/*
 * 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 2006-2008 Sun Microsystems, Inc.
 * Portions Copyright 2014-2016 ForgeRock AS.
 */
package org.opends.server.backends;

import static org.forgerock.util.Reject.*;
import static org.opends.messages.BackendMessages.*;
import static org.opends.server.util.ServerConstants.*;
import static org.opends.server.util.StaticUtils.*;

import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.Set;

import org.forgerock.i18n.LocalizableMessage;
import org.forgerock.i18n.slf4j.LocalizedLogger;
import org.forgerock.opendj.config.server.ConfigException;
import org.forgerock.opendj.ldap.ConditionResult;
import org.forgerock.opendj.ldap.ResultCode;
import org.forgerock.opendj.ldap.SearchScope;
import org.forgerock.opendj.ldap.schema.AttributeType;
import org.opends.server.admin.std.server.MemoryBackendCfg;
import org.opends.server.api.Backend;
import org.opends.server.controls.SubtreeDeleteControl;
import org.opends.server.core.AddOperation;
import org.opends.server.core.DeleteOperation;
import org.opends.server.core.DirectoryServer;
import org.opends.server.core.ModifyDNOperation;
import org.opends.server.core.ModifyOperation;
import org.opends.server.core.SearchOperation;
import org.opends.server.core.ServerContext;
import org.opends.server.types.BackupConfig;
import org.opends.server.types.BackupDirectory;
import org.opends.server.types.Control;
import org.forgerock.opendj.ldap.DN;
import org.opends.server.types.DirectoryException;
import org.opends.server.types.Entry;
import org.opends.server.types.IndexType;
import org.opends.server.types.InitializationException;
import org.opends.server.types.LDIFExportConfig;
import org.opends.server.types.LDIFImportConfig;
import org.opends.server.types.LDIFImportResult;
import org.opends.server.types.RestoreConfig;
import org.opends.server.types.SearchFilter;
import org.opends.server.util.LDIFException;
import org.opends.server.util.LDIFReader;
import org.opends.server.util.LDIFWriter;

/**
 * This class defines a very simple backend that stores its information in
 * memory.  This is primarily intended for testing purposes with small data
 * sets, as it does not have any indexing mechanism such as would be required to
 * achieve high performance with large data sets.  It is also heavily
 * synchronized for simplicity at the expense of performance, rather than
 * providing a more fine-grained locking mechanism.
 * <BR><BR>
 * Entries stored in this backend are held in a
 * <CODE>LinkedHashMap&lt;DN,Entry&gt;</CODE> object, which ensures that the
 * order in which you iterate over the entries is the same as the order in which
 * they were inserted.  By combining this with the constraint that no entry can
 * be added before its parent, you can ensure that iterating through the entries
 * will always process the parent entries before their children, which is
 * important for both search result processing and LDIF exports.
 * <BR><BR>
 * As mentioned above, no data indexing is performed, so all non-baseObject
 * searches require iteration through the entire data set.  If this is to become
 * a more general-purpose backend, then additional
 * <CODE>HashMap&lt;ByteString,Set&lt;DN&gt;&gt;</CODE> objects could be used
 * to provide that capability.
 * <BR><BR>
 * There is actually one index that does get maintained within this backend,
 * which is a mapping between the DN of an entry and the DNs of any immediate
 * children of that entry.  This is needed to efficiently determine whether an
 * entry has any children (which must not be the case for delete operations).
 */
public class MemoryBackend
       extends Backend<MemoryBackendCfg>
{
  private static final LocalizedLogger logger = LocalizedLogger.getLoggerForThisClass();



  /** The base DNs for this backend. */
  private DN[] baseDNs;

  /** The mapping between parent DNs and their immediate children. */
  private HashMap<DN,HashSet<DN>> childDNs;

  /** The base DNs for this backend, in a hash set. */
  private HashSet<DN> baseDNSet;

  /** The set of supported controls for this backend. */
  private final Set<String> supportedControls =
      Collections.singleton(OID_SUBTREE_DELETE_CONTROL);

  /** The mapping between entry DNs and the corresponding entries. */
  private LinkedHashMap<DN,Entry> entryMap;



  /**
   * Creates a new backend with the provided information.  All backend
   * implementations must implement a default constructor that use
   * <CODE>super()</CODE> to invoke this constructor.
   */
  public MemoryBackend()
  {
    super();

