/*
* 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.Set;
import java.util.Map.Entry;
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 new words temporarily until they are promoted to the user dictionary
* for longevity. Words in the auto dictionary are used to determine if it's ok
* to accept a word that's not in the main or user dictionary. Using a new word
* repeatedly will promote it to the user dictionary.
*/
public class AutoDictionary extends ExpandableDictionary {
// Weight added to a user picking a new word from the suggestion strip
static final int FREQUENCY_FOR_PICKED = 3;
// Weight added to a user typing a new word that doesn't get corrected (or is reverted)
static final int FREQUENCY_FOR_TYPED = 1;
// A word that is frequently typed and gets promoted to the user dictionary, uses this
// frequency.
static final int FREQUENCY_FOR_AUTO_ADD = 250;
// If the user touches a typed word 2 times or more, it will become valid.
private static final int VALIDITY_THRESHOLD = 2 * FREQUENCY_FOR_PICKED;
// If the user touches a typed word 4 times or more, it will be added to the user dict.
private static final int PROMOTION_THRESHOLD = 4 * FREQUENCY_FOR_PICKED;
private LatinIME mIme;
// Locale for which this auto dictionary is storing words
private String mLocale;
private HashMap<String,Integer> mPendingWrites = new HashMap<String,Integer>();
private final Object mPendingWritesLock = new Object();
private static final String DATABASE_NAME = "auto_dict.db";
private static final int DATABASE_VERSION = 1;
// These are the columns in the dictionary
// TODO: Consume less space by using a unique id for locale instead of the whole
// 2-5 character string.
private static final String COLUMN_ID = BaseColumns._ID;
private static final String COLUMN_WORD = "word";
private static final String COLUMN_FREQUENCY = "freq";
private static final String COLUMN_LOCALE = "locale";
/** Sort by descending order of frequency. */
public static final String DEFAULT_SORT_ORDER = COLUMN_FREQUENCY + " DESC";
/** Name of the words table in the auto_dict.db */
private static final String AUTODICT_TABLE_NAME = "words";
private static HashMap<String, String> sDictProjectionMap;
static {
sDictProjectionMap = new HashMap<String, String>();
sDictProjectionMap.put(COLUMN_ID, COLUMN_ID);
sDictProjectionMap.put(COLUMN_WORD, COLUMN_WORD);
sDictProjectionMap.put(COLUMN_FREQUENCY, COLUMN_FREQUENCY);
sDictProjectionMap.put(COLUMN_LOCALE, COLUMN_LOCALE);
}
private static DatabaseHelper sOpenHelper = null;
public AutoDictionary(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 boolean isValidWord(CharSequence word) {
final int frequency = getWordFrequency(word);
return frequency >= VALIDITY_THRESHOLD;
}
@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();
}
@Override
public void loadDictionaryAsync() {
// Load the words that correspond to the current input locale
Cursor cursor = query(COLUMN_LOCALE + "=?", new String[] { mLocale });
try {
if (cursor.moveToFirst()) {
int wordIndex = cursor.getColumnIndex(COLUMN_WORD);
int frequencyIndex = cursor.getColumnIndex(COLUMN_FREQUENCY);
while (!cursor.isAfterLast()) {
String word = cursor.getString(wordIndex);
int frequency = cursor.getInt(frequencyIndex);
// Safeguard against adding really long words. Stack may overflow due
// to recursive lookup
if (word.length() < getMaxWordLength()) {
super.addWord(word, frequency);
}
cursor.moveToNext();
}
}
} finally {
cursor.close();
}
}
@Override
public void addWord(String word, int addFrequency) {
final int length = word.length();
// Don't add very short or very long words.
if (length < 2 || length > getMaxWordLength()) return;
if (mIme.getCurrentWord().isAutoCapitalized()) {
// Remove caps before adding
word = Character.toLowerCase(word.charAt(0)) + word.substring(1);
}
int freq = getWordFrequency(word);
freq = freq < 0 ? addFrequency : freq + addFrequency;
super.addWord(word, freq);
if (freq >= PROMOTION_THRESHOLD) {
mIme.promoteToUserDictionary(word, FREQUENCY_FOR_AUTO_ADD);
freq = 0;
}
synchronized (mPendingWritesLock) {
// Write a null frequency if it is to be deleted from the db
mPendingWrites.put(word, freq == 0 ? null : new Integer(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 HashMap<String, Integer>();
}
}
/**
* 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("CREATE TABLE " + AUTODICT_TABLE_NAME + " ("
+ COLUMN_ID + " INTEGER PRIMARY KEY,"
+ COLUMN_WORD + " TEXT,"
+ COLUMN_FREQUENCY + " INTEGER,"
+ COLUMN_LOCALE + " TEXT"
+ ");");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w("AutoDictionary", "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + AUTODICT_TABLE_NAME);
onCreate(db);
}
}
private Cursor query(String selection, String[] selectionArgs) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
qb.setTables(AUTODICT_TABLE_NAME);
qb.setProjectionMap(sDictProjectionMap);
// Get the database and run the query
SQLiteDatabase db = sOpenHelper.getReadableDatabase();
Cursor c = qb.query(db, null, selection, selectionArgs, null, null,
DEFAULT_SORT_ORDER);
return c;
}
/**
* 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 HashMap<String, Integer> mMap;
private final DatabaseHelper mDbHelper;
private final String mLocale;
public UpdateDbTask(Context context, DatabaseHelper openHelper,
HashMap<String, Integer> pendingWrites, String locale) {
mMap = pendingWrites;
mLocale = locale;
mDbHelper = openHelper;
}
@Override
protected Void doInBackground(Void... v) {
SQLiteDatabase db = mDbHelper.getWritableDatabase();
// Write all the entries to the db
Set<Entry<String,Integer>> mEntries = mMap.entrySet();
for (Entry<String,Integer> entry : mEntries) {
Integer freq = entry.getValue();
db.delete(AUTODICT_TABLE_NAME, COLUMN_WORD + "=? AND " + COLUMN_LOCALE + "=?",
new String[] { entry.getKey(), mLocale });
if (freq != null) {
db.insert(AUTODICT_TABLE_NAME, null,
getContentValues(entry.getKey(), freq, mLocale));
}
}
return null;
}
private ContentValues getContentValues(String word, int frequency, String locale) {
ContentValues values = new ContentValues(4);
values.put(COLUMN_WORD, word);
values.put(COLUMN_FREQUENCY, frequency);
values.put(COLUMN_LOCALE, locale);
return values;
}
}
}