/*
    * Licensed to the Hipparchus project under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The Hipparchus project 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.
   */
  
  package org.hipparchus.ode;
  
  import org.hipparchus.analysis.UnivariateFunction;
  import org.hipparchus.analysis.solvers.BracketedUnivariateSolver;
  import org.hipparchus.analysis.solvers.BracketingNthOrderBrentSolver;
  import org.hipparchus.ode.events.Action;
  import org.hipparchus.ode.events.AdaptableInterval;
  import org.hipparchus.ode.events.ODEEventDetector;
  import org.hipparchus.ode.events.ODEEventHandler;
  import org.hipparchus.ode.nonstiff.EulerIntegrator;
  import org.hipparchus.ode.sampling.ODEStateInterpolator;
  import org.hipparchus.ode.sampling.ODEStepHandler;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  class AbstractIntegratorTest {
  
      @Test
      void testIntegrateWithResetDerivativesAndEventDetector() {
          // GIVEN
          final double finalTime = 1.;
          final EulerIntegrator integrator = new EulerIntegrator(finalTime);
          final TestDetector detector = new TestDetector(0.5, Action.RESET_DERIVATIVES);
          integrator.addEventDetector(detector);
          final TestProblem1 testProblem = new TestProblem1();
          final ODEState initialState = new ODEState(0., new double[2]);
          // WHEN
          integrator.integrate(testProblem, initialState, finalTime);
          // THEN
          assertTrue(detector.resetted);
      }
  
  
      @Test
      void testUpdateStepIsCalledOncePerStepWhileHandleStepIsCalledAtEachEvent() {
          // GIVEN
          final double finalTime = 3.;
          final EulerIntegrator integrator = new EulerIntegrator(finalTime);
          integrator.addStepHandler(new UpdateStepTestHandler());
          integrator.addEventDetector(new TestDetector(0.5, Action.CONTINUE));
          integrator.addEventDetector(new TestDetector(0.6, Action.CONTINUE));
          final TestProblem1 testProblem = new TestProblem1();
          final ODEState initialState = new ODEState(0., new double[2]);
          // WHEN
          integrator.integrate(testProblem, initialState, finalTime);
          // THEN
          assertEquals(1, ((UpdateStepTestHandler) integrator.getStepHandlers().get(0)).getUpdateStepCounter());
          assertEquals(3, ((UpdateStepTestHandler) integrator.getStepHandlers().get(0)).getHandlerStepCounter());
      }
  
      private static class TestDetector implements ODEEventDetector {
          boolean resetted = false;
          double rootTime;
          Action action;
  
          public TestDetector(double rootTime, Action action) {
              this.rootTime = rootTime;
              this.action = action;
          }
  
          @Override
          public void reset(ODEStateAndDerivative intermediateState, double finalTime) {
              ODEEventDetector.super.reset(intermediateState, finalTime);
              resetted = true;
          }
  
          @Override
          public AdaptableInterval getMaxCheckInterval() {
              return AdaptableInterval.of(1);
          }
  
          @Override
          public int getMaxIterationCount() {
              return 10;
          }
  
          @Override
          public BracketedUnivariateSolver<UnivariateFunction> getSolver() {
              return new BracketingNthOrderBrentSolver();
          }
 
         @Override
         public ODEEventHandler getHandler() {
             return (state, detector, increasing) -> action;
         }
 
         @Override
         public double g(ODEStateAndDerivative state) {
             return state.getTime() - rootTime;
         }
     }
 
     
     private static class UpdateStepTestHandler implements ODEStepHandler {
 
         private int handlerStepCounter = 0;
         private int updateStepCounter = 0;
 
         @Override
         public void handleStep(ODEStateInterpolator interpolator) {
             handlerStepCounter++;
         }
 
         @Override
         public void updateOnStep(ODEStateInterpolator interpolator) {
             updateStepCounter++;
         }
 
         public int getHandlerStepCounter() {
             return handlerStepCounter;
         }
 
         public int getUpdateStepCounter() {
             return updateStepCounter;
         }
     }
 }