    // Perform all initialization in initializeBackend.
  }


  /**
   * Set the base DNs for this backend.  This is used by the unit tests
   * to set the base DNs without having to provide a configuration
   * object when initializing the backend.
   * @param baseDNs The set of base DNs to be served by this memory backend.
   */
  public void setBaseDNs(DN[] baseDNs)
  {
    this.baseDNs = baseDNs;
  }

  /** {@inheritDoc} */
  @Override
  public void configureBackend(MemoryBackendCfg config, ServerContext serverContext) throws ConfigException
  {
    if (config != null)
    {
      MemoryBackendCfg cfg = config;
      DN[] baseDNs = new DN[cfg.getBaseDN().size()];
      cfg.getBaseDN().toArray(baseDNs);
      setBaseDNs(baseDNs);
    }
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void openBackend()
       throws ConfigException, InitializationException
  {
    // We won't support anything other than exactly one base DN in this
    // implementation.  If we were to add such support in the future, we would
    // likely want to separate the data for each base DN into a separate entry
    // map.
    if (baseDNs == null || baseDNs.length != 1)
    {
      LocalizableMessage message = ERR_MEMORYBACKEND_REQUIRE_EXACTLY_ONE_BASE.get();
      throw new ConfigException(message);
    }

    baseDNSet = new HashSet<>();
    Collections.addAll(baseDNSet, baseDNs);

    entryMap = new LinkedHashMap<>();
    childDNs = new HashMap<>();

    for (DN dn : baseDNs)
    {
      try
      {
        DirectoryServer.registerBaseDN(dn, this, false);
      }
      catch (Exception e)
      {
        logger.traceException(e);

        LocalizableMessage message = ERR_BACKEND_CANNOT_REGISTER_BASEDN.get(
            dn, getExceptionMessage(e));
        throw new InitializationException(message, e);
      }
    }
  }



  /**
   * Removes any data that may have been stored in this backend.
   */
  public synchronized void clearMemoryBackend()
  {
    entryMap.clear();
    childDNs.clear();
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void closeBackend()
  {
    clearMemoryBackend();

    for (DN dn : baseDNs)
    {
      try
      {
        DirectoryServer.deregisterBaseDN(dn);
      }
      catch (Exception e)
      {
        logger.traceException(e);
      }
    }
  }

  /** {@inheritDoc} */
  @Override
  public DN[] getBaseDNs()
  {
    return baseDNs;
  }

  /** {@inheritDoc} */
  @Override
  public synchronized long getEntryCount()
  {
    if (entryMap != null)
    {
      return entryMap.size();
    }

    return -1;
  }

  /** {@inheritDoc} */
  @Override
  public boolean isIndexed(AttributeType attributeType, IndexType indexType)
  {
    // All searches in this backend will always be considered indexed.
    return true;
  }

  /** {@inheritDoc} */
  @Override
  public synchronized ConditionResult hasSubordinates(DN entryDN)
         throws DirectoryException
  {
    long ret = getNumberOfSubordinates(entryDN, false);
    if(ret < 0)
    {
      return ConditionResult.UNDEFINED;
    }
    return ConditionResult.valueOf(ret != 0);
  }

  /** {@inheritDoc} */
  @Override
  public long getNumberOfEntriesInBaseDN(DN baseDN) throws DirectoryException {
    checkNotNull(baseDN, "baseDN must not be null");
    return getNumberOfSubordinates(baseDN, true) + 1;
  }

  /** {@inheritDoc} */
  @Override
  public long getNumberOfChildren(DN parentDN) throws DirectoryException {
    checkNotNull(parentDN, "parentDN must not be null");
    return getNumberOfSubordinates(parentDN, false);
  }

  private synchronized long getNumberOfSubordinates(DN entryDN, boolean includeSubtree) throws DirectoryException
  {
    // Try to look up the immediate children for the DN
    final Set<DN> children = childDNs.get(entryDN);
    if (children == null)
    {
      if(entryMap.get(entryDN) != null)
      {
        // The entry does exist but just no children.
        return 0;
      }
      return -1;
    }

    if(!includeSubtree)
    {
      return children.size();
    }
    long count = 0;
    for (DN child : children)
    {
      count += getNumberOfSubordinates(child, true);
      count++;
    }
    return count;
  }

