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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.core.fs.FSDataInputStream;
import org.apache.flink.runtime.state.filesystem.FileSegmentStateHandle;
import org.apache.flink.util.Preconditions;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.Map;

/**
 * State handle for partitionable operator state. Besides being a {@link StreamStateHandle}, this also provides a
 * map that contains the offsets to the partitions of named states in the stream.
 */
public class OperatorStreamStateHandle implements OperatorStateHandle {

	private static final Logger LOG = LoggerFactory.getLogger(OperatorStateHandle.class);

	private static final long serialVersionUID = 35876522969227335L;

	/**
	 * unique state name -> offsets for available partitions in the handle stream
	 */
	private final Map stateNameToPartitionOffsets;
	private final StreamStateHandle delegateStateHandle;
	private transient SharedStateRegistry operatorStateRegistry;

	public OperatorStreamStateHandle(
			Map stateNameToPartitionOffsets,
			StreamStateHandle delegateStateHandle) {

		this.delegateStateHandle = Preconditions.checkNotNull(delegateStateHandle);
		this.stateNameToPartitionOffsets = Preconditions.checkNotNull(stateNameToPartitionOffsets);
		operatorStateRegistry = null;
	}

	@Override
	public Map getStateNameToPartitionOffsets() {
		return stateNameToPartitionOffsets;
	}

	@Override
	public void discardState() throws Exception {
		SharedStateRegistry registry = this.operatorStateRegistry;
		final boolean isRegistered = (registry != null);

		if (delegateStateHandle instanceof FileSegmentStateHandle && isRegistered) {
			SharedStateRegistryKey registryKey = ((FileSegmentStateHandle) delegateStateHandle).getRegistryKey();
			registry.unregisterReference(registryKey);
			LOG.debug("UnregisterReference for operator segment state handle key {}, handle {}.", registryKey, delegateStateHandle);
		} else {
			delegateStateHandle.discardState();
			LOG.debug("Discard operator state directly, handle {}.", delegateStateHandle);
		}
	}

	@Override
	public void registerOperatorStatesIfNeeded(SharedStateRegistry stateRegistry) {
		// This is a quick check to avoid that we register twice with the same registry. However, the code allows to
		// register again with a different registry. The implication is that ownership is transferred to this new
		// registry. This should only happen in case of a restart, when the CheckpointCoordinator creates a new
		// SharedStateRegistry for the current attempt and the old registry becomes meaningless. We also assume that
		// an old registry object from a previous run is due to be GCed and will never be used for registration again.
		if (delegateStateHandle instanceof FileSegmentStateHandle) {
			Preconditions.checkState(operatorStateRegistry != stateRegistry,
				"The state handle has already registered its shared states to the given registry.");

			operatorStateRegistry = Preconditions.checkNotNull(stateRegistry);
			SharedStateRegistryKey registryKey = ((FileSegmentStateHandle) delegateStateHandle).getRegistryKey();
			stateRegistry.registerReference(registryKey, delegateStateHandle);
			LOG.debug("Register segment state handle for operator state key {}, state {}.", registryKey, delegateStateHandle);
		}
	}

	@Override
	public long getStateSize() {
		return delegateStateHandle.getStateSize();
	}

	@Override
	public FSDataInputStream openInputStream() throws IOException {
		return delegateStateHandle.openInputStream();
	}

	@Override
	public StreamStateHandle getDelegateStateHandle() {
		return delegateStateHandle;
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) {
			return true;
		}

		if (!(o instanceof OperatorStreamStateHandle)) {
			return false;
		}

		OperatorStreamStateHandle that = (OperatorStreamStateHandle) o;

		if (stateNameToPartitionOffsets.size() != that.stateNameToPartitionOffsets.size()) {
			return false;
		}

		for (Map.Entry entry : stateNameToPartitionOffsets.entrySet()) {
			if (!entry.getValue().equals(that.stateNameToPartitionOffsets.get(entry.getKey()))) {
				return false;
			}
		}

		return delegateStateHandle.equals(that.delegateStateHandle);
	}

	@Override
	public int hashCode() {
		int result = delegateStateHandle.hashCode();
		for (Map.Entry entry : stateNameToPartitionOffsets.entrySet()) {

			int entryHash = entry.getKey().hashCode();
			if (entry.getValue() != null) {
				entryHash += entry.getValue().hashCode();
			}
			result = 31 * result + entryHash;
		}
		return result;
	}

	@Override
	public String toString() {
		return "OperatorStateHandle{" +
				"stateNameToPartitionOffsets=" + stateNameToPartitionOffsets +
				", delegateStateHandle=" + delegateStateHandle +
				'}';
	}
}