/*
 * 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;

import org.apache.log4j.util.Filter;

/**
 * This class switches MDC values into the order (unreasonably) expected by the
 * witness files.
 */
public class MDCOrderFilter implements Filter {

    /**
     * Unexpected orders of keys. Note expected values are "va-one-one" and
     * "va-one-two".
     */
    private static final String[] patterns = new String[] { "{key2,va12}{key1,va11}", "{key2,value2}{key1,value1}" };

    /**
     * Replacement values.
     */
    private static final String[] replacements = new String[] { "{key1,va11}{key2,va12}",
	    "{key1,value1}{key2,value2}" };

    /**
     * Switch order of MDC keys when not in expected order.
     */
    public String filter(final String in) {
	if (in == null) {
	    return null;
	}

	for (int i = 0; i < patterns.length; i++) {
	    int ipos = in.indexOf(patterns[i]);
	    if (ipos >= 1) {
		return in.substring(0, ipos) + replacements[i] + in.substring(ipos + patterns[i].length());
	    }
	}
	return in;
    }
}
