1 /*
2  * Copyright (C) 2010 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.loganalysis.util.config;
18 
19 import java.lang.reflect.Field;
20 import java.util.Collection;
21 import java.util.Map;
22 
23 /**
24  * Controls the behavior when an option is specified multiple times.  Note that this enum assumes
25  * that the values to be set are not {@link Collection}s or {@link Map}s.
26  */
27 //TODO: Use libTF once this is copied over.
28 public enum OptionUpdateRule {
29     /** once an option is set, subsequent attempts to update it should be ignored. */
30     FIRST {
31         @Override
update(String optionName, Object current, Object update)32         Object update(String optionName, Object current, Object update)
33                 throws ConfigurationException {
34             if (current == null) return update;
35             return current;
36         }
37     },
38 
39     /** if an option is set multiple times, ignore all but the last value. */
40     LAST {
41         @Override
update(String optionName, Object current, Object update)42         Object update(String optionName, Object current, Object update)
43                 throws ConfigurationException {
44             return update;
45         }
46     },
47 
48     /** for {@link Comparable} options, keep the one that compares as the greatest. */
49     GREATEST {
50         @Override
update(String optionName, Object current, Object update)51         Object update(String optionName, Object current, Object update)
52                 throws ConfigurationException {
53             if (current == null) return update;
54             if (compare(optionName, current, update) < 0) {
55                 // current < update; so use the update
56                 return update;
57             } else {
58                 // current >= update; so keep current
59                 return current;
60             }
61         }
62     },
63 
64     /** for {@link Comparable} options, keep the one that compares as the least. */
65     LEAST {
66         @Override
update(String optionName, Object current, Object update)67         Object update(String optionName, Object current, Object update)
68                 throws ConfigurationException {
69             if (current == null) return update;
70             if (compare(optionName, current, update) > 0) {
71                 // current > update; so use the update
72                 return update;
73             } else {
74                 // current <= update; so keep current
75                 return current;
76             }
77         }
78     },
79 
80     /** throw a {@link ConfigurationException} if this option is set more than once. */
81     IMMUTABLE {
82         @Override
update(String optionName, Object current, Object update)83         Object update(String optionName, Object current, Object update)
84                 throws ConfigurationException {
85             if (current == null) return update;
86             throw new ConfigurationException(String.format(
87                     "Attempted to update immutable value (%s) for option \"%s\"", optionName,
88                     optionName));
89         }
90     };
91 
update(String optionName, Object current, Object update)92     abstract Object update(String optionName, Object current, Object update)
93             throws ConfigurationException;
94 
95     /**
96       * Takes the current value and the update value, and returns the value to be set.  Assumes
97       * that <code>update</code> is never null.
98       */
update(String optionName, Object optionSource, Field field, Object update)99     public Object update(String optionName, Object optionSource, Field field, Object update)
100             throws ConfigurationException {
101         Object current;
102         try {
103             current = field.get(optionSource);
104         } catch (IllegalAccessException e) {
105             throw new ConfigurationException(String.format(
106                     "internal error when setting option '%s'", optionName), e);
107         }
108         return update(optionName, current, update);
109     }
110 
111     /**
112      * Check if the objects are {@link Comparable}, and if so, compare them using
113      * {@see Comparable#compareTo}.
114      */
115     @SuppressWarnings({"unchecked", "rawtypes"})
compare(String optionName, Object current, Object update)116     private static int compare(String optionName, Object current, Object update)
117             throws ConfigurationException {
118         Comparable compCurrent;
119         if (current instanceof Comparable) {
120             compCurrent = (Comparable) current;
121         } else {
122             throw new ConfigurationException(String.format(
123                     "internal error: Class %s for option %s was used with GREATEST or LEAST " +
124                     "updateRule, but does not implement Comparable.",
125                     current.getClass().getSimpleName(), optionName));
126         }
127 
128         try {
129             return compCurrent.compareTo(update);
130         } catch (ClassCastException e) {
131             throw new ConfigurationException(String.format(
132                     "internal error: Failed to compare %s (%s) and %s (%s)",
133                     current.getClass().getName(), current, update.getClass().getName(), update), e);
134         }
135     }
136 }
137 
138