package org.neo4j.graphmatching;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;

/**
 * Represents one match found by the {@link PatternMatcher}. The match is
 * itself a graph which looks like the pattern fed to the {@link PatternMatcher}
 */
public class PatternMatch
{
	private Map<PatternNode,PatternElement> elements = 
		new HashMap<PatternNode, PatternElement>();
	private Map<PatternRelationship,Relationship> relElements = 
        new HashMap<PatternRelationship,Relationship>();
    
	PatternMatch( Map<PatternNode,PatternElement> elements, 
        Map<PatternRelationship,Relationship> relElements )
	{
		this.elements = elements;
        this.relElements = relElements;
	}
	
	/**
	 * @param node the {@link PatternNode} to get the {@link Node} for.
	 * @return the actual {@link Node} for this particular match, represented
     * by {@code node} in the pattern
	 */
	public Node getNodeFor( PatternNode node )
	{
		return elements.containsKey( node ) ?
			elements.get( node ).getNode() : null;
	}
    
    /**
     * @param rel the {@link PatternRelationship} to get the
     * {@link Relationship} for.
     * @return the actual {@link Relationship} for this particular match,
     * represented by {@code rel} in the pattern
     */
    public Relationship getRelationshipFor( PatternRelationship rel )
    {
        return relElements.containsKey( rel ) ?
            relElements.get( rel ) : null;
    }
	
	public Iterable<PatternElement> getElements()
	{
		return elements.values();
	}

	/**
	 * Used to merge two matches. An example is to merge in an "optional"
	 * subgraph match into a match.
	 * @param matches the matches to merge together.
	 * @return the merged matches as one match.
	 */
	public static PatternMatch merge( Iterable<PatternMatch> matches )
	{
		Map<PatternNode, PatternElement> matchMap =
			new HashMap<PatternNode, PatternElement>();
        Map<PatternRelationship, Relationship> relElements = 
            new HashMap<PatternRelationship, Relationship>();
		for ( PatternMatch match : matches )
		{
			for ( PatternNode node : match.elements.keySet() )
			{
				boolean exists = false;
				for ( PatternNode existingNode : matchMap.keySet() )
				{
					if ( node.getLabel().equals( existingNode.getLabel() ) )
					{
						exists = true;
						break;
					}
				}
				if ( !exists )
				{
					matchMap.put( node, match.elements.get( node ) );
                    relElements.put( 
                        match.elements.get( node ).getFromPatternRelationship(), 
                        match.elements.get( node ).getFromRelationship() );
				}
			}
		}
		PatternMatch mergedMatch = new PatternMatch( matchMap, relElements );
		return mergedMatch;
	}

	public static PatternMatch merge( PatternMatch... matches )
	{
		return merge( Arrays.asList( matches ) );
	}
}