/*
 * Copyright (C) 2011 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.spellcheck;

import android.content.Intent;
import android.content.res.Resources;
import android.service.textservice.SpellCheckerService;
import android.service.textservice.SpellCheckerService.Session;
import android.util.Log;
import android.view.textservice.SuggestionsInfo;
import android.view.textservice.TextInfo;
import android.text.TextUtils;

import com.android.inputmethod.compat.ArraysCompatUtils;
import com.android.inputmethod.keyboard.Key;
import com.android.inputmethod.keyboard.ProximityInfo;
import com.android.inputmethod.latin.Dictionary;
import com.android.inputmethod.latin.Dictionary.DataType;
import com.android.inputmethod.latin.Dictionary.WordCallback;
import com.android.inputmethod.latin.DictionaryCollection;
import com.android.inputmethod.latin.DictionaryFactory;
import com.android.inputmethod.latin.UserDictionary;
import com.android.inputmethod.latin.Utils;
import com.android.inputmethod.latin.WordComposer;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Locale;
import java.util.Map;
import java.util.TreeMap;

/**
 * Service for spell checking, using LatinIME's dictionaries and mechanisms.
 */
public class AndroidSpellCheckerService extends SpellCheckerService {
    private static final String TAG = AndroidSpellCheckerService.class.getSimpleName();
    private static final boolean DBG = false;
    private static final int POOL_SIZE = 2;

    private final static String[] EMPTY_STRING_ARRAY = new String[0];
    private final static SuggestionsInfo EMPTY_SUGGESTIONS_INFO =
            new SuggestionsInfo(0, EMPTY_STRING_ARRAY);
    private Map<String, DictionaryPool> mDictionaryPools =
            Collections.synchronizedMap(new TreeMap<String, DictionaryPool>());
    private Map<String, Dictionary> mUserDictionaries =
            Collections.synchronizedMap(new TreeMap<String, Dictionary>());

    @Override
    public Session createSession() {
        return new AndroidSpellCheckerSession();
    }

    private static class SuggestionsGatherer implements WordCallback {
        private final int DEFAULT_SUGGESTION_LENGTH = 16;
        private final ArrayList<CharSequence> mSuggestions;
        private final int[] mScores;
        private final int mMaxLength;
        private int mLength = 0;
        private boolean mSeenSuggestions = false;

        SuggestionsGatherer(final int maxLength) {
            mMaxLength = maxLength;
            mSuggestions = new ArrayList<CharSequence>(maxLength + 1);
            mScores = new int[mMaxLength];
        }

        @Override
        synchronized public boolean addWord(char[] word, int wordOffset, int wordLength, int score,
                int dicTypeId, DataType dataType) {
            final int positionIndex = ArraysCompatUtils.binarySearch(mScores, 0, mLength, score);
            // binarySearch returns the index if the element exists, and -<insertion index> - 1
            // if it doesn't. See documentation for binarySearch.
            final int insertIndex = positionIndex >= 0 ? positionIndex : -positionIndex - 1;

            mSeenSuggestions = true;
            if (mLength < mMaxLength) {
                final int copyLen = mLength - insertIndex;
                ++mLength;
                System.arraycopy(mScores, insertIndex, mScores, insertIndex + 1, copyLen);
                mSuggestions.add(insertIndex, new String(word, wordOffset, wordLength));
            } else {
                if (insertIndex == 0) return true;
                System.arraycopy(mScores, 1, mScores, 0, insertIndex);
                mSuggestions.add(insertIndex, new String(word, wordOffset, wordLength));
                mSuggestions.remove(0);
            }
            mScores[insertIndex] = score;

            return true;
        }

        public String[] getGatheredSuggestions() {
            if (!mSeenSuggestions) return null;
            if (0 == mLength) return EMPTY_STRING_ARRAY;

            if (DBG) {
                if (mLength != mSuggestions.size()) {
                    Log.e(TAG, "Suggestion size is not the same as stored mLength");
                }
            }
            Collections.reverse(mSuggestions);
            Utils.removeDupes(mSuggestions);
            // This returns a String[], while toArray() returns an Object[] which cannot be cast
            // into a String[].
            return mSuggestions.toArray(EMPTY_STRING_ARRAY);
        }
    }

