content: /*
   * Copyright (C) 2011 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.actionbarsherlock.widget;
  
  import android.content.ComponentName;
  import android.content.Context;
  import android.content.Intent;
  import android.content.pm.ResolveInfo;
  import android.database.DataSetObservable;
  import android.os.Handler;
  import android.text.TextUtils;
  import android.util.Log;
  import android.util.Xml;
  import org.xmlpull.v1.XmlPullParser;
  import org.xmlpull.v1.XmlPullParserException;
  import org.xmlpull.v1.XmlSerializer;
  
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.math.BigDecimal;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.Executor;
  import java.util.concurrent.Executors;
  
  /**
   * <p>
   * This class represents a data model for choosing a component for handing a
   * given {@link Intent}. The model is responsible for querying the system for
   * activities that can handle the given intent and order found activities
   * based on historical data of previous choices. The historical data is stored
   * in an application private file. If a client does not want to have persistent
   * choice history the file can be omitted, thus the activities will be ordered
   * based on historical usage for the current session.
   * <p>
   * </p>
   * For each backing history file there is a singleton instance of this class. Thus,
   * several clients that specify the same history file will share the same model. Note
   * that if multiple clients are sharing the same model they should implement semantically
   * equivalent functionality since setting the model intent will change the found
   * activities and they may be inconsistent with the functionality of some of the clients.
   * For example, choosing a share activity can be implemented by a single backing
   * model and two different views for performing the selection. If however, one of the
   * views is used for sharing but the other for importing, for example, then each
   * view should be backed by a separate model.
   * </p>
   * <p>
   * The way clients interact with this class is as follows:
   * </p>
   * <p>
   * <pre>
   * <code>
   *  // Get a model and set it to a couple of clients with semantically similar function.
   *  ActivityChooserModel dataModel =
   *      ActivityChooserModel.get(context, "task_specific_history_file_name.xml");
   *
   *  ActivityChooserModelClient modelClient1 = getActivityChooserModelClient1();
   *  modelClient1.setActivityChooserModel(dataModel);
   *
   *  ActivityChooserModelClient modelClient2 = getActivityChooserModelClient2();
   *  modelClient2.setActivityChooserModel(dataModel);
   *
   *  // Set an intent to choose a an activity for.
   *  dataModel.setIntent(intent);
   * <pre>
   * <code>
   * </p>
   * <p>
   * <strong>Note:</strong> This class is thread safe.
   * </p>
   *
   * @hide
   */
  class ActivityChooserModel extends DataSetObservable {
  
      /**
       * Client that utilizes an {@link ActivityChooserModel}.
       */
      public interface ActivityChooserModelClient {
  
          /**
           * Sets the {@link ActivityChooserModel}.
           *
           * @param dataModel The model.
           */
          public void setActivityChooserModel(ActivityChooserModel dataModel);
      }
  
      /**
       * Defines a sorter that is responsible for sorting the activities
       * based on the provided historical choices and an intent.
       */
      public interface ActivitySorter {
  
          /**
           * Sorts the <code>activities</code> in descending order of relevance
           * based on previous history and an intent.
           *
           * @param intent The {@link Intent}.
           * @param activities Activities to be sorted.
           * @param historicalRecords Historical records.
           */
          // This cannot be done by a simple comparator since an Activity weight
          // is computed from history. Note that Activity implements Comparable.
          public void sort(Intent intent, List<ActivityResolveInfo> activities,
                  List<HistoricalRecord> historicalRecords);
      }
  
      /**
       * Listener for choosing an activity.
       */
      public interface OnChooseActivityListener {
  
          /**
           * Called when an activity has been chosen. The client can decide whether
           * an activity can be chosen and if so the caller of
           * {@link ActivityChooserModel#chooseActivity(int)} will receive and {@link Intent}
           * for launching it.
           * <p>
           * <strong>Note:</strong> Modifying the intent is not permitted and
           *     any changes to the latter will be ignored.
           * </p>
           *
           * @param host The listener's host model.
           * @param intent The intent for launching the chosen activity.
           * @return Whether the intent is handled and should not be delivered to clients.
           *
           * @see ActivityChooserModel#chooseActivity(int)
           */
          public boolean onChooseActivity(ActivityChooserModel host, Intent intent);
      }
  
