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/*
 * 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.runtime.state;

import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerConfigSnapshot;
import org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.core.io.VersionedIOReadableWritable;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.util.Preconditions;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Serialization proxy for all meta data in keyed state backends. In the future we might also requiresMigration the actual state
 * serialization logic here.
 */
public class KeyedBackendSerializationProxy extends VersionedIOReadableWritable {

	public static final int VERSION = 4;

	//TODO allow for more (user defined) compression formats + backwards compatibility story.
	/** This specifies if we use a compressed format write the key-groups */
	private boolean usingKeyGroupCompression;

	private TypeSerializer keySerializer;
	private TypeSerializerConfigSnapshot keySerializerConfigSnapshot;

	private List> stateMetaInfoSnapshots;

	private ClassLoader userCodeClassLoader;

	public KeyedBackendSerializationProxy(ClassLoader userCodeClassLoader) {
		this.userCodeClassLoader = Preconditions.checkNotNull(userCodeClassLoader);
	}

	public KeyedBackendSerializationProxy(
			TypeSerializer keySerializer,
			List> stateMetaInfoSnapshots,
			boolean compression) {

		this.usingKeyGroupCompression = compression;

		this.keySerializer = Preconditions.checkNotNull(keySerializer);
		this.keySerializerConfigSnapshot = Preconditions.checkNotNull(keySerializer.snapshotConfiguration());

		Preconditions.checkNotNull(stateMetaInfoSnapshots);
		Preconditions.checkArgument(stateMetaInfoSnapshots.size() <= Short.MAX_VALUE);
		this.stateMetaInfoSnapshots = stateMetaInfoSnapshots;
	}

	public List> getStateMetaInfoSnapshots() {
		return stateMetaInfoSnapshots;
	}

	public TypeSerializer getKeySerializer() {
		return keySerializer;
	}

	public TypeSerializerConfigSnapshot getKeySerializerConfigSnapshot() {
		return keySerializerConfigSnapshot;
	}

	public boolean isUsingKeyGroupCompression() {
		return usingKeyGroupCompression;
	}

	@Override
	public int getVersion() {
		return VERSION;
	}

	@Override
	public int[] getCompatibleVersions() {
		// we are compatible with version 3 (Flink 1.3.x) and version 1 & 2 (Flink 1.2.x)
		return new int[] {VERSION, 3, 2, 1};
	}

	@Override
	public void write(DataOutputView out) throws IOException {
		super.write(out);

		// write the compression format used to write each key-group
		out.writeBoolean(usingKeyGroupCompression);

		// write in a way to be fault tolerant of read failures when deserializing the key serializer
		TypeSerializerSerializationUtil.writeSerializersAndConfigsWithResilience(
				out,
				Collections.singletonList(
					new Tuple2, TypeSerializerConfigSnapshot>(keySerializer, keySerializerConfigSnapshot)));

		// write individual registered keyed state metainfos
		out.writeShort(stateMetaInfoSnapshots.size());
		for (RegisteredKeyedBackendStateMetaInfo.Snapshot metaInfo : stateMetaInfoSnapshots) {
			KeyedBackendStateMetaInfoSnapshotReaderWriters
				.getWriterForVersion(VERSION, metaInfo)
				.writeStateMetaInfo(out);
		}
	}

	@SuppressWarnings("unchecked")
	@Override
	public void read(DataInputView in) throws IOException {
		super.read(in);

		final int readVersion = getReadVersion();

		if (readVersion >= 4) {
			usingKeyGroupCompression = in.readBoolean();
		} else {
			usingKeyGroupCompression = false;
		}

		// only starting from version 3, we have the key serializer and its config snapshot written
		if (readVersion >= 3) {
			Tuple2, TypeSerializerConfigSnapshot> keySerializerAndConfig =
					TypeSerializerSerializationUtil.readSerializersAndConfigsWithResilience(in, userCodeClassLoader).get(0);
			this.keySerializer = (TypeSerializer) keySerializerAndConfig.f0;
			this.keySerializerConfigSnapshot = keySerializerAndConfig.f1;
		} else {
			this.keySerializer = TypeSerializerSerializationUtil.tryReadSerializer(in, userCodeClassLoader);
			this.keySerializerConfigSnapshot = null;
		}

		int numKvStates = in.readShort();
		stateMetaInfoSnapshots = new ArrayList<>(numKvStates);
		for (int i = 0; i < numKvStates; i++) {
			stateMetaInfoSnapshots.add(
				KeyedBackendStateMetaInfoSnapshotReaderWriters
					.getReaderForVersion(getReadVersion(), userCodeClassLoader)
					.readStateMetaInfo(in));
		}
	}
}