/*
* Copyright (C) 2010 Google 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.s16.inputmethod.skeyboard;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.os.AsyncTask;
import android.provider.BaseColumns;
import android.util.Log;
/**
* Stores all the pairs user types in databases. Prune the database if the size
* gets too big. Unlike AutoDictionary, it even stores the pairs that are already
* in the dictionary.
*/
public class UserBigramDictionary extends ExpandableDictionary {
private static final String TAG = "UserBigramDictionary";
/** Any pair being typed or picked */
private static final int FREQUENCY_FOR_TYPED = 2;
/** Maximum frequency for all pairs */
private static final int FREQUENCY_MAX = 127;
/**
* If this pair is typed 6 times, it would be suggested.
* Should be smaller than ContactsDictionary.FREQUENCY_FOR_CONTACTS_BIGRAM
*/
protected static final int SUGGEST_THRESHOLD = 6 * FREQUENCY_FOR_TYPED;
/** Maximum number of pairs. Pruning will start when databases goes above this number. */
private static int sMaxUserBigrams = 10000;
/**
* When it hits maximum bigram pair, it will delete until you are left with
* only (sMaxUserBigrams - sDeleteUserBigrams) pairs.
* Do not keep this number small to avoid deleting too often.
*/
private static int sDeleteUserBigrams = 1000;
/**
* Database version should increase if the database structure changes
*/
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "userbigram_dict.db";
/** Name of the words table in the database */
private static final String MAIN_TABLE_NAME = "main";
// TODO: Consume less space by using a unique id for locale instead of the whole
// 2-5 character string. (Same TODO from AutoDictionary)
private static final String MAIN_COLUMN_ID = BaseColumns._ID;
private static final String MAIN_COLUMN_WORD1 = "word1";
private static final String MAIN_COLUMN_WORD2 = "word2";
private static final String MAIN_COLUMN_LOCALE = "locale";
/** Name of the frequency table in the database */
private static final String FREQ_TABLE_NAME = "frequency";
private static final String FREQ_COLUMN_ID = BaseColumns._ID;
private static final String FREQ_COLUMN_PAIR_ID = "pair_id";
private static final String FREQ_COLUMN_FREQUENCY = "freq";
private final LatinIME mIme;
/** Locale for which this auto dictionary is storing words */
private String mLocale;
private HashSet<Bigram> mPendingWrites = new HashSet<Bigram>();
private final Object mPendingWritesLock = new Object();
private static volatile boolean sUpdatingDB = false;
private final static HashMap<String, String> sDictProjectionMap;
static {
sDictProjectionMap = new HashMap<String, String>();
sDictProjectionMap.put(MAIN_COLUMN_ID, MAIN_COLUMN_ID);
sDictProjectionMap.put(MAIN_COLUMN_WORD1, MAIN_COLUMN_WORD1);
sDictProjectionMap.put(MAIN_COLUMN_WORD2, MAIN_COLUMN_WORD2);
sDictProjectionMap.put(MAIN_COLUMN_LOCALE, MAIN_COLUMN_LOCALE);
sDictProjectionMap.put(FREQ_COLUMN_ID, FREQ_COLUMN_ID);
sDictProjectionMap.put(FREQ_COLUMN_PAIR_ID, FREQ_COLUMN_PAIR_ID);
sDictProjectionMap.put(FREQ_COLUMN_FREQUENCY, FREQ_COLUMN_FREQUENCY);
}
private static DatabaseHelper sOpenHelper = null;
private static class Bigram {
String word1;
String word2;
int frequency;
Bigram(String word1, String word2, int frequency) {
this.word1 = word1;
this.word2 = word2;
this.frequency = frequency;
}
@Override
public boolean equals(Object bigram) {
Bigram bigram2 = (Bigram) bigram;
return (word1.equals(bigram2.word1) && word2.equals(bigram2.word2));
}
@Override
public int hashCode() {
return (word1 + " " + word2).hashCode();
}
}
public void setDatabaseMax(int maxUserBigram) {
sMaxUserBigrams = maxUserBigram;
}
public void setDatabaseDelete(int deleteUserBigram) {
sDeleteUserBigrams = deleteUserBigram;
}
public UserBigramDictionary(Context context, LatinIME ime, String locale, int dicTypeId) {
super(context, dicTypeId);
mIme = ime;
mLocale = locale;
if (sOpenHelper == null) {
sOpenHelper = new DatabaseHelper(getContext());
}
if (mLocale != null && mLocale.length() > 1) {
loadDictionary();
}
}
@Override
public void close() {
flushPendingWrites();
// Don't close the database as locale changes will require it to be reopened anyway
// Also, the database is written to somewhat frequently, so it needs to be kept alive
// throughout the life of the process.