      /**
       * Flag for selecting debug mode.
       */
      private static final boolean DEBUG = false;
  
      /**
       * Tag used for logging.
       */
      private static final String LOG_TAG = ActivityChooserModel.class.getSimpleName();
  
      /**
       * The root tag in the history file.
       */
      private static final String TAG_HISTORICAL_RECORDS = "historical-records";
  
      /**
       * The tag for a record in the history file.
       */
      private static final String TAG_HISTORICAL_RECORD = "historical-record";
  
      /**
       * Attribute for the activity.
       */
      private static final String ATTRIBUTE_ACTIVITY = "activity";
  
      /**
       * Attribute for the choice time.
       */
      private static final String ATTRIBUTE_TIME = "time";
  
      /**
       * Attribute for the choice weight.
       */
      private static final String ATTRIBUTE_WEIGHT = "weight";
  
      /**
       * The default name of the choice history file.
       */
      public static final String DEFAULT_HISTORY_FILE_NAME =
          "activity_choser_model_history.xml";
  
      /**
       * The default maximal length of the choice history.
       */
      public static final int DEFAULT_HISTORY_MAX_LENGTH = 50;
  
      /**
       * The amount with which to inflate a chosen activity when set as default.
       */
      private static final int DEFAULT_ACTIVITY_INFLATION = 5;
  
      /**
       * Default weight for a choice record.
       */
      private static final float DEFAULT_HISTORICAL_RECORD_WEIGHT = 1.0f;
  
      /**
       * The extension of the history file.
       */
      private static final String HISTORY_FILE_EXTENSION = ".xml";
  
      /**
       * An invalid item index.
       */
      private static final int INVALID_INDEX = -1;
  
      /**
       * Lock to guard the model registry.
       */
      private static final Object sRegistryLock = new Object();
  
      /**
       * This the registry for data models.
       */
      private static final Map<String, ActivityChooserModel> sDataModelRegistry =
          new HashMap<String, ActivityChooserModel>();
  
      /**
       * Lock for synchronizing on this instance.
       */
      private final Object mInstanceLock = new Object();
  
      /**
       * List of activities that can handle the current intent.
       */
      private final List<ActivityResolveInfo> mActivites = new ArrayList<ActivityResolveInfo>();
  
      /**
       * List with historical choice records.
       */
      private final List<HistoricalRecord> mHistoricalRecords = new ArrayList<HistoricalRecord>();
  
      /**
       * Context for accessing resources.
       */
      private final Context mContext;
  
      /**
       * The name of the history file that backs this model.
       */
      private final String mHistoryFileName;
  
      /**
       * The intent for which a activity is being chosen.
       */
      private Intent mIntent;
  
      /**
       * The sorter for ordering activities based on intent and past choices.
       */
      private ActivitySorter mActivitySorter = new DefaultSorter();
  
      /**
       * The maximal length of the choice history.
       */
      private int mHistoryMaxSize = DEFAULT_HISTORY_MAX_LENGTH;
  
      /**
       * Flag whether choice history can be read. In general many clients can
       * share the same data model and {@link #readHistoricalData()} may be called
       * by arbitrary of them any number of times. Therefore, this class guarantees
       * that the very first read succeeds and subsequent reads can be performed
       * only after a call to {@link #persistHistoricalData()} followed by change
       * of the share records.
       */
      private boolean mCanReadHistoricalData = true;
  
      /**
       * Flag whether the choice history was read. This is used to enforce that
       * before calling {@link #persistHistoricalData()} a call to
       * {@link #persistHistoricalData()} has been made. This aims to avoid a
       * scenario in which a choice history file exits, it is not read yet and
       * it is overwritten. Note that always all historical records are read in
       * full and the file is rewritten. This is necessary since we need to
       * purge old records that are outside of the sliding window of past choices.
       */
      private boolean mReadShareHistoryCalled = false;
  
      /**
       * Flag whether the choice records have changed. In general many clients can
       * share the same data model and {@link #persistHistoricalData()} may be called
       * by arbitrary of them any number of times. Therefore, this class guarantees
       * that choice history will be persisted only if it has changed.
       */
      private boolean mHistoricalRecordsChanged = true;
  
