/*
 * 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.CompatibilityUtil;
import org.apache.flink.api.common.typeutils.CompositeTypeSerializerConfigSnapshot;
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.api.common.typeutils.UnloadableDummyTypeSerializer;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.types.Row;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.Arrays;
import java.util.List;

import static org.apache.flink.api.java.typeutils.runtime.NullMaskUtils.readIntoAndCopyNullMask;
import static org.apache.flink.api.java.typeutils.runtime.NullMaskUtils.readIntoNullMask;
import static org.apache.flink.api.java.typeutils.runtime.NullMaskUtils.writeNullMask;
import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * Serializer for {@link Row}.
 */
@Internal
public final class RowSerializer extends TypeSerializer<Row> {

	private static final long serialVersionUID = 1L;

	private final TypeSerializer<Object>[] fieldSerializers;

	private final int arity;

	private transient boolean[] nullMask;

	@SuppressWarnings("unchecked")
	public RowSerializer(TypeSerializer<?>[] fieldSerializers) {
		this.fieldSerializers = (TypeSerializer<Object>[]) checkNotNull(fieldSerializers);
		this.arity = fieldSerializers.length;
		this.nullMask = new boolean[fieldSerializers.length];
	}

	/**
	 * Returns the serializers for the fields in the row.
	 *
	 * @return The serializers for the fields in the row.
	 */
	public TypeSerializer<?>[] getFieldSerializers() {
		return fieldSerializers;
	}

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

	@Override
	public TypeSerializer<Row> duplicate() {
		TypeSerializer<?>[] duplicateFieldSerializers = new TypeSerializer[fieldSerializers.length];
		for (int i = 0; i < fieldSerializers.length; i++) {
			duplicateFieldSerializers[i] = fieldSerializers[i].duplicate();
		}
		return new RowSerializer(duplicateFieldSerializers);
	}

	@Override
	public Row createInstance() {
		return new Row(fieldSerializers.length);
	}

	@Override
	public Row copy(Row from) {
		int len = fieldSerializers.length;

		if (from.getArity() != len) {
			throw new RuntimeException("Row arity of from does not match serializers.");
		}

		Row result = new Row(len);
		for (int i = 0; i < len; i++) {
			Object fromField = from.getField(i);
			if (fromField != null) {
				Object copy = fieldSerializers[i].copy(fromField);
				result.setField(i, copy);
			} else {
				result.setField(i, null);
			}
		}
		return result;
	}

	@Override
	public Row copy(Row from, Row reuse) {
		int len = fieldSerializers.length;

		// cannot reuse, do a non-reuse copy
		if (reuse == null) {
			return copy(from);
		}

		if (from.getArity() != len || reuse.getArity() != len) {
			throw new RuntimeException(
				"Row arity of reuse or from is incompatible with this RowSerializer.");
		}

		for (int i = 0; i < len; i++) {
			Object fromField = from.getField(i);
			if (fromField != null) {
				Object reuseField = reuse.getField(i);
				if (reuseField != null) {
					Object copy = fieldSerializers[i].copy(fromField, reuseField);
					reuse.setField(i, copy);
				} else {
					Object copy = fieldSerializers[i].copy(fromField);
					reuse.setField(i, copy);
				}
			} else {
				reuse.setField(i, null);
			}
		}
		return reuse;
	}

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

	public int getArity() {
		return arity;
	}

	@Override
	public void serialize(Row record, DataOutputView target) throws IOException {
		int len = fieldSerializers.length;

		if (record.getArity() != len) {
			throw new RuntimeException("Row arity of from does not match serializers.");
		}

		// write a null mask
		writeNullMask(len, record, target);

		// serialize non-null fields
		for (int i = 0; i < len; i++) {
			Object o = record.getField(i);
			if (o != null) {
				fieldSerializers[i].serialize(o, target);
			}
		}
	}


	@Override
	public Row deserialize(DataInputView source) throws IOException {
		int len = fieldSerializers.length;

		Row result = new Row(len);

