/*******************************************************************************
 * 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.layer0.util;

import java.util.Collection;

import org.simantics.databoard.Accessors;
import org.simantics.databoard.accessor.Accessor;
import org.simantics.databoard.accessor.error.AccessorConstructionException;
import org.simantics.databoard.accessor.error.AccessorException;
import org.simantics.databoard.accessor.event.Event;
import org.simantics.databoard.accessor.interestset.InterestSet;
import org.simantics.databoard.binding.Binding;
import org.simantics.db.ReadGraph;
import org.simantics.db.RequestProcessor;
import org.simantics.db.Resource;
import org.simantics.db.WriteGraph;
import org.simantics.db.common.request.WriteRequest;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.procedure.Listener;
import org.simantics.db.request.Read;

public class GraphAccessorUtils {

	static private class ValueReadRequest implements Read<Object> {
		Resource resource;
		Binding binding;
		
		public ValueReadRequest(Resource resource, Binding binding) {
			this.resource = resource;
			this.binding = binding;
		}

		@Override
		public Object perform(ReadGraph graph) throws DatabaseException {
			return graph.getValue(resource, binding);
		}
	}
	

	static private class ValueReadRequest2 implements Read<Object> {
		Resource resource;
		Resource relation;
		Object defaultValue;
		Binding binding;
		
		public ValueReadRequest2(Resource resource, Resource relation, Object defaultValue, Binding binding) {
			this.resource = resource;
			this.relation = relation;
			this.defaultValue = defaultValue;
			this.binding = binding;
		}

		@Override
		public Object perform(ReadGraph graph) throws DatabaseException {
			Object value = graph.getPossibleRelatedValue(resource, relation, binding);
			if(value != null)
				return value;
			else
				return defaultValue;
		}
	}
		
	static private class ValueReadListener implements Listener<Object> {

		Binding binding;
		Accessor accessor;		
		
		public ValueReadListener(Binding binding) {
			this.binding = binding;
		}

		@Override
		public void exception(Throwable t) {
		}

		@Override
		public void execute(Object result) {
			if(accessor == null)
				try {
					accessor = Accessors.getAccessor(binding, result);					
				} catch (AccessorConstructionException e) {
					e.printStackTrace();
				}
			else
				try {
					if(!binding.equals(accessor.getValue(binding), result))
						accessor.setValue(binding, result);
				} catch (AccessorException e) {
					e.printStackTrace();
				}			
		}

		@Override
		public boolean isDisposed() {
			// TODO Auto-generated method stub
			return false;
		}
		
	}
	
	static private class AccessorListener implements Accessor.Listener {

		Accessor accessor;
		RequestProcessor rp;
		Resource resource;
		Binding binding;
		
		public AccessorListener(Accessor accessor, RequestProcessor rp,
				Resource resource, Binding binding) {
			this.accessor = accessor;
			this.rp = rp;
			this.resource = resource;
			this.binding = binding;
		}

		@Override
		public void onEvents(Collection<Event> event) {
			rp.asyncRequest(new WriteRequest() {				
				@Override
				public void perform(WriteGraph graph) throws DatabaseException {
					try {
						Object a = accessor.getValue(binding);
						Object b = graph.getValue(resource, binding);
						if(!binding.equals(a, b))
							graph.claimValue(resource, a, binding);
					} catch (AccessorException e) {
						throw new DatabaseException(e);
					}
				}
			});
		}
		
	}
	
	static private class AccessorListener2 implements Accessor.Listener {

		Accessor accessor;
		RequestProcessor rp;
		Resource resource;
		Resource relation;
		Binding binding;
		
		public AccessorListener2(Accessor accessor, RequestProcessor rp,
				Resource resource, Resource relation, Binding binding) {
			this.accessor = accessor;
			this.rp = rp;
			this.resource = resource;
			this.relation = relation;
			this.binding = binding;
		}

		@Override
		public void onEvents(Collection<Event> event) {
			rp.asyncRequest(new WriteRequest() {				
				@Override
				public void perform(WriteGraph graph) throws DatabaseException {
					try {
						Object a = accessor.getValue(binding);
						
						Resource valueResource = graph.getPossibleObject(resource, relation);
						if(valueResource == null) {
							valueResource = graph.newResource(); 
							graph.claim(resource, relation, valueResource);
							graph.claimValue(valueResource, a, binding);
						}
						else {
							Object b = graph.getValue(valueResource, binding);
							if(!binding.equals(a, b))
								graph.claimLiteral(resource, relation, a, binding);
						}
					} catch (AccessorException e) {
						throw new DatabaseException(e);
					}
				}
			});
		}
		
	}
	
	public static Accessor create(RequestProcessor rp, Resource resource, Binding binding) throws DatabaseException {
		ValueReadRequest request = new ValueReadRequest(resource, binding);
		ValueReadListener listener = new ValueReadListener(binding);
		rp.syncRequest(request, listener);
		try {
			listener.accessor.addListener(
				new AccessorListener(listener.accessor, rp, resource, binding), 
				InterestSet.newInterestSet(listener.accessor.type(), true, false, true),
				null, null);
		} catch (AccessorException e) {
			e.printStackTrace();
		}
		return listener.accessor;		
	}
	
	public static Accessor create(RequestProcessor rp, Resource resource, Resource relation, Object defaultValue, Binding binding) throws DatabaseException {
		ValueReadRequest2 request = new ValueReadRequest2(resource, relation, defaultValue, binding);
		ValueReadListener listener = new ValueReadListener(binding);
		rp.syncRequest(request, listener);
		try {
			listener.accessor.addListener(
				new AccessorListener2(listener.accessor, rp, resource, relation, binding), 
				InterestSet.newInterestSet(listener.accessor.type(), true, false, true),
				null, null);
		} catch (AccessorException e) {
			e.printStackTrace();
		}
		return listener.accessor;		
	}
	
}