/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.db.common.request;

import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.request.ReadExt;
import org.simantics.db.service.QueryControl;

abstract public class TransientResourceRead<R> extends BinaryRead<Object,Resource,R> implements ReadExt {

    protected static final Object WITH_PARENT = new Object();

    public TransientResourceRead(ReadGraph graph, Resource parameter) throws DatabaseException {
        this(graph, graph.getService(QueryControl.class), parameter);
    }

    public TransientResourceRead(ReadGraph graph, QueryControl qc, Resource parameter) throws DatabaseException {
        super(resolveFirstParameter(graph, qc), parameter);
    }

    final private static Object resolveFirstParameter(ReadGraph graph, QueryControl qc) throws DatabaseException {
        if(qc.hasParentRequest(graph)) return WITH_PARENT;
        else return graph.getModificationCounter();
    }

    @Override
    final public R perform(ReadGraph _graph) throws DatabaseException {
        if(parameter == WITH_PARENT) {
            return perform(_graph, parameter2);
        } else {
            QueryControl qc = _graph.getService(QueryControl.class);
            return qc.syncRequestIndependent(_graph, new UniqueRead<R>() {
                @Override
                public R perform(ReadGraph graph) throws DatabaseException {
                    return TransientResourceRead.this.perform(graph, parameter2);
                }
            });
        }
    }

    abstract public R perform(ReadGraph graph, Resource parameter) throws DatabaseException;

    @Override
    public boolean isImmutable(ReadGraph graph) throws DatabaseException {
        return graph.isImmutable(parameter2);
    }

}