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/*
 * Copyright 2024 Responsive Computing, Inc.
 *
 * 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 dev.responsive.kafka.internal.db;

import static org.apache.kafka.streams.state.StateSerdes.TIMESTAMP_SIZE;

import dev.responsive.kafka.internal.utils.SessionKey;
import java.nio.ByteBuffer;
import java.util.function.Predicate;
import org.apache.kafka.clients.consumer.ConsumerRecord;

public class SessionKeySpec implements KeySpec {

  private final Predicate withinRetention;

  public SessionKeySpec(final Predicate withinRetention) {
    this.withinRetention = withinRetention;
  }

  @Override
  public SessionKey keyFromRecord(final ConsumerRecord record) {
    final byte[] key = record.key();
    return new SessionKey(
        extractKeyBytes(key),
        extractStartTimestamp(key),
        extractEndTimestamp(key)
    );
  }

  @Override
  public boolean retain(final SessionKey key) {
    return withinRetention.test(key);
  }

  /*
   * Inspired from KafkaStream internal functions within SessionKeySchema.
   */
  @Override
  public int sizeInBytes(final SessionKey key) {
    return (key == null ? 0 : key.key.get().length) + 2 * TIMESTAMP_SIZE;
  }

  /*
   * Inspired from KafkaStream internal functions within SessionKeySchema.
   */
  private static byte[] extractKeyBytes(final byte[] binaryKey) {
    final byte[] bytes = new byte[binaryKey.length - 2 * TIMESTAMP_SIZE];
    System.arraycopy(binaryKey, 0, bytes, 0, bytes.length);
    return bytes;
  }

  /*
   * Inspired from KafkaStream internal functions within SessionKeySchema.
   */
  private static long extractEndTimestamp(final byte[] binaryKey) {
    return ByteBuffer.wrap(binaryKey).getLong(binaryKey.length - 2 * TIMESTAMP_SIZE);
  }

  /*
   * Inspired from KafkaStream internal functions within SessionKeySchema.
   */
  private static long extractStartTimestamp(final byte[] binaryKey) {
    return ByteBuffer.wrap(binaryKey).getLong(binaryKey.length - TIMESTAMP_SIZE);
  }
}