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Spring Kafka Support
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/*
 * Copyright 2016-2017 the original author or authors.
 *
 * Licensed 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.springframework.kafka.support;

import java.util.Objects;

import org.apache.kafka.common.TopicPartition;

/**
 * A configuration container to represent a topic name, partition number and, optionally,
 * an initial offset for it. The initial offset can be:
 * 
 * {@code null} - do nothing;
 * positive (including {@code 0}) - seek to EITHER the absolute offset within the
 * partition or an offset relative to the current position for this consumer, depending
 * on {@link #isRelativeToCurrent()}.
 * 
 * negative - seek to EITHER the offset relative to the current last offset within
 * the partition: {@code consumer.seekToEnd() + initialOffset} OR the relative to the
 * current offset for this consumer (if any), depending on
 * {@link #isRelativeToCurrent()}.
 * 
 * Offsets are applied when the container is {@code start()}ed.
 *
 * @author Artem Bilan
 * @author Gary Russell
 */
public class TopicPartitionInitialOffset {

	/**
	 * Enumeration for "special" seeks.
	 */
	public enum SeekPosition {

		/**
		 * Seek to the beginning.
		 */
		BEGINNING,

		/**
		 * Seek to the end.
		 */
		END
	}

	private final TopicPartition topicPartition;

	private final Long initialOffset;

	private final boolean relativeToCurrent;

	private final SeekPosition position;

	/**
	 * Construct an instance with no initial offset management.
	 * @param topic the topic.
	 * @param partition the partition.
	 */
	public TopicPartitionInitialOffset(String topic, int partition) {
		this(topic, partition, null, false);
	}

	/**
	 * Construct an instance with the provided initial offset with
	 * {@link #isRelativeToCurrent()} false.
	 * @param topic the topic.
	 * @param partition the partition.
	 * @param initialOffset the initial offset.
	 * @see #TopicPartitionInitialOffset(String, int, Long, boolean)
	 */
	public TopicPartitionInitialOffset(String topic, int partition, Long initialOffset) {
		this(topic, partition, initialOffset, false);
	}

	/**
	 * Construct an instance with the provided initial offset.
	 * @param topic the topic.
	 * @param partition the partition.
	 * @param initialOffset the initial offset.
	 * @param relativeToCurrent true for the initial offset to be relative to
	 * the current consumer position, false for a positive initial offset to
	 * be absolute and a negative offset relative to the current end of the
	 * partition.
	 * @since 1.1
	 */
	public TopicPartitionInitialOffset(String topic, int partition, Long initialOffset, boolean relativeToCurrent) {
		this.topicPartition = new TopicPartition(topic, partition);
		this.initialOffset = initialOffset;
		this.relativeToCurrent = relativeToCurrent;
		this.position = null;
	}

	/**
	 * Construct an instance with the provided {@link SeekPosition}.
	 * @param topic the topic.
	 * @param partition the partition.
	 * @param position {@link SeekPosition}.
	 * @since 1.3
	 */
	public TopicPartitionInitialOffset(String topic, int partition, SeekPosition position) {
		this.topicPartition = new TopicPartition(topic, partition);
		this.initialOffset = null;
		this.relativeToCurrent = false;
		this.position = position;
	}

	public TopicPartition topicPartition() {
		return this.topicPartition;
	}

	public int partition() {
		return this.topicPartition.partition();
	}

	public String topic() {
		return this.topicPartition.topic();
	}

	public Long initialOffset() {
		return this.initialOffset;
	}

	public boolean isRelativeToCurrent() {
		return this.relativeToCurrent;
	}

	public SeekPosition getPosition() {
		return this.position;
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) {
			return true;
		}
		if (o == null || getClass() != o.getClass()) {
			return false;
		}
		TopicPartitionInitialOffset that = (TopicPartitionInitialOffset) o;
		return Objects.equals(this.topicPartition, that.topicPartition);
	}

	@Override
	public int hashCode() {
		return this.topicPartition.hashCode();
	}

	@Override
	public String toString() {
		return "TopicPartitionInitialOffset{" +
				"topicPartition=" + this.topicPartition +
				", initialOffset=" + this.initialOffset +
				", relativeToCurrent=" + this.relativeToCurrent +
				(this.position == null ? "" : (", position=" + this.position.name())) +
				'}';
	}

}