/*
 * Copyright (C) 2013 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.android.dialer.database;

import android.content.ContentValues;
import android.content.Context;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteStatement;
import android.net.Uri;
import android.os.AsyncTask;
import android.provider.BaseColumns;
import android.provider.ContactsContract;
import android.provider.ContactsContract.CommonDataKinds.Phone;
import android.provider.ContactsContract.Contacts;
import android.provider.ContactsContract.Data;
import android.provider.ContactsContract.Directory;
import android.text.TextUtils;
import android.util.Log;

import com.android.contacts.common.util.StopWatch;
import com.android.dialer.R;
import com.android.dialer.dialpad.SmartDialNameMatcher;
import com.android.dialer.dialpad.SmartDialPrefix;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Database helper for smart dial. Designed as a singleton to make sure there is
 * only one access point to the database. Provides methods to maintain, update,
 * and query the database.
 */
public class DialerDatabaseHelper extends SQLiteOpenHelper {
    private static final String TAG = "DialerDatabaseHelper";
    private static final boolean DEBUG = false;

    private static DialerDatabaseHelper sSingleton = null;

    private static final Object mLock = new Object();
    private static final AtomicBoolean sInUpdate = new AtomicBoolean(false);
    private final Context mContext;

    /**
     * SmartDial DB version ranges:
     * <pre>
     *   0-98   KeyLimePie
     * </pre>
     */
    public static final int DATABASE_VERSION = 4;
    public static final String DATABASE_NAME = "dialer.db";

    /**
     * Saves the last update time of smart dial databases to shared preferences.
     */
    private static final String DATABASE_LAST_CREATED_SHARED_PREF = "com.android.dialer";
    private static final String LAST_UPDATED_MILLIS = "last_updated_millis";
    private static final String DATABASE_VERSION_PROPERTY = "database_version";

    private static final int MAX_ENTRIES = 20;

    public interface Tables {
        /** Saves the necessary smart dial information of all contacts. */
        static final String SMARTDIAL_TABLE = "smartdial_table";
        /** Saves all possible prefixes to refer to a contacts.*/
        static final String PREFIX_TABLE = "prefix_table";
        /** Database properties for internal use */
        static final String PROPERTIES = "properties";
    }

    public interface SmartDialDbColumns {
        static final String _ID = "id";
        static final String DATA_ID = "data_id";
        static final String NUMBER = "phone_number";
        static final String CONTACT_ID = "contact_id";
        static final String LOOKUP_KEY = "lookup_key";
        static final String DISPLAY_NAME_PRIMARY = "display_name";
        static final String PHOTO_ID = "photo_id";
        static final String LAST_TIME_USED = "last_time_used";
        static final String TIMES_USED = "times_used";
        static final String STARRED = "starred";
        static final String IS_SUPER_PRIMARY = "is_super_primary";
        static final String IN_VISIBLE_GROUP = "in_visible_group";
        static final String IS_PRIMARY = "is_primary";
        static final String LAST_SMARTDIAL_UPDATE_TIME = "last_smartdial_update_time";
    }

    public static interface PrefixColumns extends BaseColumns {
        static final String PREFIX = "prefix";
        static final String CONTACT_ID = "contact_id";
    }

    public interface PropertiesColumns {
        String PROPERTY_KEY = "property_key";
        String PROPERTY_VALUE = "property_value";
    }

    /** Query options for querying the contact database.*/
    public static interface PhoneQuery {
       static final Uri URI = Phone.CONTENT_URI.buildUpon().
               appendQueryParameter(ContactsContract.DIRECTORY_PARAM_KEY,
                       String.valueOf(Directory.DEFAULT)).
               appendQueryParameter(ContactsContract.REMOVE_DUPLICATE_ENTRIES, "true").
               build();

       static final String[] PROJECTION = new String[] {
            Phone._ID,                          // 0
            Phone.TYPE,                         // 1
            Phone.LABEL,                        // 2
            Phone.NUMBER,                       // 3
            Phone.CONTACT_ID,                   // 4
            Phone.LOOKUP_KEY,                   // 5
            Phone.DISPLAY_NAME_PRIMARY,         // 6
            Phone.PHOTO_ID,                     // 7
            Data.LAST_TIME_USED,                // 8
            Data.TIMES_USED,                    // 9
            Contacts.STARRED,                   // 10
            Data.IS_SUPER_PRIMARY,              // 11
            Contacts.IN_VISIBLE_GROUP,          // 12
            Data.IS_PRIMARY,                    // 13
        };

        static final int PHONE_ID = 0;
        static final int PHONE_TYPE = 1;
        static final int PHONE_LABEL = 2;
        static final int PHONE_NUMBER = 3;
        static final int PHONE_CONTACT_ID = 4;
        static final int PHONE_LOOKUP_KEY = 5;
        static final int PHONE_DISPLAY_NAME = 6;
        static final int PHONE_PHOTO_ID = 7;
        static final int PHONE_LAST_TIME_USED = 8;
        static final int PHONE_TIMES_USED = 9;
        static final int PHONE_STARRED = 10;
        static final int PHONE_IS_SUPER_PRIMARY = 11;
        static final int PHONE_IN_VISIBLE_GROUP = 12;
        static final int PHONE_IS_PRIMARY = 13;

