1   /* Copyright 2002-2018 CS Systèmes d'Information
2    * Licensed to CS Systèmes d'Information (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.errors.OrekitException;
20  import org.orekit.propagation.SpacecraftState;
21  import org.orekit.time.AbsoluteDate;
22  
23  /** This interface is a space-dynamics aware fixed size step handler.
24   *
25   * <p>It mirrors the <code>FixedStepHandler</code> interface from <a
26   * href="https://hipparchus.org/">Hipparchus</a> but provides
27   * a space-dynamics interface to the methods.</p>
28   * @author Luc Maisonobe
29   */
30  @FunctionalInterface
31  public interface OrekitFixedStepHandler {
32  
33      /** Initialize step handler at the start of a propagation.
34       * <p>
35       * This method is called once at the start of the propagation. It
36       * may be used by the step handler to initialize some internal data
37       * if needed.
38       * </p>
39       * <p>
40       * The default implementation does nothing
41       * </p>
42       * @param s0 initial state
43       * @param t target time for the integration
44       * @exception OrekitException if step handler cannot be initialized
45       * @deprecated as of 9.0, replaced by {@link #init(SpacecraftState, AbsoluteDate, double)}
46       */
47      @Deprecated
48      default void init(SpacecraftState s0, AbsoluteDate t)
49          throws OrekitException {
50          // nothing by default
51      }
52  
53      /** Initialize step handler at the start of a propagation.
54       * <p>
55       * This method is called once at the start of the propagation. It
56       * may be used by the step handler to initialize some internal data
57       * if needed.
58       * </p>
59       * <p>
60       * The default implementation currently calls the deprecated
61       * {@link #init(SpacecraftState, AbsoluteDate)} which does nothing by
62       * default. When that method is removed the default implementation will do
63       * nothing.
64       * </p>
65       * @param s0 initial state
66       * @param t target time for the integration
67       * @param step the duration in seconds of the fixed step. This value is
68       *             positive even if propagation is backwards.
69       * @exception OrekitException if step handler cannot be initialized
70       * @since 9.0
71       */
72      default void init(SpacecraftState s0, AbsoluteDate t, double step)
73          throws OrekitException {
74          // as of 9.0, the default implementation calls the DEPRECATED version
75          // without a step size, which does nothing by default but may have
76          // been overridden by users
77          // When the deprecated version is removed, the default implementation
78          // will do nothing
79          init(s0, t);
80      }
81  
82      /** Handle the current step.
83       * @param currentState current state at step time
84       * @param isLast if true, this is the last integration step
85       * @exception OrekitException if step cannot be handled
86       */
87      void handleStep(SpacecraftState currentState, boolean isLast)
88          throws OrekitException;
89  
90  }