      /**
       * Hander for scheduling work on client tread.
       */
      private final Handler mHandler = new Handler();
  
      /**
       * Policy for controlling how the model handles chosen activities.
       */
      private OnChooseActivityListener mActivityChoserModelPolicy;
  
      /**
       * Gets the data model backed by the contents of the provided file with historical data.
       * Note that only one data model is backed by a given file, thus multiple calls with
       * the same file name will return the same model instance. If no such instance is present
       * it is created.
       * <p>
       * <strong>Note:</strong> To use the default historical data file clients should explicitly
       * pass as file name {@link #DEFAULT_HISTORY_FILE_NAME}. If no persistence of the choice
       * history is desired clients should pass <code>null</code> for the file name. In such
       * case a new model is returned for each invocation.
       * </p>
       *
       * <p>
       * <strong>Always use difference historical data files for semantically different actions.
       * For example, sharing is different from importing.</strong>
       * </p>
       *
       * @param context Context for loading resources.
       * @param historyFileName File name with choice history, <code>null</code>
       *        if the model should not be backed by a file. In this case the activities
       *        will be ordered only by data from the current session.
       *
       * @return The model.
       */
      public static ActivityChooserModel get(Context context, String historyFileName) {
          synchronized (sRegistryLock) {
              ActivityChooserModel dataModel = sDataModelRegistry.get(historyFileName);
              if (dataModel == null) {
                  dataModel = new ActivityChooserModel(context, historyFileName);
                  sDataModelRegistry.put(historyFileName, dataModel);
              }
              dataModel.readHistoricalData();
              return dataModel;
          }
      }
  
      /**
       * Creates a new instance.
       *
       * @param context Context for loading resources.
       * @param historyFileName The history XML file.
       */
      private ActivityChooserModel(Context context, String historyFileName) {
          mContext = context.getApplicationContext();
          if (!TextUtils.isEmpty(historyFileName)
                  && !historyFileName.endsWith(HISTORY_FILE_EXTENSION)) {
              mHistoryFileName = historyFileName + HISTORY_FILE_EXTENSION;
          } else {
              mHistoryFileName = historyFileName;
          }
      }
  
      /**
       * Sets an intent for which to choose a activity.
       * <p>
       * <strong>Note:</strong> Clients must set only semantically similar
       * intents for each data model.
       * <p>
       *
       * @param intent The intent.
       */
      public void setIntent(Intent intent) {
          synchronized (mInstanceLock) {
              if (mIntent == intent) {
                  return;
              }
              mIntent = intent;
              loadActivitiesLocked();
          }
      }
  
      /**
       * Gets the intent for which a activity is being chosen.
       *
       * @return The intent.
       */
      public Intent getIntent() {
          synchronized (mInstanceLock) {
              return mIntent;
          }
      }
  
      /**
       * Gets the number of activities that can handle the intent.
       *
       * @return The activity count.
       *
       * @see #setIntent(Intent)
       */
      public int getActivityCount() {
          synchronized (mInstanceLock) {
              return mActivites.size();
          }
      }
  
      /**
       * Gets an activity at a given index.
       *
       * @return The activity.
       *
       * @see ActivityResolveInfo
       * @see #setIntent(Intent)
       */
      public ResolveInfo getActivity(int index) {
          synchronized (mInstanceLock) {
              return mActivites.get(index).resolveInfo;
          }
      }
  
      /**
       * Gets the index of a the given activity.
       *
       * @param activity The activity index.
       *
       * @return The index if found, -1 otherwise.
       */
      public int getActivityIndex(ResolveInfo activity) {
          List<ActivityResolveInfo> activities = mActivites;
          final int activityCount = activities.size();
          for (int i = 0; i < activityCount; i++) {
              ActivityResolveInfo currentActivity = activities.get(i);
              if (currentActivity.resolveInfo == activity) {
                  return i;
              }
          }
          return INVALID_INDEX;
      }
  
