package no.birkett.kiwi.inequality;

import org.junit.Test;

import no.birkett.kiwi.DuplicateConstraintException;
import no.birkett.kiwi.Expression;
import no.birkett.kiwi.Solver;
import no.birkett.kiwi.Symbolics;
import no.birkett.kiwi.UnsatisfiableConstraintException;
import no.birkett.kiwi.Variable;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

/**
 * Created by alex on 31/01/16.
 */
public class VariableExpression {
    private static double EPSILON = 1.0e-8;

    @Test
    public void lessThanEqualTo() throws DuplicateConstraintException, UnsatisfiableConstraintException {
        Variable x = new Variable("x");
        Solver solver = new Solver();
        solver.addConstraint(Symbolics.lessThanOrEqualTo(x, new Expression(100)));
        solver.updateVariables();
        assertTrue(x.getValue() <= 100);
        solver.addConstraint(Symbolics.equals(x, 90));
        solver.updateVariables();
        assertEquals(x.getValue(), 90, EPSILON);
    }

    @Test(expected = UnsatisfiableConstraintException.class)
    public void lessThanEqualToUnsatisfiable() throws DuplicateConstraintException, UnsatisfiableConstraintException {
        Variable x = new Variable("x");
        Solver solver = new Solver();
        solver.addConstraint(Symbolics.lessThanOrEqualTo(x, new Expression(100)));
        solver.updateVariables();
        assertTrue(x.getValue() <= 100);
        solver.addConstraint(Symbolics.equals(x, 110));
        solver.updateVariables();
    }

    @Test
    public void greaterThanEqualTo() throws DuplicateConstraintException, UnsatisfiableConstraintException {
        Variable x = new Variable("x");
        Solver solver = new Solver();
        solver.addConstraint(Symbolics.greaterThanOrEqualTo(x, new Expression(100)));
        solver.updateVariables();
        assertTrue(x.getValue() >= 100);
        solver.addConstraint(Symbolics.equals(x, 110));
        solver.updateVariables();
        assertEquals(x.getValue(), 110, EPSILON);
    }

    @Test(expected = UnsatisfiableConstraintException.class)
    public void greaterThanEqualToUnsatisfiable() throws DuplicateConstraintException, UnsatisfiableConstraintException {
        Variable x = new Variable("x");
        Solver solver = new Solver();
        solver.addConstraint(Symbolics.greaterThanOrEqualTo(x, 100));
        solver.updateVariables();
        assertTrue(x.getValue() >= 100);
        solver.addConstraint(Symbolics.equals(x, 90));
        solver.updateVariables();
    }
}