/*
 * Copyright (C) 2008 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.Context;
import android.content.res.AssetFileDescriptor;
import android.util.Log;

import java.util.Arrays;

/**
 * Implements a static, compacted, binary dictionary of standard words.
 */
public class BinaryDictionary extends Dictionary {

    /**
     * There is difference between what java and native code can handle.
     * This value should only be used in BinaryDictionary.java
     * It is necessary to keep it at this value because some languages e.g. German have
     * really long words.
     */
    protected static final int MAX_WORD_LENGTH = 48;

    private static final String TAG = "BinaryDictionary";
    private static final int MAX_ALTERNATIVES = 16;
    private static final int MAX_WORDS = 18;
    private static final int MAX_BIGRAMS = 60;

    private static final int TYPED_LETTER_MULTIPLIER = 2;

    private static final BinaryDictionary sInstance = new BinaryDictionary();
    private int mDicTypeId;
    private int mNativeDict;
    private long mDictLength;
    private final int[] mInputCodes = new int[MAX_WORD_LENGTH * MAX_ALTERNATIVES];
    private final char[] mOutputChars = new char[MAX_WORD_LENGTH * MAX_WORDS];
    private final char[] mOutputChars_bigrams = new char[MAX_WORD_LENGTH * MAX_BIGRAMS];
    private final int[] mFrequencies = new int[MAX_WORDS];
    private final int[] mFrequencies_bigrams = new int[MAX_BIGRAMS];

    static {
        try {
            System.loadLibrary("jni_latinime");
        } catch (UnsatisfiedLinkError ule) {
            Log.e(TAG, "Could not load native library jni_latinime");
        }
    }

    private BinaryDictionary() {
    }

    /**
     * Initialize a dictionary from a raw resource file
     * @param context application context for reading resources
     * @param resId the resource containing the raw binary dictionary
     * @return initialized instance of BinaryDictionary
     */
    public static BinaryDictionary initDictionary(Context context, int resId, int dicTypeId) {
        synchronized (sInstance) {
            sInstance.closeInternal();
            if (resId != 0) {
                sInstance.loadDictionary(context, resId);
                sInstance.mDicTypeId = dicTypeId;
            }
        }
        return sInstance;
    }

    private native int openNative(String sourceDir, long dictOffset, long dictSize,
            int typedLetterMultiplier, int fullWordMultiplier, int maxWordLength,
            int maxWords, int maxAlternatives);
    private native void closeNative(int dict);
    private native boolean isValidWordNative(int nativeData, char[] word, int wordLength);
    private native int getSuggestionsNative(int dict, int[] inputCodes, int codesSize,
            char[] outputChars, int[] frequencies,
            int[] nextLettersFrequencies, int nextLettersSize);
    private native int getBigramsNative(int dict, char[] prevWord, int prevWordLength,
            int[] inputCodes, int inputCodesLength, char[] outputChars, int[] frequencies,
            int maxWordLength, int maxBigrams, int maxAlternatives);

    private final void loadDictionary(Context context, int resId) {
        try {
            final AssetFileDescriptor afd = context.getResources().openRawResourceFd(resId);
            if (afd == null) {
                Log.e(TAG, "Found the resource but it is compressed. resId=" + resId);
                return;
            }
            mNativeDict = openNative(context.getApplicationInfo().sourceDir,
                    afd.getStartOffset(), afd.getLength(),
                    TYPED_LETTER_MULTIPLIER, FULL_WORD_FREQ_MULTIPLIER,
                    MAX_WORD_LENGTH, MAX_WORDS, MAX_ALTERNATIVES);
            mDictLength = afd.getLength();
        } catch (android.content.res.Resources.NotFoundException e) {
            Log.e(TAG, "Could not find the resource. resId=" + resId);
            return;
        }
    }

    @Override
    public void getBigrams(final WordComposer codes, final CharSequence previousWord,
            final WordCallback callback, int[] nextLettersFrequencies) {
        if (mNativeDict == 0) return;

        char[] chars = previousWord.toString().toCharArray();
        Arrays.fill(mOutputChars_bigrams, (char) 0);
        Arrays.fill(mFrequencies_bigrams, 0);

        int codesSize = codes.size();
        Arrays.fill(mInputCodes, -1);
        int[] alternatives = codes.getCodesAt(0);
        System.arraycopy(alternatives, 0, mInputCodes, 0,
                Math.min(alternatives.length, MAX_ALTERNATIVES));

        int count = getBigramsNative(mNativeDict, chars, chars.length, mInputCodes, codesSize,
                mOutputChars_bigrams, mFrequencies_bigrams, MAX_WORD_LENGTH, MAX_BIGRAMS,
                MAX_ALTERNATIVES);

        for (int j = 0; j < count; ++j) {
            if (mFrequencies_bigrams[j] < 1) break;
            final int start = j * MAX_WORD_LENGTH;
            int len = 0;
            while (len <  MAX_WORD_LENGTH && mOutputChars_bigrams[start + len] != 0) {
                ++len;
            }
            if (len > 0) {
                callback.addWord(mOutputChars_bigrams, start, len, mFrequencies_bigrams[j],
                        mDicTypeId, DataType.BIGRAM);
            }
        }
    }

    @Override
    public void getWords(final WordComposer codes, final WordCallback callback,
            int[] nextLettersFrequencies) {
        if (mNativeDict == 0) return;

        final int codesSize = codes.size();
        // Won't deal with really long words.
        if (codesSize > MAX_WORD_LENGTH - 1) return;

        Arrays.fill(mInputCodes, -1);
        for (int i = 0; i < codesSize; i++) {
            int[] alternatives = codes.getCodesAt(i);
            System.arraycopy(alternatives, 0, mInputCodes, i * MAX_ALTERNATIVES,
                    Math.min(alternatives.length, MAX_ALTERNATIVES));
        }
        Arrays.fill(mOutputChars, (char) 0);
        Arrays.fill(mFrequencies, 0);

        int count = getSuggestionsNative(mNativeDict, mInputCodes, codesSize, mOutputChars,
                mFrequencies, nextLettersFrequencies,
                nextLettersFrequencies != null ? nextLettersFrequencies.length : 0);

        for (int j = 0; j < count; ++j) {
            if (mFrequencies[j] < 1) break;
            final int start = j * MAX_WORD_LENGTH;
            int len = 0;
            while (len < MAX_WORD_LENGTH && mOutputChars[start + len] != 0) {
                ++len;
            }
            if (len > 0) {
                callback.addWord(mOutputChars, start, len, mFrequencies[j], mDicTypeId,
                        DataType.UNIGRAM);
            }
        }
    }

    @Override
    public boolean isValidWord(CharSequence word) {
        if (word == null) return false;
        char[] chars = word.toString().toCharArray();
        return isValidWordNative(mNativeDict, chars, chars.length);
    }

    public long getSize() {
        return mDictLength; // This value is initialized in loadDictionary()
    }

    @Override
    public synchronized void close() {
        closeInternal();
    }

    private void closeInternal() {
        if (mNativeDict != 0) {
            closeNative(mNativeDict);
            mNativeDict = 0;
            mDictLength = 0;
        }
    }

    @Override
    protected void finalize() throws Throwable {
        try {
            closeInternal();
        } finally {
            super.finalize();
        }
    }
}