  /** {@inheritDoc} */
  @Override
  public synchronized Entry getEntry(DN entryDN)
  {
    Entry entry = entryMap.get(entryDN);
    if (entry != null)
    {
      entry = entry.duplicate(true);
    }

    return entry;
  }

  /** {@inheritDoc} */
  @Override
  public synchronized boolean entryExists(DN entryDN)
  {
    return entryMap.containsKey(entryDN);
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void addEntry(Entry entry, AddOperation addOperation)
         throws DirectoryException
  {
    Entry e = entry.duplicate(false);

    // See if the target entry already exists.  If so, then fail.
    DN entryDN = e.getName();
    if (entryMap.containsKey(entryDN))
    {
      throw new DirectoryException(ResultCode.ENTRY_ALREADY_EXISTS,
          ERR_MEMORYBACKEND_ENTRY_ALREADY_EXISTS.get(entryDN));
    }


    // If the entry is one of the base DNs, then add it.
    if (baseDNSet.contains(entryDN))
    {
      entryMap.put(entryDN, e);
      return;
    }


    // Get the parent DN and ensure that it exists in the backend.
    DN parentDN = DirectoryServer.getParentDNInSuffix(entryDN);
    if (parentDN == null)
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_MEMORYBACKEND_ENTRY_DOESNT_BELONG.get(entryDN));
    }
    else if (! entryMap.containsKey(parentDN))
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_MEMORYBACKEND_PARENT_DOESNT_EXIST.get(entryDN, parentDN));
    }

    entryMap.put(entryDN, e);
    HashSet<DN> children = childDNs.get(parentDN);
    if (children == null)
    {
      children = new HashSet<>();
      childDNs.put(parentDN, children);
    }

    children.add(entryDN);
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void deleteEntry(DN entryDN,
                                       DeleteOperation deleteOperation)
         throws DirectoryException
  {
    // Make sure the entry exists.  If not, then throw an exception.
    if (! entryMap.containsKey(entryDN))
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_BACKEND_ENTRY_DOESNT_EXIST.get(entryDN, getBackendID()));
    }


    // Check to see if the entry contains a subtree delete control.
    boolean subtreeDelete = deleteOperation != null
        && deleteOperation.getRequestControl(SubtreeDeleteControl.DECODER) != null;

    HashSet<DN> children = childDNs.get(entryDN);
    if (subtreeDelete)
    {
      if (children != null)
      {
        HashSet<DN> childrenCopy = new HashSet<>(children);
        for (DN childDN : childrenCopy)
        {
          try
          {
            deleteEntry(childDN, null);
          }
          catch (Exception e)
          {
            // This shouldn't happen, but we want the delete to continue anyway
            // so just ignore it if it does for some reason.
            logger.traceException(e);
          }
        }
      }
    }
    else
    {
      // Make sure the entry doesn't have any children.  If it does, then throw
      // an exception.
      if (children != null && !children.isEmpty())
      {
        throw new DirectoryException(ResultCode.NOT_ALLOWED_ON_NONLEAF,
            ERR_MEMORYBACKEND_CANNOT_DELETE_ENTRY_WITH_CHILDREN.get(entryDN));
      }
    }


    // Remove the entry from the backend.  Also remove the reference to it from
    // its parent, if applicable.
    childDNs.remove(entryDN);
    entryMap.remove(entryDN);

    DN parentDN = DirectoryServer.getParentDNInSuffix(entryDN);
    if (parentDN != null)
    {
      HashSet<DN> parentsChildren = childDNs.get(parentDN);
      if (parentsChildren != null)
      {
        parentsChildren.remove(entryDN);
        if (parentsChildren.isEmpty())
        {
          childDNs.remove(parentDN);
        }
      }
    }
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void replaceEntry(Entry oldEntry, Entry newEntry,
      ModifyOperation modifyOperation) throws DirectoryException
  {
    Entry e = newEntry.duplicate(false);

    // Make sure the entry exists.  If not, then throw an exception.
    DN entryDN = e.getName();
    if (! entryMap.containsKey(entryDN))
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_BACKEND_ENTRY_DOESNT_EXIST.get(entryDN, getBackendID()));
    }


