/*
 * 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.java.typeutils.runtime;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.typeutils.CompatibilityResult;
import org.apache.flink.api.common.typeutils.TypeDeserializerAdapter;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.TypeSerializerConfigSnapshot;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.types.Either;

import java.io.IOException;

import static org.apache.flink.types.Either.Left;
import static org.apache.flink.types.Either.Right;

/**
 * A {@link TypeSerializer} for the {@link Either} type of the Java class.
 *
 * @param <L> the Left value type
 * @param <R> the Right value type
 */
@Internal
public class EitherSerializer<L, R> extends TypeSerializer<Either<L, R>> {

	private static final long serialVersionUID = 1L;

	private final TypeSerializer<L> leftSerializer;

	private final TypeSerializer<R> rightSerializer;

	public EitherSerializer(TypeSerializer<L> leftSerializer, TypeSerializer<R> rightSerializer) {
		this.leftSerializer = leftSerializer;
		this.rightSerializer = rightSerializer;
	}

	@Override
	public boolean isImmutableType() {
		return false;
	}

	@Override
	public TypeSerializer<Either<L, R>> duplicate() {
		TypeSerializer<L> duplicateLeft = leftSerializer.duplicate();
		TypeSerializer<R> duplicateRight = rightSerializer.duplicate();

		if ((leftSerializer != duplicateLeft) || (rightSerializer != duplicateRight)) {
			// stateful
			return new EitherSerializer<L, R>(duplicateLeft, duplicateRight);
		}
		else {
			return this;
		}
	}


	@Override
	public Either<L, R> createInstance() {
		// We arbitrarily always create a Right value instance.
		return Right(rightSerializer.createInstance());
	}

	@Override
	public Either<L, R> copy(Either<L, R> from) {
		if (from.isLeft()) {
			L left = from.left();
			L copyLeft = leftSerializer.copy(left);
			return Left(copyLeft);
		}
		else {
			R right = from.right();
			R copyRight = rightSerializer.copy(right);
			return Right(copyRight);
		}
	}

	@Override
	public Either<L, R> copy(Either<L, R> from, Either<L, R> reuse) {
		if (from.isLeft()) {
			Left<L, R> to = Either.obtainLeft(reuse, leftSerializer);
			L left = leftSerializer.copy(from.left(), to.left());
			to.setValue(left);
			return to;
		} else {
			Right<L, R> to = Either.obtainRight(reuse, rightSerializer);
			R right = rightSerializer.copy(from.right(), to.right());
			to.setValue(right);
			return to;
		}
	}

	@Override
	public int getLength() {
		return -1;
	}

	@Override
	public void serialize(Either<L, R> record, DataOutputView target) throws IOException {
		if (record.isLeft()) {
			target.writeBoolean(true);
			leftSerializer.serialize(record.left(), target);
		}
		else {
			target.writeBoolean(false);
			rightSerializer.serialize(record.right(), target);
		}
	}

	@Override
	public Either<L, R> deserialize(DataInputView source) throws IOException {
		boolean isLeft = source.readBoolean();
		if (isLeft) {
			return Left(leftSerializer.deserialize(source));
		}
		else {
			return Right(rightSerializer.deserialize(source));
		}
	}

	@Override
	public Either<L, R> deserialize(Either<L, R> reuse, DataInputView source) throws IOException {
		boolean isLeft = source.readBoolean();
		if (isLeft) {
			Left<L, R> to = Either.obtainLeft(reuse, leftSerializer);
			L left = leftSerializer.deserialize(to.left(), source);
			to.setValue(left);
			return to;
		} else {
			Right<L, R> to = Either.obtainRight(reuse, rightSerializer);
			R right = rightSerializer.deserialize(to.right(), source);
			to.setValue(right);
			return to;
		}
	}

	@Override
	public void copy(DataInputView source, DataOutputView target) throws IOException {
		boolean isLeft = source.readBoolean();
		target.writeBoolean(isLeft);
		if (isLeft) {
			leftSerializer.copy(source, target);
		}
		else {
			rightSerializer.copy(source, target);
		}
	}

	@SuppressWarnings("unchecked")
	@Override
	public boolean equals(Object obj) {
		if (obj instanceof EitherSerializer) {
			EitherSerializer<L, R> other = (EitherSerializer<L, R>) obj;

			return other.canEqual(this) &&
				leftSerializer.equals(other.leftSerializer) &&
				rightSerializer.equals(other.rightSerializer);
		} else {
			return false;
		}
	}

	@Override
	public boolean canEqual(Object obj) {
		return obj instanceof EitherSerializer;
	}

	@Override
	public int hashCode() {
		return 17 * leftSerializer.hashCode() + rightSerializer.hashCode();
	}

	// --------------------------------------------------------------------------------------------
	// Serializer configuration snapshotting & compatibility
	// --------------------------------------------------------------------------------------------

	@Override
	public EitherSerializerConfigSnapshot snapshotConfiguration() {
		return new EitherSerializerConfigSnapshot(
				leftSerializer.snapshotConfiguration(),
				rightSerializer.snapshotConfiguration());
	}

	@Override
	public CompatibilityResult<Either<L, R>> ensureCompatibility(TypeSerializerConfigSnapshot configSnapshot) {
		if (configSnapshot instanceof EitherSerializerConfigSnapshot) {
			TypeSerializerConfigSnapshot[] leftRightSerializerConfigSnapshots =
				((EitherSerializerConfigSnapshot) configSnapshot).getNestedSerializerConfigSnapshots();

			CompatibilityResult<L> leftCompatResult = leftSerializer.ensureCompatibility(leftRightSerializerConfigSnapshots[0]);
			CompatibilityResult<R> rightCompatResult = rightSerializer.ensureCompatibility(leftRightSerializerConfigSnapshots[1]);

			if (!leftCompatResult.isRequiresMigration() && !rightCompatResult.isRequiresMigration()) {
				return CompatibilityResult.compatible();
			} else {
				if (leftCompatResult.getConvertDeserializer() != null && rightCompatResult.getConvertDeserializer() != null) {
					return CompatibilityResult.requiresMigration(
						new EitherSerializer<>(
							new TypeDeserializerAdapter<>(leftCompatResult.getConvertDeserializer()),
							new TypeDeserializerAdapter<>(rightCompatResult.getConvertDeserializer())));
				}
			}
		}

		return CompatibilityResult.requiresMigration();
	}
}