Rename the user history dictionary.

UserBigramDictionary -> UserHistoryDictionary.

Also update all methods, strings and comments, except those needed
for backward compatibility (which only include the name of the
database file).

Change-Id: I0bccea29880dc566b90100575b83baaa947b03ae

1 files changed, 457 insertions, 0 deletions

diff --git a/java/src/com/android/inputmethod/latin/UserHistoryDictionary.java b/java/src/com/android/inputmethod/latin/UserHistoryDictionary.java
new file mode 100644
index 000000000..4e798460c
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/UserHistoryDictionary.java
@@ -0,0 +1,457 @@
+/*
+ * Copyright (C) 2010 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.inputmethod.latin;
+
+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;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+
+/**
+ * Locally gathers stats about the words user types and various other signals like auto-correction
+ * cancellation or manual picks. This allows the keyboard to adapt to the typist over time.
+ */
+public class UserHistoryDictionary extends ExpandableDictionary {
+    private static final String TAG = "UserHistoryDictionary";
+
+    /** 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;
+
+    /** Maximum number of pairs. Pruning will start when databases goes above this number. */
+    private static int sMaxHistoryBigrams = 10000;
+
+    /**
+     * When it hits maximum bigram pair, it will delete until you are left with
+     * only (sMaxHistoryBigrams - sDeleteHistoryBigrams) pairs.
+     * Do not keep this number small to avoid deleting too often.
+     */
+    private static int sDeleteHistoryBigrams = 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.
+    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 {
+        public final String mWord1;
+        public final String mWord2;
+        public final int mFrequency;
+
+        Bigram(String word1, String word2, int frequency) {
+            this.mWord1 = word1;
+            this.mWord2 = word2;
+            this.mFrequency = frequency;
+        }
+
+        @Override
+        public boolean equals(Object bigram) {
+            if (!(bigram instanceof Bigram)) {
+                return false;
+            }
+            final Bigram bigram2 = (Bigram) bigram;
+            final boolean eq1 =
+                    mWord1 == null ? bigram2.mWord1 == null : mWord1.equals(bigram2.mWord1);
+            if (!eq1) {
+                return false;
+            }
+            return mWord2 == null ? bigram2.mWord2 == null : mWord2.equals(bigram2.mWord2);
+        }
+
+        @Override
+        public int hashCode() {
+            return (mWord1 + " " + mWord2).hashCode();
+        }
+    }
+
+    public void setDatabaseMax(int maxHistoryBigram) {
+        sMaxHistoryBigrams = maxHistoryBigram;
+    }
+
+    public void setDatabaseDelete(int deleteHistoryBigram) {
+        sDeleteHistoryBigrams = deleteHistoryBigram;
+    }
+
+    public UserHistoryDictionary(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();
+    }
+
+    /**
+     * Return whether the passed charsequence is in the dictionary.
+     */
+    @Override
+    public boolean isValidWord(final CharSequence word) {
+        // TODO: figure out what is the correct thing to do here.
+        return false;
+    }
+
+    /**
+     * Pair will be added to the user history dictionary.
+     *
+     * The first word may be null. That means we don't know the context, in other words,
+     * it's only a unigram. The first word may also be an empty string : this means start
+     * context, as in beginning of a sentence for example.
+     * The second word may not be null (a NullPointerException would be thrown).
+     */
+    public int addToUserHistory(final String word1, String word2) {
+        // remove caps if second word is autocapitalized
+        if (mIme != null && mIme.isAutoCapitalized()) {
+            word2 = Character.toLowerCase(word2.charAt(0)) + word2.substring(1);
+        }
+        super.addWord(word2, FREQUENCY_FOR_TYPED);
+        // Do not insert a word as a bigram of itself
+        if (word2.equals(word1)) {
+            return 0;
+        }
+
+        int freq;
+        if (null == word1) {
+            freq = FREQUENCY_FOR_TYPED;
+        } else {
+            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(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
+        final Cursor cursor = query(MAIN_COLUMN_LOCALE + "=?", new String[] { mLocale });
+        if (null == cursor) return;
+        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 (null == word1) {
+                        super.addWord(word2, frequency);
+                    } else 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 static 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
+        try {
+            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;
+        } catch (android.database.sqlite.SQLiteCantOpenDatabaseException e) {
+            // Can't open the database : presumably we can't access storage. That may happen
+            // when the device is wedged; do a best effort to still start the keyboard.
+            return null;
+        }
+    }
+
+    /**
+     * 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(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 static 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 > sMaxHistoryBigrams) {
+                    int numDeleteRows = (totalRowCount - sMaxHistoryBigrams) + sDeleteHistoryBigrams;
+                    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 = null;
+            try {
+                db = mDbHelper.getWritableDatabase();
+            } catch (android.database.sqlite.SQLiteCantOpenDatabaseException e) {
+                // If we can't open the db, don't do anything. Exit through the next test
+                // for non-nullity of the db variable.
+            }
+            if (null == db) {
+                // Not much we can do. Just exit.
+                sUpdatingDB = false;
+                return null;
+            }
+            db.execSQL("PRAGMA foreign_keys = ON;");
+            // Write all the entries to the db
+            Iterator<Bigram> iterator = mMap.iterator();
+            while (iterator.hasNext()) {
+                // TODO: this process of making a text search for each pair each time
+                // is terribly inefficient. Optimize this.
+                Bigram bi = iterator.next();
+
+                // find pair id
+                final Cursor c;
+                if (null != bi.mWord1) {
+                    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.mWord1, bi.mWord2, mLocale }, null, null, null);
+                } else {
+                    c = db.query(MAIN_TABLE_NAME, new String[] { MAIN_COLUMN_ID },
+                            MAIN_COLUMN_WORD1 + " IS NULL AND " + MAIN_COLUMN_WORD2 + "=? AND "
+                            + MAIN_COLUMN_LOCALE + "=?",
+                            new String[] { bi.mWord2, 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.mWord1, bi.mWord2, mLocale));
+                    pairId = pairIdLong.intValue();
+                }
+                c.close();
+
+                // insert new frequency
+                db.insert(FREQ_TABLE_NAME, null, getFrequencyContentValues(pairId, bi.mFrequency));
+            }
+            checkPruneData(db);
+            sUpdatingDB = false;
+
+            return null;
+        }
+
+        private static 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 static 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;
+        }
+    }
+
+}