update!: overhauled to align with the sabi-rust

src/main/java/com/github/sttk/sabi/AsyncGroup.java

@@ -4,38 +4,43 @@
  */
 package com.github.sttk.sabi;
 
+import com.github.sttk.sabi.internal.AsyncGroupImpl;
+
 /**
- * An interface for asynchronously executing multiple {@link Runner} instances and waiting for their
- * completion.
+ * Manages asynchronous background tasks executed during data source and data connection lifecycle
+ * events.
+ *
+ * <p>An instance of {@code AsyncGroup} is passed to methods of {@link DataSrc} (such as {@link
+ * DataSrc#setup(AsyncGroup)}) and {@link DataConn} (such as {@link DataConn#commit(AsyncGroup)} and
+ * {@link DataConn#rollback(AsyncGroup)}). Implementations of data sources and data connections can
+ * register background asynchronous operations (such as parallel cleanup or pre-commit validations)
+ * using the {@link #add(Runner)} method.
  *
- * <p>Implementations of this interface allow adding multiple {@link Runner} objects, which are then
- * executed concurrently. The group waits until all added runners have finished their execution. Any
- * errors occurring during the execution of a {@link Runner} are stored and can be retrieved by
- * their names in a map.
+ * <p>All registered {@link Runner} tasks are managed by this group and executed asynchronously. If
+ * any registered task fails, is interrupted, or throws an unhandled runtime exception,
+ * corresponding error records defined in this interface are produced to report the failure.
  */
-public sealed interface AsyncGroup permits com.github.sttk.sabi.internal.AsyncGroupImpl {
+public sealed interface AsyncGroup permits AsyncGroupImpl {
 
-  /**
-   * Represents the reason for a new {@link com.github.sttk.errs.Err} exception object when an
-   * exception occurred during the execution of a {@link Runner} and the exception class was not the
-   * {@link com.github.sttk.errs.Err}.
-   */
+  /** Indicates that a registered {@link Runner} task failed during its execution. */
   record RunnerFailed() {}
 
-  /**
-   * Represents the reason for an {@link com.github.sttk.errs.Err} exception object when the
-   * creation of a thread for asynchronous execution of a {@link Runner} fails.
-   */
+  /** Indicates that a registered {@link Runner} task execution was interrupted. */
   record RunnerInterrupted() {}
 
-  /** Represents an unexpected {@link RuntimeException} that occurred. */
-  record RuntimeExceptionOccurred() {}
+  /**
+   * Indicates that an unhandled runtime exception was thrown during the execution of a registered
+   * {@link Runner} task.
+   */
+  record RuntimeExceptionOccured() {}
 
   /**
-   * Adds a {@link Runner} to this group for asynchronous execution. The added runner will be
-   * executed in a separate thread.
+   * Adds a background task to be executed asynchronously by this group.
+   *
+   * <p>The task is encapsulated in a {@link Runner} functional interface and scheduled for parallel
+   * asynchronous execution.
    *
-   * @param runner The {@link Runner} to be added and executed asynchronously.
+   * @param runner the {@link Runner} task to be added and executed asynchronously
    */
-  void add(final Runner runner);
+  void add(Runner runner);
 }

src/main/java/com/github/sttk/sabi/DataAcc.java

@@ -7,25 +7,29 @@
 import com.github.sttk.errs.Err;
 
 /**
- * An interface designed for implementing data access operations through default methods in its
- * sub-interfaces.
+ * Provides access to named {@link DataConn} data connection instances.
  *
- * <p>Sub-interfaces of {@code DataAcc} are expected to define and implement data access methods as
- * default methods. Within these default methods, the connection to the underlying data store should
- * be obtained using the {@link #getDataConn(String, Class)} method provided by this interface. This
- * design promotes a clear separation of concerns, allowing data access logic to be encapsulated
- * within the interface itself.
+ * <p>This interface defines the contract for retrieving managed data connections registered under
+ * specific names within a data access scope (such as a {@link DataHub}). Application business logic
+ * uses this interface to obtain connection objects required to perform database or external service
+ * operations.
  */
 public interface DataAcc {
+
   /**
-   * Retrieves a connection to a data store. This method is intended to be used by default methods
-   * in sub-interfaces to obtain the necessary connection for performing data access operations.
+   * Retrieves a data connection associated with the specified data source name and casts it to the
+   * requested connection class type.
+   *
+   * <p>If a connection for the given {@code name} has already been created within the current
+   * transaction or execution scope, that connection instance is returned. Otherwise, a new
+   * connection is created via the corresponding registered data source.
    *
-   * @param <C> The type of the data connection, which must extend {@link DataConn}.
-   * @param name The name identifying the specific data connection to retrieve.
-   * @param cls The {@link Class} object representing the type of the desired data connection.
-   * @return A data connection object of the specified type.
-   * @throws Err if an error occurs while obtaining the data connection.
+   * @param <C> the expected type of {@link DataConn}
+   * @param name the registered logical name of the data source
+   * @param cls the {@link Class} representing the target connection type {@code C}
+   * @return the data connection instance associated with the specified name
+   * @throws Err if no data source with the specified name is found, if creating the connection
+   *     fails or yields null, or if the connection cannot be cast to the target type
    */
   <C extends DataConn> C getDataConn(String name, Class<C> cls) throws Err;
 }

src/main/java/com/github/sttk/sabi/DataConn.java

@@ -5,78 +5,105 @@
 package com.github.sttk.sabi;
 
 import com.github.sttk.errs.Err;
+import java.util.List;
 
