/*
    * 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
    *
    *      https://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.
   */
  
  /*
   * This is not the original file distributed by the Apache Software Foundation
   * It has been modified by the Hipparchus project
   */
  package org.hipparchus.ode.events;
  
  import org.hipparchus.analysis.UnivariateFunction;
  import org.hipparchus.analysis.solvers.BracketedUnivariateSolver;
  import org.hipparchus.analysis.solvers.BracketingNthOrderBrentSolver;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.exception.MathIllegalStateException;
  import org.hipparchus.ode.ODEIntegrator;
  import org.hipparchus.ode.ODEState;
  import org.hipparchus.ode.ODEStateAndDerivative;
  import org.hipparchus.ode.OrdinaryDifferentialEquation;
  import org.hipparchus.ode.nonstiff.DormandPrince853Integrator;
  import org.hipparchus.ode.nonstiff.GraggBulirschStoerIntegrator;
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  public class ReappearingEventTest {
  
      @Test
      void testDormandPrince()
          throws MathIllegalArgumentException, MathIllegalStateException {
          double tEnd = test(1);
          assertEquals(10.0, tEnd, 1e-7);
      }
  
      @Test
      void testGragg()
          throws MathIllegalArgumentException, MathIllegalStateException {
          double tEnd = test(2);
          assertEquals(10.0, tEnd, 1e-7);
      }
  
      public double test(int integratorType)
          throws MathIllegalArgumentException, MathIllegalStateException {
          double e = 1e-15;
          ODEIntegrator integrator = (integratorType == 1) ?
                                     new DormandPrince853Integrator(e, 100.0, 1e-7, 1e-7) :
                                     new GraggBulirschStoerIntegrator(e, 100.0, 1e-7, 1e-7);
          integrator.addEventDetector(new Event(0.1, e, 1000));
          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(), new ODEState(t0, y), tEnd).getTime();
      }
  
      private static class Ode implements OrdinaryDifferentialEquation {
          public int getDimension() {
              return 7;
          }
  
          public double[] computeDerivatives(double t, double[] y) {
              double[] yDot = new double[y.length];
              Arrays.fill(yDot, 1.0);
              return yDot;
          }
      }
  
      /** State events for this unit test. */
      protected static class Event implements ODEEventDetector {
  
          private final AdaptableInterval             maxCheck;
          private final int                           maxIter;
          private final BracketingNthOrderBrentSolver solver;
  
          /** Constructor for the {@link Event} class.
           * @param maxCheck maximum checking interval, must be strictly positive (s)
           * @param threshold convergence threshold (s)
           * @param maxIter maximum number of iterations in the event time search
           */
          public Event(final double maxCheck, final double threshold, final int maxIter) {
              this.maxCheck  = (s, isForward) -> maxCheck;
              this.maxIter   = maxIter;
              this.solver    = new BracketingNthOrderBrentSolver(0, threshold, 0, 5);
          }
  
         public AdaptableInterval getMaxCheckInterval() {
             return maxCheck;
         }
 
         public int getMaxIterationCount() {
             return maxIter;
         }
 
         public BracketedUnivariateSolver<UnivariateFunction> getSolver() {
             return solver;
         }
 
         public ODEEventHandler getHandler() {
             return (state, detector, increasing) -> Action.STOP;
         }
 
         public double g(ODEStateAndDerivative s) {
             return s.getPrimaryState()[6] - 15.0;
         }
 
     }
 
 }