      /**
       * Chooses a activity to handle the current intent. This will result in
       * adding a historical record for that action and construct intent with
       * its component name set such that it can be immediately started by the
       * client.
       * <p>
       * <strong>Note:</strong> By calling this method the client guarantees
       * that the returned intent will be started. This intent is returned to
       * the client solely to let additional customization before the start.
       * </p>
       *
       * @return An {@link Intent} for launching the activity or null if the
       *         policy has consumed the intent.
       *
       * @see HistoricalRecord
       * @see OnChooseActivityListener
       */
      public Intent chooseActivity(int index) {
          ActivityResolveInfo chosenActivity = mActivites.get(index);
  
          ComponentName chosenName = new ComponentName(
                  chosenActivity.resolveInfo.activityInfo.packageName,
                  chosenActivity.resolveInfo.activityInfo.name);
  
          Intent choiceIntent = new Intent(mIntent);
          choiceIntent.setComponent(chosenName);
  
          if (mActivityChoserModelPolicy != null) {
              // Do not allow the policy to change the intent.
              Intent choiceIntentCopy = new Intent(choiceIntent);
              final boolean handled = mActivityChoserModelPolicy.onChooseActivity(this,
                      choiceIntentCopy);
              if (handled) {
                  return null;
              }
          }
  
          HistoricalRecord historicalRecord = new HistoricalRecord(chosenName,
                  System.currentTimeMillis(), DEFAULT_HISTORICAL_RECORD_WEIGHT);
          addHisoricalRecord(historicalRecord);
  
          return choiceIntent;
      }
  
      /**
       * Sets the listener for choosing an activity.
       *
       * @param listener The listener.
       */
      public void setOnChooseActivityListener(OnChooseActivityListener listener) {
          mActivityChoserModelPolicy = listener;
      }
  
      /**
       * Gets the default activity, The default activity is defined as the one
       * with highest rank i.e. the first one in the list of activities that can
       * handle the intent.
       *
       * @return The default activity, <code>null</code> id not activities.
       *
       * @see #getActivity(int)
       */
      public ResolveInfo getDefaultActivity() {
          synchronized (mInstanceLock) {
              if (!mActivites.isEmpty()) {
                  return mActivites.get(0).resolveInfo;
              }
          }
          return null;
      }
  
      /**
       * Sets the default activity. The default activity is set by adding a
       * historical record with weight high enough that this activity will
       * become the highest ranked. Such a strategy guarantees that the default
       * will eventually change if not used. Also the weight of the record for
       * setting a default is inflated with a constant amount to guarantee that
       * it will stay as default for awhile.
       *
       * @param index The index of the activity to set as default.
       */
      public void setDefaultActivity(int index) {
          ActivityResolveInfo newDefaultActivity = mActivites.get(index);
          ActivityResolveInfo oldDefaultActivity = mActivites.get(0);
  
          final float weight;
          if (oldDefaultActivity != null) {
              // Add a record with weight enough to boost the chosen at the top.
              weight = oldDefaultActivity.weight - newDefaultActivity.weight
                  + DEFAULT_ACTIVITY_INFLATION;
          } else {
              weight = DEFAULT_HISTORICAL_RECORD_WEIGHT;
          }
  
          ComponentName defaultName = new ComponentName(
                  newDefaultActivity.resolveInfo.activityInfo.packageName,
                  newDefaultActivity.resolveInfo.activityInfo.name);
          HistoricalRecord historicalRecord = new HistoricalRecord(defaultName,
                  System.currentTimeMillis(), weight);
          addHisoricalRecord(historicalRecord);
      }
  
      /**
       * Reads the history data from the backing file if the latter
       * was provided. Calling this method more than once before a call
       * to {@link #persistHistoricalData()} has been made has no effect.
       * <p>
       * <strong>Note:</strong> Historical data is read asynchronously and
       *       as soon as the reading is completed any registered
       *       {@link DataSetObserver}s will be notified. Also no historical
       *       data is read until this method is invoked.
       * <p>
       */
      private void readHistoricalData() {
          synchronized (mInstanceLock) {
              if (!mCanReadHistoricalData || !mHistoricalRecordsChanged) {
                  return;
              }
              mCanReadHistoricalData = false;
              mReadShareHistoryCalled = true;
              if (!TextUtils.isEmpty(mHistoryFileName)) {
                  /*AsyncTask.*/SERIAL_EXECUTOR.execute(new HistoryLoader());
              }
          }
      }
  
      private static final Executor SERIAL_EXECUTOR = Executors.newSingleThreadExecutor();
  
