/*
 * 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(final 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.
     */
    protected abstract String convert(LoggingEvent event);

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

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

        final 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(final StringBuffer sbuf, final int length) {
        int l = length;
        while (l >= 32) {
            sbuf.append(SPACES[5]);
            l -= 32;
        }

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