    // Replace the old entry with the new one.
    entryMap.put(entryDN, e);
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void renameEntry(DN currentDN, Entry entry,
                                       ModifyDNOperation modifyDNOperation)
         throws DirectoryException
  {
    Entry e = entry.duplicate(false);

    // Make sure that the target entry exists.
    if (! entryMap.containsKey(currentDN))
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_BACKEND_ENTRY_DOESNT_EXIST.get(currentDN, getBackendID()));
    }


    // Make sure that the target entry doesn't have any children.
    HashSet<DN> children  = childDNs.get(currentDN);
    if (children != null)
    {
      if (children.isEmpty())
      {
        childDNs.remove(currentDN);
      }
      else
      {
        throw new DirectoryException(ResultCode.NOT_ALLOWED_ON_NONLEAF,
            ERR_MEMORYBACKEND_CANNOT_RENAME_ENRY_WITH_CHILDREN.get(currentDN));
      }
    }


    // Make sure that no entry exists with the new DN.
    if (entryMap.containsKey(e.getName()))
    {
      throw new DirectoryException(ResultCode.ENTRY_ALREADY_EXISTS,
          ERR_MEMORYBACKEND_ENTRY_ALREADY_EXISTS.get(e.getName()));
    }


    // Make sure that the new DN is in this backend.
    boolean matchFound = false;
    for (DN dn : baseDNs)
    {
      if (dn.isSuperiorOrEqualTo(e.getName()))
      {
        matchFound = true;
        break;
      }
    }

    if (! matchFound)
    {
      throw new DirectoryException(ResultCode.UNWILLING_TO_PERFORM,
          ERR_MEMORYBACKEND_CANNOT_RENAME_TO_ANOTHER_BACKEND.get(currentDN));
    }


    // Make sure that the parent of the new entry exists.
    DN parentDN = DirectoryServer.getParentDNInSuffix(e.getName());
    if (parentDN == null || !entryMap.containsKey(parentDN))
    {
      throw new DirectoryException(ResultCode.NO_SUCH_OBJECT,
          ERR_MEMORYBACKEND_RENAME_PARENT_DOESNT_EXIST.get(currentDN, parentDN));
    }


    // Delete the current entry and add the new one.
    deleteEntry(currentDN, null);
    addEntry(e, null);
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void search(SearchOperation searchOperation)
         throws DirectoryException
  {
    // Get the base DN, scope, and filter for the search.
    DN           baseDN = searchOperation.getBaseDN();
    SearchScope  scope  = searchOperation.getScope();
    SearchFilter filter = searchOperation.getFilter();


    // Make sure the base entry exists if it's supposed to be in this backend.
    Entry baseEntry = entryMap.get(baseDN);
    if (baseEntry == null && handlesEntry(baseDN))
    {
      DN matchedDN = DirectoryServer.getParentDNInSuffix(baseDN);
      while (matchedDN != null)
      {
        if (entryMap.containsKey(matchedDN))
        {
          break;
        }

        matchedDN = DirectoryServer.getParentDNInSuffix(matchedDN);
      }

      LocalizableMessage message =
          ERR_BACKEND_ENTRY_DOESNT_EXIST.get(baseDN, getBackendID());
      throw new DirectoryException(
              ResultCode.NO_SUCH_OBJECT, message, matchedDN, null);
    }

    if (baseEntry != null)
    {
      baseEntry = baseEntry.duplicate(true);
    }


    // If it's a base-level search, then just get that entry and return it if it
    // matches the filter.
    if (scope == SearchScope.BASE_OBJECT)
    {
      if (filter.matchesEntry(baseEntry))
      {
        searchOperation.returnEntry(baseEntry, new LinkedList<Control>());
      }
    }
    else
    {
      // Walk through all entries and send the ones that match.
      for (Entry e : entryMap.values())
      {
        e = e.duplicate(true);
        if (e.matchesBaseAndScope(baseDN, scope) && filter.matchesEntry(e))
        {
          searchOperation.returnEntry(e, new LinkedList<Control>());
        }
      }
    }
  }

  /** {@inheritDoc} */
  @Override
  public Set<String> getSupportedControls()
  {
    return supportedControls;
  }

