/*
 * 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.runtime.operators.windowing;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;

/**
 * Stores the value and the timestamp of the record.
 *
 * @param <T> The type encapsulated value
 */
@PublicEvolving
public class TimestampedValue<T> {

	/** The actual value held by this record. */
	private T value;

	/** The timestamp of the record. */
	private long timestamp;

	/** Flag whether the timestamp is actually set. */
	private boolean hasTimestamp;

	/**
	 * Creates a new TimestampedValue. The record does not have a timestamp.
	 */
	public TimestampedValue(T value) {
		this.value = value;
	}

	/**
	 * Creates a new TimestampedValue wrapping the given value. The timestamp is set to the
	 * given timestamp.
	 *
	 * @param value The value to wrap in this {@link TimestampedValue}
	 * @param timestamp The timestamp in milliseconds
	 */
	public TimestampedValue(T value, long timestamp) {
		this.value = value;
		this.timestamp = timestamp;
		this.hasTimestamp = true;
	}

	/**
	 * @return The value wrapped in this {@link TimestampedValue}.
	 */
	public T getValue() {
		return value;
	}

	/**
	 * @return The timestamp associated with this stream value in milliseconds.
     */
	public long getTimestamp() {
		if (hasTimestamp) {
			return timestamp;
		} else {
			throw new IllegalStateException(
					"Record has no timestamp. Is the time characteristic set to 'ProcessingTime', or " +
							"did you forget to call 'DataStream.assignTimestampsAndWatermarks(...)'?");
		}
	}

	/**
	 * Checks whether this record has a timestamp.
	 *
	 * @return True if the record has a timestamp, false if not.
	 */
	public boolean hasTimestamp() {
		return hasTimestamp;
	}

	/**
	 * Creates a {@link StreamRecord} from this TimestampedValue.
     */
	public StreamRecord<T> getStreamRecord() {
		StreamRecord<T> streamRecord = new StreamRecord<>(value);
		if (hasTimestamp) {
			streamRecord.setTimestamp(timestamp);
		}
		return streamRecord;
	}

	/**
	 * Creates a TimestampedValue from given {@link StreamRecord}.
	 *
	 * @param streamRecord The StreamRecord object from which TimestampedValue is to be created.
     */
	public static <T> TimestampedValue<T> from(StreamRecord<T> streamRecord) {
		if (streamRecord.hasTimestamp()) {
			return new TimestampedValue<>(streamRecord.getValue(), streamRecord.getTimestamp());
		} else {
			return new TimestampedValue<>(streamRecord.getValue());
		}
	}
}