1   /* Copyright 2002-2025 CS GROUP
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *   http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.orekit.propagation.sampling;
18  
19  import org.orekit.propagation.SpacecraftState;
20  import org.orekit.time.AbsoluteDate;
21  
22  /** This interface is a space-dynamics aware fixed size step handler.
23   *
24   * <p>It mirrors the <code>FixedStepHandler</code> interface from <a
25   * href="https://hipparchus.org/">Hipparchus</a> but provides
26   * a space-dynamics interface to the methods.</p>
27   * @author Luc Maisonobe
28   */
29  @FunctionalInterface
30  public interface OrekitFixedStepHandler {
31  
32      /** Initialize step handler at the start of a propagation.
33       * <p>
34       * This method is called once at the start of the propagation. It
35       * may be used by the step handler to initialize some internal data
36       * if needed.
37       * </p>
38       * @param s0 initial state
39       * @param t target time for the integration
40       * @param step the duration in seconds of the fixed step. This value is
41       *             positive even if propagation is backwards.
42       * @since 9.0
43       */
44      default void init(final SpacecraftState s0, final AbsoluteDate t, final double step) {
45      }
46  
47      /** Handle the current step.
48       * @param currentState current state at step time
49       */
50      void handleStep(SpacecraftState currentState);
51  
52      /**
53       * Finalize propagation.
54       * @param finalState state at propagation end
55       * @since 11.0
56       */
57      default void finish(final SpacecraftState finalState) {
58          // nothing by default
59      }
60  
61  }