package org.apache.kafka.server.policy;

import org.apache.kafka.common.Configurable;
import org.apache.kafka.common.errors.PolicyViolationException;
import org.apache.kafka.common.Record;

/**
 * <p>An interface for enforcing a policy on message in topics.
 *
 * <p>Common use case is requiring that the messages has desired format.
 *
 * <p>If <code>message.policy.class.name</code> is defined, Kafka will create an instance of the specified class
 * for each topic using the default constructor and will then pass the broker configs to its <code>configure()</code> method. During
 * broker shutdown, the <code>close()</code> method will be invoked so that resources can be released (if necessary).
 */
public interface RecordsPolicy extends Configurable, AutoCloseable {
    /**
     * Validate the records and throw a <code>PolicyViolationException</code> with a suitable error
     * message if the records for the provided topic do not satisfy this policy.
     *
     * Clients will receive the POLICY_VIOLATION error code along with the exception's message. Note that validation
     * failure only affects the relevant topic, other topics in the request will still be processed.
     *
     * @param records Records to validate.
     * @param partition Partition number.
     * @throws PolicyViolationException if the records do not satisfy this policy.
     */
    void validate(String topic, int partition, Iterable<? extends Record> records) throws PolicyViolationException;
}

package org.apache.kafka.common;

import java.nio.ByteBuffer;
import org.apache.kafka.common.header.Header;
import org.apache.kafka.server.policy.RecordsPolicy;

/**
 * A log record is a tuple consisting of a unique offset in the log, a sequence number assigned by
 * the producer, a timestamp, a key and a value.
 *
 * @see RecordsPolicy
 */
public interface Record {
    /**
     * Get the record's timestamp.
     * @return the record's timestamp
     */
    long timestamp();

    /**
     * Check whether this record has a key
     * @return true if there is a key, false otherwise
     */
    boolean hasKey();

    /**
     * Get the record's key.
     * @return the key or null if there is none
     */
    ByteBuffer key();

    /**
     * Check whether a value is present (i.e. if the value is not null)
     * @return true if so, false otherwise
     */
    boolean hasValue();

    /**
     * Get the record's value
     * @return the (nullable) value
     */
    ByteBuffer value();

    /**
     * Get the headers. For magic versions 1 and below, this always returns an empty array.
     *
     * @return the array of headers
     */
    Header[] headers();
}