package org.simantics.db.layer0.util;

import java.util.ArrayList;

import org.simantics.databoard.util.URIStringUtils;
import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.common.uri.UnescapedChildMapOfResource;
import org.simantics.db.exception.DatabaseException;
import org.simantics.layer0.Layer0;

public class RelativeReference {
    public final Resource base;
    public final String path;
    
    public RelativeReference(Resource base, String path) {
        this.base = base;
        this.path = path;
    }
    
    public Resource resolve(ReadGraph graph) throws DatabaseException {
        return resolve(graph, base, path);
    }

    public static Resource resolve(ReadGraph graph, 
            Resource base, 
            String path) throws DatabaseException {
        String[] splitPath = path.split("/");
        for(String name : splitPath) {            
            base = graph.syncRequest(new UnescapedChildMapOfResource(base)).get(
                    URIStringUtils.unescape(name)
                    );
            if(base == null)
                return null;                    
        }
        return base;
    }
    
    public static RelativeReference createReference(ReadGraph graph, Resource baseType, Resource resource) throws DatabaseException {
        ArrayList<String> path = new ArrayList<String>();
        Layer0 L0 = Layer0.getInstance(graph);
        try {
            while(!graph.isInstanceOf(resource, baseType)) {
                path.add((String)graph.getRelatedValue(resource, L0.HasName));
                resource = graph.getSingleObject(resource, L0.PartOf);
            }
        } catch(DatabaseException e) {
            return null;
        }
        StringBuilder b = new StringBuilder();
        for(int i=path.size()-1;i>=0;--i) {
            b.append(URIStringUtils.escape(path.get(i)));
            if(i > 0)
                b.append('/');
        }
        return new RelativeReference(resource, b.toString());
    }
}