/*
 * 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.streaming.connectors.kafka.internals;

/**
 * The state that the Flink Kafka Consumer holds for each Kafka partition.
 * Includes the Kafka descriptor for partitions.
 * 
 * <p>This class describes the most basic state (only the offset), subclasses
 * define more elaborate state, containing current watermarks and timestamp
 * extractors.
 * 
 * @param <KPH> The type of the Kafka partition descriptor, which varies across Kafka versions.
 */
public class KafkaTopicPartitionState<KPH> {
	
	// ------------------------------------------------------------------------

	/** The Flink description of a Kafka partition */
	private final KafkaTopicPartition partition;

	/** The Kafka description of a Kafka partition (varies across different Kafka versions) */
	private final KPH kafkaPartitionHandle;
	
	/** The offset within the Kafka partition that we already processed */
	private volatile long offset;

	/** The offset of the Kafka partition that has been committed */
	private volatile long committedOffset;

	// ------------------------------------------------------------------------
	
	public KafkaTopicPartitionState(KafkaTopicPartition partition, KPH kafkaPartitionHandle) {
		this.partition = partition;
		this.kafkaPartitionHandle = kafkaPartitionHandle;
		this.offset = KafkaTopicPartitionStateSentinel.OFFSET_NOT_SET;
		this.committedOffset = KafkaTopicPartitionStateSentinel.OFFSET_NOT_SET;
	}

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

	/**
	 * Gets Flink's descriptor for the Kafka Partition.
	 * @return The Flink partition descriptor.
	 */
	public final KafkaTopicPartition getKafkaTopicPartition() {
		return partition;
	}

	/**
	 * Gets Kafka's descriptor for the Kafka Partition.
	 * @return The Kafka partition descriptor.
	 */
	public final KPH getKafkaPartitionHandle() {
		return kafkaPartitionHandle;
	}

	public final String getTopic() {
		return partition.getTopic();
	}

	public final int getPartition() {
		return partition.getPartition();
	}

	/**
	 * The current offset in the partition. This refers to the offset last element that
	 * we retrieved and emitted successfully. It is the offset that should be stored in
	 * a checkpoint.
	 */
	public final long getOffset() {
		return offset;
	}

	public final void setOffset(long offset) {
		this.offset = offset;
	}

	public final boolean isOffsetDefined() {
		return offset != KafkaTopicPartitionStateSentinel.OFFSET_NOT_SET;
	}

	public final void setCommittedOffset(long offset) {
		this.committedOffset = offset;
	}

	public final long getCommittedOffset() {
		return committedOffset;
	}

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

	@Override
	public String toString() {
		return "Partition: " + partition + ", KafkaPartitionHandle=" + kafkaPartitionHandle
				+ ", offset=" + (isOffsetDefined() ? String.valueOf(offset) : "(not set)");
	}
}