1   /* Copyright 2002-2021 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  
18  package org.orekit.frames;
19  
20  import org.hipparchus.CalculusFieldElement;
21  import org.orekit.time.AbsoluteDate;
22  import org.orekit.time.FieldAbsoluteDate;
23  
24  /** Utility for Transform providers.
25   * @author Luc Maisonobe
26   * @since 9.2
27   */
28  public class TransformProviderUtils {
29  
30      /** Identity provider.
31       * <p>
32       * The transforms generated by this providers are always {@link Transform#IDENTITY}.
33       * </p>
34       */
35      public static final TransformProvider IDENTITY_PROVIDER = new TransformProvider() {
36  
37          /** Serializable UID. */
38          private static final long serialVersionUID = 20180330L;
39  
40          /** {@inheritDoc}
41           * <p>
42           * Always returns {@link Transform#IDENTITY}
43           * </p>
44           */
45          @Override
46          public Transform getTransform(final AbsoluteDate date) {
47              return Transform.IDENTITY;
48          }
49  
50          /** {@inheritDoc}
51           * <p>
52           * Always returns {@link FieldTransform#getIdentity(org.hipparchus.Field)}
53           * </p>
54           */
55          @Override
56          public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
57              return FieldTransform.getIdentity(date.getField());
58          }
59  
60      };
61  
62      /** Private constructor.
63       * <p>This class is a utility class, it should neither have a public
64       * nor a default constructor. This private constructor prevents
65       * the compiler from generating one automatically.</p>
66       */
67      private TransformProviderUtils() {
68      }
69  
70      /** Reverse a transform provider.
71       * @param provider provider to reverse
72       * @return a new provider which provide a transform similar to
73       * {@code provider.getTransform(date).getInverse()}
74       */
75      public static TransformProvider getReversedProvider(final TransformProvider provider) {
76          return new TransformProvider() {
77  
78              /** serializable UID. */
79              private static final long serialVersionUID = 20180330L;
80  
81              /** {@inheritDoc} */
82              @Override
83              public Transform getTransform(final AbsoluteDate date) {
84                  return provider.getTransform(date).getInverse();
85              }
86  
87              /** {@inheritDoc} */
88              @Override
89              public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
90                  return provider.getTransform(date).getInverse();
91              }
92  
93          };
94      }
95  
96      /** Combine two transform providers.
97       * @param first first provider to apply
98       * @param second second provider to apply
99       * @return a new provider which provide a transform similar to
100      * {@code new Transform(date, first.getTransform(date), second.getTransform(date))}
101      */
102     public static TransformProvider getCombinedProvider(final TransformProvider first,
103                                                         final TransformProvider second) {
104         return new TransformProvider() {
105 
106             /** serializable UID. */
107             private static final long serialVersionUID = 20180330L;
108 
109             /** {@inheritDoc} */
110             @Override
111             public Transform getTransform(final AbsoluteDate date) {
112                 return new Transform(date, first.getTransform(date), second.getTransform(date));
113             }
114 
115             /** {@inheritDoc} */
116             @Override
117             public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
118                 return new FieldTransform<>(date, first.getTransform(date), second.getTransform(date));
119             }
120 
121         };
122     }
123 
124 }