/*
 *  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.xdbm.search.impl;


import java.util.ArrayList;
import java.util.List;

import org.apache.directory.api.ldap.model.entry.Value;
import org.apache.directory.api.ldap.model.exception.LdapException;
import org.apache.directory.api.ldap.model.filter.*;
import org.apache.directory.api.ldap.model.schema.AttributeType;
import org.apache.directory.api.ldap.model.schema.SchemaManager;
import org.apache.directory.api.ldap.model.schema.normalizers.NameComponentNormalizer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * A filter visitor which normalizes leaf node values as it visits them.  It also removes
 * leaf nodes from branches whose attributeType is undefined.  It obviously cannot remove
 * a leaf node from a filter which is only a leaf node.  Checks to see if a filter is a
 * leaf node with undefined attributeTypes should be done outside this visitor.
 *
 * Since this visitor may remove filter nodes it may produce negative results on filters,
 * like NOT branch nodes without a child or AND and OR nodes with one or less children.  This
 * might make some partition implementations choke.  To avoid this problem we clean up branch
 * nodes that don't make sense.  For example all BranchNodes without children are just
 * removed.  An AND and OR BranchNode with a single child is replaced with it's child for
 * all but the topmost branchnode which we cannot replace.  So again the top most branch
 * node must be inspected by code outside of this visitor.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class FilterNormalizingVisitor implements FilterVisitor
{
    /** logger used by this class */
    private static final Logger log = LoggerFactory.getLogger( FilterNormalizingVisitor.class );

    /** the name component normalizer used by this visitor */
    private final NameComponentNormalizer ncn;

    /** the global schemaManager used to resolve OIDs for attributeType ids */
    private final SchemaManager schemaManager;

    /**
     * Chars which need to be escaped in a filter
     * '\0' | '(' | ')' | '*' | '\'
     */
    private static final boolean[] FILTER_CHAR =
        { true, false, false, false, false, false, false, false, // 00 -> 07 NULL
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 08 -> 0F
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 10 -> 17
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 18 -> 1F
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 20 -> 27
            true,
            true,
            true,
            false,
            false,
            false,
            false,
            false, // 28 -> 2F '(', ')', '*'
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 30 -> 37
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 38 -> 3F 
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 40 -> 47
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 48 -> 4F
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 50 -> 57
            false,
            false,
            false,
            false,
            true,
            false,
            false,
            false, // 58 -> 5F '\'
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 60 -> 67
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 68 -> 6F
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false, // 70 -> 77
            false,
            false,
            false,
            false,
            false,
            false,
            false,
            false // 78 -> 7F
    };


    /**
     * Check if the given char is a filter escaped char
     * &lt;filterEscapedChars&gt; ::= '\0' | '(' | ')' | '*' | '\'
     *
     * @param c the char we want to test
     * @return true if the char is a pair char only
     */
    public static boolean isFilterChar( char c )
    {
        return ( ( ( c | 0x7F ) == 0x7F ) && FILTER_CHAR[c & 0x7f] );
    }


    /**
     * 
     * Creates a new instance of NormalizingVisitor.
     *
     * @param ncn The name component normalizer to use
     * @param registries The global registries
     */
    public FilterNormalizingVisitor( NameComponentNormalizer ncn, SchemaManager schemaManager )
    {
        this.ncn = ncn;
        this.schemaManager = schemaManager;
    }


    /**
     * A private method used to normalize a value. At this point, the value
     * is a Value<byte[]>, we have to translate it to a Value<String> if its
     * AttributeType is H-R. Then we have to normalize the value accordingly
     * to the AttributeType Normalizer.
     * 
     * @param attribute The attribute's ID
     * @param value The value to normalize
     * @return the normalized value
     */
    private Value normalizeValue( String attribute, String value )
    {
        try
        {
            AttributeType attributeType = schemaManager.lookupAttributeTypeRegistry( attribute );

            return new Value( attributeType, value );
        }
        catch ( LdapException ne )
        {
            log.warn( "Failed to normalize filter value: {}", ne.getMessage(), ne );
            return null;
        }
    }


