/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * <p>This source code is licensed under the MIT license found in the LICENSE file in the root
 * directory of this source tree.
 */
package com.facebook.react;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.IBinder;
import android.os.PowerManager;
import androidx.annotation.Nullable;
import com.facebook.infer.annotation.Assertions;
import com.facebook.react.bridge.ReactContext;
import com.facebook.react.bridge.UiThreadUtil;
import com.facebook.react.jstasks.HeadlessJsTaskConfig;
import com.facebook.react.jstasks.HeadlessJsTaskContext;
import com.facebook.react.jstasks.HeadlessJsTaskEventListener;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * Base class for running JS without a UI. Generally, you only need to override {@link
 * #getTaskConfig}, which is called for every {@link #onStartCommand}. The result, if not {@code
 * null}, is used to run a JS task.
 *
 * <p>If you need more fine-grained control over how tasks are run, you can override {@link
 * #onStartCommand} and call {@link #startTask} depending on your custom logic.
 *
 * <p>If you're starting a {@code HeadlessJsTaskService} from a {@code BroadcastReceiver} (e.g.
 * handling push notifications), make sure to call {@link #acquireWakeLockNow} before returning from
 * {@link BroadcastReceiver#onReceive}, to make sure the device doesn't go to sleep before the
 * service is started.
 */
public abstract class HeadlessJsTaskService extends Service implements HeadlessJsTaskEventListener {

  private final Set<Integer> mActiveTasks = new CopyOnWriteArraySet<>();
  private static @Nullable PowerManager.WakeLock sWakeLock;

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    HeadlessJsTaskConfig taskConfig = getTaskConfig(intent);
    if (taskConfig != null) {
      startTask(taskConfig);
      return START_REDELIVER_INTENT;
    }
    return START_NOT_STICKY;
  }

  /**
   * Called from {@link #onStartCommand} to create a {@link HeadlessJsTaskConfig} for this intent.
   *
   * @param intent the {@link Intent} received in {@link #onStartCommand}.
   * @return a {@link HeadlessJsTaskConfig} to be used with {@link #startTask}, or {@code null} to
   *     ignore this command.
   */
  protected @Nullable HeadlessJsTaskConfig getTaskConfig(Intent intent) {
    return null;
  }

  /**
   * Acquire a wake lock to ensure the device doesn't go to sleep while processing background tasks.
   */
  @SuppressLint("WakelockTimeout")
  public static void acquireWakeLockNow(Context context) {
    if (sWakeLock == null || !sWakeLock.isHeld()) {
      PowerManager powerManager =
          Assertions.assertNotNull((PowerManager) context.getSystemService(POWER_SERVICE));
      sWakeLock =
          powerManager.newWakeLock(
              PowerManager.PARTIAL_WAKE_LOCK, HeadlessJsTaskService.class.getCanonicalName());
      sWakeLock.setReferenceCounted(false);
      sWakeLock.acquire();
    }
  }

  @Override
  public @Nullable IBinder onBind(Intent intent) {
    return null;
  }

  /**
   * Start a task. This method handles starting a new React instance if required.
   *
   * <p>Has to be called on the UI thread.
   *
   * @param taskConfig describes what task to start and the parameters to pass to it
   */
  protected void startTask(final HeadlessJsTaskConfig taskConfig) {
    UiThreadUtil.assertOnUiThread();
    acquireWakeLockNow(this);
    final ReactInstanceManager reactInstanceManager =
        getReactNativeHost().getReactInstanceManager();
    ReactContext reactContext = reactInstanceManager.getCurrentReactContext();
    if (reactContext == null) {
      reactInstanceManager.addReactInstanceEventListener(
          new ReactInstanceManager.ReactInstanceEventListener() {
            @Override
            public void onReactContextInitialized(ReactContext reactContext) {
              invokeStartTask(reactContext, taskConfig);
              reactInstanceManager.removeReactInstanceEventListener(this);
            }
          });
      reactInstanceManager.createReactContextInBackground();
    } else {
      invokeStartTask(reactContext, taskConfig);
    }
  }

  private void invokeStartTask(ReactContext reactContext, final HeadlessJsTaskConfig taskConfig) {
    final HeadlessJsTaskContext headlessJsTaskContext =
        HeadlessJsTaskContext.getInstance(reactContext);
    headlessJsTaskContext.addTaskEventListener(this);

    UiThreadUtil.runOnUiThread(
        new Runnable() {
          @Override
          public void run() {
            int taskId = headlessJsTaskContext.startTask(taskConfig);
            mActiveTasks.add(taskId);
          }
        });
  }

  @Override
  public void onDestroy() {
    super.onDestroy();

    if (getReactNativeHost().hasInstance()) {
      ReactInstanceManager reactInstanceManager = getReactNativeHost().getReactInstanceManager();
      ReactContext reactContext = reactInstanceManager.getCurrentReactContext();
      if (reactContext != null) {
        HeadlessJsTaskContext headlessJsTaskContext =
            HeadlessJsTaskContext.getInstance(reactContext);
        headlessJsTaskContext.removeTaskEventListener(this);
      }
    }
    if (sWakeLock != null) {
      sWakeLock.release();
    }
  }

  @Override
  public void onHeadlessJsTaskStart(int taskId) {}

  @Override
  public void onHeadlessJsTaskFinish(int taskId) {
    mActiveTasks.remove(taskId);
    if (mActiveTasks.size() == 0) {
      stopSelf();
    }
  }

  /**
   * Get the {@link ReactNativeHost} used by this app. By default, assumes {@link #getApplication()}
   * is an instance of {@link ReactApplication} and calls {@link
   * ReactApplication#getReactNativeHost()}. Override this method if your application class does not
   * implement {@code ReactApplication} or you simply have a different mechanism for storing a
   * {@code ReactNativeHost}, e.g. as a static field somewhere.
   */
  protected ReactNativeHost getReactNativeHost() {
    return ((ReactApplication) getApplication()).getReactNativeHost();
  }
}