        /** Selects only rows that have been updated after a certain time stamp.*/
        static final String SELECT_UPDATED_CLAUSE =
                Phone.CONTACT_LAST_UPDATED_TIMESTAMP + " > ?";

        /** Ignores contacts that have an unreasonably long lookup key. These are likely to be
         * the result of multiple (> 50) merged raw contacts, and are likely to cause
         * OutOfMemoryExceptions within SQLite, or cause memory allocation problems later on
         * when iterating through the cursor set (see b/13133579)
         */
        static final String SELECT_IGNORE_LOOKUP_KEY_TOO_LONG_CLAUSE =
                "length(" + Phone.LOOKUP_KEY + ") < 1000";

        static final String SELECTION = SELECT_UPDATED_CLAUSE + " AND " +
                SELECT_IGNORE_LOOKUP_KEY_TOO_LONG_CLAUSE;
    }

    /** Query options for querying the deleted contact database.*/
    public static interface DeleteContactQuery {
       static final Uri URI = ContactsContract.DeletedContacts.CONTENT_URI;

       static final String[] PROJECTION = new String[] {
            ContactsContract.DeletedContacts.CONTACT_ID,                          // 0
            ContactsContract.DeletedContacts.CONTACT_DELETED_TIMESTAMP,           // 1
        };

        static final int DELETED_CONTACT_ID = 0;
        static final int DELECTED_TIMESTAMP = 1;

        /** Selects only rows that have been deleted after a certain time stamp.*/
        public static final String SELECT_UPDATED_CLAUSE =
                ContactsContract.DeletedContacts.CONTACT_DELETED_TIMESTAMP + " > ?";
    }

    /**
     * Gets the sorting order for the smartdial table. This computes a SQL "ORDER BY" argument by
     * composing contact status and recent contact details together.
     */
    private static interface SmartDialSortingOrder {
        /** Current contacts - those contacted within the last 3 days (in milliseconds) */
        static final long LAST_TIME_USED_CURRENT_MS = 3L * 24 * 60 * 60 * 1000;
        /** Recent contacts - those contacted within the last 30 days (in milliseconds) */
        static final long LAST_TIME_USED_RECENT_MS = 30L * 24 * 60 * 60 * 1000;

        /** Time since last contact. */
        static final String TIME_SINCE_LAST_USED_MS = "( ?1 - " +
                Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.LAST_TIME_USED + ")";

        /** Contacts that have been used in the past 3 days rank higher than contacts that have
         * been used in the past 30 days, which rank higher than contacts that have not been used
         * in recent 30 days.
         */
        static final String SORT_BY_DATA_USAGE =
                "(CASE WHEN " + TIME_SINCE_LAST_USED_MS + " < " + LAST_TIME_USED_CURRENT_MS +
                " THEN 0 " +
                " WHEN " + TIME_SINCE_LAST_USED_MS + " < " + LAST_TIME_USED_RECENT_MS +
                " THEN 1 " +
                " ELSE 2 END)";

        /** This sort order is similar to that used by the ContactsProvider when returning a list
         * of frequently called contacts.
         */
        static final String SORT_ORDER =
                Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.STARRED + " DESC, "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.IS_SUPER_PRIMARY + " DESC, "
                + SORT_BY_DATA_USAGE + ", "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.TIMES_USED + " DESC, "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.IN_VISIBLE_GROUP + " DESC, "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.DISPLAY_NAME_PRIMARY + ", "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.CONTACT_ID + ", "
                + Tables.SMARTDIAL_TABLE + "." + SmartDialDbColumns.IS_PRIMARY + " DESC";
    }

    /**
     * Simple data format for a contact, containing only information needed for showing up in
     * smart dial interface.
     */
    public static class ContactNumber {
        public final long id;
        public final long dataId;
        public final String displayName;
        public final String phoneNumber;
        public final String lookupKey;
        public final long photoId;

        public ContactNumber(long id, long dataID, String displayName, String phoneNumber,
                String lookupKey, long photoId) {
            this.dataId = dataID;
            this.id = id;
            this.displayName = displayName;
            this.phoneNumber = phoneNumber;
            this.lookupKey = lookupKey;
            this.photoId = photoId;
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(id, dataId, displayName, phoneNumber, lookupKey, photoId);
        }