    /**
     * Visit a PresenceNode. If the attribute exists, the node is returned, otherwise
     * null is returned.
     * 
     * @param node the node to visit
     * @return The visited node
     */
    private ExprNode visitPresenceNode( PresenceNode node )
    {
        node.setAttributeType( node.getAttributeType() );
        return node;
    }


    /**
     * Visit a SimpleNode. If the attribute exists, the node is returned, otherwise
     * null is returned. SimpleNodes are :
     *  - ApproximateNode
     *  - EqualityNode
     *  - GreaterEqNode
     *  - LesserEqNode
     *  
     * @param node the node to visit
     * @return the visited node
     */
    private ExprNode visitSimpleNode( SimpleNode node )
    {
        // still need this check here in case the top level is a leaf node
        // with an undefined attributeType for its attribute
        if ( !ncn.isDefined( node.getAttribute() ) )
        {
            return null;
        }

        Value normalized;
        
        if ( node.getValue().isSchemaAware() )
        {
            normalized = node.getValue();
        }
        else
        {
            normalized = normalizeValue( node.getAttribute(), node.getValue().getString() );
        }

        if ( normalized == null )
        {
            return null;
        }

        node.setAttribute( node.getAttribute() );
        node.setValue( normalized );
        return node;
    }


    /**
     * Visit a SubstringNode. If the attribute exists, the node is returned, otherwise
     * null is returned. 
     * 
     * Normalizing substring value is pretty complex. It's not currently implemented...
     * 
     * @param node the node to visit
     * @return the visited node
     */
    private ExprNode visitSubstringNode( SubstringNode node )
    {
        // still need this check here in case the top level is a leaf node
        // with an undefined attributeType for its attribute
        if ( !ncn.isDefined( node.getAttribute() ) )
        {
            return null;
        }
        
        String nodeAttribute = node.getAttribute();

        Value normInitial = null;

        if ( node.getInitial() != null )
        {
            normInitial = normalizeValue( nodeAttribute, node.getInitial() );

            if ( normInitial == null )
            {
                return null;
            }
        }

        List<String> normAnys = null;

        if ( ( node.getAny() != null ) && ( node.getAny().size() != 0 ) )
        {
            normAnys = new ArrayList<String>( node.getAny().size() );

            for ( String any : node.getAny() )
            {
                Value normAny = normalizeValue( nodeAttribute, any );

                if ( normAny != null )
                {
                    normAnys.add( normAny.getString() );
                }
            }

            if ( normAnys.size() == 0 )
            {
                return null;
            }
        }

        Value normFinal = null;

        if ( node.getFinal() != null )
        {
            normFinal = normalizeValue( nodeAttribute, node.getFinal() );

            if ( normFinal == null )
            {
                return null;
            }
        }

        node.setAttribute( node.getAttribute() );

        if ( normInitial != null )
        {
            node.setInitial( normInitial.getString() );
        }
        else
        {
            node.setInitial( null );
        }

        node.setAny( normAnys );

        if ( normFinal != null )
        {
            node.setFinal( normFinal.getString() );
        }
        else
        {
            node.setFinal( null );
        }

        return node;
    }


    /**
     * Visit a ExtensibleNode. If the attribute exists, the node is returned, otherwise
     * null is returned. 
     * 
     * TODO implement the logic for ExtensibleNode
     * 
     * @param node the node to visit
     * @return the visited node
     */
    private ExprNode visitExtensibleNode( ExtensibleNode node )
    {
        node.setAttributeType( node.getAttributeType() );
        return node;
    }


    /**
     * Visit a BranchNode. BranchNodes are :
     *  - AndNode
     *  - NotNode
     *  - OrNode
     *  
     * @param node the node to visit
     * @return the visited node
     */
    private ExprNode visitBranchNode( BranchNode node )
    {
        // Two differente cases :
        // - AND or OR
        // - NOT

        if ( node instanceof NotNode )
        {
            // Manage the NOT
            ExprNode child = node.getFirstChild();

