/*
 *  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.event;


import static org.apache.directory.api.ldap.model.message.SearchScope.OBJECT;
import static org.apache.directory.api.ldap.model.message.SearchScope.ONELEVEL;
import static org.apache.directory.api.ldap.model.message.SearchScope.SUBTREE;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.apache.directory.api.ldap.model.constants.SchemaConstants;
import org.apache.directory.api.ldap.model.entry.Entry;
import org.apache.directory.api.ldap.model.exception.LdapException;
import org.apache.directory.api.ldap.model.message.SearchScope;
import org.apache.directory.api.ldap.model.name.Dn;
import org.apache.directory.server.core.api.CoreSession;
import org.apache.directory.server.core.api.DirectoryService;
import org.apache.directory.server.core.api.InterceptorEnum;
import org.apache.directory.server.core.api.entry.ClonedServerEntry;
import org.apache.directory.server.core.api.event.DirectoryListener;
import org.apache.directory.server.core.api.event.Evaluator;
import org.apache.directory.server.core.api.event.EventType;
import org.apache.directory.server.core.api.event.ExpressionEvaluator;
import org.apache.directory.server.core.api.event.NotificationCriteria;
import org.apache.directory.server.core.api.event.RegistrationEntry;
import org.apache.directory.server.core.api.interceptor.BaseInterceptor;
import org.apache.directory.server.core.api.interceptor.context.AddOperationContext;
import org.apache.directory.server.core.api.interceptor.context.DeleteOperationContext;
import org.apache.directory.server.core.api.interceptor.context.LookupOperationContext;
import org.apache.directory.server.core.api.interceptor.context.ModifyOperationContext;
import org.apache.directory.server.core.api.interceptor.context.MoveAndRenameOperationContext;
import org.apache.directory.server.core.api.interceptor.context.MoveOperationContext;
import org.apache.directory.server.core.api.interceptor.context.OperationContext;
import org.apache.directory.server.core.api.interceptor.context.RenameOperationContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An {@link org.apache.directory.server.core.api.interceptor.Interceptor} based service for notifying {@link
 * DirectoryListener}s of changes to the DIT.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class EventInterceptor extends BaseInterceptor
{
    /** A logger for this class */
    private static final Logger LOG = LoggerFactory.getLogger( EventInterceptor.class );

    private Evaluator evaluator;
    private ExecutorService executor;


    /**
     * Creates a new instance of a EventInterceptor.
     */
    public EventInterceptor()
    {
        super( InterceptorEnum.EVENT_INTERCEPTOR );
    }


    /**
     * Initialize the event interceptor. It creates a pool of executor which will be used
     * to call the listeners in separate threads.
     */
    public void init( DirectoryService directoryService ) throws LdapException
    {
        LOG.info( "Initializing ..." );
        super.init( directoryService );

        evaluator = new ExpressionEvaluator( schemaManager );
        
        ThreadFactory threadFactory = new ThreadFactory() 
        {
            @Override
            public Thread newThread( Runnable runnable ) 
            {
                Thread newThread = Executors.defaultThreadFactory().newThread( runnable );
                newThread.setDaemon( true );
                
                return newThread;
            }
        };
        
        executor = new ThreadPoolExecutor( 1, 10, 1000, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>( 100 ),
            threadFactory );

        this.directoryService.setEventService( new DefaultEventService( directoryService ) );
        LOG.info( "Initialization complete." );
    }


    /**
     * Call the listener passing it the context.
     */
    private void fire( final OperationContext opContext, EventType type, final DirectoryListener listener )
    {
        switch ( type )
        {
            case ADD:
                if ( listener.isSynchronous() )
                {
                    listener.entryAdded( ( AddOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryAdded( ( AddOperationContext ) opContext );
                        }
                    } );
                }

                break;

            case DELETE:
                if ( listener.isSynchronous() )
                {
                    listener.entryDeleted( ( DeleteOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryDeleted( ( DeleteOperationContext ) opContext );
                        }
                    } );
                }

                break;

            case MODIFY:
                if ( listener.isSynchronous() )
                {
                    listener.entryModified( ( ModifyOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryModified( ( ModifyOperationContext ) opContext );
                        }
                    } );
                }

                break;

            case MOVE:
                if ( listener.isSynchronous() )
                {
                    listener.entryMoved( ( MoveOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryMoved( ( MoveOperationContext ) opContext );
                        }
                    } );
                }

                break;

            case RENAME:
                if ( listener.isSynchronous() )
                {
                    listener.entryRenamed( ( RenameOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryRenamed( ( RenameOperationContext ) opContext );
                        }
                    } );
                }

                break;

            case MOVE_AND_RENAME:
                if ( listener.isSynchronous() )
                {
                    listener.entryMovedAndRenamed( ( MoveAndRenameOperationContext ) opContext );
                }
                else
                {
                    executor.execute( new Runnable()
                    {
                        public void run()
                        {
                            listener.entryMovedAndRenamed( ( MoveAndRenameOperationContext ) opContext );
                        }
                    } );
                }

                break;

            default:
                throw new IllegalArgumentException( "Unexpected event type " + type );
        }
    }


    /**
     * {@inheritDoc}
     */
    public void add( final AddOperationContext addContext ) throws LdapException
    {
        next( addContext );

        List<RegistrationEntry> selecting = getSelectingRegistrations( addContext.getDn(), addContext.getEntry() );

        if ( selecting.isEmpty() )
        {
            return;
        }

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isAdd( registration.getCriteria().getEventMask() ) )
            {
                fire( addContext, EventType.ADD, registration.getListener() );
            }
        }
    }


