/**
 * 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.storm.serialization;

import java.util.Map;
import java.util.zip.GZIPInputStream;

/**
 * Always writes gzip out, but tests incoming to see if it's gzipped. If it is, deserializes with gzip. If not, uses {@link
 * org.apache.storm.serialization.ThriftSerializationDelegate} to deserialize. Any logic needing to be enabled via {@link
 * #prepare(java.util.Map)} is passed through to both delegates.
 */
public class GzipBridgeThriftSerializationDelegate implements SerializationDelegate {

    // Split up GZIP_MAGIC into readable bytes
    private static final byte GZIP_MAGIC_FIRST_BYTE = (byte) GZIPInputStream.GZIP_MAGIC;
    private static final byte GZIP_MAGIC_SECOND_BYTE = (byte) (GZIPInputStream.GZIP_MAGIC >> 8);
    private ThriftSerializationDelegate defaultDelegate = new ThriftSerializationDelegate();
    private GzipThriftSerializationDelegate gzipDelegate = new GzipThriftSerializationDelegate();

    @Override
    public void prepare(Map<String, Object> topoConf) {
        defaultDelegate.prepare(topoConf);
        gzipDelegate.prepare(topoConf);
    }

    @Override
    public byte[] serialize(Object object) {
        return gzipDelegate.serialize(object);
    }

    @Override
    public <T> T deserialize(byte[] bytes, Class<T> clazz) {
        if (isGzipped(bytes)) {
            return gzipDelegate.deserialize(bytes, clazz);
        } else {
            return defaultDelegate.deserialize(bytes, clazz);
        }
    }

    /**
     * Looks ahead to see if the GZIP magic constant is heading {@code bytes}.
     */
    private boolean isGzipped(byte[] bytes) {
        return (bytes.length > 1) && (bytes[0] == GZIP_MAGIC_FIRST_BYTE)
               && (bytes[1] == GZIP_MAGIC_SECOND_BYTE);
    }
}