len);
		sbuf.append(s);
	    }
	} else
	    sbuf.append(s);
    }

    static String[] SPACES = { " ", "  ", "    ", "        ", // 1,2,4,8 spaces
	    "                ", // 16 spaces
	    "                                " }; // 32 spaces

    /**
     * Fast space padding method.
     */
    public void spacePad(StringBuffer sbuf, int length) {
	while (length >= 32) {
	    sbuf.append(SPACES[5]);
	    length -= 32;
	}

	for (int i = 4; i >= 0; i--) {
	    if ((length & (1 << i)) != 0) {
		sbuf.append(SPACES[i]);
	    }
	}
    }
}