        @Override
        public boolean equals(Object object) {
            if (this == object) {
                return true;
            }
            if (object instanceof ContactNumber) {
                final ContactNumber that = (ContactNumber) object;
                return Objects.equal(this.id, that.id)
                        && Objects.equal(this.dataId, that.dataId)
                        && Objects.equal(this.displayName, that.displayName)
                        && Objects.equal(this.phoneNumber, that.phoneNumber)
                        && Objects.equal(this.lookupKey, that.lookupKey)
                        && Objects.equal(this.photoId, that.photoId);
            }
            return false;
        }
    }

    /**
     * Data format for finding duplicated contacts.
     */
    private class ContactMatch {
        private final String lookupKey;
        private final long id;

        public ContactMatch(String lookupKey, long id) {
            this.lookupKey = lookupKey;
            this.id = id;
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(lookupKey, id);
        }

        @Override
        public boolean equals(Object object) {
            if (this == object) {
                return true;
            }
            if (object instanceof ContactMatch) {
                final ContactMatch that = (ContactMatch) object;
                return Objects.equal(this.lookupKey, that.lookupKey)
                        && Objects.equal(this.id, that.id);
            }
            return false;
        }
    }

    /**
     * Access function to get the singleton instance of DialerDatabaseHelper.
     */
    public static synchronized DialerDatabaseHelper getInstance(Context context) {
        if (DEBUG) {
            Log.v(TAG, "Getting Instance");
        }
        if (sSingleton == null) {
            // Use application context instead of activity context because this is a singleton,
            // and we don't want to leak the activity if the activity is not running but the
            // dialer database helper is still doing work.
            sSingleton = new DialerDatabaseHelper(context.getApplicationContext(),
                    DATABASE_NAME);
        }
        return sSingleton;
    }

    /**
     * Returns a new instance for unit tests. The database will be created in memory.
     */
    @VisibleForTesting
    static DialerDatabaseHelper getNewInstanceForTest(Context context) {
        return new DialerDatabaseHelper(context, null);
    }

    protected DialerDatabaseHelper(Context context, String databaseName) {
        this(context, databaseName, DATABASE_VERSION);
    }

    protected DialerDatabaseHelper(Context context, String databaseName, int dbVersion) {
        super(context, databaseName, null, dbVersion);
        mContext = Preconditions.checkNotNull(context, "Context must not be null");
    }

    /**
     * Creates tables in the database when database is created for the first time.
     *
     * @param db The database.
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        setupTables(db);
    }

    private void setupTables(SQLiteDatabase db) {
        dropTables(db);
        db.execSQL("CREATE TABLE " + Tables.SMARTDIAL_TABLE + " (" +
                SmartDialDbColumns._ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                SmartDialDbColumns.DATA_ID + " INTEGER, " +
                SmartDialDbColumns.NUMBER + " TEXT," +
                SmartDialDbColumns.CONTACT_ID + " INTEGER," +
                SmartDialDbColumns.LOOKUP_KEY + " TEXT," +
                SmartDialDbColumns.DISPLAY_NAME_PRIMARY + " TEXT, " +
                SmartDialDbColumns.PHOTO_ID + " INTEGER, " +
                SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME + " LONG, " +
                SmartDialDbColumns.LAST_TIME_USED + " LONG, " +
                SmartDialDbColumns.TIMES_USED + " INTEGER, " +
                SmartDialDbColumns.STARRED + " INTEGER, " +
                SmartDialDbColumns.IS_SUPER_PRIMARY + " INTEGER, " +
                SmartDialDbColumns.IN_VISIBLE_GROUP + " INTEGER, " +
                SmartDialDbColumns.IS_PRIMARY + " INTEGER" +
        ");");

        db.execSQL("CREATE TABLE " + Tables.PREFIX_TABLE + " (" +
                PrefixColumns._ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
                PrefixColumns.PREFIX + " TEXT COLLATE NOCASE, " +
                PrefixColumns.CONTACT_ID + " INTEGER" +
                ");");

        db.execSQL("CREATE TABLE " + Tables.PROPERTIES + " (" +
                PropertiesColumns.PROPERTY_KEY + " TEXT PRIMARY KEY, " +
                PropertiesColumns.PROPERTY_VALUE + " TEXT " +
                ");");

        setProperty(db, DATABASE_VERSION_PROPERTY, String.valueOf(DATABASE_VERSION));
        resetSmartDialLastUpdatedTime();
    }

    public void dropTables(SQLiteDatabase db) {
        db.execSQL("DROP TABLE IF EXISTS " + Tables.PREFIX_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + Tables.SMARTDIAL_TABLE);
        db.execSQL("DROP TABLE IF EXISTS " + Tables.PROPERTIES);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldNumber, int newNumber) {
        // Disregard the old version and new versions provided by SQLiteOpenHelper, we will read
        // our own from the database.

