/*
 * 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.flink.api.common.typeutils;

import org.apache.flink.annotation.Internal;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.core.io.VersionedIOReadableWritable;
import org.apache.flink.util.Preconditions;

/**
 * A {@code TypeSerializerConfigSnapshot} is a point-in-time view of a {@link TypeSerializer's} configuration.
 * The configuration snapshot of a serializer is persisted along with checkpoints of the managed state that the
 * serializer is registered to.
 *
 * <p>The persisted configuration may later on be used by new serializers to ensure serialization compatibility
 * for the same managed state. In order for new serializers to be able to ensure this, the configuration snapshot
 * should encode sufficient information about:
 *
 * <ul>
 *   <li><strong>Parameter settings of the serializer:</strong> parameters of the serializer include settings
 *   required to setup the serializer, or the state of the serializer if it is stateful. If the serializer
 *   has nested serializers, then the configuration snapshot should also contain the parameters of the nested
 *   serializers.</li>
 *
 *   <li><strong>Serialization schema of the serializer:</strong> the data format used by the serializer.</li>
 * </ul>
 *
 * <p>NOTE: Implementations must contain the default empty nullary constructor. This is required to be able to
 * deserialize the configuration snapshot from its binary form.
 */
@PublicEvolving
public abstract class TypeSerializerConfigSnapshot extends VersionedIOReadableWritable {

	/** The user code class loader; only relevant if this configuration instance was deserialized from binary form. */
	private ClassLoader userCodeClassLoader;

	/**
	 * Set the user code class loader.
	 * Only relevant if this configuration instance was deserialized from binary form.
	 *
	 * <p>This method is not part of the public user-facing API, and cannot be overriden.
	 *
	 * @param userCodeClassLoader user code class loader.
	 */
	@Internal
	public final void setUserCodeClassLoader(ClassLoader userCodeClassLoader) {
		this.userCodeClassLoader = Preconditions.checkNotNull(userCodeClassLoader);
	}

	/**
	 * Returns the user code class loader.
	 * Only relevant if this configuration instance was deserialized from binary form.
	 *
	 * @return the user code class loader
	 */
	@Internal
	public final ClassLoader getUserCodeClassLoader() {
		return userCodeClassLoader;
	}

	public abstract boolean equals(Object obj);

	public abstract int hashCode();
}