      /**
       * Persists the history data to the backing file if the latter
       * was provided. Calling this method before a call to {@link #readHistoricalData()}
       * throws an exception. Calling this method more than one without choosing an
       * activity has not effect.
       *
       * @throws IllegalStateException If this method is called before a call to
       *         {@link #readHistoricalData()}.
       */
      private void persistHistoricalData() {
          synchronized (mInstanceLock) {
              if (!mReadShareHistoryCalled) {
                  throw new IllegalStateException("No preceding call to #readHistoricalData");
              }
              if (!mHistoricalRecordsChanged) {
                  return;
              }
              mHistoricalRecordsChanged = false;
              mCanReadHistoricalData = true;
              if (!TextUtils.isEmpty(mHistoryFileName)) {
                  /*AsyncTask.*/SERIAL_EXECUTOR.execute(new HistoryPersister());
              }
          }
      }
  
      /**
       * Sets the sorter for ordering activities based on historical data and an intent.
       *
       * @param activitySorter The sorter.
       *
       * @see ActivitySorter
       */
      public void setActivitySorter(ActivitySorter activitySorter) {
          synchronized (mInstanceLock) {
              if (mActivitySorter == activitySorter) {
                  return;
              }
              mActivitySorter = activitySorter;
              sortActivities();
          }
      }
  
      /**
       * Sorts the activities based on history and an intent. If
       * a sorter is not specified this a default implementation is used.
       *
       * @see #setActivitySorter(ActivitySorter)
       */
      private void sortActivities() {
          synchronized (mInstanceLock) {
              if (mActivitySorter != null && !mActivites.isEmpty()) {
                  mActivitySorter.sort(mIntent, mActivites,
                          Collections.unmodifiableList(mHistoricalRecords));
                  notifyChanged();
              }
          }
      }
  
      /**
       * Sets the maximal size of the historical data. Defaults to
       * {@link #DEFAULT_HISTORY_MAX_LENGTH}
       * <p>
       *   <strong>Note:</strong> Setting this property will immediately
       *   enforce the specified max history size by dropping enough old
       *   historical records to enforce the desired size. Thus, any
       *   records that exceed the history size will be discarded and
       *   irreversibly lost.
       * </p>
       *
       * @param historyMaxSize The max history size.
       */
      public void setHistoryMaxSize(int historyMaxSize) {
          synchronized (mInstanceLock) {
              if (mHistoryMaxSize == historyMaxSize) {
                  return;
              }
              mHistoryMaxSize = historyMaxSize;
              pruneExcessiveHistoricalRecordsLocked();
              sortActivities();
          }
      }
  
      /**
       * Gets the history max size.
       *
       * @return The history max size.
       */
      public int getHistoryMaxSize() {
          synchronized (mInstanceLock) {
              return mHistoryMaxSize;
          }
      }
  
      /**
       * Gets the history size.
       *
       * @return The history size.
       */
      public int getHistorySize() {
          synchronized (mInstanceLock) {
              return mHistoricalRecords.size();
          }
      }
  
      /**
       * Adds a historical record.
       *
       * @param historicalRecord The record to add.
       * @return True if the record was added.
       */
      private boolean addHisoricalRecord(HistoricalRecord historicalRecord) {
          synchronized (mInstanceLock) {
              final boolean added = mHistoricalRecords.add(historicalRecord);
              if (added) {
                  mHistoricalRecordsChanged = true;
                  pruneExcessiveHistoricalRecordsLocked();
                  persistHistoricalData();
                  sortActivities();
              }
              return added;
          }
      }
  
      /**
       * Prunes older excessive records to guarantee {@link #mHistoryMaxSize}.
       */
      private void pruneExcessiveHistoricalRecordsLocked() {
          List<HistoricalRecord> choiceRecords = mHistoricalRecords;
          final int pruneCount = choiceRecords.size() - mHistoryMaxSize;
          if (pruneCount <= 0) {
              return;
          }
          mHistoricalRecordsChanged = true;
          for (int i = 0; i < pruneCount; i++) {
              HistoricalRecord prunedRecord = choiceRecords.remove(0);
              if (DEBUG) {
                  Log.i(LOG_TAG, "Pruned: " + prunedRecord);
              }
          }
      }
  