 /**
- * The interface that abstracts a connection per session to an external data service, such as a
- * database, file system, or messaging service.
+ * Represents a data connection participating in transaction lifecycles managed by a {@link
+ * DataHub}.
  *
- * <p>Its primary purpose is to enable cohesive transaction operations across multiple external data
- * services within a single transaction context. Implementations of this interface provide the
- * concrete input/output operations for their respective data services.
- *
- * <p>Methods declared within this interface are designed to handle transactional logic. The
- * AsyncGroup parameter in various methods allows for asynchronous processing when commit or
- * rollback operations are time-consuming.
+ * <p>Implementations encapsulate connection state and operations for external resources such as
+ * relational databases, NoSQL stores, or web services. During a transaction, connections progress
+ * through pre-commit, commit, and post-commit phases, and support rollback and failure reporting
+ * when errors occur.
  */
 public interface DataConn {
+
   /**
-   * Commits the changes made within the current session to the external data service. This method
-   * is responsible for finalizing all operations performed since the last commit or rollback.
+   * Represents an error when one or more data connections fail during the pre-commit phase.
    *
-   * @param ag An {@link AsyncGroup} that can be used to perform asynchronous operations if the
-   *     commit process is time-consuming.
-   * @throws Err if an error occurs during the commit operation.
+   * @param errors the list of error entries detailing connection names and failure causes
    */
-  void commit(AsyncGroup ag) throws Err;
+  public record FailToPreCommitDataConn(List<ErrEntry> errors) {}
 
   /**
-   * Performs any necessary pre-commit operations. This method is called before the {@link
-   * #commit(AsyncGroup)} method.
+   * Represents an error when one or more data connections fail during the commit phase.
    *
-   * @param ag An {@link AsyncGroup} that can be used for asynchronous pre-commit tasks.
-   * @throws Err if an error occurs during the pre-commit operation.
+   * @param errors the list of error entries detailing connection names and failure causes
    */
-  default void preCommit(AsyncGroup ag) throws Err {}
+  public record FailToCommitDataConn(List<ErrEntry> errors) {}
+
+  /**
+   * Represents an error when one or more data connections fail during the post-commit phase.
+   *
+   * @param errors the list of error entries detailing connection names and failure causes
+   */
+  public record FailToPostCommitDataConn(List<ErrEntry> errors) {}
+
+  ///
+
+  /**
+   * Commits changes made through this connection.
+   *
+   * <p>Async background tasks may be registered to the provided {@link AsyncGroup} during commit
+   * processing.
+   *
+   * @param ag the asynchronous group for registering background tasks
+   * @throws Err if committing the transaction changes fails
+   */
+  void commit(AsyncGroup ag) throws Err;
 
   /**
-   * Performs any necessary post-commit operations. This method is called after the {@link
-   * #commit(AsyncGroup)} method has successfully completed.
+   * Prepares this connection for commit prior to the main commit phase.
+   *
+   * <p>The default implementation does nothing. Subclasses can override this method to perform
+   * pre-commit checks or flush pending writes.
    *
-   * @param ag An {@link AsyncGroup} that can be used for asynchronous post-commit tasks.
+   * @param ag the asynchronous group for registering background tasks
+   * @throws Err if pre-commit preparation or validation fails
    */
-  default void postCommit(AsyncGroup ag) {}
+  default void preCommit(AsyncGroup ag) throws Err {}
 
   /**
-   * Indicates whether a force-back operation should be performed. A force-back is a mechanism to
-   * revert the committed changes when this connection had been already committed but the other
-   * connection had failed.
+   * Performs post-commit operations after all connections in a transaction have successfully
+   * committed.
    *
-   * @return {@code true} if a force-back is required, {@code false} otherwise.
+   * <p>The default implementation does nothing. Subclasses can override this method to perform
+   * cleanup or trigger post-commit notifications.
+   *
+   * @param ag the asynchronous group for registering background tasks
+   * @throws Err if post-commit processing fails
    */
-  default boolean shouldForceBack() {
-    return false;
-  }
+  default void postCommit(AsyncGroup ag) throws Err {}
 
   /**
-   * Rolls back the changes made within the current session, discarding all operations performed
-   * since the last commit or rollback.
+   * Checks whether this connection has been successfully committed.
    *
-   * @param ag An {@link AsyncGroup} that can be used to perform asynchronous operations if the
-   *     rollback process is time-consuming.
+   * @return {@code true} if this connection was committed; {@code false} otherwise
    */
-  void rollback(AsyncGroup ag);
+  boolean isCommitted();
 
   /**
-   * Performs a force-back operation to revert the committed changes when this connection had been
-   * already committed but the other connection had failed.
+   * Rolls back changes made through this connection.
+   *
+   * <p>This method is invoked when a transaction fails and must restore the connection or
+   * underlying storage to its pre-transaction state.
    *
-   * @param ag An {@link AsyncGroup} that can be used for asynchronous force-back tasks.
+   * @param ag the asynchronous group for registering background tasks
+   * @throws Err if rolling back connection changes fails
    */
-  default void forceBack(AsyncGroup ag) {}
+  void rollback(AsyncGroup ag) throws Err;
 
   /**
-   * Closes the connection to the external data service, releasing any associated resources. This
-   * method should be called to ensure proper resource management.
+   * Notifies this connection of a transaction failure with detailed failure reports.
+   *
+   * <p>The default implementation does nothing. Implementations can inspect failure reports to log
+   * diagnostics or take recovery actions.
+   *
+   * @param ag the asynchronous group for registering background tasks
+   * @param reports the list of transaction failure reports
    */
+  default void onTxnFailure(AsyncGroup ag, List<TxnFailureReport> reports) {}
+
+  /** Closes and disposes of this data connection, releasing any held resources. */
   void close();
 }