1   /* Copyright 2022-2025 Luc Maisonobe
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.utils;
18  
19  import org.orekit.time.AbsoluteDate;
20  
21  /** Expunge policy to apply when a {@link org.orekit.utils.TimeSpanMap} exceeds its capacity.
22   * @author Luc Maisonobe
23   * @since 13.1
24   */
25  public enum ExpungePolicy {
26  
27      /** Expunge the span before the first transition.
28       * <p>
29       * Note that if we add data to the map in reverse chronological order, then entries
30       * exceeding capacity are expunged as soon as we attempt to add them, so this
31       * policy should probably not be used in reverse chronological order.
32       * </p>
33       */
34      EXPUNGE_EARLIEST {
35          boolean expungeEarliest(final AbsoluteDate date,
36                                  final AbsoluteDate earliest, final AbsoluteDate latest) {
37              return true;
38          }
39      },
40  
41      /** Expunge the span after the latest transition.
42       * <p>
43       * Note that if we add data to the map in chronological order, then entries
44       * exceeding capacity are expunged as soon as we attempt to add them, so this
45       * policy should probably not be used in chronological order.
46       * </p>
47       */
48      EXPUNGE_LATEST {
49          boolean expungeEarliest(final AbsoluteDate date,
50                                  final AbsoluteDate earliest, final AbsoluteDate latest) {
51              return false;
52          }
53      },
54  
55      /** Expunge either the earliest or latest span, depending on which is farthest from the last added transition. */
56      EXPUNGE_FARTHEST {
57          boolean expungeEarliest(final AbsoluteDate date,
58                                  final AbsoluteDate earliest, final AbsoluteDate latest) {
59              return date.durationFrom(earliest) >= latest.durationFrom(date);
60          }
61      };
62  
63      /** Check if data to be expunged is the earliest data.
64       * @param date current date
65       * @param earliest earliest date
66       * @param latest latest date
67       * @return true if data to be expunged is the earliest data
68       */
69      abstract boolean expungeEarliest(AbsoluteDate date, AbsoluteDate earliest, AbsoluteDate latest);
70  
71  }