// mOpenHelper.close();
super.close();
}
/**
* Pair will be added to the userbigram database.
*/
public int addBigrams(String word1, String word2) {
// remove caps
if (mIme != null && mIme.getCurrentWord().isAutoCapitalized()) {
word2 = Character.toLowerCase(word2.charAt(0)) + word2.substring(1);
}
int freq = super.addBigram(word1, word2, FREQUENCY_FOR_TYPED);
if (freq > FREQUENCY_MAX) freq = FREQUENCY_MAX;
synchronized (mPendingWritesLock) {
if (freq == FREQUENCY_FOR_TYPED || mPendingWrites.isEmpty()) {
mPendingWrites.add(new Bigram(word1, word2, freq));
} else {
Bigram bi = new Bigram(word1, word2, freq);
mPendingWrites.remove(bi);
mPendingWrites.add(bi);
}
}
return freq;
}
/**
* Schedules a background thread to write any pending words to the database.
*/
public void flushPendingWrites() {
synchronized (mPendingWritesLock) {
// Nothing pending? Return
if (mPendingWrites.isEmpty()) return;
// Create a background thread to write the pending entries
new UpdateDbTask(getContext(), sOpenHelper, mPendingWrites, mLocale).execute();
// Create a new map for writing new entries into while the old one is written to db
mPendingWrites = new HashSet<Bigram>();
}
}
/** Used for testing purpose **/
void waitUntilUpdateDBDone() {
synchronized (mPendingWritesLock) {
while (sUpdatingDB) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
return;
}
}
@Override
public void loadDictionaryAsync() {
// Load the words that correspond to the current input locale
Cursor cursor = query(MAIN_COLUMN_LOCALE + "=?", new String[] { mLocale });
try {
if (cursor.moveToFirst()) {
int word1Index = cursor.getColumnIndex(MAIN_COLUMN_WORD1);
int word2Index = cursor.getColumnIndex(MAIN_COLUMN_WORD2);
int frequencyIndex = cursor.getColumnIndex(FREQ_COLUMN_FREQUENCY);
while (!cursor.isAfterLast()) {
String word1 = cursor.getString(word1Index);
String word2 = cursor.getString(word2Index);
int frequency = cursor.getInt(frequencyIndex);
// Safeguard against adding really long words. Stack may overflow due
// to recursive lookup
if (word1.length() < MAX_WORD_LENGTH && word2.length() < MAX_WORD_LENGTH) {
super.setBigram(word1, word2, frequency);
}
cursor.moveToNext();
}
}
} finally {
cursor.close();
}
}
/**
* Query the database
*/
private Cursor query(String selection, String[] selectionArgs) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
// main INNER JOIN frequency ON (main._id=freq.pair_id)
qb.setTables(MAIN_TABLE_NAME + " INNER JOIN " + FREQ_TABLE_NAME + " ON ("
+ MAIN_TABLE_NAME + "." + MAIN_COLUMN_ID + "=" + FREQ_TABLE_NAME + "."
+ FREQ_COLUMN_PAIR_ID +")");
qb.setProjectionMap(sDictProjectionMap);
// Get the database and run the query
SQLiteDatabase db = sOpenHelper.getReadableDatabase();
Cursor c = qb.query(db,
new String[] { MAIN_COLUMN_WORD1, MAIN_COLUMN_WORD2, FREQ_COLUMN_FREQUENCY },
selection, selectionArgs, null, null, null);
return c;
}
/**
* This class helps open, create, and upgrade the database file.
