1/**
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5 * use this file except in compliance with the License. You may obtain a copy of
6 * the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations under
14 * the License.
15 */
16
17package com.android.inputmethod.dictionarypack;
18
19import android.app.AlarmManager;
20import android.app.PendingIntent;
21import android.app.Service;
22import android.content.Context;
23import android.content.Intent;
24import android.os.IBinder;
25import android.util.Log;
26import android.widget.Toast;
27
28import com.android.inputmethod.latin.BinaryDictionaryFileDumper;
29import com.android.inputmethod.latin.R;
30import com.android.inputmethod.latin.common.LocaleUtils;
31
32import java.util.Locale;
33import java.util.Random;
34import java.util.concurrent.LinkedBlockingQueue;
35import java.util.concurrent.ThreadPoolExecutor;
36import java.util.concurrent.TimeUnit;
37
38import javax.annotation.Nonnull;
39
40/**
41 * Service that handles background tasks for the dictionary provider.
42 *
43 * This service provides the context for the long-running operations done by the
44 * dictionary provider. Those include:
45 * - Checking for the last update date and scheduling the next update. This runs every
46 *   day around midnight, upon reception of the DATE_CHANGED_INTENT_ACTION broadcast.
47 *   Every four days, it schedules an update of the metadata with the alarm manager.
48 * - Issuing the order to update the metadata. This runs every four days, between 0 and
49 *   6, upon reception of the UPDATE_NOW_INTENT_ACTION broadcast sent by the alarm manager
50 *   as a result of the above action.
51 * - Handling a download that just ended. These come in two flavors:
52 *   - Metadata is finished downloading. We should check whether there are new dictionaries
53 *     available, and download those that we need that have new versions.
54 *   - A dictionary file finished downloading. We should put the file ready for a client IME
55 *     to access, and mark the current state as such.
56 */
57public final class DictionaryService extends Service {
58    private static final String TAG = DictionaryService.class.getSimpleName();
59
60    /**
61     * The package name, to use in the intent actions.
62     */
63    private static final String PACKAGE_NAME = "com.android.inputmethod.latin";
64
65    /**
66     * The action of the date changing, used to schedule a periodic freshness check
67     */
68    private static final String DATE_CHANGED_INTENT_ACTION =
69            Intent.ACTION_DATE_CHANGED;
70
71    /**
72     * The action of displaying a toast to warn the user an automatic download is starting.
73     */
74    /* package */ static final String SHOW_DOWNLOAD_TOAST_INTENT_ACTION =
75            PACKAGE_NAME + ".SHOW_DOWNLOAD_TOAST_INTENT_ACTION";
76
77    /**
78     * A locale argument, as a String.
79     */
80    /* package */ static final String LOCALE_INTENT_ARGUMENT = "locale";
81
82    /**
83     * How often, in milliseconds, we want to update the metadata. This is a
84     * floor value; actually, it may happen several hours later, or even more.
85     */
86    private static final long UPDATE_FREQUENCY_MILLIS = TimeUnit.DAYS.toMillis(4);
87
88    /**
89     * We are waked around midnight, local time. We want to wake between midnight and 6 am,
90     * roughly. So use a random time between 0 and this delay.
91     */
92    private static final int MAX_ALARM_DELAY_MILLIS = (int)TimeUnit.HOURS.toMillis(6);
93
94    /**
95     * How long we consider a "very long time". If no update took place in this time,
96     * the content provider will trigger an update in the background.
97     */
98    private static final long VERY_LONG_TIME_MILLIS = TimeUnit.DAYS.toMillis(14);
99
100    /**
101     * After starting a download, how long we wait before considering it may be stuck. After this
102     * period is elapsed, if the keyboard tries to download again, then we cancel and re-register
103     * the request; if it's within this time, we just leave it be.
104     * It's important to note that we do not re-submit the request merely because the time is up.
105     * This is only to decide whether to cancel the old one and re-requesting when the keyboard
106     * fires a new request for the same data.