      /**
       * Loads the activities.
       */
      private void loadActivitiesLocked() {
          mActivites.clear();
          if (mIntent != null) {
              List<ResolveInfo> resolveInfos =
                  mContext.getPackageManager().queryIntentActivities(mIntent, 0);
              final int resolveInfoCount = resolveInfos.size();
              for (int i = 0; i < resolveInfoCount; i++) {
                  ResolveInfo resolveInfo = resolveInfos.get(i);
                  mActivites.add(new ActivityResolveInfo(resolveInfo));
              }
              sortActivities();
          } else {
              notifyChanged();
          }
      }
  
      /**
       * Represents a record in the history.
       */
      public final static class HistoricalRecord {
  
          /**
           * The activity name.
           */
          public final ComponentName activity;
  
          /**
           * The choice time.
           */
          public final long time;
  
          /**
           * The record weight.
           */
          public final float weight;
  
          /**
           * Creates a new instance.
           *
           * @param activityName The activity component name flattened to string.
           * @param time The time the activity was chosen.
           * @param weight The weight of the record.
           */
          public HistoricalRecord(String activityName, long time, float weight) {
              this(ComponentName.unflattenFromString(activityName), time, weight);
          }
  
          /**
           * Creates a new instance.
           *
           * @param activityName The activity name.
           * @param time The time the activity was chosen.
           * @param weight The weight of the record.
           */
          public HistoricalRecord(ComponentName activityName, long time, float weight) {
              this.activity = activityName;
              this.time = time;
              this.weight = weight;
          }
  
          @Override
          public int hashCode() {
              final int prime = 31;
              int result = 1;
              result = prime * result + ((activity == null) ? 0 : activity.hashCode());
              result = prime * result + (int) (time ^ (time >>> 32));
              result = prime * result + Float.floatToIntBits(weight);
              return result;
          }
  
          @Override
          public boolean equals(Object obj) {
              if (this == obj) {
                  return true;
              }
              if (obj == null) {
                  return false;
              }
              if (getClass() != obj.getClass()) {
                  return false;
              }
              HistoricalRecord other = (HistoricalRecord) obj;
              if (activity == null) {
                  if (other.activity != null) {
                      return false;
                  }
              } else if (!activity.equals(other.activity)) {
                  return false;
              }
              if (time != other.time) {
                  return false;
              }
              if (Float.floatToIntBits(weight) != Float.floatToIntBits(other.weight)) {
                  return false;
              }
              return true;
          }
  
          @Override
          public String toString() {
              StringBuilder builder = new StringBuilder();
              builder.append("[");
              builder.append("; activity:").append(activity);
              builder.append("; time:").append(time);
              builder.append("; weight:").append(new BigDecimal(weight));
              builder.append("]");
              return builder.toString();
          }
      }
  
      /**
       * Represents an activity.
       */
      public final class ActivityResolveInfo implements Comparable<ActivityResolveInfo> {
  
          /**
           * The {@link ResolveInfo} of the activity.
           */
          public final ResolveInfo resolveInfo;
  
          /**
           * Weight of the activity. Useful for sorting.
           */
          public float weight;
  
          /**
           * Creates a new instance.
           *
           * @param resolveInfo activity {@link ResolveInfo}.
           */
          public ActivityResolveInfo(ResolveInfo resolveInfo) {
              this.resolveInfo = resolveInfo;
          }
  
          @Override
          public int hashCode() {
              return 31 + Float.floatToIntBits(weight);
          }
  
          @Override
          public boolean equals(Object obj) {
              if (this == obj) {
                  return true;
              }
              if (obj == null) {
                  return false;
              }
              if (getClass() != obj.getClass()) {
                  return false;
              }
              ActivityResolveInfo other = (ActivityResolveInfo) obj;
              if (Float.floatToIntBits(weight) != Float.floatToIntBits(other.weight)) {
                  return false;
              }
              return true;
          }
  
          public int compareTo(ActivityResolveInfo another) {
               return  Float.floatToIntBits(another.weight) - Float.floatToIntBits(weight);
          }
  
