1   /* Copyright 2002-2016 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.time;
18  
19  import java.io.Serializable;
20  
21  /** Interface for time scales.
22   * <p>This is the interface representing all time scales. Time scales are related
23   * to each other by some offsets that may be discontinuous (for example
24   * the {@link UTCScale UTC scale} with respect to the {@link TAIScale
25   * TAI scale}).</p>
26   * @author Luc Maisonobe
27   * @see AbsoluteDate
28   */
29  public interface TimeScale extends Serializable {
30  
31      /** Get the offset to convert locations from {@link TAIScale} to instance.
32       * @param date conversion date
33       * @return offset in seconds to add to a location in <em>{@link TAIScale}
34       * time scale</em> to get a location in <em>instance time scale</em>
35       * @see #offsetToTAI(DateComponents, TimeComponents)
36       */
37      double offsetFromTAI(AbsoluteDate date);
38  
39      /** Get the offset to convert locations from instance to {@link TAIScale}.
40       * @param date date location in the time scale
41       * @param time time location in the time scale
42       * @return offset in seconds to add to a location in <em>instance time scale</em>
43       * to get a location in <em>{@link TAIScale} time scale</em>
44       * @see #offsetFromTAI(AbsoluteDate)
45       */
46      default double offsetToTAI(final DateComponents date, final TimeComponents time) {
47          final AbsoluteDate reference = new AbsoluteDate(date, time, TimeScalesFactory.getTAI());
48          double offset = 0;
49          for (int i = 0; i < 8; i++) {
50              offset = -offsetFromTAI(reference.shiftedBy(offset));
51          }
52          return offset;
53      }
54  
55      /** Check if date is within a leap second introduction <em>in this time scale</em>.
56       * <p>
57       * This method will return false for all time scales that do <em>not</em>
58       * implement leap seconds, even if the date corresponds to a leap second
59       * in {@link UTCScale UTC scale}.
60       * </p>
61       * @param date date to check
62       * @return true if time is within a leap second introduction
63       */
64      default boolean insideLeap(final AbsoluteDate date) {
65          return false;
66      }
67  
68      /** Check length of the current minute <em>in this time scale</em>.
69       * <p>
70       * This method will return 60 for all time scales that do <em>not</em>
71       * implement leap seconds, even if the date corresponds to a leap second
72       * in {@link UTCScale UTC scale}, and 61 for time scales that do implement
73       * leap second when the current date is within the last minute before the
74       * leap, or during the leap itself.
75       * </p>
76       * @param date date to check
77       * @return 60 or 61 depending on leap seconds introduction
78       */
79      default int minuteDuration(final AbsoluteDate date) {
80          return 60;
81      }
82  
83      /** Get the value of the previous leap.
84       * <p>
85       * This method will return 0.0 for all time scales that do <em>not</em>
86       * implement leap seconds.
87       * </p>
88       * @param date date to check
89       * @return value of the previous leap
90       */
91      default double getLeap(final AbsoluteDate date) {
92          return 0;
93      }
94  
95      /** Get the name time scale.
96       * @return name of the time scale
97       */
98      String getName();
99  
100 }