Reland of "precache: Move the java files into //components/precache/android"

chrome/android/java/src/org/chromium/chrome/browser/precache/PrecacheServiceLauncher.java

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.precache;
+
+import android.app.AlarmManager;
+import android.app.PendingIntent;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.content.SharedPreferences.Editor;
+import android.os.PowerManager;
+import android.os.PowerManager.WakeLock;
+import android.os.SystemClock;
+import android.preference.PreferenceManager;
+
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.components.precache.DeviceState;
+
+/**
+ * BroadcastReceiver that determines when conditions are right for precaching, and starts the
+ * {@link PrecacheService} if they are. Conditions are right for precaching when the device is
+ * connected to power, Wi-Fi, interactivity (e.g., the screen) is off, and at least
+ * |WAIT_UNTIL_NEXT_PRECACHE_MS| have passed since the last time precaching was done.
+ */
+public class PrecacheServiceLauncher extends BroadcastReceiver {
+    private static final String TAG = "PrecacheServiceLauncher";
+
+    @VisibleForTesting
+    static final String PREF_IS_PRECACHING_ENABLED = "precache.is_precaching_enabled";
+
+    @VisibleForTesting
+    static final String PREF_PRECACHE_LAST_TIME = "precache.last_time";
+
+    @VisibleForTesting
+    static final String ACTION_ALARM =
+            "org.chromium.chrome.browser.precache.PrecacheServiceLauncher.ALARM";
+
+    private static final int INTERACTIVE_STATE_POLLING_PERIOD_MS = 15 * 60 * 1000;  // 15 minutes.
+    static final int WAIT_UNTIL_NEXT_PRECACHE_MS = 4 * 60 * 60 * 1000;  // 4 hours.
+
+    private static WakeLock sWakeLock = null;
+
+    private DeviceState mDeviceState = DeviceState.getInstance();
+
+    @VisibleForTesting
+    void setDeviceState(DeviceState deviceState) {
+        mDeviceState = deviceState;
+    }
+
+    /**
+     * Set whether or not precaching is enabled. If precaching is enabled, this receiver will start
+     * the PrecacheService when it receives an intent. If precaching is disabled, any running
+     * PrecacheService will be stopped, and this receiver will do nothing when it receives an
+     * intent.
+     *
+     * @param context The Context to use.
+     * @param enabled Whether or not precaching is enabled.
+     */
+    public static void setIsPrecachingEnabled(Context context, boolean enabled) {
+        Editor editor = PreferenceManager.getDefaultSharedPreferences(context).edit();
+        editor.putBoolean(PREF_IS_PRECACHING_ENABLED, enabled);
+        editor.apply();
+
+        if (!enabled) {
+            // Stop any running PrecacheService. If PrecacheService is not running, then this does
+            // nothing.
+            Intent serviceIntent = new Intent(null, null, context, PrecacheService.class);
+            context.stopService(serviceIntent);
+        }
+    }
+
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean isPrecachingEnabled = prefs.getBoolean(PREF_IS_PRECACHING_ENABLED, false);
+        long lastPrecacheTimeMs = prefs.getLong(PREF_PRECACHE_LAST_TIME, 0L);
+        if (lastPrecacheTimeMs > getElapsedRealtimeOnSystem()) {
+            // System.elapsedRealtime() counts milliseconds since boot, so if the device has been
+            // rebooted since the last time precaching was performed, reset lastPrecacheTimeMs to 0.
+            lastPrecacheTimeMs = 0L;
+        }
+
+        // Do nothing if precaching is disabled.
+        if (!isPrecachingEnabled) return;
+
+        boolean isPowerConnected = mDeviceState.isPowerConnected(context);
+        boolean isWifiAvailable = mDeviceState.isWifiAvailable(context);
+        boolean isInteractive = mDeviceState.isInteractive(context);
+        boolean areConditionsGoodForPrecaching =
+                isPowerConnected && isWifiAvailable && !isInteractive;
+        long timeSinceLastPrecacheMs = getElapsedRealtimeOnSystem() - lastPrecacheTimeMs;
+        boolean hasEnoughTimePassedSinceLastPrecache =
+                timeSinceLastPrecacheMs >= WAIT_UNTIL_NEXT_PRECACHE_MS;
+
+        // Only start precaching when an alarm action is received. This is to prevent situations
+        // such as power being connected, precaching starting, then precaching being immediately
+        // canceled because the screen turns on in response to power being connected.
+        if (ACTION_ALARM.equals(intent.getAction())
+                && areConditionsGoodForPrecaching
+                && hasEnoughTimePassedSinceLastPrecache) {
+            // Store a pref indicating that precaching is starting now.
