/*******************************************************************************
 * 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.equation.ext;

import java.util.Iterator;

import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.common.utils.NameUtils;
import org.simantics.db.common.utils.OrderedSetUtils;
import org.simantics.db.exception.DatabaseException;
import org.simantics.equation.EquationResources;
import org.simantics.equation.solver.ExpressionSolver;
import org.simantics.equation.solver.Solver;

public class ElementExpressionSolver implements ExpressionSolver {
	
	private Oper sum = new Sum();
	private Oper sub = new Sub();
	private Oper mul = new Mul();
	private Oper div = new Div();
	
	@Override
	public void evaluate(Solver solver, ReadGraph g, Resource t) throws DatabaseException {
		Iterator<Resource> it = OrderedSetUtils.iterator(g, t.get());
		double res = getNumber(solver, g, it.next());
		while (it.hasNext()) {
			Oper op = getOperator(g, it.next());
			double v = getNumber(solver, g, it.next());
			res = op.evaluate(res, v);
		}
		
		solver.setValue(g.getSingleObject(t, EquationResources.equationResource.HasTarget), new double[]{res});
	}
	
	private double getNumber(Solver solver, ReadGraph g, Resource number) throws DatabaseException {
		// TODO : assumes that HasVariable points to Double while it can point to any Property
		return solver.getDoubleValue(g, g.getSingleObject(number, EquationResources.equationResource.HasVariable));
	}
	
	private Oper getOperator(ReadGraph g, Resource operator) throws DatabaseException {
		if (operator.get().equals(EquationResources.equationResource.Addition))
			return sum;
		else if (operator.get().equals(EquationResources.equationResource.Subtraction))
			return sub;
		else if (operator.get().equals(EquationResources.equationResource.Multiplication))
			return mul;
		else if (operator.get().equals(EquationResources.equationResource.Division))
			return div;
		throw new RuntimeException("Unknown operation " + NameUtils.getSafeName(g, operator));
		
	}
	
	private interface Oper {
		double evaluate(double d1, double d2);
	}
	
	private class Sum implements Oper {
		@Override
		public double evaluate(double d1, double d2) {
			return d1 + d2;
		}
	}
	
	private class Sub implements Oper {
		@Override
		public double evaluate(double d1, double d2) {
			return d1 - d2;
		}
	}
	
	private class Mul implements Oper {
		@Override
		public double evaluate(double d1, double d2) {
			return d1 * d2;
		}
	}
	
	private class Div implements Oper {
		@Override
		public double evaluate(double d1, double d2) {
			return d1 / d2;
		}
	}
	
	

}