/*
 * The contents of this file are subject to the terms of the Common Development and
 * Distribution License (the License). You may not use this file except in compliance with the
 * License.
 *
 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
 * specific language governing permission and limitations under the License.
 *
 * When distributing Covered Software, include this CDDL Header Notice in each file and include
 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
 * Header, with the fields enclosed by brackets [] replaced by your own identifying
 * information: "Portions Copyright [year] [name of copyright owner]".
 *
 * Copyright 2014-2015 ForgeRock AS.
 * Portions Copyright 2026 3A Systems, LLC.
 */
package org.opends.server.backends.pluggable.spi;

import java.io.Closeable;
import java.util.Set;

import org.forgerock.opendj.config.server.ConfigException;
import org.opends.server.types.BackupConfig;
import org.opends.server.types.BackupDirectory;
import org.opends.server.types.DirectoryException;
import org.opends.server.types.RestoreConfig;

/**
 * This interface abstracts the underlying storage engine,
 * isolating the pluggable backend generic code from a particular storage engine implementation.
 */
public interface Storage extends Closeable
{

  /**
   * Starts the import operation.
   * @return a new Importer object which must be closed to release all resources
   * @throws ConfigException
   *           if there is a problem with the configuration
   * @throws StorageRuntimeException
   *           if a problem occurs with the underlying storage engine
   * @see #close() to release all resources once import is finished
   */
  Importer startImport() throws ConfigException, StorageRuntimeException;

  /**
   * Opens the storage engine to allow executing operations on it.
   *
   * @param accessMode
   *           Specify the access mode to this storage.
   * @throws NullPointerException
   *           if accessMode is null.
   * @throws Exception
   *           if a problem occurs with the underlying storage engine
   * @see #close() to release all resources once import is finished
   */
  void open(AccessMode accessMode) throws Exception;

  /**
   * Executes a read operation. In case of a read operation rollback, implementations must propagate the failure
   * to the caller rather than replay the operation: unlike {@link WriteOperation}, a {@link ReadOperation} is not
   * required to be idempotent, and several of them are not - they write to a stream, print, or accumulate state
   * that a second attempt would double.
   *
   * @param <T>
   *          type of the value returned
   * @param readOperation
   *          the read operation to execute
   * @return the value read by the read operation
   * @throws Exception
   *           if a problem occurs with the underlying storage engine
   */
  <T> T read(ReadOperation<T> readOperation) throws Exception;

  /**
   * Executes a write operation. In case of a write operation rollback, implementations may replay the write
   * operation rather than propagate the failure: a {@link WriteOperation} is required to be idempotent for
   * exactly that reason. A replay must be bounded - by a number of attempts, by a window of time, or by both -
   * so that a conflict which does not clear reaches the caller instead of being retried forever. The pluggable
   * backend holds locks across this method, up to the exclusive lock of an entry container, and every thread
   * waiting on one of those locks waits for as long as this method does.
   * <p>
   * A caller that mutates state around this method must handle that bound being spent. Removing an entry from an
   * in-memory map before the write so that a replay still finds the work to do, or reading configuration back out
   * of the operation once it returns, both assume the write is applied; when it is not, this method throws with
   * that state already changed and the transaction not applied, and the caller is the only place that can reconcile
   * the two.
   *
   * @param writeOperation
   *          the write operation to execute
   * @throws Exception
   *           if a problem occurs with the underlying storage engine, including a conflict that outlasted the
   *           replays the implementation makes
   */
  void write(WriteOperation writeOperation) throws Exception;

  /**
   * Remove all files for a backend of this storage.
   *
   * @throws StorageRuntimeException if removal fails
   */
  void removeStorageFiles() throws StorageRuntimeException;

  /**
   * Returns the current status of the storage.
   *
   * @return the current status of the storage
   */
  StorageStatus getStorageStatus();

  /**
   * Returns {@code true} if this storage supports backup and restore.
   *
   * @return {@code true} if this storage supports backup and restore.
   */
  boolean supportsBackupAndRestore();

  /**
   * Creates a backup for this storage.
   *
   * @param backupConfig
   *          The configuration to use when performing the backup.
   * @throws DirectoryException
   *           If a Directory Server error occurs.
   */
  void createBackup(BackupConfig backupConfig) throws DirectoryException;

  /**
   * Removes a backup for this storage.
   *
   * @param backupDirectory
   *          The backup directory structure with which the specified backup is
   *          associated.
   * @param backupID
   *          The backup ID for the backup to be removed.
   * @throws DirectoryException
   *           If it is not possible to remove the specified backup.
   */
  void removeBackup(BackupDirectory backupDirectory, String backupID) throws DirectoryException;

  /**
   * Restores a backup for this storage.
   *
   * @param restoreConfig
   *          The configuration to use when performing the restore.
   * @throws DirectoryException
   *           If a Directory Server error occurs.
   */
  void restoreBackup(RestoreConfig restoreConfig) throws DirectoryException;

  /**
   * Lists the trees that exist in this storage.
   *
   * @return a set of {@link TreeName}s representing the trees that exist in this storage
   */
  Set<TreeName> listTrees();

  @Override
  void close();
}