*/
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("PRAGMA foreign_keys = ON;");
db.execSQL("CREATE TABLE " + MAIN_TABLE_NAME + " ("
+ MAIN_COLUMN_ID + " INTEGER PRIMARY KEY,"
+ MAIN_COLUMN_WORD1 + " TEXT,"
+ MAIN_COLUMN_WORD2 + " TEXT,"
+ MAIN_COLUMN_LOCALE + " TEXT"
+ ");");
db.execSQL("CREATE TABLE " + FREQ_TABLE_NAME + " ("
+ FREQ_COLUMN_ID + " INTEGER PRIMARY KEY,"
+ FREQ_COLUMN_PAIR_ID + " INTEGER,"
+ FREQ_COLUMN_FREQUENCY + " INTEGER,"
+ "FOREIGN KEY(" + FREQ_COLUMN_PAIR_ID + ") REFERENCES " + MAIN_TABLE_NAME
+ "(" + MAIN_COLUMN_ID + ")" + " ON DELETE CASCADE"
+ ");");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + MAIN_TABLE_NAME);
db.execSQL("DROP TABLE IF EXISTS " + FREQ_TABLE_NAME);
onCreate(db);
}
}
/**
* Async task to write pending words to the database so that it stays in sync with
* the in-memory trie.
*/
private static class UpdateDbTask extends AsyncTask<Void, Void, Void> {
private final HashSet<Bigram> mMap;
private final DatabaseHelper mDbHelper;
private final String mLocale;
public UpdateDbTask(Context context, DatabaseHelper openHelper,
HashSet<Bigram> pendingWrites, String locale) {
mMap = pendingWrites;
mLocale = locale;
mDbHelper = openHelper;
}
/** Prune any old data if the database is getting too big. */
private void checkPruneData(SQLiteDatabase db) {
db.execSQL("PRAGMA foreign_keys = ON;");
Cursor c = db.query(FREQ_TABLE_NAME, new String[] { FREQ_COLUMN_PAIR_ID },
null, null, null, null, null);
try {
int totalRowCount = c.getCount();
// prune out old data if we have too much data
if (totalRowCount > sMaxUserBigrams) {
int numDeleteRows = (totalRowCount - sMaxUserBigrams) + sDeleteUserBigrams;
int pairIdColumnId = c.getColumnIndex(FREQ_COLUMN_PAIR_ID);
c.moveToFirst();
int count = 0;
while (count < numDeleteRows && !c.isAfterLast()) {
String pairId = c.getString(pairIdColumnId);
// Deleting from MAIN table will delete the frequencies
// due to FOREIGN KEY .. ON DELETE CASCADE
db.delete(MAIN_TABLE_NAME, MAIN_COLUMN_ID + "=?",
new String[] { pairId });
c.moveToNext();
count++;
}
}
} finally {
c.close();
}
}
@Override
protected void onPreExecute() {
sUpdatingDB = true;
}
@Override
protected Void doInBackground(Void... v) {
SQLiteDatabase db = mDbHelper.getWritableDatabase();
db.execSQL("PRAGMA foreign_keys = ON;");
// Write all the entries to the db
Iterator<Bigram> iterator = mMap.iterator();
while (iterator.hasNext()) {
Bigram bi = iterator.next();
// find pair id
Cursor c = db.query(MAIN_TABLE_NAME, new String[] { MAIN_COLUMN_ID },
MAIN_COLUMN_WORD1 + "=? AND " + MAIN_COLUMN_WORD2 + "=? AND "
+ MAIN_COLUMN_LOCALE + "=?",
new String[] { bi.word1, bi.word2, mLocale }, null, null, null);
int pairId;
if (c.moveToFirst()) {
// existing pair
pairId = c.getInt(c.getColumnIndex(MAIN_COLUMN_ID));
db.delete(FREQ_TABLE_NAME, FREQ_COLUMN_PAIR_ID + "=?",
new String[] { Integer.toString(pairId) });
} else {
// new pair
Long pairIdLong = db.insert(MAIN_TABLE_NAME, null,
getContentValues(bi.word1, bi.word2, mLocale));
pairId = pairIdLong.intValue();
}
c.close();
// insert new frequency
db.insert(FREQ_TABLE_NAME, null, getFrequencyContentValues(pairId, bi.frequency));
}
checkPruneData(db);
sUpdatingDB = false;
return null;
}
private ContentValues getContentValues(String word1, String word2, String locale) {
ContentValues values = new ContentValues(3);
values.put(MAIN_COLUMN_WORD1, word1);
values.put(MAIN_COLUMN_WORD2, word2);
values.put(MAIN_COLUMN_LOCALE, locale);
return values;
}
private ContentValues getFrequencyContentValues(int pairId, int frequency) {
ContentValues values = new ContentValues(2);
values.put(FREQ_COLUMN_PAIR_ID, pairId);
values.put(FREQ_COLUMN_FREQUENCY, frequency);
return values;
}
}
}