        int oldVersion;

        oldVersion = getPropertyAsInt(db, DATABASE_VERSION_PROPERTY, 0);

        if (oldVersion == 0) {
            Log.e(TAG, "Malformed database version..recreating database");
        }

        if (oldVersion < 4) {
            setupTables(db);
            return;
        }

        if (oldVersion != DATABASE_VERSION) {
            throw new IllegalStateException(
                    "error upgrading the database to version " + DATABASE_VERSION);
        }

        setProperty(db, DATABASE_VERSION_PROPERTY, String.valueOf(DATABASE_VERSION));
    }

    /**
     * Stores a key-value pair in the {@link Tables#PROPERTIES} table.
     */
    public void setProperty(String key, String value) {
        setProperty(getWritableDatabase(), key, value);
    }

    public void setProperty(SQLiteDatabase db, String key, String value) {
        final ContentValues values = new ContentValues();
        values.put(PropertiesColumns.PROPERTY_KEY, key);
        values.put(PropertiesColumns.PROPERTY_VALUE, value);
        db.replace(Tables.PROPERTIES, null, values);
    }

    /**
     * Returns the value from the {@link Tables#PROPERTIES} table.
     */
    public String getProperty(String key, String defaultValue) {
        return getProperty(getReadableDatabase(), key, defaultValue);
    }

    public String getProperty(SQLiteDatabase db, String key, String defaultValue) {
        try {
            final Cursor cursor = db.query(Tables.PROPERTIES,
                    new String[] {PropertiesColumns.PROPERTY_VALUE},
                            PropertiesColumns.PROPERTY_KEY + "=?",
                    new String[] {key}, null, null, null);
            String value = null;
            try {
                if (cursor.moveToFirst()) {
                    value = cursor.getString(0);
                }
            } finally {
                cursor.close();
            }
            return value != null ? value : defaultValue;
        } catch (SQLiteException e) {
            return defaultValue;
        }
    }

    public int getPropertyAsInt(SQLiteDatabase db, String key, int defaultValue) {
        final String stored = getProperty(db, key, "");
        try {
            return Integer.parseInt(stored);
        } catch (NumberFormatException e) {
            return defaultValue;
        }
    }

    private void resetSmartDialLastUpdatedTime() {
        final SharedPreferences databaseLastUpdateSharedPref = mContext.getSharedPreferences(
                DATABASE_LAST_CREATED_SHARED_PREF, Context.MODE_PRIVATE);
        final SharedPreferences.Editor editor = databaseLastUpdateSharedPref.edit();
        editor.putLong(LAST_UPDATED_MILLIS, 0);
        editor.commit();
    }

    /**
     * Starts the database upgrade process in the background.
     */
    public void startSmartDialUpdateThread() {
        new SmartDialUpdateAsyncTask().execute();
    }

    private class SmartDialUpdateAsyncTask extends AsyncTask {
        @Override
        protected Object doInBackground(Object[] objects) {
            if (DEBUG) {
                Log.v(TAG, "Updating database");
            }
            updateSmartDialDatabase();
            return null;
        }

        @Override
        protected void onCancelled() {
            if (DEBUG) {
                Log.v(TAG, "Updating Cancelled");
            }
            super.onCancelled();
        }

        @Override
        protected void onPostExecute(Object o) {
            if (DEBUG) {
                Log.v(TAG, "Updating Finished");
            }
            super.onPostExecute(o);
        }
    }
    /**
     * Removes rows in the smartdial database that matches the contacts that have been deleted
     * by other apps since last update.
     *
     * @param db Database pointer to the dialer database.
     * @param last_update_time Time stamp of last update on the smartdial database
     */
    private void removeDeletedContacts(SQLiteDatabase db, String last_update_time) {
        final Cursor deletedContactCursor = mContext.getContentResolver().query(
                DeleteContactQuery.URI,
                DeleteContactQuery.PROJECTION,
                DeleteContactQuery.SELECT_UPDATED_CLAUSE,
                new String[] {last_update_time}, null);
        if (deletedContactCursor == null) {
            return;
        }

        db.beginTransaction();
        try {
            while (deletedContactCursor.moveToNext()) {
                final Long deleteContactId =
                        deletedContactCursor.getLong(DeleteContactQuery.DELETED_CONTACT_ID);
                db.delete(Tables.SMARTDIAL_TABLE,
                        SmartDialDbColumns.CONTACT_ID + "=" + deleteContactId, null);
                db.delete(Tables.PREFIX_TABLE,
                        PrefixColumns.CONTACT_ID + "=" + deleteContactId, null);
            }

            db.setTransactionSuccessful();
        } finally {
            deletedContactCursor.close();
            db.endTransaction();
        }
    }

    /**
     * Removes potentially corrupted entries in the database. These contacts may be added before
     * the previous instance of the dialer was destroyed for some reason. For data integrity, we
     * delete all of them.

