Support BetterTogether feature flags in services code.

/*

 * Copyright (C) 2023 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.android.server.media;

import android.annotation.StringDef;

import android.provider.DeviceConfig;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/* package */ class MediaFeatureFlagManager {

    /**

     * Namespace for media better together features.

     */

    private static final String NAMESPACE_MEDIA_BETTER_TOGETHER = "media_better_together";

    @StringDef(prefix = "FEATURE_", value = {

        FEATURE_IS_USING_LEGACY_BLUETOOTH_CONTROLLER

    })

    @Target({ ElementType.TYPE_USE, ElementType.TYPE_PARAMETER })

    @Retention(RetentionPolicy.SOURCE)

    /* package */ @interface MediaFeatureFlag {}

    /**

     * Whether to use old legacy implementation of BluetoothRouteController or new

     * 'Audio Strategies'-aware controller.

     */

    /* package */ static final @MediaFeatureFlag String

            FEATURE_IS_USING_LEGACY_BLUETOOTH_CONTROLLER =

            "BluetoothRouteController__enable_legacy_bluetooth_routes_controller";

    private static final MediaFeatureFlagManager sInstance = new MediaFeatureFlagManager();

    private MediaFeatureFlagManager() {

        // Empty to prevent instantiation.

    }

    /* package */ MediaFeatureFlagManager getInstance() {

        return sInstance;

    }

    /**

     * Returns a boolean value from {@link DeviceConfig} from the system_time namespace, or

     * {@code defaultValue} if there is no explicit value set.

     */

    public boolean getBoolean(@MediaFeatureFlag String key, boolean defaultValue) {

        return DeviceConfig.getBoolean(NAMESPACE_MEDIA_BETTER_TOGETHER, key, defaultValue);

    }

}