Issue 4399 - Add WebView inheritor with ad blocking

libadblockplus-android-settings/src/org/adblockplus/libadblockplus/android/settings/AdblockHelper.java

Index: libadblockplus-android-settings/src/org/adblockplus/libadblockplus/android/settings/AdblockHelper.java
diff --git a/libadblockplus-android-settings/src/org/adblockplus/libadblockplus/android/settings/AdblockHelper.java b/libadblockplus-android-settings/src/org/adblockplus/libadblockplus/android/settings/AdblockHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..0840fa3e182bd8896eae3fb937c1415504657cdb
--- /dev/null
+++ b/libadblockplus-android-settings/src/org/adblockplus/libadblockplus/android/settings/AdblockHelper.java
@@ -0,0 +1,222 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2016 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.adblockplus.libadblockplus.android.settings;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.util.Log;
+
+import org.adblockplus.libadblockplus.android.AdblockEngine;
+import org.adblockplus.libadblockplus.android.Utils;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * AdblockHelper shared resources
+ * (singleton)
+ */
+public class AdblockHelper
+{
+  private static final String TAG = Utils.getTag(AdblockHelper.class);
+
+  /**
+   * Suggested preference name
+   */
+  public static final String PREFERENCE_NAME = "ADBLOCK";
+  private static AdblockHelper _instance;
+
+  private Context context;
+  private boolean developmentBuild;
+  private String preferenceName;
+  private AdblockEngine engine;
+  private AdblockSettingsStorage storage;
+  private CountDownLatch engineCreated;
+
+  /*
+    Simple ARC management for AdblockEngine
+    Use `retain` and `release`
+   */
+
+  private AtomicInteger referenceCounter = new AtomicInteger(0);
+
+  // singleton
+  protected AdblockHelper()
+  {
+    // prevents instantiation
+  }
+
+  /**
+   * Use to get AdblockHelper instance
+   * @return adblock instance
+   */
+  public static synchronized AdblockHelper get()
+  {
+    if (_instance == null)
+    {
+      _instance = new AdblockHelper();
+    }
+
+    return _instance;
+  }
+
+  public AdblockEngine getEngine()
+  {
+    return engine;
+  }
+
+  public AdblockSettingsStorage getStorage()
+  {
+    return storage;
+  }
+
+  /**
+   * Init with context
+   * @param context application context
+   * @param developmentBuild debug or release?
+   * @param preferenceName Shared Preferences name
+   */
+  public void init(Context context, boolean developmentBuild, String preferenceName)
+  {
+    this.context = context.getApplicationContext();
+    this.developmentBuild = developmentBuild;
+    this.preferenceName = preferenceName;
+  }
+
+  private void createAdblock()
+  {
+    Log.d(TAG, "Creating adblock engine ...");
+
+    // read and apply current settings
+    SharedPreferences prefs = context.getSharedPreferences(preferenceName, Context.MODE_PRIVATE);
+    storage = new SharedPrefsStorage(prefs);
+
+    // latch is required for async (see `waitForReady()`)
+    engineCreated = new CountDownLatch(1);
+
+    engine = AdblockEngine.create(
+      AdblockEngine.generateAppInfo(context, developmentBuild),
+      context.getCacheDir().getAbsolutePath(),
+      true); // `true` as we need element hiding
+    Log.d(TAG, "AdblockHelper engine created");
+
+    AdblockSettings settings = storage.load();
+    if (settings != null)
+    {
+      Log.d(TAG, "Applying saved adblock settings to adblock engine");
+      // apply last saved settings to adblock engine
+
+      // all the settings except `enabled` and whitelisted domains are saved by adblock engine itself
+      engine.setEnabled(settings.isAdblockEnabled());
+      engine.setWhitelistedDomains(settings.getWhitelistedDomains());
+    }
+    else
+    {
+      Log.w(TAG, "No saved adblock settings");
+    }
+
+    // unlock waiting client thread
+    engineCreated.countDown();
+  }
+
+  /**
+   * Wait until everything is ready (used for `retain(true)`)
+   * Warning: locks current thread
+   */
+  public void waitForReady()
+  {
+    if (engineCreated == null)
+    {
+      throw new RuntimeException("AdblockHelper Plus usage exception: call retain(...) first");
+    }
+
+    try
+    {
+      Log.d(TAG, "Waiting for ready ...");
+      engineCreated.await();
+      Log.d(TAG, "Ready");
+    }
+    catch (InterruptedException e)
+    {
+      Log.w(TAG, "Interrupted", e);
+    }
+  }
+
+  private void disposeAdblock()
+  {
+    Log.w(TAG, "Disposing adblock engine");
+
+    engine.dispose();
+    engine = null;
+
+    // to unlock waiting client in WaitForReady()
+    engineCreated.countDown();
+    engineCreated = null;
+
+    storage = null;
+  }
+
+  /**
+   * Get registered clients count
+   * @return registered clients count
+   */
+  public int getCounter()
+  {
+    return referenceCounter.get();
+  }
+
+  /**
+   * Register AdblockHelper engine client
+   * @param asynchronous If `true` engines will be created in background thread without locking of
+   *                     current thread. Use waitForReady() before getEngine() later.
+   *                     If `false` locks current thread.
+   */
+  public synchronized void retain(boolean asynchronous)
+  {
+    if (referenceCounter.getAndIncrement() == 0)
+    {
+      if (!asynchronous)
+      {
+        createAdblock();
+      }
+      else
+      {
+        new Thread(new Runnable()
+        {
+          @Override
+          public void run()
+          {
+            createAdblock();
+          }
+        }).start();
+      }
+    }
+  }
+
+  /**
+   * Unregister AdblockHelper engine client
+   */
+  public synchronized void release()
+  {
+    if (referenceCounter.decrementAndGet() == 0)
+    {
+      waitForReady();
+      disposeAdblock();
+    }
+  }
+}