     * @param db Database pointer to the dialer database.
     * @param last_update_time Time stamp of last successful update of the dialer database.
     */
    private void removePotentiallyCorruptedContacts(SQLiteDatabase db, String last_update_time) {
        db.delete(Tables.PREFIX_TABLE,
                PrefixColumns.CONTACT_ID + " IN " +
                "(SELECT " + SmartDialDbColumns.CONTACT_ID + " FROM " + Tables.SMARTDIAL_TABLE +
                " WHERE " + SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME + " > " +
                last_update_time + ")",
                null);
        db.delete(Tables.SMARTDIAL_TABLE,
                SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME + " > " + last_update_time, null);
    }

    /**
     * Removes all entries in the smartdial contact database.
     */
    @VisibleForTesting
    void removeAllContacts(SQLiteDatabase db) {
        db.delete(Tables.SMARTDIAL_TABLE, null, null);
        db.delete(Tables.PREFIX_TABLE, null, null);
    }

    /**
     * Counts number of rows of the prefix table.
     */
    @VisibleForTesting
    int countPrefixTableRows(SQLiteDatabase db) {
        return (int)DatabaseUtils.longForQuery(db, "SELECT COUNT(1) FROM " + Tables.PREFIX_TABLE,
                null);
    }

    /**
     * Removes rows in the smartdial database that matches updated contacts.
     *
     * @param db Database pointer to the smartdial database
     * @param updatedContactCursor Cursor pointing to the list of recently updated contacts.
     */
    private void removeUpdatedContacts(SQLiteDatabase db, Cursor updatedContactCursor) {
        db.beginTransaction();
        try {
            while (updatedContactCursor.moveToNext()) {
                final Long contactId = updatedContactCursor.getLong(PhoneQuery.PHONE_CONTACT_ID);

                db.delete(Tables.SMARTDIAL_TABLE, SmartDialDbColumns.CONTACT_ID + "=" +
                        contactId, null);
                db.delete(Tables.PREFIX_TABLE, PrefixColumns.CONTACT_ID + "=" +
                        contactId, null);
            }

            db.setTransactionSuccessful();
        } finally {
            db.endTransaction();
        }
    }

    /**
     * Inserts updated contacts as rows to the smartdial table.
     *
     * @param db Database pointer to the smartdial database.
     * @param updatedContactCursor Cursor pointing to the list of recently updated contacts.
     * @param currentMillis Current time to be recorded in the smartdial table as update timestamp.
     */
    @VisibleForTesting
    protected void insertUpdatedContactsAndNumberPrefix(SQLiteDatabase db,
            Cursor updatedContactCursor, Long currentMillis) {
        db.beginTransaction();
        try {
            final String sqlInsert = "INSERT INTO " + Tables.SMARTDIAL_TABLE + " (" +
                    SmartDialDbColumns.DATA_ID + ", " +
                    SmartDialDbColumns.NUMBER + ", " +
                    SmartDialDbColumns.CONTACT_ID + ", " +
                    SmartDialDbColumns.LOOKUP_KEY + ", " +
                    SmartDialDbColumns.DISPLAY_NAME_PRIMARY + ", " +
                    SmartDialDbColumns.PHOTO_ID + ", " +
                    SmartDialDbColumns.LAST_TIME_USED + ", " +
                    SmartDialDbColumns.TIMES_USED + ", " +
                    SmartDialDbColumns.STARRED + ", " +
                    SmartDialDbColumns.IS_SUPER_PRIMARY + ", " +
                    SmartDialDbColumns.IN_VISIBLE_GROUP+ ", " +
                    SmartDialDbColumns.IS_PRIMARY + ", " +
                    SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME + ") " +
                    " VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
            final SQLiteStatement insert = db.compileStatement(sqlInsert);

            final String numberSqlInsert = "INSERT INTO " + Tables.PREFIX_TABLE + " (" +
                    PrefixColumns.CONTACT_ID + ", " +
                    PrefixColumns.PREFIX  + ") " +
                    " VALUES (?, ?)";
            final SQLiteStatement numberInsert = db.compileStatement(numberSqlInsert);

            updatedContactCursor.moveToPosition(-1);
            while (updatedContactCursor.moveToNext()) {
                insert.clearBindings();

                // Handle string columns which can possibly be null first. In the case of certain
                // null columns (due to malformed rows possibly inserted by third-party apps
                // or sync adapters), skip the phone number row.
                final String number = updatedContactCursor.getString(PhoneQuery.PHONE_NUMBER);
                if (TextUtils.isEmpty(number)) {
                    continue;
                } else {
                    insert.bindString(2, number);
                }

                final String lookupKey = updatedContactCursor.getString(
                        PhoneQuery.PHONE_LOOKUP_KEY);
                if (TextUtils.isEmpty(lookupKey)) {
                    continue;
                } else {
                    insert.bindString(4, lookupKey);
                }

