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Neo4j property value system.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.values.virtual;

import java.util.Arrays;
import java.util.Comparator;

import org.neo4j.values.AnyValue;
import org.neo4j.values.AnyValueWriter;
import org.neo4j.values.Comparison;
import org.neo4j.values.TernaryComparator;
import org.neo4j.values.VirtualValue;

import static org.neo4j.memory.HeapEstimator.shallowSizeOfInstance;
import static org.neo4j.values.AnyValueWriter.EntityMode.REFERENCE;
import static org.neo4j.values.utils.ValueMath.HASH_CONSTANT;

public abstract class PathValue extends VirtualPathValue
{
    public abstract NodeValue startNode();

    public abstract NodeValue endNode();

    public abstract RelationshipValue lastRelationship();

    public abstract NodeValue[] nodes();

    public abstract RelationshipValue[] relationships();

    @Override
    public long startNodeId()
    {
        return startNode().id();
    }

    @Override
    public long endNodeId()
    {
        return endNode().id();
    }

    @Override
    public long[] nodeIds()
    {
        var nodes = nodes();
        var nodeIds = new long[nodes.length];
        for ( int i = 0; i < nodeIds.length; i++ )
        {
            nodeIds[i] = nodes[i].id();
        }
        return nodeIds;
    }

    @Override
    public long[] relationshipIds()
    {
        var relationionships = relationships();
        var relIds = new long[relationionships.length];
        for ( int i = 0; i < relIds.length; i++ )
        {
            relIds[i] = relationionships[i].id();
        }
        return relIds;
    }

    @Override
    public boolean equals( VirtualValue other )
    {
        if ( other instanceof PathValue )
        {
            PathValue that = (PathValue) other;
            return size() == that.size() &&
                   Arrays.equals( nodes(), that.nodes() ) &&
                   Arrays.equals( relationships(), that.relationships() );
        }
        else
        {
            return super.equals( other );
        }
    }

    @Override
    protected int computeHashToMemoize()
    {
        NodeValue[] nodes = nodes();
        VirtualRelationshipValue[] relationships = relationships();
        int result = nodes[0].hashCode();
        for ( int i = 1; i < nodes.length; i++ )
        {
            result += HASH_CONSTANT * (result + relationships[i - 1].hashCode());
            result += HASH_CONSTANT * (result + nodes[i].hashCode());
        }
        return result;
    }

    @Override
    public  void writeTo( AnyValueWriter writer ) throws E
    {
        if ( writer.entityMode() == REFERENCE )
        {
            writer.writePathReference( nodeIds(), relationshipIds() );
        }
        else
        {
            writer.writePath( nodes(), relationships() );
        }
    }

    @Override
    public int unsafeCompareTo( VirtualValue other, Comparator comparator )
    {
        if ( other instanceof PathValue )
        {
            PathValue otherPath = (PathValue) other;
            NodeValue[] nodes = nodes();
            RelationshipValue[] relationships = relationships();
            NodeValue[] otherNodes = otherPath.nodes();
            RelationshipValue[] otherRelationships = otherPath.relationships();

            int x = nodes[0].unsafeCompareTo( otherNodes[0], comparator );
            if ( x == 0 )
            {
                int i = 0;
                int length = Math.min( relationships.length, otherRelationships.length );

                while ( x == 0 && i < length )
                {
                    x = relationships[i].unsafeCompareTo( otherRelationships[i], comparator );
                    ++i;
                }

                if ( x == 0 )
                {
                    x = Integer.compare( relationships.length, otherRelationships.length );
                }
            }

            return x;
        }
        else
        {
            return super.unsafeCompareTo( other, comparator );
        }
    }

    @Override
    public Comparison unsafeTernaryCompareTo( VirtualValue other, TernaryComparator comparator )
    {
        return Comparison.from( unsafeCompareTo( other, comparator ) );
    }

    @Override
    public String toString()
    {
        NodeValue[] nodes = nodes();
        RelationshipValue[] relationships = relationships();
        StringBuilder sb = new StringBuilder( getTypeName() + "{" );
        int i = 0;
        for ( ; i < relationships.length; i++ )
        {
            sb.append( nodes[i] );
            sb.append( relationships[i] );
        }
        sb.append( nodes[i] );
        sb.append( '}' );
        return sb.toString();
    }

    @Override
    public ListValue asList()
    {
        NodeValue[] nodes = nodes();
        RelationshipValue[] relationships = relationships();
        int size = nodes.length + relationships.length;
        ListValueBuilder builder = ListValueBuilder.newListBuilder( size );
        for ( int i = 0; i < size; i++ )
        {
            if ( i % 2 == 0 )
            {
                builder.add( nodes[i / 2] );
            }
            else
            {
                builder.add( relationships[i / 2] );
            }
        }
        return builder.build();
    }

    @Override
    public int size()
    {
        return relationships().length;
    }

    private static final long DIRECT_PATH_SHALLOW_SIZE = shallowSizeOfInstance( DirectPathValue.class );
    static class DirectPathValue extends PathValue
    {
        private final NodeValue[] nodes;
        private final RelationshipValue[] edges;
        private final long payloadSize;

        DirectPathValue( NodeValue[] nodes, RelationshipValue[] edges, long payloadSize )
        {
            assert nodes != null;
            assert edges != null;
            assert nodes.length == edges.length + 1;

            this.nodes = nodes;
            this.edges = edges;
            this.payloadSize = payloadSize;
        }

        @Override
        public NodeValue startNode()
        {
            return nodes[0];
        }

        @Override
        public NodeValue endNode()
        {
            return nodes[nodes.length - 1];
        }

        @Override
        public RelationshipValue lastRelationship()
        {
            assert edges.length > 0;
            return edges[edges.length - 1];
        }

        @Override
        public NodeValue[] nodes()
        {
            return nodes;
        }

        @Override
        public RelationshipValue[] relationships()
        {
            return edges;
        }

        @Override
        public long estimatedHeapUsage()
        {
            return DIRECT_PATH_SHALLOW_SIZE + payloadSize;
        }
    }
}