  /** {@inheritDoc} */
  @Override
  public Set<String> getSupportedFeatures()
  {
    return Collections.emptySet();
  }

  /** {@inheritDoc} */
  @Override
  public boolean supports(BackendOperation backendOperation)
  {
    switch (backendOperation)
    {
    case LDIF_EXPORT:
    case LDIF_IMPORT:
      return true;

    default:
      return false;
    }
  }

  /** {@inheritDoc} */
  @Override
  public synchronized void exportLDIF(LDIFExportConfig exportConfig)
         throws DirectoryException
  {
    // Create the LDIF writer.
    LDIFWriter ldifWriter;
    try
    {
      ldifWriter = new LDIFWriter(exportConfig);
    }
    catch (Exception e)
    {
      logger.traceException(e);

      throw new DirectoryException(DirectoryServer.getServerErrorResultCode(),
          ERR_MEMORYBACKEND_CANNOT_CREATE_LDIF_WRITER.get(e), e);
    }


    // Walk through all the entries and write them to LDIF.
    DN entryDN = null;
    try
    {
      for (Entry entry : entryMap.values())
      {
        entryDN = entry.getName();
        ldifWriter.writeEntry(entry);
      }
    }
    catch (Exception e)
    {
      throw new DirectoryException(DirectoryServer.getServerErrorResultCode(),
          ERR_MEMORYBACKEND_CANNOT_WRITE_ENTRY_TO_LDIF.get(entryDN, e), e);
    }
    finally
    {
      close(ldifWriter);
    }
  }

  /** {@inheritDoc} */
  @Override
  public synchronized LDIFImportResult importLDIF(LDIFImportConfig importConfig, ServerContext serverContext)
      throws DirectoryException
  {
    clearMemoryBackend();

    LDIFReader reader;
    try
    {
      reader = new LDIFReader(importConfig);
    }
    catch (Exception e)
    {
      throw new DirectoryException(DirectoryServer.getServerErrorResultCode(),
          ERR_MEMORYBACKEND_CANNOT_CREATE_LDIF_READER.get(e), e);
    }


    try
    {
      while (true)
      {
        Entry e = null;
        try
        {
          e = reader.readEntry();
          if (e == null)
          {
            break;
          }
        }
        catch (LDIFException le)
        {
          if (! le.canContinueReading())
          {
            throw new DirectoryException(DirectoryServer.getServerErrorResultCode(),
                ERR_MEMORYBACKEND_ERROR_READING_LDIF.get(e), le);
          }
          else
          {
            continue;
          }
        }

        try
        {
          addEntry(e, null);
        }
        catch (DirectoryException de)
        {
          reader.rejectLastEntry(de.getMessageObject());
        }
      }

      return new LDIFImportResult(reader.getEntriesRead(),
                                  reader.getEntriesRejected(),
                                  reader.getEntriesIgnored());
    }
    catch (DirectoryException de)
    {
      throw de;
    }
    catch (Exception e)
    {
      throw new DirectoryException(DirectoryServer.getServerErrorResultCode(),
          ERR_MEMORYBACKEND_ERROR_DURING_IMPORT.get(e), e);
    }
    finally
    {
      reader.close();
    }
  }

  /** {@inheritDoc} */
  @Override
  public void createBackup(BackupConfig backupConfig)
         throws DirectoryException
  {
    LocalizableMessage message = ERR_MEMORYBACKEND_BACKUP_RESTORE_NOT_SUPPORTED.get();
    throw new DirectoryException(ResultCode.UNWILLING_TO_PERFORM, message);
  }

  /** {@inheritDoc} */
  @Override
  public void removeBackup(BackupDirectory backupDirectory,
                           String backupID)
         throws DirectoryException
  {
    LocalizableMessage message = ERR_MEMORYBACKEND_BACKUP_RESTORE_NOT_SUPPORTED.get();
    throw new DirectoryException(ResultCode.UNWILLING_TO_PERFORM, message);
  }

  /** {@inheritDoc} */
  @Override
  public void restoreBackup(RestoreConfig restoreConfig)
         throws DirectoryException
  {
    LocalizableMessage message = ERR_MEMORYBACKEND_BACKUP_RESTORE_NOT_SUPPORTED.get();
    throw new DirectoryException(ResultCode.UNWILLING_TO_PERFORM, message);
  }
}