/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * docs/licenses/cddl.txt
 * or http://www.opensource.org/licenses/cddl1.php.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * docs/licenses/cddl.txt.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying information:
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 * CDDL HEADER END
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 *
 *      Copyright 2010-2018 Ping Identity Corporation
 */
package com.unboundid.directory.sdk.sync.api;



import java.sql.SQLException;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import com.unboundid.directory.sdk.common.internal.Configurable;
import com.unboundid.directory.sdk.common.internal.ExampleUsageProvider;
import com.unboundid.directory.sdk.common.internal.UnboundIDExtension;
import com.unboundid.directory.sdk.sync.config.JDBCSyncDestinationConfig;
import com.unboundid.directory.sdk.sync.internal.SynchronizationServerExtension;
import com.unboundid.directory.sdk.sync.types.SyncOperation;
import com.unboundid.directory.sdk.sync.types.SyncServerContext;
import com.unboundid.directory.sdk.sync.types.TransactionContext;
import com.unboundid.ldap.sdk.Entry;
import com.unboundid.ldap.sdk.Modification;
import com.unboundid.util.Extensible;
import com.unboundid.util.ThreadSafety;
import com.unboundid.util.ThreadSafetyLevel;
import com.unboundid.util.args.ArgumentException;
import com.unboundid.util.args.ArgumentParser;



/**
 * This class defines an API that must be implemented by extensions
 * in order to synchronize data into a relational database. Since the UnboundID
 * Synchronization Server is LDAP-centric,
 * this API allows you to take LDAP entries and split them out into
 * database content and make the appropriate updates. The lifecycle of a sync
 * operation is as follows:
 * <ol>
 * <li>Detect change at the synchronization source</li>
 * <li>Fetch full source entry</li>
 * <li>Perform any mappings and compute the equivalent destination entry</li>
 * <li>Fetch full destination entry</li>
 * <li>Diff the computed destination entry and actual destination entry</li>
 * <li>Apply the minimal set of changes at the destination to bring it in sync
 * </li>
 * </ol>
 * This implies that the {@link #fetchEntry(TransactionContext, Entry,
 * SyncOperation)} method will
 * always be called once prior to any of the other methods in this class.
 * <p>
 * In several places a {@link TransactionContext} is provided, which allows
 * controlled access to the target database. By default, methods in this class
 * are always provided with a fresh connection (i.e. a new transaction), and the
 * Synchronization Server will always commit or rollback the transaction
 * automatically, depending on how the method returns. If a method call returns
 * successfully, then the transaction will be committed. If an exception is
 * thrown, then the transaction will be rolled back. In rare situations, it
 * might be necessary for an implementation to perform its own commit or
 * rollback of transactions by calling methods on {@link TransactionContext}.
 * <p>
 * Several of these methods throw {@link SQLException}, which should be used in
 * the case of any database access error. For other types of errors, runtime
 * exceptions may be used (IllegalStateException, NullPointerException, etc.).
 * The Synchronization Server will automatically retry operations that fail, up
 * to a configurable amount of attempts. The exception to this rule is if a
 * SQLException is thrown with a SQL state string beginning with "08"; this
 * indicates a connection error, and in this case the operation is retried
 * indefinitely.  For these reasons implementers should refrain from handling
 * or wrapping any {@link SQLException} and instead let it be handled by the
 * calling code.
 * <BR>
 * <H2>Configuring JDBC Sync Destinations</H2>
 * In order to configure a JDBC sync destination based on this API and
 * written in Java, use a command like:
 * <PRE>
 *      dsconfig create-sync-destination \
 *           --destination-name "<I>{destination-name}</I>" \
 *           --type third-party-jdbc \
 *           --set "server:{server-name}" \
 *           --set "extension-class:<I>{class-name}</I>" \
 *           --set "extension-argument:<I>{name=value}</I>"
 * </PRE>
 * where "<I>{destination-name}</I>" is the name to use for the JDBC sync
 * destination instance, "<I>{server-name}</I>" is the name of the JDBC external
 * server that will be used as the sync destination, "<I>{class-name}</I>" is
 * the fully-qualified name of the Java class written using this API, and
 * "<I>{name=value}</I>" represents name-value pairs for any arguments to
 * provide to the JDBC sync destination.  If multiple arguments should be
 * provided to the JDBC sync destination, then the
 * "<CODE>--set extension-argument:<I>{name=value}</I></CODE>" option should be
 * provided multiple times.
 */
@Extensible()
@SynchronizationServerExtension(appliesToLocalContent=false,
     appliesToSynchronizedContent=true)
public abstract class JDBCSyncDestination implements UnboundIDExtension,
                                                     Configurable,
                                                     ExampleUsageProvider
{
  /**
   * Creates a new instance of this JDBC Sync Destination.  All sync
   * destination implementations must include a default constructor, but any
   * initialization should generally be done in the
   * {@link #initializeJDBCSyncDestination} method.
   */
  public JDBCSyncDestination()
  {
    //no implementation is required
  }



  /**
   * {@inheritDoc}
   */
  public abstract String getExtensionName();



  /**
   * {@inheritDoc}
   */
  public abstract String[] getExtensionDescription();



  /**
   * {@inheritDoc}
   */
  public Map<List<String>,String> getExamplesArgumentSets()
  {
    return Collections.emptyMap();
  }



  /**
   * {@inheritDoc}
   */
  public void defineConfigArguments(final ArgumentParser parser)
         throws ArgumentException
  {
    // No arguments will be allowed by default.
  }