107     */
108    public static final long NO_CANCEL_DOWNLOAD_PERIOD_MILLIS = TimeUnit.SECONDS.toMillis(30);
109
110    /**
111     * An executor that serializes tasks given to it.
112     */
113    private ThreadPoolExecutor mExecutor;
114    private static final int WORKER_THREAD_TIMEOUT_SECONDS = 15;
115
116    @Override
117    public void onCreate() {
118        // By default, a thread pool executor does not timeout its core threads, so it will
119        // never kill them when there isn't any work to do any more. That would mean the service
120        // can never die! By creating it this way and calling allowCoreThreadTimeOut, we allow
121        // the single thread to time out after WORKER_THREAD_TIMEOUT_SECONDS = 15 seconds, allowing
122        // the process to be reclaimed by the system any time after that if it's not doing
123        // anything else.
124        // Executors#newSingleThreadExecutor creates a ThreadPoolExecutor but it returns the
125        // superclass ExecutorService which does not have the #allowCoreThreadTimeOut method,
126        // so we can't use that.
127        mExecutor = new ThreadPoolExecutor(1 /* corePoolSize */, 1 /* maximumPoolSize */,
128                WORKER_THREAD_TIMEOUT_SECONDS /* keepAliveTime */,
129                TimeUnit.SECONDS /* unit for keepAliveTime */,
130                new LinkedBlockingQueue<Runnable>() /* workQueue */);
131        mExecutor.allowCoreThreadTimeOut(true);
132    }
133
134    @Override
135    public void onDestroy() {
136    }
137
138    @Override
139    public IBinder onBind(Intent intent) {
140        // This service cannot be bound
141        return null;
142    }
143
144    /**
145     * Executes an explicit command.
146     *
147     * This is the entry point for arbitrary commands that are executed upon reception of certain
148     * events that should be executed on the context of this service. The supported commands are:
149     * - Check last update time and possibly schedule an update of the data for later.
150     *     This is triggered every day, upon reception of the DATE_CHANGED_INTENT_ACTION broadcast.
151     * - Update data NOW.
152     *     This is normally received upon trigger of the scheduled update.
153     * - Handle a finished download.
154     *     This executes the actions that must be taken after a file (metadata or dictionary data
155     *     has been downloaded (or failed to download).
156     * The commands that can be spun an another thread will be executed serially, in order, on
157     * a worker thread that is created on demand and terminates after a short while if there isn't
158     * any work left to do.
159     */
160    @Override
161    public synchronized int onStartCommand(final Intent intent, final int flags,
162            final int startId) {
163        final DictionaryService self = this;
164        if (SHOW_DOWNLOAD_TOAST_INTENT_ACTION.equals(intent.getAction())) {
165            final String localeString = intent.getStringExtra(LOCALE_INTENT_ARGUMENT);
166            if (localeString == null) {
167                Log.e(TAG, "Received " + intent.getAction() + " without locale; skipped");
168            } else {
169                // This is a UI action, it can't be run in another thread
170                showStartDownloadingToast(
171                        this, LocaleUtils.constructLocaleFromString(localeString));
172            }
173        } else {
174            // If it's a command that does not require UI, arrange for the work to be done on a
175            // separate thread, so that we can return right away. The executor will spawn a thread
176            // if necessary, or reuse a thread that has become idle as appropriate.
177            // DATE_CHANGED or UPDATE_NOW are examples of commands that can be done on another
178            // thread.
179            mExecutor.submit(new Runnable() {
180                @Override
181                public void run() {
182                    dispatchBroadcast(self, intent);
183                    // Since calls to onStartCommand are serialized, the submissions to the executor
184                    // are serialized. That means we are guaranteed to call the stopSelfResult()
185                    // in the same order that we got them, so we don't need to take care of the
186                    // order.
