PlatformDataKey.java

/*
 * Copyright 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 androidx.wear.protolayout.expression;

import androidx.annotation.NonNull;
import androidx.annotation.RestrictTo;

/**
 * Represent a {@link DynamicDataKey} that references real-time data from the platform.
 *
 * <p> The [namespace, key] tuple creates the actual reference, so that a single key can refer to
 * two different sources in two different namespaces.
 *
 * <p> The namespace must not be empty. Additionally, the "protolayout" namespace (and its
 * lowercase and uppercase variations) are reserved for the default platform data sources and
 * should not be used for any custom OEM data source. To choose the namespace that does not
 * conflict with an existing one, use a unique prefix for your namespace, for example, company
 * name or product name.
 *
 * @param <T> The data type of the dynamic values that this key is bound to.
 */
public final class PlatformDataKey<T extends DynamicBuilders.DynamicType> extends DynamicDataKey<T>
{
    @NonNull private static final String RESERVED_NAMESPACE = "protolayout";

    /**
     * Create a {@link PlatformDataKey} with the specified key in the given namespace.
     *
     * @param namespace The namespace of the key for the platform data source.
     * @param key The key that references the platform data source.
     */
    public PlatformDataKey(@NonNull String namespace, @NonNull String key) {
        super(namespace, key);
        if (namespace.isEmpty()) {
            throw new IllegalArgumentException("Custom data source namespace must not be empty.");
        }

        if (RESERVED_NAMESPACE.equalsIgnoreCase(namespace)) {
            throw new IllegalArgumentException(String.format(
                    "Custom data source must not use the reserved namespace:%s",
                    RESERVED_NAMESPACE));
        }
    }

    /**
     * Create a {@link PlatformDataKey} with the specified key in the reserved namespace.
     * This should only be used by protolayout library internally for default platform data sources.
     *
     * @param key The key that references the platform data source
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public PlatformDataKey(@NonNull String key) {
        super(RESERVED_NAMESPACE, key);
    }
}