            ExprNode result = ( ExprNode ) visit( child );

            if ( result == null )
            {
                return null;
            }
            else if ( result instanceof BranchNode )
            {
                List<ExprNode> newChildren = new ArrayList<ExprNode>( 1 );
                newChildren.add( result );
                node.setChildren( newChildren );
                return node;
            }
            else if ( result instanceof LeafNode )
            {
                List<ExprNode> newChildren = new ArrayList<ExprNode>( 1 );
                newChildren.add( result );
                node.setChildren( newChildren );
                return node;
            }
        }
        else
        {
            // Manage AND and OR nodes.
            BranchNode branchNode = node;
            List<ExprNode> children = node.getChildren();

            // For AND and OR, we may have more than one children.
            // We may have to remove some of them, so let's create
            // a new handler to store the correct nodes.
            List<ExprNode> newChildren = new ArrayList<ExprNode>( children.size() );

            // Now, iterate through all the children
            for ( int i = 0; i < children.size(); i++ )
            {
                ExprNode child = children.get( i );

                ExprNode result = ( ExprNode ) visit( child );

                if ( result != null )
                {
                    // As the node is correct, add it to the children 
                    // list.
                    newChildren.add( result );
                }
            }

            if ( ( branchNode instanceof AndNode ) && ( newChildren.size() != children.size() ) )
            {
                return null;
            }

            if ( newChildren.size() == 0 )
            {
                // No more children, return null
                return null;
            }
            else if ( newChildren.size() == 1 )
            {
                // As we only have one child, return it
                // to the caller.
                return newChildren.get( 0 );
            }
            else
            {
                branchNode.setChildren( newChildren );
            }
        }

        return node;
    }


    /**
     * Visit the tree, normalizing the leaves and recusrsively visit the branches.
     * 
     * Here are the leaves we are visiting :
     * - PresenceNode ( attr =* )
     * - ExtensibleNode ( ? )
     * - SubStringNode ( attr = *X*Y* )
     * - ApproximateNode ( attr ~= value )
     * - EqualityNode ( attr = value )
     * - GreaterEqNode ( attr >= value )
     * - LessEqNode ( attr <= value )
     * 
     * The PresencNode is managed differently from other nodes, as it just check
     * for the attribute, not the value.
     * 
     * @param node the node to visit
     * @return the visited node
     */
    public Object visit( ExprNode node )
    {
        // -------------------------------------------------------------------
        // Handle PresenceNodes
        // -------------------------------------------------------------------

        if ( node instanceof PresenceNode )
        {
            return visitPresenceNode( ( PresenceNode ) node );
        }

        // -------------------------------------------------------------------
        // Handle BranchNodes (AndNode, NotNode and OrNode)
        // -------------------------------------------------------------------

        else if ( node instanceof BranchNode )
        {
            return visitBranchNode( ( BranchNode ) node );
        }

        // -------------------------------------------------------------------
        // Handle SimpleNodes (ApproximateNode, EqualityNode, GreaterEqNode,
        // and LesserEqNode) 
        // -------------------------------------------------------------------

        else if ( node instanceof SimpleNode )
        {
            return visitSimpleNode( ( SimpleNode ) node );
        }
        else if ( node instanceof ExtensibleNode )
        {
            return visitExtensibleNode( ( ExtensibleNode ) node );
        }
        else if ( node instanceof SubstringNode )
        {
            return visitSubstringNode( ( SubstringNode ) node );
        }
        else
        {
            return null;
        }
    }


    public boolean canVisit( ExprNode node )
    {
        return true;
    }


    public boolean isPrefix()
    {
        return false;
    }


    public List<ExprNode> getOrder( BranchNode node, List<ExprNode> children )
    {
        return children;
    }
}