  /**
   * This hook is called when a Sync Pipe first starts up, or when the
   * <i>resync</i> process first starts up. Any initialization of this sync
   * destination should be performed here. This method should generally store
   * the {@link SyncServerContext} in a class
   * member so that it can be used elsewhere in the implementation.
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * The default implementation is empty.
   *
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   * @param  serverContext  A handle to the server context for the server in
   *                        which this extension is running.
   * @param  config         The general configuration for this sync destination.
   * @param  parser         The argument parser which has been initialized from
   *                        the configuration for this JDBC sync destination.
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_NOT_THREADSAFE)
  public void initializeJDBCSyncDestination(
                                         final TransactionContext ctx,
                                         final SyncServerContext serverContext,
                                         final JDBCSyncDestinationConfig config,
                                         final ArgumentParser parser)
  {
    // No initialization will be performed by default.
  }



  /**
   * This hook is called when a Sync Pipe shuts down, or when the <i>resync</i>
   * process shuts down. Any clean-up of this sync destination should be
   * performed here.
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * The default implementation is empty.
   *
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_NOT_THREADSAFE)
  public void finalizeJDBCSyncDestination(
                                      final TransactionContext ctx)
  {
    //No implementation required by default.
  }



  /**
   * Return a full destination entry (in LDAP form) from the database,
   * corresponding to the source {@link Entry} that is passed in.
   * This method should perform any queries necessary to gather the latest
   * values for all the attributes to be synchronized and return them in an
   * Entry.
   * <p>
   * Note that the if the source entry was renamed (see
   * {@link SyncOperation#isModifyDN}), the
   * <code>destEntryMappedFromSrc</code> will have the new DN; the old DN can
   * be obtained by calling
   * {@link SyncOperation#getDestinationEntryBeforeChange()} and getting the DN
   * from there. This method should return the entry in its existing form
   * (i.e. with the old DN, before it is changed).
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * This method <b>must be thread safe</b>, as it will be called repeatedly and
   * concurrently by each of the Sync Pipe worker threads as they process
   * entries.
   *
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   * @param destEntryMappedFromSrc
   *          the LDAP entry which corresponds to the database "entry" to fetch
   * @param  operation
   *          the sync operation for this change
   * @return a full LDAP Entry, or null if no such entry exists.
   * @throws SQLException
   *           if there is an error fetching the entry
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_THREADSAFE)
  public abstract Entry fetchEntry(final TransactionContext ctx,
                                   final Entry destEntryMappedFromSrc,
                                   final SyncOperation operation)
                                              throws SQLException;



  /**
   * Creates a full database "entry", corresponding to the LDAP
   * {@link Entry} that is passed in. This method should perform any inserts and
   * updates necessary to make sure the entry is fully created on the database.
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * This method <b>must be thread safe</b>, as it will be called repeatedly and
   * concurrently by the Sync Pipe worker threads as they process CREATE
   * operations.
   *
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   * @param entryToCreate
   *          the LDAP entry which corresponds to the database "entry" to create
   * @param  operation
   *          the sync operation for this change
   * @throws SQLException
   *           if there is an error creating the entry
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_THREADSAFE)
  public abstract void createEntry(final TransactionContext ctx,
                                   final Entry entryToCreate,
                                   final SyncOperation operation)
                                      throws SQLException;



  /**
   * Modify an "entry" in the database, corresponding to the LDAP
   * {@link Entry} that is passed in. This method may perform multiple updates
   * (including inserting or deleting rows) in order to fully synchronize the
   * entire entry on the database.
   * <p>
   * Note that the if the source entry was renamed (see
   * {@link SyncOperation#isModifyDN}), the <code>fetchedDestEntry</code> will
   * have the old DN; the new DN can be obtained by calling
   * {@link SyncOperation#getDestinationEntryAfterChange()} and getting the DN
   * from there.
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * This method <b>must be thread safe</b>, as it will be called repeatedly and
   * concurrently by the Sync Pipe worker threads as they process MODIFY
   * operations.
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   * @param fetchedDestEntry
   *          the LDAP entry which corresponds to the database "entry" to modify
   * @param modsToApply
   *          a list of Modification objects which should be applied
   * @param  operation
   *          the sync operation for this change
   * @throws SQLException
   *           if there is an error modifying the entry
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_THREADSAFE)
  public abstract void modifyEntry(final TransactionContext ctx,
                                   final Entry fetchedDestEntry,
                                   final List<Modification> modsToApply,
                                   final SyncOperation operation)
                                          throws SQLException;



  /**
   * Delete a full "entry" from the database, corresponding to the LDAP
   * {@link Entry} that is passed in. This method may perform multiple deletes
   * or updates if necessary to fully delete the entry from the database.
   * <p>
   * A {@link TransactionContext} is provided, which allows
   * controlled access to the target database. The context will contain a fresh
   * fresh connection (i.e. a new transaction), and the Synchronization Server
   * will always commit or rollback the transaction automatically, depending on
   * whether this method returns normally or throws an exception. See the class
   * level documentation for warnings and additional details.
   * <p>
   * This method <b>must be thread safe</b>, as it will be called repeatedly and
   * concurrently by the Sync Pipe worker threads as they process DELETE
   * operations.
   *
   * @param ctx
   *          a TransactionContext which provides a valid JDBC connection to the
   *          database.
   * @param fetchedDestEntry
   *          the LDAP entry which corresponds to the database "entry" to delete
   * @param  operation
   *          the sync operation for this change
   * @throws SQLException
   *           if there is an error deleting the entry
   */
  @ThreadSafety(level = ThreadSafetyLevel.METHOD_THREADSAFE)
  public abstract void deleteEntry(final TransactionContext ctx,
                                   final Entry fetchedDestEntry,
                                   final SyncOperation operation)
                                        throws SQLException;
}