          @Override
          public String toString() {
              StringBuilder builder = new StringBuilder();
              builder.append("[");
              builder.append("resolveInfo:").append(resolveInfo.toString());
              builder.append("; weight:").append(new BigDecimal(weight));
              builder.append("]");
              return builder.toString();
          }
      }
  
      /**
       * Default activity sorter implementation.
       */
      private final class DefaultSorter implements ActivitySorter {
          private static final float WEIGHT_DECAY_COEFFICIENT = 0.95f;
  
          private final Map<String, ActivityResolveInfo> mPackageNameToActivityMap =
              new HashMap<String, ActivityResolveInfo>();
  
          public void sort(Intent intent, List<ActivityResolveInfo> activities,
                  List<HistoricalRecord> historicalRecords) {
              Map<String, ActivityResolveInfo> packageNameToActivityMap =
                  mPackageNameToActivityMap;
              packageNameToActivityMap.clear();
  
              final int activityCount = activities.size();
              for (int i = 0; i < activityCount; i++) {
                  ActivityResolveInfo activity = activities.get(i);
                  activity.weight = 0.0f;
                  String packageName = activity.resolveInfo.activityInfo.packageName;
                  packageNameToActivityMap.put(packageName, activity);
              }
  
              final int lastShareIndex = historicalRecords.size() - 1;
              float nextRecordWeight = 1;
              for (int i = lastShareIndex; i >= 0; i--) {
                  HistoricalRecord historicalRecord = historicalRecords.get(i);
                  String packageName = historicalRecord.activity.getPackageName();
                  ActivityResolveInfo activity = packageNameToActivityMap.get(packageName);
                  if (activity != null) {
                      activity.weight += historicalRecord.weight * nextRecordWeight;
                      nextRecordWeight = nextRecordWeight * WEIGHT_DECAY_COEFFICIENT;
                  }
              }
  
              Collections.sort(activities);
  
              if (DEBUG) {
                  for (int i = 0; i < activityCount; i++) {
                      Log.i(LOG_TAG, "Sorted: " + activities.get(i));
                  }
              }
          }
      }
  
      /**
       * Command for reading the historical records from a file off the UI thread.
       */
      private final class HistoryLoader implements Runnable {
  
         public void run() {
              FileInputStream fis = null;
              try {
                  fis = mContext.openFileInput(mHistoryFileName);
              } catch (FileNotFoundException fnfe) {
                  if (DEBUG) {
                      Log.i(LOG_TAG, "Could not open historical records file: " + mHistoryFileName);
                  }
                  return;
              }
              try {
                  XmlPullParser parser = Xml.newPullParser();
                  parser.setInput(fis, null);
  
                  int type = XmlPullParser.START_DOCUMENT;
                  while (type != XmlPullParser.END_DOCUMENT && type != XmlPullParser.START_TAG) {
                      type = parser.next();
                  }
  
                  if (!TAG_HISTORICAL_RECORDS.equals(parser.getName())) {
                      throw new XmlPullParserException("Share records file does not start with "
                              + TAG_HISTORICAL_RECORDS + " tag.");
                  }
  
                  List<HistoricalRecord> readRecords = new ArrayList<HistoricalRecord>();
  
                  while (true) {
                      type = parser.next();
                      if (type == XmlPullParser.END_DOCUMENT) {
                          break;
                      }
                      if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
                          continue;
                      }
                      String nodeName = parser.getName();
                      if (!TAG_HISTORICAL_RECORD.equals(nodeName)) {
                          throw new XmlPullParserException("Share records file not well-formed.");
                      }
  
                      String activity = parser.getAttributeValue(null, ATTRIBUTE_ACTIVITY);
                      final long time =
                          Long.parseLong(parser.getAttributeValue(null, ATTRIBUTE_TIME));
                      final float weight =
                          Float.parseFloat(parser.getAttributeValue(null, ATTRIBUTE_WEIGHT));
  
