/*
 * Copyright (C) 2017 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.googlecode.android_scripting.service;

import android.app.AlarmManager;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

import com.google.common.base.Preconditions;
import com.googlecode.android_scripting.BaseApplication;
import com.googlecode.android_scripting.ForegroundService;
import com.googlecode.android_scripting.IntentBuilders;
import com.googlecode.android_scripting.NotificationIdFactory;
import com.googlecode.android_scripting.R;
import com.googlecode.android_scripting.activity.TriggerManager;
import com.googlecode.android_scripting.event.Event;
import com.googlecode.android_scripting.event.EventObserver;
import com.googlecode.android_scripting.facade.EventFacade;
import com.googlecode.android_scripting.facade.FacadeConfiguration;
import com.googlecode.android_scripting.facade.FacadeManager;
import com.googlecode.android_scripting.trigger.EventGenerationControllingObserver;
import com.googlecode.android_scripting.trigger.Trigger;
import com.googlecode.android_scripting.trigger.TriggerRepository;
import com.googlecode.android_scripting.trigger.TriggerRepository.TriggerRepositoryObserver;

/**
 * The trigger service takes care of installing triggers serialized to the preference storage.
 *
 * <p>
 * The service also installs an alarm that keeps it running, unless the user force-quits the
 * service.
 *
 * <p>
 * When no triggers are installed the service shuts down silently as to not consume resources
 * unnecessarily.
 *
 */
public class TriggerService extends ForegroundService {
  private static final String CHANNEL_ID = "trigger_service_channel";
  private static final int NOTIFICATION_ID = NotificationIdFactory.create();
  private static final long PING_MILLIS = 10 * 1000 * 60;

  private final IBinder mBinder;
  private TriggerRepository mTriggerRepository;
  private FacadeManager mFacadeManager;
  private EventFacade mEventFacade;

  public class LocalBinder extends Binder {
    public TriggerService getService() {
      return TriggerService.this;
    }
  }

  public TriggerService() {
    super(NOTIFICATION_ID);
    mBinder = new LocalBinder();
  }

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

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

    mFacadeManager =
        new FacadeManager(FacadeConfiguration.getSdkLevel(), this, null,
            FacadeConfiguration.getFacadeClasses());
    mEventFacade = mFacadeManager.getReceiver(EventFacade.class);

    mTriggerRepository = ((BaseApplication) getApplication()).getTriggerRepository();
    mTriggerRepository.bootstrapObserver(new RepositoryObserver());
    mTriggerRepository.bootstrapObserver(new EventGenerationControllingObserver(mFacadeManager));
    installAlarm();
  }

  @Override
  public void onStart(Intent intent, int startId) {
    if (mTriggerRepository.isEmpty()) {
      stopSelfResult(startId);
      return;
    }
  }

  protected void createNotificationChannel() {
    NotificationManager notificationManager = getNotificationManager();
    CharSequence name = getString(R.string.notification_channel_name);
    String description = getString(R.string.notification_channel_description);
    int importance = NotificationManager.IMPORTANCE_DEFAULT;
    NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);
    channel.setDescription(description);
    channel.enableLights(false);
    channel.enableVibration(false);
    notificationManager.createNotificationChannel(channel);
  }

  /** Returns the notification to display whenever the service is running. */
  @Override
  protected Notification createNotification() {
    createNotificationChannel();
    Intent notificationIntent = new Intent(this, TriggerManager.class);
    Notification.Builder builder = new Notification.Builder(this, CHANNEL_ID);
    builder.setSmallIcon(R.drawable.sl4a_logo_48)
           .setTicker("SL4A Trigger Service started.")
           .setWhen(System.currentTimeMillis())
           .setContentTitle("SL4A Trigger Service")
           .setContentText("Tap to view triggers")
           .setContentIntent(PendingIntent.getActivity(this, 0, notificationIntent,
                   PendingIntent.FLAG_IMMUTABLE));
    Notification notification = builder.build();
    notification.flags = Notification.FLAG_NO_CLEAR | Notification.FLAG_ONGOING_EVENT;
    return notification;
  }

  private class TriggerEventObserver implements EventObserver {
    private final Trigger mTrigger;

    public TriggerEventObserver(Trigger trigger) {
      mTrigger = trigger;
    }

    @Override
    public void onEventReceived(Event event) {
      mTrigger.handleEvent(event, TriggerService.this);
    }
  }

  private class RepositoryObserver implements TriggerRepositoryObserver {
    int mTriggerCount = 0;

    @Override
    public void onPut(Trigger trigger) {
      mTriggerCount++;
      mEventFacade.addNamedEventObserver(trigger.getEventName(), new TriggerEventObserver(trigger));
    }

    @Override
    public void onRemove(Trigger trigger) {
      Preconditions.checkArgument(mTriggerCount > 0);
      // TODO(damonkohler): Tear down EventObserver associated with trigger.
      if (--mTriggerCount == 0) {
        // TODO(damonkohler): Use stopSelfResult() which would require tracking startId.
        stopSelf();
      }
    }
  }

  private void installAlarm() {
    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
    alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + PING_MILLIS,
        PING_MILLIS, IntentBuilders.buildTriggerServicePendingIntent(this));
  }

  private void uninstallAlarm() {
    AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
    alarmManager.cancel(IntentBuilders.buildTriggerServicePendingIntent(this));
  }

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