+            Editor editor = prefs.edit();
+            editor.putLong(PREF_PRECACHE_LAST_TIME, getElapsedRealtimeOnSystem());
+            editor.apply();
+
+            setAlarm(context, Math.max(
+                    INTERACTIVE_STATE_POLLING_PERIOD_MS, WAIT_UNTIL_NEXT_PRECACHE_MS));
+
+            acquireWakeLockAndStartService(context);
+        } else {
+            if (isPowerConnected && isWifiAvailable) {
+                // If we're just waiting for non-interactivity (e.g., the screen to be off), or for
+                // enough time to pass after Wi-Fi or power has been connected, then set an alarm
+                // for the next time to check the device state. We can't receive SCREEN_ON/OFF
+                // intents as is done for detecting changes in power and connectivity, because
+                // SCREEN_ON/OFF intents are only delivered to BroadcastReceivers that are
+                // registered dynamically in code, but the PrecacheServiceLauncher is registered in
+                // the Android manifest.
+                setAlarm(context, Math.max(INTERACTIVE_STATE_POLLING_PERIOD_MS,
+                        WAIT_UNTIL_NEXT_PRECACHE_MS - timeSinceLastPrecacheMs));
+            } else {
+                // If the device doesn't have connected power or doesn't have Wi-Fi, then there's no
+                // point in setting an alarm.
+                cancelAlarm(context);
+            }
+        }
+    }
+
+    /** Release the wakelock if it is held. */
+    @VisibleForTesting
+    protected static void releaseWakeLock() {
+        ThreadUtils.assertOnUiThread();
+        if (sWakeLock != null && sWakeLock.isHeld()) sWakeLock.release();
+    }
+
+    /**
+     * Acquire the wakelock and start the PrecacheService.
+     *
+     * @param context The Context to use to start the service.
+     */
+    private void acquireWakeLockAndStartService(Context context) {
+        acquireWakeLock(context);
+        startPrecacheService(context);
+    }
+
+    @VisibleForTesting
+    protected void startPrecacheService(Context context) {
+        Intent serviceIntent = new Intent(
+                PrecacheService.ACTION_START_PRECACHE, null, context, PrecacheService.class);
+        context.startService(serviceIntent);
+    }
+
+    @VisibleForTesting
+    protected void acquireWakeLock(Context context) {
+        ThreadUtils.assertOnUiThread();
+        if (sWakeLock == null) {
+            PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
+            sWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
+        }
+        sWakeLock.acquire();
+    }
+
+    /**
+     * Get a PendingIntent for setting an alarm to notify the PrecacheServiceLauncher.
+     *
+     * @param context The Context to use for the PendingIntent.
+     * @return The PendingIntent.
+     */
+    private static PendingIntent getPendingAlarmIntent(Context context) {
+        return PendingIntent.getBroadcast(context, 0,
+                new Intent(ACTION_ALARM, null, context, PrecacheServiceLauncher.class),
+                PendingIntent.FLAG_UPDATE_CURRENT);
+    }
+
+    /**
+     * Set an alarm to notify the PrecacheServiceLauncher in the future.
+     *
+     * @param context The Context to use.
+     * @param delayMs Delay in milliseconds before the alarm goes off.
+     */
+    private void setAlarm(Context context, long delayMs) {
+        setAlarmOnSystem(context, AlarmManager.ELAPSED_REALTIME_WAKEUP,
+                getElapsedRealtimeOnSystem() + delayMs, getPendingAlarmIntent(context));
+    }
+
+    /**
+     * Set the alarm on the system using the given parameters. This method can be overridden in
+     * tests.
+     */
+    @VisibleForTesting
+    protected void setAlarmOnSystem(Context context, int type, long triggerAtMillis,
+            PendingIntent operation) {
+        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
+        alarmManager.set(type, triggerAtMillis, operation);
+    }
+
+    /**
+     * Cancel a previously set alarm, if there is one. This method can be overridden in tests.
+     *
+     * @param context The Context to use.
+     */
+    private void cancelAlarm(Context context) {
+        cancelAlarmOnSystem(context, getPendingAlarmIntent(context));
+    }
+
+    /** Cancel a previously set alarm on the system. This method can be overridden in tests. */
+    @VisibleForTesting
+    protected void cancelAlarmOnSystem(Context context, PendingIntent operation) {
+        AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
+        alarmManager.cancel(operation);
+    }
+
+    @VisibleForTesting
+    protected long getElapsedRealtimeOnSystem() {
+        return SystemClock.elapsedRealtime();
+    }
+}
+