                      HistoricalRecord readRecord = new HistoricalRecord(activity, time,
                              weight);
                      readRecords.add(readRecord);
  
                      if (DEBUG) {
                          Log.i(LOG_TAG, "Read " + readRecord.toString());
                      }
                  }
  
                  if (DEBUG) {
                      Log.i(LOG_TAG, "Read " + readRecords.size() + " historical records.");
                  }
  
                  synchronized (mInstanceLock) {
                      Set<HistoricalRecord> uniqueShareRecords =
                          new LinkedHashSet<HistoricalRecord>(readRecords);
  
                      // Make sure no duplicates. Example: Read a file with
                      // one record, add one record, persist the two records,
                      // add a record, read the persisted records - the
                      // read two records should not be added again.
                      List<HistoricalRecord> historicalRecords = mHistoricalRecords;
                      final int historicalRecordsCount = historicalRecords.size();
                      for (int i = historicalRecordsCount - 1; i >= 0; i--) {
                          HistoricalRecord historicalRecord = historicalRecords.get(i);
                          uniqueShareRecords.add(historicalRecord);
                      }
  
                      if (historicalRecords.size() == uniqueShareRecords.size()) {
                          return;
                      }
  
                      // Make sure the oldest records go to the end.
                      historicalRecords.clear();
                      historicalRecords.addAll(uniqueShareRecords);
  
                      mHistoricalRecordsChanged = true;
  
                      // Do this on the client thread since the client may be on the UI
                      // thread, wait for data changes which happen during sorting, and
                      // perform UI modification based on the data change.
                      mHandler.post(new Runnable() {
                          public void run() {
                              pruneExcessiveHistoricalRecordsLocked();
                              sortActivities();
                          }
                      });
                  }
              } catch (XmlPullParserException xppe) {
                  Log.e(LOG_TAG, "Error reading historical recrod file: " + mHistoryFileName, xppe);
              } catch (IOException ioe) {
                  Log.e(LOG_TAG, "Error reading historical recrod file: " + mHistoryFileName, ioe);
              } finally {
                  if (fis != null) {
                      try {
                          fis.close();
                      } catch (IOException ioe) {
                          /* ignore */
                      }
                  }
              }
          }
      }
  
      /**
       * Command for persisting the historical records to a file off the UI thread.
       */
      private final class HistoryPersister implements Runnable {
  
          public void run() {
              FileOutputStream fos = null;
              List<HistoricalRecord> records = null;
  
              synchronized (mInstanceLock) {
                  records = new ArrayList<HistoricalRecord>(mHistoricalRecords);
              }
  
              try {
                  fos = mContext.openFileOutput(mHistoryFileName, Context.MODE_PRIVATE);
              } catch (FileNotFoundException fnfe) {
                  Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, fnfe);
                  return;
              }
  
              XmlSerializer serializer = Xml.newSerializer();
  
              try {
                  serializer.setOutput(fos, null);
                  serializer.startDocument("UTF-8", true);
                  serializer.startTag(null, TAG_HISTORICAL_RECORDS);
  
                  final int recordCount = records.size();
                  for (int i = 0; i < recordCount; i++) {
                      HistoricalRecord record = records.remove(0);
                      serializer.startTag(null, TAG_HISTORICAL_RECORD);
                      serializer.attribute(null, ATTRIBUTE_ACTIVITY, record.activity.flattenToString());
                      serializer.attribute(null, ATTRIBUTE_TIME, String.valueOf(record.time));
                      serializer.attribute(null, ATTRIBUTE_WEIGHT, String.valueOf(record.weight));
                      serializer.endTag(null, TAG_HISTORICAL_RECORD);
                      if (DEBUG) {
                          Log.i(LOG_TAG, "Wrote " + record.toString());
                      }
                  }
  
                  serializer.endTag(null, TAG_HISTORICAL_RECORDS);
                  serializer.endDocument();
  
                  if (DEBUG) {
                      Log.i(LOG_TAG, "Wrote " + recordCount + " historical records.");
                  }
              } catch (IllegalArgumentException iae) {
                  Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, iae);
              } catch (IllegalStateException ise) {
                  Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, ise);
              } catch (IOException ioe) {
                  Log.e(LOG_TAG, "Error writing historical recrod file: " + mHistoryFileName, ioe);
              } finally {
                  if (fos != null) {
                      try {
                          fos.close();
                      } catch (IOException e) {
                          /* ignore */
                      }
                  }
              }
          }
      }
  }
  