/*
 * Copyright (C) 2015 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.test.runner.intent;

import java.util.concurrent.atomic.AtomicReference;

/** Exposes an implementation of {@link IntentMonitor} to users. */
public final class IntentMonitorRegistry {

  private static final AtomicReference<IntentMonitor> monitorRef =
      new AtomicReference<IntentMonitor>(null);

  /**
   * Returns the IntentMonitor. This monitor is not guaranteed to be present under all'
   * instrumentations.
   *
   * @throws IllegalStateException if no monitor has been registered.
   */
  public static IntentMonitor getInstance() {
    IntentMonitor instance = monitorRef.get();
    if (null == instance) {
      throw new IllegalStateException(
          "No intent monitor registered! Are you running under an "
              + "Instrumentation which registers intent monitors?");
    }
    return instance;
  }

  /**
   * Stores the given {@link IntentMonitor} instance in the registry. Passing null removes the
   * monitor from the registry.
   */
  public static void registerInstance(IntentMonitor monitor) {
    monitorRef.set(monitor);
  }

  private IntentMonitorRegistry() {
    // no instance
  }
}