187                    stopSelfResult(startId);
188                }
189            });
190        }
191        return Service.START_REDELIVER_INTENT;
192    }
193
194    static void dispatchBroadcast(final Context context, final Intent intent) {
195        final String action = intent.getAction();
196        if (DATE_CHANGED_INTENT_ACTION.equals(action)) {
197            // This happens when the date of the device changes. This normally happens
198            // at midnight local time, but it may happen if the user changes the date
199            // by hand or something similar happens.
200            checkTimeAndMaybeSetupUpdateAlarm(context);
201        } else if (DictionaryPackConstants.UPDATE_NOW_INTENT_ACTION.equals(action)) {
202            // Intent to trigger an update now.
203            UpdateHandler.tryUpdate(context);
204        } else if (DictionaryPackConstants.INIT_AND_UPDATE_NOW_INTENT_ACTION.equals(action)) {
205            // Initialize the client Db.
206            final String mClientId = context.getString(R.string.dictionary_pack_client_id);
207            BinaryDictionaryFileDumper.initializeClientRecordHelper(context, mClientId);
208
209            // Updates the metadata and the download the dictionaries.
210            UpdateHandler.tryUpdate(context);
211        } else {
212            UpdateHandler.downloadFinished(context, intent);
213        }
214    }
215
216    /**
217     * Setups an alarm to check for updates if an update is due.
218     */
219    private static void checkTimeAndMaybeSetupUpdateAlarm(final Context context) {
220        // Of all clients, if the one that hasn't been updated for the longest
221        // is still more recent than UPDATE_FREQUENCY_MILLIS, do nothing.
222        if (!isLastUpdateAtLeastThisOld(context, UPDATE_FREQUENCY_MILLIS)) return;
223
224        PrivateLog.log("Date changed - registering alarm");
225        AlarmManager alarmManager = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
226
227        // Best effort to wake between midnight and MAX_ALARM_DELAY_MILLIS in the morning.
228        // It doesn't matter too much if this is very inexact.
229        final long now = System.currentTimeMillis();
230        final long alarmTime = now + new Random().nextInt(MAX_ALARM_DELAY_MILLIS);
231        final Intent updateIntent = new Intent(DictionaryPackConstants.UPDATE_NOW_INTENT_ACTION);
232        final PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0,
233                updateIntent, PendingIntent.FLAG_CANCEL_CURRENT);
234
235        // We set the alarm in the type that doesn't forcefully wake the device
236        // from sleep, but fires the next time the device actually wakes for any
237        // other reason.
238        if (null != alarmManager) alarmManager.set(AlarmManager.RTC, alarmTime, pendingIntent);
239    }
240
241    /**
242     * Utility method to decide whether the last update is older than a certain time.
243     *
244     * @return true if at least `time' milliseconds have elapsed since last update, false otherwise.
245     */
246    private static boolean isLastUpdateAtLeastThisOld(final Context context, final long time) {
247        final long now = System.currentTimeMillis();
248        final long lastUpdate = MetadataDbHelper.getOldestUpdateTime(context);
249        PrivateLog.log("Last update was " + lastUpdate);
250        return lastUpdate + time < now;
251    }
252
253    /**
254     * Refreshes data if it hasn't been refreshed in a very long time.
255     *
256     * This will check the last update time, and if it's been more than VERY_LONG_TIME_MILLIS,
257     * update metadata now - and possibly take subsequent update actions.
258     */
259    public static void updateNowIfNotUpdatedInAVeryLongTime(final Context context) {
260        if (!isLastUpdateAtLeastThisOld(context, VERY_LONG_TIME_MILLIS)) return;
261        UpdateHandler.tryUpdate(context);
262    }
263
264    /**
265     * Shows a toast informing the user that an automatic dictionary download is starting.
266     */
267    private static void showStartDownloadingToast(final Context context,
268            @Nonnull final Locale locale) {
269        final String toastText = String.format(
270                context.getString(R.string.toast_downloading_suggestions),
271                locale.getDisplayName());
272        Toast.makeText(context, toastText, Toast.LENGTH_LONG).show();
273    }
274}
275