/*
 * 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.kafka.streams.state;

import org.apache.kafka.streams.KeyValue;

import java.util.Objects;

/**
 * Combines a value from a {@link KeyValue} with a timestamp.
 *
 * @param <V>
 */
public final class ValueAndTimestamp<V> {
    private final V value;
    private final long timestamp;

    private ValueAndTimestamp(final V value,
                              final long timestamp) {
        this.value = value;
        this.timestamp = timestamp;
    }

    /**
     * Create a new {@link ValueAndTimestamp} instance if the provided {@code value} is not {@code null}.
     *
     * @param value      the value
     * @param timestamp  the timestamp
     * @param <V> the type of the value
     * @return a new {@link ValueAndTimestamp} instance if the provided {@code value} is not {@code null};
     *         otherwise {@code null} is returned
     */
    public static <V> ValueAndTimestamp<V> make(final V value,
                                                final long timestamp) {
        return value == null ? null : new ValueAndTimestamp<>(value, timestamp);
    }

    /**
     * Create a new {@link ValueAndTimestamp} instance. The provided {@code value} may be {@code null}.
     *
     * @param value      the value
     * @param timestamp  the timestamp
     * @param <V> the type of the value
     * @return a new {@link ValueAndTimestamp} instance
     */
    public static <V> ValueAndTimestamp<V> makeAllowNullable(
        final V value, final long timestamp) {
        return new ValueAndTimestamp<>(value, timestamp);
    }

    /**
     * Return the wrapped {@code value} of the given {@code valueAndTimestamp} parameter
     * if the parameter is not {@code null}.
     *
     * @param valueAndTimestamp a {@link ValueAndTimestamp} instance; can be {@code null}
     * @param <V> the type of the value
     * @return the wrapped {@code value} of {@code valueAndTimestamp} if not {@code null}; otherwise {@code null}
     */
    public static <V> V getValueOrNull(final ValueAndTimestamp<V> valueAndTimestamp) {
        return valueAndTimestamp == null ? null : valueAndTimestamp.value();
    }

    public V value() {
        return value;
    }

    public long timestamp() {
        return timestamp;
    }

    @Override
    public String toString() {
        return "<" + value + "," + timestamp + ">";
    }

    @Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        final ValueAndTimestamp<?> that = (ValueAndTimestamp<?>) o;
        return timestamp == that.timestamp &&
            Objects.equals(value, that.value);
    }

    @Override
    public int hashCode() {
        return Objects.hash(value, timestamp);
    }
}