    /**
     * {@inheritDoc}
     */
    public void delete( final DeleteOperationContext deleteContext ) throws LdapException
    {
        next( deleteContext );

        List<RegistrationEntry> selecting = getSelectingRegistrations( deleteContext.getDn(), deleteContext.getEntry() );

        if ( selecting.isEmpty() )
        {
            return;
        }

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isDelete( registration.getCriteria().getEventMask() ) )
            {
                fire( deleteContext, EventType.DELETE, registration.getListener() );
            }
        }
    }


    /**
     * {@inheritDoc}
     */
    public void modify( final ModifyOperationContext modifyContext ) throws LdapException
    {
        Entry oriEntry = modifyContext.getEntry();

        // modification was already done when this flag is turned on, move to sending the events
        if ( !modifyContext.isPushToEvtInterceptor() )
        {
            next( modifyContext );
        }

        List<RegistrationEntry> selecting = getSelectingRegistrations( modifyContext.getDn(), oriEntry );

        if ( selecting.isEmpty() )
        {
            return;
        }

        // Get the modified entry
        CoreSession session = modifyContext.getSession();
        LookupOperationContext lookupContext = new LookupOperationContext( session, modifyContext.getDn(),
            SchemaConstants.ALL_ATTRIBUTES_ARRAY );

        Entry alteredEntry = directoryService.getPartitionNexus().lookup( lookupContext );
        modifyContext.setAlteredEntry( alteredEntry );

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isModify( registration.getCriteria().getEventMask() ) )
            {
                fire( modifyContext, EventType.MODIFY, registration.getListener() );
            }
        }
    }


    /**
     * {@inheritDoc}
     */
    public void move( MoveOperationContext moveContext ) throws LdapException
    {
        Entry oriEntry = moveContext.getOriginalEntry();

        next( moveContext );

        List<RegistrationEntry> selecting = getSelectingRegistrations( moveContext.getDn(), oriEntry );

        if ( selecting.isEmpty() )
        {
            return;
        }

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isMove( registration.getCriteria().getEventMask() ) )
            {
                fire( moveContext, EventType.MOVE, registration.getListener() );
            }
        }
    }


    /**
     * {@inheritDoc}
     */
    public void moveAndRename( final MoveAndRenameOperationContext moveAndRenameContext ) throws LdapException
    {
        Entry oriEntry = moveAndRenameContext.getOriginalEntry();
        next( moveAndRenameContext );

        List<RegistrationEntry> selecting = getSelectingRegistrations( moveAndRenameContext.getDn(), oriEntry );

        if ( selecting.isEmpty() )
        {
            return;
        }

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isMoveAndRename( registration.getCriteria().getEventMask() ) )
            {
                fire( moveAndRenameContext, EventType.MOVE_AND_RENAME, registration.getListener() );
            }
        }
    }


    /**
     * {@inheritDoc}
     */
    public void rename( RenameOperationContext renameContext ) throws LdapException
    {
        Entry oriEntry = ( ( ClonedServerEntry ) renameContext.getEntry() ).getOriginalEntry();

        next( renameContext );

        List<RegistrationEntry> selecting = getSelectingRegistrations( renameContext.getDn(), oriEntry );

        if ( selecting.isEmpty() )
        {
            return;
        }

        // Get the modified entry
        CoreSession session = renameContext.getSession();
        LookupOperationContext lookupContext = new LookupOperationContext( session, renameContext.getNewDn(),
            SchemaConstants.ALL_ATTRIBUTES_ARRAY );

        Entry alteredEntry = directoryService.getPartitionNexus().lookup( lookupContext );
        renameContext.setModifiedEntry( alteredEntry );

        for ( final RegistrationEntry registration : selecting )
        {
            if ( EventType.isRename( registration.getCriteria().getEventMask() ) )
            {
                fire( renameContext, EventType.RENAME, registration.getListener() );
            }
        }
    }


    /**
     * Find a list of registrationEntries given an entry and a name. We check against
     * the criteria for each registrationEntry
     */
    private List<RegistrationEntry> getSelectingRegistrations( Dn name, Entry entry ) throws LdapException
    {
        List<RegistrationEntry> registrations = directoryService.getEventService().getRegistrationEntries();

        if ( registrations.isEmpty() )
        {
            return Collections.emptyList();
        }

        List<RegistrationEntry> selecting = new ArrayList<RegistrationEntry>();

        for ( RegistrationEntry registration : registrations )
        {
            NotificationCriteria criteria = registration.getCriteria();

            Dn base = criteria.getBase();

            SearchScope scope = criteria.getScope();
            
            boolean inscope = false;
            
            // fix for DIRSERVER-1502
            if ( ( scope == OBJECT ) && name.equals( base ) )
            {
                inscope = true;
            }
            else if ( ( scope == ONELEVEL ) && name.getParent().equals( base ) )
            {
                inscope = true;
            }
            else if ( ( scope == SUBTREE ) && ( name.isDescendantOf( base ) || name.equals( base ) ) )
            {
                inscope = true;
            } 
            
            if ( inscope && evaluator.evaluate( criteria.getFilter(), base, entry ) )
            {
                selecting.add( registration );
            }
        }

        return selecting;
    }

    
    /**
     * {@inheritDoc}
     */
    @Override
    public void destroy()
    {
       executor.shutdown();
    }
}
