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      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
     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
     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
     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
     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
     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 
     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       */
     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"})
    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