                final String displayName = updatedContactCursor.getString(
                        PhoneQuery.PHONE_DISPLAY_NAME);
                if (displayName == null) {
                    insert.bindString(5, mContext.getResources().getString(R.string.missing_name));
                } else {
                    insert.bindString(5, displayName);
                }
                insert.bindLong(1, updatedContactCursor.getLong(PhoneQuery.PHONE_ID));
                insert.bindLong(3, updatedContactCursor.getLong(PhoneQuery.PHONE_CONTACT_ID));
                insert.bindLong(6, updatedContactCursor.getLong(PhoneQuery.PHONE_PHOTO_ID));
                insert.bindLong(7, updatedContactCursor.getLong(PhoneQuery.PHONE_LAST_TIME_USED));
                insert.bindLong(8, updatedContactCursor.getInt(PhoneQuery.PHONE_TIMES_USED));
                insert.bindLong(9, updatedContactCursor.getInt(PhoneQuery.PHONE_STARRED));
                insert.bindLong(10, updatedContactCursor.getInt(PhoneQuery.PHONE_IS_SUPER_PRIMARY));
                insert.bindLong(11, updatedContactCursor.getInt(PhoneQuery.PHONE_IN_VISIBLE_GROUP));
                insert.bindLong(12, updatedContactCursor.getInt(PhoneQuery.PHONE_IS_PRIMARY));
                insert.bindLong(13, currentMillis);
                insert.executeInsert();
                final String contactPhoneNumber =
                        updatedContactCursor.getString(PhoneQuery.PHONE_NUMBER);
                final ArrayList<String> numberPrefixes =
                        SmartDialPrefix.parseToNumberTokens(contactPhoneNumber);

                for (String numberPrefix : numberPrefixes) {
                    numberInsert.bindLong(1, updatedContactCursor.getLong(
                            PhoneQuery.PHONE_CONTACT_ID));
                    numberInsert.bindString(2, numberPrefix);
                    numberInsert.executeInsert();
                    numberInsert.clearBindings();
                }
            }

            db.setTransactionSuccessful();
        } finally {
            db.endTransaction();
        }
    }

    /**
     * Inserts prefixes of contact names to the prefix table.
     *
     * @param db Database pointer to the smartdial database.
     * @param nameCursor Cursor pointing to the list of distinct updated contacts.
     */
    @VisibleForTesting
    void insertNamePrefixes(SQLiteDatabase db, Cursor nameCursor) {
        final int columnIndexName = nameCursor.getColumnIndex(
                SmartDialDbColumns.DISPLAY_NAME_PRIMARY);
        final int columnIndexContactId = nameCursor.getColumnIndex(SmartDialDbColumns.CONTACT_ID);

        db.beginTransaction();
        try {
            final String sqlInsert = "INSERT INTO " + Tables.PREFIX_TABLE + " (" +
                    PrefixColumns.CONTACT_ID + ", " +
                    PrefixColumns.PREFIX  + ") " +
                    " VALUES (?, ?)";
            final SQLiteStatement insert = db.compileStatement(sqlInsert);

            while (nameCursor.moveToNext()) {
                /** Computes a list of prefixes of a given contact name. */
                final ArrayList<String> namePrefixes =
                        SmartDialPrefix.generateNamePrefixes(nameCursor.getString(columnIndexName));

                for (String namePrefix : namePrefixes) {
                    insert.bindLong(1, nameCursor.getLong(columnIndexContactId));
                    insert.bindString(2, namePrefix);
                    insert.executeInsert();
                    insert.clearBindings();
                }
            }

            db.setTransactionSuccessful();
        } finally {
            db.endTransaction();
        }
    }

    /**
     * Updates the smart dial and prefix database.
     * This method queries the Delta API to get changed contacts since last update, and updates the
     * records in smartdial database and prefix database accordingly.
     * It also queries the deleted contact database to remove newly deleted contacts since last
     * update.
     */
    public void updateSmartDialDatabase() {
        final SQLiteDatabase db = getWritableDatabase();

        synchronized(mLock) {
            if (DEBUG) {
                Log.v(TAG, "Starting to update database");
            }
            final StopWatch stopWatch = DEBUG ? StopWatch.start("Updating databases") : null;

            /** Gets the last update time on the database. */
            final SharedPreferences databaseLastUpdateSharedPref = mContext.getSharedPreferences(
                    DATABASE_LAST_CREATED_SHARED_PREF, Context.MODE_PRIVATE);
            final String lastUpdateMillis = String.valueOf(
                    databaseLastUpdateSharedPref.getLong(LAST_UPDATED_MILLIS, 0));

            if (DEBUG) {
                Log.v(TAG, "Last updated at " + lastUpdateMillis);
            }
            /** Queries the contact database to get contacts that have been updated since the last
             * update time.
             */
            final Cursor updatedContactCursor = mContext.getContentResolver().query(PhoneQuery.URI,
                    PhoneQuery.PROJECTION, PhoneQuery.SELECTION,
                    new String[]{lastUpdateMillis}, null);

