/*
 * 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 java.io.IOException;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.DataOutputView;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.types.NormalizableKey;
import org.apache.flink.util.InstantiationUtil;

/**
 * TypeComparator for all types that extend Comparable.
 */
@Internal
public class GenericTypeComparator<T extends Comparable<T>> extends TypeComparator<T> {

	private static final long serialVersionUID = 1L;

	private final boolean ascending;

	private final Class<T> type;

	private TypeSerializer<T> serializer;

	private transient T reference;

	private transient T tmpReference;

	@SuppressWarnings("rawtypes")
	private final TypeComparator[] comparators = new TypeComparator[] {this};

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

	public GenericTypeComparator(boolean ascending, TypeSerializer<T> serializer, Class<T> type) {
		this.ascending = ascending;
		this.serializer = serializer;
		this.type = type;
	}

	private GenericTypeComparator(GenericTypeComparator<T> toClone) {
		this.ascending = toClone.ascending;
		this.serializer = toClone.serializer.duplicate();
		this.type = toClone.type;
	}

	@Override
	public int hash(T record) {
		return record.hashCode();
	}

	@Override
	public void setReference(T toCompare) {
		this.reference = this.serializer.copy(toCompare);
	}

	@Override
	public boolean equalToReference(T candidate) {
		return candidate.equals(this.reference);
	}

	@Override
	public int compareToReference(TypeComparator<T> referencedComparator) {
		T otherRef = ((GenericTypeComparator<T>) referencedComparator).reference;
		int cmp = otherRef.compareTo(this.reference);

		return this.ascending ? cmp : -cmp;
	}

	@Override
	public int compare(T first, T second) {
		int cmp = first.compareTo(second);
		return this.ascending ? cmp : -cmp;
	}

	@Override
	public int compareSerialized(final DataInputView firstSource, final DataInputView secondSource) throws IOException {

		if (this.reference == null) {
			this.reference = this.serializer.createInstance();
		}

		if (this.tmpReference == null) {
			this.tmpReference = this.serializer.createInstance();
		}

		this.reference = this.serializer.deserialize(this.reference, firstSource);
		this.tmpReference = this.serializer.deserialize(this.tmpReference, secondSource);

		int cmp = this.reference.compareTo(this.tmpReference);
		return this.ascending ? cmp : -cmp;
	}

	@Override
	public boolean supportsNormalizedKey() {
		return NormalizableKey.class.isAssignableFrom(this.type);
	}

	@Override
	public int getNormalizeKeyLen() {
		if (this.reference == null) {
			this.reference = InstantiationUtil.instantiate(this.type);
		}

		NormalizableKey<?> key = (NormalizableKey<?>) this.reference;
		return key.getMaxNormalizedKeyLen();
	}

	@Override
	public boolean isNormalizedKeyPrefixOnly(int keyBytes) {
		return keyBytes < getNormalizeKeyLen();
	}

	@Override
	public void putNormalizedKey(T record, MemorySegment target, int offset, int numBytes) {
		NormalizableKey<?> key = (NormalizableKey<?>) record;
		key.copyNormalizedKey(target, offset, numBytes);
	}

	@Override
	public boolean invertNormalizedKey() {
		return !ascending;
	}

	@Override
	public TypeComparator<T> duplicate() {
		return new GenericTypeComparator<T>(this);
	}

	@Override
	public int extractKeys(Object record, Object[] target, int index) {
		target[index] = record;
		return 1;
	}

	@SuppressWarnings("rawtypes")
	@Override
	public TypeComparator[] getFlatComparators() {
		return comparators;
	}

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

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

	@Override
	public void writeWithKeyNormalization(T record, DataOutputView target) throws IOException {
		throw new UnsupportedOperationException();
	}

	@Override
	public T readWithKeyDenormalization(T reuse, DataInputView source) throws IOException {
		throw new UnsupportedOperationException();
	}
}