package org.simantics.db.layer0.adapter;

import org.simantics.db.ConverterComputationalValue;
import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.exception.RuntimeDatabaseException;
import org.simantics.db.layer0.variable.Variable;
import org.simantics.scl.runtime.SCLContext;
import org.simantics.scl.runtime.function.Function1;
import org.simantics.scl.runtime.function.FunctionImpl3;

abstract public class ContextualRelatedValue implements ConverterComputationalValue {

    @SuppressWarnings("unchecked")
	@Override
    public <T> T getValue(ReadGraph graph, Resource resource) throws DatabaseException {
        
        return (T)new FunctionImpl3<ReadGraph, Resource, Object, Object>() {

            @Override
            public Object apply(ReadGraph graph, Resource converter, Object context) {
                SCLContext sclContext = SCLContext.getCurrent();
                Object oldGraph = sclContext.get("graph");
                try {
                    if(context instanceof Variable) {
                        Variable variable = (Variable)context;
                        try {
                            Function1<Object,Object> fn = getFunction(graph, variable.getParent(graph).getRepresents(graph), variable.getRepresents(graph), variable.getPredicateResource(graph));
                            sclContext.put("graph", graph);
                            return fn.apply(variable);
                        } catch (DatabaseException e) {
                            throw new RuntimeDatabaseException(e);
                        }
                    } if (context instanceof Resource) {
                        Resource resource = (Resource)context;
                        try {
                            /*
                             * Here converter is the object and context is the subject
                             */
                        	Function1<Object,Object> fn = getFunction(graph, resource, converter, null);
                            return fn.apply(resource);
                        } catch (DatabaseException e) {
                            throw new RuntimeDatabaseException(e);
                        }
                    } else {
                        throw new IllegalStateException("Unknown context " + context);
                    }
                } finally {
                    sclContext.put("graph", oldGraph);
                }
            }

        };
        
    }

}