            /** Sets the time after querying the database as the current update time. */
            final Long currentMillis = System.currentTimeMillis();

            if (DEBUG) {
                stopWatch.lap("Queried the Contacts database");
            }

            if (updatedContactCursor == null) {
                if (DEBUG) {
                    Log.e(TAG, "SmartDial query received null for cursor");
                }
                return;
            }

            /** Prevents the app from reading the dialer database when updating. */
            sInUpdate.getAndSet(true);

            /** Removes contacts that have been deleted. */
            removeDeletedContacts(db, lastUpdateMillis);
            removePotentiallyCorruptedContacts(db, lastUpdateMillis);

            if (DEBUG) {
                stopWatch.lap("Finished deleting deleted entries");
            }

            try {
                /** If the database did not exist before, jump through deletion as there is nothing
                 * to delete.
                 */
                if (!lastUpdateMillis.equals("0")) {
                    /** Removes contacts that have been updated. Updated contact information will be
                     * inserted later.
                     */
                    removeUpdatedContacts(db, updatedContactCursor);
                    if (DEBUG) {
                        stopWatch.lap("Finished deleting updated entries");
                    }
                }

                /** Inserts recently updated contacts to the smartdial database.*/
                insertUpdatedContactsAndNumberPrefix(db, updatedContactCursor, currentMillis);
                if (DEBUG) {
                    stopWatch.lap("Finished building the smart dial table");
                }
            } finally {
                /** Inserts prefixes of phone numbers into the prefix table.*/
                updatedContactCursor.close();
            }

            /** Gets a list of distinct contacts which have been updated, and adds the name prefixes
             * of these contacts to the prefix table.
             */
            final Cursor nameCursor = db.rawQuery(
                    "SELECT DISTINCT " +
                    SmartDialDbColumns.DISPLAY_NAME_PRIMARY + ", " + SmartDialDbColumns.CONTACT_ID +
                    " FROM " + Tables.SMARTDIAL_TABLE +
                    " WHERE " + SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME +
                    " = " + Long.toString(currentMillis),
                    new String[] {});
            if (DEBUG) {
                stopWatch.lap("Queried the smart dial table for contact names");
            }

            if (nameCursor != null) {
                try {
                    /** Inserts prefixes of names into the prefix table.*/
                    insertNamePrefixes(db, nameCursor);
                    if (DEBUG) {
                        stopWatch.lap("Finished building the name prefix table");
                    }
                } finally {
                    nameCursor.close();
                }
            }

            /** Creates index on contact_id for fast JOIN operation. */
            db.execSQL("CREATE INDEX IF NOT EXISTS smartdial_contact_id_index ON " +
                    Tables.SMARTDIAL_TABLE + " (" + SmartDialDbColumns.CONTACT_ID  + ");");
            /** Creates index on last_smartdial_update_time for fast SELECT operation. */
            db.execSQL("CREATE INDEX IF NOT EXISTS smartdial_last_update_index ON " +
                    Tables.SMARTDIAL_TABLE + " (" +
                    SmartDialDbColumns.LAST_SMARTDIAL_UPDATE_TIME + ");");
            /** Creates index on sorting fields for fast sort operation. */
            db.execSQL("CREATE INDEX IF NOT EXISTS smartdial_sort_index ON " +
                    Tables.SMARTDIAL_TABLE + " (" +
                    SmartDialDbColumns.STARRED + ", " +
                    SmartDialDbColumns.IS_SUPER_PRIMARY + ", " +
                    SmartDialDbColumns.LAST_TIME_USED + ", " +
                    SmartDialDbColumns.TIMES_USED + ", " +
                    SmartDialDbColumns.IN_VISIBLE_GROUP +  ", " +
                    SmartDialDbColumns.DISPLAY_NAME_PRIMARY + ", " +
                    SmartDialDbColumns.CONTACT_ID + ", " +
                    SmartDialDbColumns.IS_PRIMARY +
                    ");");
            /** Creates index on prefix for fast SELECT operation. */
            db.execSQL("CREATE INDEX IF NOT EXISTS nameprefix_index ON " +
                    Tables.PREFIX_TABLE + " (" + PrefixColumns.PREFIX + ");");
            /** Creates index on contact_id for fast JOIN operation. */
            db.execSQL("CREATE INDEX IF NOT EXISTS nameprefix_contact_id_index ON " +
                    Tables.PREFIX_TABLE + " (" + PrefixColumns.CONTACT_ID + ");");

            if (DEBUG) {
                stopWatch.lap(TAG + "Finished recreating index");
            }

