/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.math4.legacy.ode.events;
  
  import org.junit.Assert;
  
  import java.util.Arrays;
  
  import org.apache.commons.math4.legacy.analysis.solvers.PegasusSolver;
  import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
  import org.apache.commons.math4.legacy.exception.MaxCountExceededException;
  import org.apache.commons.math4.legacy.exception.NoBracketingException;
  import org.apache.commons.math4.legacy.exception.NumberIsTooSmallException;
  import org.apache.commons.math4.legacy.ode.FirstOrderDifferentialEquations;
  import org.apache.commons.math4.legacy.ode.FirstOrderIntegrator;
  import org.apache.commons.math4.legacy.ode.nonstiff.DormandPrince853Integrator;
  import org.apache.commons.math4.legacy.ode.nonstiff.GraggBulirschStoerIntegrator;
  import org.junit.Test;
  
  public class ReappearingEventTest {
      @Test
      public void testDormandPrince()
          throws DimensionMismatchException, NumberIsTooSmallException,
                 MaxCountExceededException, NoBracketingException {
          double tEnd = test(1);
          Assert.assertEquals(10.0, tEnd, 1e-7);
      }
  
      @Test
      public void testGragg()
          throws DimensionMismatchException, NumberIsTooSmallException,
                 MaxCountExceededException, NoBracketingException {
          double tEnd = test(2);
          Assert.assertEquals(10.0, tEnd, 1e-7);
      }
  
      public double test(int integratorType)
          throws DimensionMismatchException, NumberIsTooSmallException,
                 MaxCountExceededException, NoBracketingException {
          double e = 1e-15;
          FirstOrderIntegrator integrator;
          integrator = (integratorType == 1)
                       ? new DormandPrince853Integrator(e, 100.0, 1e-7, 1e-7)
                       : new GraggBulirschStoerIntegrator(e, 100.0, 1e-7, 1e-7);
          PegasusSolver rootSolver = new PegasusSolver(e, e);
          integrator.addEventHandler(new Event(), 0.1, e, 1000, rootSolver);
          double t0 = 6.0;
          double tEnd = 10.0;
          double[] y = {2.0, 2.0, 2.0, 4.0, 2.0, 7.0, 15.0};
          return integrator.integrate(new Ode(), t0, y, tEnd, y);
      }
  
      private static final class Ode implements FirstOrderDifferentialEquations {
          @Override
          public int getDimension() {
              return 7;
          }
  
          @Override
          public void computeDerivatives(double t, double[] y, double[] yDot) {
              Arrays.fill(yDot, 1.0);
          }
      }
  
      /** State events for this unit test. */
      protected static class Event implements EventHandler {
  
          @Override
          public void init(double t0, double[] y0, double t) {
          }
  
          @Override
          public double g(double t, double[] y) {
              return y[6] - 15.0;
          }
  
          @Override
          public Action eventOccurred(double t, double[] y, boolean increasing) {
              return Action.STOP;
          }
  
          @Override
          public void resetState(double t, double[] y) {
              // Never called.
          }
     }
 }