1 /*
2  * Copyright (C) 2023 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 android.flags;
18 
19 import android.annotation.NonNull;
20 
21 /**
22  * Base class for constants read via {@link android.flags.FeatureFlags}.
23  *
24  * @param <T> The type of value that this flag stores. E.g. Boolean or String.
25  *
26  * @hide
27  */
28 public interface Flag<T> {
29     /** The namespace for a flag. Should combine uniquely with its name. */
30     @NonNull
getNamespace()31     String getNamespace();
32 
33     /** The name of the flag. Should combine uniquely with its namespace. */
34     @NonNull
getName()35     String getName();
36 
37     /** The value of this flag if no override has been set. Null values are not supported. */
38     @NonNull
getDefault()39     T getDefault();
40 
41     /** Returns true if the value of this flag can change at runtime. */
isDynamic()42     default boolean isDynamic() {
43         return false;
44     }
45 
46     /**
47      * Add human-readable details to the flag. Flag client's are not required to set this.
48      *
49      * See {@link #getLabel()}, {@link #getDescription()}, and {@link #getCategoryName()}.
50      *
51      * @return Returns `this`, to make a fluent api.
52      */
defineMetaData(String label, String description, String categoryName)53     Flag<T> defineMetaData(String label, String description, String categoryName);
54 
55     /**
56      * A human-readable name for the flag. Defaults to {@link #getName()}
57      *
58      * See {@link #defineMetaData(String, String, String)}
59      */
60     @NonNull
getLabel()61     default String getLabel() {
62         return getName();
63     }
64 
65     /**
66      * A human-readable description for the flag. Defaults to null if unset.
67      *
68      * See {@link #defineMetaData(String, String, String)}
69      */
getDescription()70     default String getDescription() {
71         return null;
72     }
73 
74     /**
75      * A human-readable category name for the flag. Defaults to null if unset.
76      *
77      * See {@link #defineMetaData(String, String, String)}
78      */
getCategoryName()79     default String getCategoryName() {
80         return null;
81     }
82 }
83