            /** Updates the database index statistics.*/
            db.execSQL("ANALYZE " + Tables.SMARTDIAL_TABLE);
            db.execSQL("ANALYZE " + Tables.PREFIX_TABLE);
            db.execSQL("ANALYZE smartdial_contact_id_index");
            db.execSQL("ANALYZE smartdial_last_update_index");
            db.execSQL("ANALYZE nameprefix_index");
            db.execSQL("ANALYZE nameprefix_contact_id_index");
            if (DEBUG) {
                stopWatch.stopAndLog(TAG + "Finished updating index stats", 0);
            }

            sInUpdate.getAndSet(false);

            final SharedPreferences.Editor editor = databaseLastUpdateSharedPref.edit();
            editor.putLong(LAST_UPDATED_MILLIS, currentMillis);
            editor.commit();
        }
    }

    /**
     * Returns a list of candidate contacts where the query is a prefix of the dialpad index of
     * the contact's name or phone number.
     *
     * @param query The prefix of a contact's dialpad index.
     * @return A list of top candidate contacts that will be suggested to user to match their input.
     */
    public ArrayList<ContactNumber>  getLooseMatches(String query,
            SmartDialNameMatcher nameMatcher) {
        final boolean inUpdate = sInUpdate.get();
        if (inUpdate) {
            return Lists.newArrayList();
        }

        final SQLiteDatabase db = getReadableDatabase();

        /** Uses SQL query wildcard '%' to represent prefix matching.*/
        final String looseQuery = query + "%";

        final ArrayList<ContactNumber> result = Lists.newArrayList();

        final StopWatch stopWatch = DEBUG ? StopWatch.start(":Name Prefix query") : null;

        final String currentTimeStamp = Long.toString(System.currentTimeMillis());

        /** Queries the database to find contacts that have an index matching the query prefix. */
        final Cursor cursor = db.rawQuery("SELECT " +
                SmartDialDbColumns.DATA_ID + ", " +
                SmartDialDbColumns.DISPLAY_NAME_PRIMARY + ", " +
                SmartDialDbColumns.PHOTO_ID + ", " +
                SmartDialDbColumns.NUMBER + ", " +
                SmartDialDbColumns.CONTACT_ID + ", " +
                SmartDialDbColumns.LOOKUP_KEY +
                " FROM " + Tables.SMARTDIAL_TABLE + " WHERE " +
                SmartDialDbColumns.CONTACT_ID + " IN " +
                    " (SELECT " + PrefixColumns.CONTACT_ID +
                    " FROM " + Tables.PREFIX_TABLE +
                    " WHERE " + Tables.PREFIX_TABLE + "." + PrefixColumns.PREFIX +
                    " LIKE '" + looseQuery + "')" +
                " ORDER BY " + SmartDialSortingOrder.SORT_ORDER,
                new String[] {currentTimeStamp});

        if (DEBUG) {
            stopWatch.lap("Prefix query completed");
        }

        /** Gets the column ID from the cursor.*/
        final int columnDataId = 0;
        final int columnDisplayNamePrimary = 1;
        final int columnPhotoId = 2;
        final int columnNumber = 3;
        final int columnId = 4;
        final int columnLookupKey = 5;
        if (DEBUG) {
            stopWatch.lap("Found column IDs");
        }

        final Set<ContactMatch> duplicates = new HashSet<ContactMatch>();
        int counter = 0;
        try {
            if (DEBUG) {
                stopWatch.lap("Moved cursor to start");
            }
            /** Iterates the cursor to find top contact suggestions without duplication.*/
            while ((cursor.moveToNext()) && (counter < MAX_ENTRIES)) {
                final long dataID = cursor.getLong(columnDataId);
                final String displayName = cursor.getString(columnDisplayNamePrimary);
                final String phoneNumber = cursor.getString(columnNumber);
                final long id = cursor.getLong(columnId);
                final long photoId = cursor.getLong(columnPhotoId);
                final String lookupKey = cursor.getString(columnLookupKey);

                /** If a contact already exists and another phone number of the contact is being
                 * processed, skip the second instance.
                 */
                final ContactMatch contactMatch = new ContactMatch(lookupKey, id);
                if (duplicates.contains(contactMatch)) {
                    continue;
                }

                /**
                 * If the contact has either the name or number that matches the query, add to the
                 * result.
                 */
                final boolean nameMatches = nameMatcher.matches(displayName);
                final boolean numberMatches =
                        (nameMatcher.matchesNumber(phoneNumber, query) != null);
                if (nameMatches || numberMatches) {
                    /** If a contact has not been added, add it to the result and the hash set.*/
                    duplicates.add(contactMatch);
                    result.add(new ContactNumber(id, dataID, displayName, phoneNumber, lookupKey,
                            photoId));
                    counter++;
                    if (DEBUG) {
                        stopWatch.lap("Added one result");
                    }
                }
            }

            if (DEBUG) {
                stopWatch.stopAndLog(TAG + "Finished loading cursor", 0);
            }
        } finally {
            cursor.close();
        }
        return result;
    }
}