/*
 * 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.logging.log4j.core.pattern;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.message.Message;
import org.apache.logging.log4j.message.MultiformatMessage;
import org.apache.logging.log4j.util.StringBuilderFormattable;

/**
 * Returns the event's rendered message in a StringBuilder.
 */
@Plugin(name = "MessagePatternConverter", category = PatternConverter.CATEGORY)
@ConverterKeys({ "m", "msg", "message" })
public final class MessagePatternConverter extends LogEventPatternConverter {

    private final String[] formats;
    private final Configuration config;

    /**
     * Private constructor.
     * @param options options, may be null.
     */
    private MessagePatternConverter(final Configuration config, final String[] options) {
        super("Message", "message");
        formats = options;
        this.config = config;
    }

    /**
     * Obtains an instance of pattern converter.
     *
     * @param config The Configuration.
     * @param options options, may be null.
     * @return instance of pattern converter.
     */
    public static MessagePatternConverter newInstance(final Configuration config, final String[] options) {
        return new MessagePatternConverter(config, options);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void format(final LogEvent event, final StringBuilder toAppendTo) {
        final Message msg = event.getMessage();
        if (msg instanceof StringBuilderFormattable) {
            ((StringBuilderFormattable) msg).formatTo(toAppendTo);

            // TODO can we optimize this?
            if (config != null) {
                final int offset = toAppendTo.length();
                for (int i = offset; i < toAppendTo.length() - 1; i++) {
                    if (toAppendTo.charAt(i) == '$' && toAppendTo.charAt(i + 1) == '{') {
                        final String value = toAppendTo.substring(offset, toAppendTo.length());
                        toAppendTo.setLength(offset);
                        toAppendTo.append(config.getStrSubstitutor().replace(event, value));
                    }
                }
            }
            return;
        }
        if (msg != null) {
            String result;
            if (msg instanceof MultiformatMessage) {
                result = ((MultiformatMessage) msg).getFormattedMessage(formats);
            } else {
                result = msg.getFormattedMessage();
            }
            if (result != null) {
                toAppendTo.append(config != null && result.contains("${") ?
                        config.getStrSubstitutor().replace(event, result) : result);
            } else {
                toAppendTo.append("null");
            }
        }
    }
}

@@ -2413,24 +2413,76 @@
 mattable) %7B%0A
+            final int offset = toAppendTo.length();%0A
             
@@ -2617,64 +2617,8 @@
 ) %7B%0A
-                final int offset = toAppendTo.length();%0A
     

Revert "Move the offset closer to its use sites (inside the if block)."