/*
 *  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.referral;


import java.util.HashSet;
import java.util.Set;

import javax.naming.InvalidNameException;

import org.apache.directory.shared.ldap.name.LdapDN;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * A simple lookup table of normalized referral distinguished names.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 * @version $Rev$
 */
public class ReferralLut
{
    /** the logger for this class */
    private static final Logger log = LoggerFactory.getLogger( ReferralLut.class );
    
    /** the set of names in the LUT */
    private Set<String> names = new HashSet<String>();


    // -----------------------------------------------------------------------
    // Methods to access the LUT: all names are expected to be normalized
    // -----------------------------------------------------------------------

    /**
     * Checks if a the entry at a name is a referral.
     * 
     * @param dn the normalized name of the referral
     */
    public boolean isReferral( LdapDN dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        return names.contains( dn.getNormName() );
    }


    /**
     * Checks if a the entry at a name is a referral.
     * 
     * @param dn the normalized name of the referral
     */
    public boolean isReferral( String dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        return names.contains( dn );
    }


    /**
     * Gets the normalized name of the farthest ancestor that is a referral. If the argument 
     * is a referral it will not be returned.  Only ancestor's (includes parent) are considered.
     * 
     * @param dn the name to get the farthest ancestor referral name for
     * @return the farthest referral ancestor
     */
    public LdapDN getFarthestReferralAncestor( LdapDN dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        LdapDN farthest = new LdapDN();
        
        for ( int ii = 0; ii < dn.size(); ii++ )
        {
            farthest.addNormalized( dn.getRdn( ii ) );

            // do not return dn if it is the farthest referral
            if ( isReferral( farthest ) && ( farthest.size() != dn.size() ) )
            {
                return farthest;
            }
        }
        
        return null;
    }


    /**
     * Gets the normalized name of the nearest ancestor that is a referral.  If the argument
     * is a referral it will not be returned.  Only ancestor's (includes parent) are considered.
     * 
     * @param dn the name to get the nearest ancestor referral name for
     * @return the nearest referral ancestor or null if one does not exist
     */
    public LdapDN getNearestReferralAncestor( LdapDN dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        LdapDN cloned = ( LdapDN ) dn.clone();

        // do not return the argument dn if it is a referral (skip it)
        if ( cloned.size() > 0 )
        {
            try
            {
                cloned.remove( cloned.size() - 1 );
            }
            catch ( InvalidNameException e )
            {
                log.error( "Should never get this when removing from a cloned normalized name!", e );
            }
        }
        else
        {
            return null;
        }

        while ( !isReferral( cloned ) && ( cloned.size() > 0 ) )
        {
            try
            {
                cloned.remove( cloned.size() - 1 );
            }
            catch ( InvalidNameException e )
            {
                log.error( "Should never get this when removing from a cloned normalized name!", e );
            }
        }
        
        return cloned.isEmpty() ? null : cloned;
    }


    // -----------------------------------------------------------------------
    // Methods that notify this lookup table of changes to referrals
    // -----------------------------------------------------------------------

    /**
     * Called to add an entry to the LUT when a referral is added.
     * 
     * @param dn the normalized name of the added referral
     */
    public void referralAdded( LdapDN dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        if ( !names.add( dn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "found " + dn.getUpName() + " in refname lut while adding it" );
        }
    }


    /**
     * Called to add an entry to the LUT when a referral is added.
     * 
     * @param dn the normalized name of the added referral
     */
    public void referralAdded( String dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        if ( !names.add( dn ) && log.isWarnEnabled() )
        {
            log.warn( "found " + dn + " in refname lut while adding it" );
        }
    }


    /**
     * Called delete an entry from the LUT when a referral is deleted.
     * 
     * @param dn the normalized name of the deleted referral
     */
    public void referralDeleted( LdapDN dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        if ( !names.remove( dn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find " + dn.getUpName() + " in refname lut while deleting it" );
        }
    }


    /**
     * Called delete an entry from the LUT when a referral is deleted.
     * 
     * @param dn the normalized name of the deleted referral
     */
    public void referralDeleted( String dn )
    {
        if ( dn == null )
        {
            throw new IllegalArgumentException( "dn cannot be null" );
        }
        
        if ( !names.remove( dn ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find " + dn + " in refname lut while deleting it" );
        }
    }


    /**
     * Called to update the LUT when the name of the referral changes due to 
     * a rename or move in the DIT.
     * 
     * @param oldDn the normalized old name for the referral
     * @param newDn the normalized new name for the referral
     */
    public void referralChanged( LdapDN oldDn, LdapDN newDn )
    {
        if ( ( oldDn == null ) || ( newDn == null ) )
        {
            throw new IllegalArgumentException( "old or new dn cannot be null" );
        }
        
        if ( !names.remove( oldDn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find old name (" + oldDn.getUpName() + ") in refname lut while moving or renaming it" );
        }

        if ( !names.add( newDn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "found new name (" + newDn.getUpName() + ") in refname lut while moving or renaming " + oldDn );
        }
    }


    /**
     * Called to update the LUT when the name of the referral changes due to 
     * a rename or move in the DIT.
     * 
     * @param oldDn the normalized old name for the referral
     * @param newDn the normalized new name for the referral
     */
    public void referralChanged( String oldDn, String newDn )
    {
        if ( ( oldDn == null ) || ( newDn == null ) )
        {
            throw new IllegalArgumentException( "old or new dn cannot be null" );
        }

        if ( !names.remove( oldDn ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find old name (" + oldDn + ") in refname lut while moving or renaming it" );
        }

        if ( !names.add( newDn ) && log.isWarnEnabled() )
        {
            log.warn( "found new name (" + newDn + ") in refname lut while moving or renaming " + oldDn );
        }
    }


    /**
     * Called to update the LUT when the name of the referral changes due to 
     * a rename or move in the DIT.
     * 
     * @param oldDn the normalized old name for the referral
     * @param newDn the normalized new name for the referral
     */
    public void referralChanged( LdapDN oldDn, String newDn )
    {
        if ( ( oldDn == null ) || ( newDn == null ) )
        {
            throw new IllegalArgumentException( "old or new dn cannot be null" );
        }

        if ( !names.remove( oldDn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find old name (" + oldDn.getUpName() + ") in refname lut while moving or renaming it" );
        }
        
        if ( !names.add( newDn ) && log.isWarnEnabled() )
        {
            log.warn( "found new name (" + newDn + ") in refname lut while moving or renaming " + oldDn );
        }
    }


    /**
     * Called to update the LUT when the name of the referral changes due to 
     * a rename or move in the DIT.
     * 
     * @param oldDn the normalized old name for the referral
     * @param newDn the normalized new name for the referral
     */
    public void referralChanged( String oldDn, LdapDN newDn )
    {
        if ( ( oldDn == null ) || ( newDn == null ) )
        {
            throw new IllegalArgumentException( "old or new dn cannot be null" );
        }
        
        if ( !names.remove( oldDn ) && log.isWarnEnabled() )
        {
            log.warn( "cound not find old name (" + oldDn + ") in refname lut while moving or renaming it" );
        }
        
        if ( !names.add( newDn.getNormName() ) && log.isWarnEnabled() )
        {
            log.warn( "found new name (" + newDn.getUpName() + ") in refname lut while moving or renaming " + oldDn );
        }
    }
}