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 * Copyright (C) 2026, Leo Galambos
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package zeroecho.pki.util.async;

import java.time.Instant;
import java.util.Optional;

/**
 * Target endpoint that owns/executes operations and can be asked for their
 * status.
 *
 * <p>
 * The bus uses endpoints to:
 * </p>
 * <ul>
 * <li>poll open operations on {@link AsyncBus#sweep(Instant)} (restart
 * recovery),</li>
 * <li>deliver status/result updates via
 * {@link AsyncBus#update(Object, AsyncStatus, Optional)}.</li>
 * </ul>
 *
 * @param <OpId> operation id type
 * @param <Res>  result type
 */
public interface AsyncEndpoint<OpId, Res> {

    /**
     * Returns a best-effort current status for a known operation.
     *
     * <p>
     * Endpoints should return a terminal status if the operation is complete. If
     * unknown, endpoints may return an empty optional.
     * </p>
     *
     * @param opId operation id (never {@code null})
     * @return status if known
     */
    Optional<AsyncStatus> status(OpId opId);

    /**
     * Returns a best-effort result for a successful operation.
     *
     * <p>
     * Endpoints should return a value only if the operation has succeeded and the
     * result is retrievable. If results are stored elsewhere, this may return
     * empty.
     * </p>
     *
     * @param opId operation id (never {@code null})
     * @return result if available
     */
    Optional<Res> result(OpId opId);
}
