/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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.facebook.buck.android.support.exopackage;

import java.io.File;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import android.content.Context;
import android.util.Log;

/**
 * Loads pre-dexed jars installed by the exopackage installer into our ClassLoader.
 * <p>
 * See http://android-developers.blogspot.com/2011/07/custom-class-loading-in-dalvik.html for an
 * explanation of how an app can load pre-dexed libraries. This class goes a step further and then
 * hacks the system class loader so these can be referenced by default. This logic has to run
 * before any class that references the code in these dexes is loaded.
 */
public class ExopackageDexLoader {

  private static final String TAG = "ExopackageDexLoader";

  private ExopackageDexLoader() {}

  /**
   * Load JARs installed by Buck's Exopackage installer and add them to
   * the Application ClassLoader.
   *
   * @param context The application context.
   */
  @SuppressWarnings("PMD.CollapsibleIfStatements")
  public static void loadExopackageJars(Context context) {
    File containingDirectory = new File(
        "/data/local/tmp/exopackage/" + context.getPackageName() + "/secondary-dex");

    List<File> dexJars = new ArrayList<>();
    Set<String> expectedOdexSet = new HashSet<>();

    File[] files = containingDirectory.listFiles();
    if (files != null) {
      for (File file : files) {
        if (file.getName().equals("metadata.txt")) {
          continue;
        }
        if (!file.getName().endsWith(".dex.jar")) {
          Log.w(TAG, "Skipping unexpected file in exopackage directory: " + file.getName());
          continue;
        }
        dexJars.add(file);
        expectedOdexSet.add(file.getName().replaceFirst("\\.jar$", ".dex"));
      }
    }

    File dexOptDir = context.getDir("exopackage_dex_opt", Context.MODE_PRIVATE);
    SystemClassLoaderAdder.installDexJars(context.getClassLoader(), dexOptDir, dexJars);

    File[] odexes = dexOptDir.listFiles();
    if (odexes != null) {
      for (File odex : odexes) {
        if (!expectedOdexSet.contains(odex.getName())) {
          if (!odex.delete()) {
            Log.w(TAG, "Failed to delete stale odex: " + odex.getAbsolutePath());
          }
        }
      }
    }
  }
}