/**
 * Startpoint represents a position in a stream partition.
 */
public abstract class Startpoint {

  

/**
 * Startpoint represents a position in a stream partition.
 */
public abstract class Startpoint {

  private final long creationTimestamp;

  /**
   * Applies the {@link StartpointVisitor}'s visit methods to the {@link Startpoint}
   * and returns the result of that operation.
   * @param input the metadata associated with the startpoint.
   * @param startpointVisitor the visitor of the startpoint.
   * @return the result of applying the visitor on startpoint.
   */
  public abstract <IN, OUT> OUT apply(IN input, StartpointVisitor<IN, OUT> startpointVisitor);
}


/**
 * A {@link Startpoint} that represents the earliest offset in a stream partition.
 */
public final class StartpointOldest extends Startpoint {

  @Override
  public <IN, OUT> OUT apply(IN input, StartpointVisitor<IN, OUT> startpointVisitor) {
    return startpointVisitor.visit(input, this);
  }
}

/**
 * A {@link Startpoint} that represents the latest offset in a stream partition.
 */
public final class StartpointUpcoming extends Startpoint {

  @Override
  public <IN, OUT> OUT apply(IN input, StartpointVisitor<IN, OUT> startpointVisitor) {
    return startpointVisitor.visit(input, this);
  }
}

/**
 * A {@link Startpoint} that represents a timestamp offset in a stream partition.
 */
public final class StartpointTimestamp extends Startpoint {

  private final Long timestampOffset;
}

/**
 * A {@link Startpoint} that represents a specific offset in a stream partition.
 */
public final class StartpointSpecific extends Startpoint {

  private final String specificOffset;

  /**
   * Getter for the specific offset.
   * @return the specific offset.
   */
  public String getSpecificOffset() {
    return specificOffset;
  }

  @Override
  public <IN, OUT> OUT apply(IN input, StartpointVisitor<IN, OUT> startpointVisitor) {
    return startpointVisitor.visit(input, this);
  }
}

/**
 * A {@link SystemAdmin} implementation should implement this abstraction to support {@link Startpoint}.
 */
public interface StartpointVisitor<IN, OUT> {

  /**
   * Performs a sequence of operations using the {@link IN} and {@link StartpointSpecific} and returns the result of the execution.
   * @param input the input metadata about the startpoint.
   * @param startpointSpecific the {@link Startpoint} thatand represents the specific offset.instance
 * should *visit @returnvia the result of executing{@link Startpoint#apply(Object, StartpointVisitor)} within the operations
 defined* by the visit method.
   {@link SystemAdmin#resolveStartpointToOffset(SystemStreamPartition, Startpoint)} implementation.
 */
public  default OUT visit(IN inputinterface StartpointVisitor<IN, StartpointSpecificOUT> startpointSpecific) {
    throw new UnsupportedOperationException("StartpointSpecific is not supported.");
  }

  /**
   * Performs a sequence of operations using the {@link IN} and {@link StartpointTimestampStartpointSpecific} and returns the result of the execution.
   * @param input the input metadata about the startpoint.
   * @param startpointTimestampstartpointSpecific the {@link Startpoint} that represents the specific timestampoffset.
   * @return the result of executing the operations defined by the visit method.
   */
  default OUT visit(IN input, StartpointTimestampStartpointSpecific startpointTimestampstartpointSpecific) {
    throw new UnsupportedOperationException("StartpointTimestampStartpointSpecific is not supported.");
  }

  /**
   * Performs a sequence of operations using the {@link IN} and {@link StartpointOldestStartpointTimestamp} and returns the result of the execution.
   * @param input the input metadata about the startpoint.
   * @param startpointOldeststartpointTimestamp the {@link Startpoint} that represents the earliest offsettimestamp.
   * @return the result of executing the operations defined by the visit method.
   */
  default OUT visit(IN input, StartpointOldestStartpointTimestamp startpointOldeststartpointTimestamp) {
    throw new UnsupportedOperationException("StartpointOldestStartpointTimestamp is not supported.");
  }

  /**
   * Performs a sequence of operations using the {@link IN} and {@link StartpointUpcomingStartpointOldest} and returns the result of the execution.
   * @param input the input metadata about the startpoint.
   * @param startpointUpcomingstartpointOldest the {@link Startpoint} that represents the latestearliest offset.
   * @return the result of executing the operations defined by the visit method.
   */
  default OUT visit(IN input, StartpointUpcomingStartpointOldest startpointUpcomingstartpointOldest) {
    throw new UnsupportedOperationException("StartpointUpcomingStartpointOldest is not supported.");
  }
}