/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *  
 *    http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License. 
 *  
 */

package org.apache.directory.server.core.trigger;

import org.apache.directory.server.constants.ApacheSchemaConstants;
import org.apache.directory.server.core.DirectoryService;
import org.apache.directory.server.core.entry.ServerEntry;
import org.apache.directory.server.core.entry.ServerSearchResult;
import org.apache.directory.server.core.interceptor.context.ModifyOperationContext;
import org.apache.directory.server.core.interceptor.context.SearchOperationContext;
import org.apache.directory.server.core.partition.PartitionNexus;
import org.apache.directory.server.schema.registries.AttributeTypeRegistry;
import org.apache.directory.server.schema.registries.Registries;
import org.apache.directory.shared.ldap.constants.SchemaConstants;
import org.apache.directory.shared.ldap.entry.EntryAttribute;
import org.apache.directory.shared.ldap.entry.Modification;
import org.apache.directory.shared.ldap.entry.Value;
import org.apache.directory.shared.ldap.filter.EqualityNode;
import org.apache.directory.shared.ldap.filter.ExprNode;
import org.apache.directory.shared.ldap.message.AliasDerefMode;
import org.apache.directory.shared.ldap.name.LdapDN;
import org.apache.directory.shared.ldap.schema.NormalizerMappingResolver;
import org.apache.directory.shared.ldap.schema.OidNormalizer;
import org.apache.directory.shared.ldap.trigger.TriggerSpecification;
import org.apache.directory.shared.ldap.trigger.TriggerSpecificationParser;
import org.apache.directory.shared.ldap.entry.client.ClientStringValue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.naming.NamingEnumeration;
import javax.naming.NamingException;
import javax.naming.directory.SearchControls;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


/**
 * A cache for Trigger Specifications which responds to specific events to
 * perform cache house keeping as trigger subentries are added, deleted
 * and modified.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 * @version $Rev:$
 */
public class TriggerSpecCache
{
    /** the attribute id for prescriptive trigger: prescriptiveTrigger */
    private static final String PRESCRIPTIVE_TRIGGER_ATTR = "prescriptiveTriggerSpecification";

    /** the logger for this class */
    private static final Logger LOG = LoggerFactory.getLogger( TriggerSpecCache.class );

    /** a map of strings to TriggerSpecification collections */
    private final Map<String, List<TriggerSpecification>> triggerSpecs = new HashMap<String, List<TriggerSpecification>>();
    /** a handle on the partition nexus */
    private final PartitionNexus nexus;
    /** a normalizing TriggerSpecification parser */
    private final TriggerSpecificationParser triggerSpecParser;


    /**
     * Creates a TriggerSpecification cache.
     *
     * @param directoryService the directory service core
     * @throws NamingException with problems initializing cache
     */
    public TriggerSpecCache( DirectoryService directoryService ) throws NamingException
    {
        this.nexus = directoryService.getPartitionNexus();
        final AttributeTypeRegistry registry = directoryService.getRegistries().getAttributeTypeRegistry();
        triggerSpecParser = new TriggerSpecificationParser( new NormalizerMappingResolver()
            {
                public Map<String, OidNormalizer> getNormalizerMapping() throws NamingException
                {
                    return registry.getNormalizerMapping();
                }
            });
        initialize( directoryService.getRegistries() );
    }


    private void initialize( Registries registries ) throws NamingException
    {
        // search all naming contexts for trigger subentenries
        // generate TriggerSpecification arrays for each subentry
        // add that subentry to the hash
        Iterator<String> suffixes = nexus.listSuffixes( null );
        