		// read null mask
		readIntoNullMask(len, source, nullMask);

		for (int i = 0; i < len; i++) {
			if (nullMask[i]) {
				result.setField(i, null);
			} else {
				result.setField(i, fieldSerializers[i].deserialize(source));
			}
		}

		return result;
	}

	@Override
	public Row deserialize(Row reuse, DataInputView source) throws IOException {
		int len = fieldSerializers.length;

		if (reuse.getArity() != len) {
			throw new RuntimeException("Row arity of from does not match serializers.");
		}

		// read null mask
		readIntoNullMask(len, source, nullMask);

		for (int i = 0; i < len; i++) {
			if (nullMask[i]) {
				reuse.setField(i, null);
			} else {
				Object reuseField = reuse.getField(i);
				if (reuseField != null) {
					reuse.setField(i, fieldSerializers[i].deserialize(reuseField, source));
				} else {
					reuse.setField(i, fieldSerializers[i].deserialize(source));
				}
			}
		}

		return reuse;
	}

	@Override
	public void copy(DataInputView source, DataOutputView target) throws IOException {
		int len = fieldSerializers.length;

		// copy null mask
		readIntoAndCopyNullMask(len, source, target, nullMask);

		for (int i = 0; i < len; i++) {
			if (!nullMask[i]) {
				fieldSerializers[i].copy(source, target);
			}
		}
	}

	@Override
	public boolean equals(Object obj) {
		if (canEqual(obj)) {
			RowSerializer other = (RowSerializer) obj;
			if (this.fieldSerializers.length == other.fieldSerializers.length) {
				for (int i = 0; i < this.fieldSerializers.length; i++) {
					if (!this.fieldSerializers[i].equals(other.fieldSerializers[i])) {
						return false;
					}
				}
				return true;
			}
		}

		return false;
	}

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

	@Override
	public int hashCode() {
		return Arrays.hashCode(fieldSerializers);
	}

	// --------------------------------------------------------------------------------------------

	private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
		in.defaultReadObject();
		this.nullMask = new boolean[fieldSerializers.length];
	}

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

	@Override
	public RowSerializerConfigSnapshot snapshotConfiguration() {
		return new RowSerializerConfigSnapshot(fieldSerializers);
	}

	@Override
	public CompatibilityResult<Row> ensureCompatibility(TypeSerializerConfigSnapshot configSnapshot) {
		if (configSnapshot instanceof RowSerializerConfigSnapshot) {
			List<Tuple2<TypeSerializer<?>, TypeSerializerConfigSnapshot>> previousFieldSerializersAndConfigs =
				((RowSerializerConfigSnapshot) configSnapshot).getNestedSerializersAndConfigs();

			if (previousFieldSerializersAndConfigs.size() == fieldSerializers.length) {
				boolean requireMigration = false;
				TypeSerializer<?>[] convertDeserializers = new TypeSerializer<?>[fieldSerializers.length];

				CompatibilityResult<?> compatResult;
				int i = 0;
				for (Tuple2<TypeSerializer<?>, TypeSerializerConfigSnapshot> f : previousFieldSerializersAndConfigs) {
					compatResult = CompatibilityUtil.resolveCompatibilityResult(
							f.f0,
							UnloadableDummyTypeSerializer.class,
							f.f1,
							fieldSerializers[i]);

					if (compatResult.isRequiresMigration()) {
						requireMigration = true;

						if (compatResult.getConvertDeserializer() == null) {
							// one of the field serializers cannot provide a fallback deserializer
							return CompatibilityResult.requiresMigration();
						} else {
							convertDeserializers[i] =
								new TypeDeserializerAdapter<>(compatResult.getConvertDeserializer());
						}
					}

					i++;
				}

				if (requireMigration) {
					return CompatibilityResult.requiresMigration(new RowSerializer(convertDeserializers));
				} else {
					return CompatibilityResult.compatible();
				}
			}
		}

		return CompatibilityResult.requiresMigration();
	}

	public static final class RowSerializerConfigSnapshot extends CompositeTypeSerializerConfigSnapshot {

		private static final int VERSION = 1;

		/** This empty nullary constructor is required for deserializing the configuration. */
		public RowSerializerConfigSnapshot() {}

		public RowSerializerConfigSnapshot(TypeSerializer[] fieldSerializers) {
			super(fieldSerializers);
		}

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