        while ( suffixes.hasNext() )
        {
            String suffix = suffixes.next();
            LdapDN baseDn = new LdapDN( suffix );
            ExprNode filter = new EqualityNode( SchemaConstants.OBJECT_CLASS_AT, 
                    new ClientStringValue( ApacheSchemaConstants.TRIGGER_EXECUTION_SUBENTRY_OC ) );
            SearchControls ctls = new SearchControls();
            ctls.setSearchScope( SearchControls.SUBTREE_SCOPE );
            NamingEnumeration<ServerSearchResult> results = 
                nexus.search( new SearchOperationContext( registries, baseDn, AliasDerefMode.DEREF_ALWAYS, filter, ctls ) );
            
            while ( results.hasMore() )
            {
                ServerSearchResult result = results.next();
                LdapDN subentryDn = result.getDn();
                ServerEntry resultEntry = result.getServerEntry();
                EntryAttribute triggerSpec = resultEntry.get( PRESCRIPTIVE_TRIGGER_ATTR );
                
                if ( triggerSpec == null )
                {
                    LOG.warn( "Found triggerExecutionSubentry '" + subentryDn + "' without any " + PRESCRIPTIVE_TRIGGER_ATTR );
                    continue;
                }

                LdapDN normSubentryName = subentryDn.normalize( registries.getAttributeTypeRegistry().getNormalizerMapping() );
                subentryAdded( normSubentryName, resultEntry );
            }
            
            results.close();
        }
    }


    private boolean hasPrescriptiveTrigger( ServerEntry entry ) throws NamingException
    {
        // only do something if the entry contains prescriptiveTrigger
        EntryAttribute triggerSpec = entry.get( PRESCRIPTIVE_TRIGGER_ATTR );

        return triggerSpec != null;
    }


    public void subentryAdded( LdapDN normName, ServerEntry entry ) throws NamingException
    {
        // only do something if the entry contains prescriptiveTrigger
        EntryAttribute triggerSpec = entry.get( PRESCRIPTIVE_TRIGGER_ATTR );
        
        if ( triggerSpec == null )
        {
            return;
        }
        
        List<TriggerSpecification> subentryTriggerSpecs = new ArrayList<TriggerSpecification>();
        
        for ( Value<?> value:triggerSpec )
        {
            TriggerSpecification item = null;

            try
            {
                item = triggerSpecParser.parse( ( String ) value.get() );
                subentryTriggerSpecs.add( item );
            }
            catch ( ParseException e )
            {
                String msg = "TriggerSpecification parser failure on '" + item + "'. Cannnot add Trigger Specificaitons to TriggerSpecCache.";
                LOG.error( msg, e );
            }
            
        }
        
        triggerSpecs.put( normName.toString(), subentryTriggerSpecs );
    }


    public void subentryDeleted( LdapDN normName, ServerEntry entry ) throws NamingException
    {
        if ( !hasPrescriptiveTrigger( entry ) )
        {
            return;
        }

        triggerSpecs.remove( normName.toString() );
    }


    public void subentryModified( ModifyOperationContext opContext, ServerEntry entry ) throws NamingException
    {
        if ( !hasPrescriptiveTrigger( entry ) )
        {
            return;
        }

        LdapDN normName = opContext.getDn();
        List<Modification> mods = opContext.getModItems();

        boolean isTriggerSpecModified = false;

        for ( Modification mod : mods )
        {
            isTriggerSpecModified |= mod.getAttribute().contains( PRESCRIPTIVE_TRIGGER_ATTR );
        }
        
        if ( isTriggerSpecModified )
        {
            subentryDeleted( normName, entry );
            subentryAdded( normName, entry );
        }
    }


    public List<TriggerSpecification> getSubentryTriggerSpecs( String subentryDn )
    {
        List<TriggerSpecification> subentryTriggerSpecs = triggerSpecs.get( subentryDn );
        if ( subentryTriggerSpecs == null )
        {
            return Collections.emptyList();
        }
        return Collections.unmodifiableList( subentryTriggerSpecs );
    }


    public void subentryRenamed( LdapDN oldName, LdapDN newName )
    {
        triggerSpecs.put( newName.toString(), triggerSpecs.remove( oldName.toString() ) );
    }
}