    @Override
    public boolean onUnbind(final Intent intent) {
        final Map<String, DictionaryPool> oldPools = mDictionaryPools;
        mDictionaryPools = Collections.synchronizedMap(new TreeMap<String, DictionaryPool>());
        final Map<String, Dictionary> oldUserDictionaries = mUserDictionaries;
        mUserDictionaries = Collections.synchronizedMap(new TreeMap<String, Dictionary>());
        for (DictionaryPool pool : oldPools.values()) {
            pool.close();
        }
        for (Dictionary dict : oldUserDictionaries.values()) {
            dict.close();
        }
        return false;
    }

    private DictionaryPool getDictionaryPool(final String locale) {
        DictionaryPool pool = mDictionaryPools.get(locale);
        if (null == pool) {
            final Locale localeObject = Utils.constructLocaleFromString(locale);
            pool = new DictionaryPool(POOL_SIZE, this, localeObject);
            mDictionaryPools.put(locale, pool);
        }
        return pool;
    }

    public DictAndProximity createDictAndProximity(final Locale locale) {
        final ProximityInfo proximityInfo = ProximityInfo.createSpellCheckerProximityInfo();
        final Resources resources = getResources();
        final int fallbackResourceId = Utils.getMainDictionaryResourceId(resources);
        final DictionaryCollection dictionaryCollection =
                DictionaryFactory.createDictionaryFromManager(this, locale, fallbackResourceId);
        final String localeStr = locale.toString();
        Dictionary userDict = mUserDictionaries.get(localeStr);
        if (null == userDict) {
            userDict = new UserDictionary(this, localeStr);
            mUserDictionaries.put(localeStr, userDict);
        }
        dictionaryCollection.addDictionary(userDict);
        return new DictAndProximity(dictionaryCollection, proximityInfo);
    }

    private class AndroidSpellCheckerSession extends Session {
        // Immutable, but need the locale which is not available in the constructor yet
        DictionaryPool mDictionaryPool;
        // Likewise
        Locale mLocale;

        @Override
        public void onCreate() {
            final String localeString = getLocale();
            mDictionaryPool = getDictionaryPool(localeString);
            mLocale = Utils.constructLocaleFromString(localeString);
        }

        // Note : this must be reentrant
        /**
         * Gets a list of suggestions for a specific string. This returns a list of possible
         * corrections for the text passed as an argument. It may split or group words, and
         * even perform grammatical analysis.
         */
        @Override
        public SuggestionsInfo onGetSuggestions(final TextInfo textInfo,
                final int suggestionsLimit) {
            final String text = textInfo.getText();

            if (TextUtils.isEmpty(text)) return EMPTY_SUGGESTIONS_INFO;

            final SuggestionsGatherer suggestionsGatherer =
                    new SuggestionsGatherer(suggestionsLimit);
            final WordComposer composer = new WordComposer();
            final int length = text.length();
            for (int i = 0; i < length; ++i) {
                final int character = text.codePointAt(i);
                final int proximityIndex = SpellCheckerProximityInfo.getIndexOf(character);
                final int[] proximities;
                if (-1 == proximityIndex) {
                    proximities = new int[] { character };
                } else {
                    proximities = Arrays.copyOfRange(SpellCheckerProximityInfo.PROXIMITY,
                            proximityIndex, proximityIndex + SpellCheckerProximityInfo.ROW_SIZE);
                }
                composer.add(character, proximities,
                        WordComposer.NOT_A_COORDINATE, WordComposer.NOT_A_COORDINATE);
            }

            boolean isInDict = true;
            try {
                final DictAndProximity dictInfo = mDictionaryPool.take();
                dictInfo.mDictionary.getWords(composer, suggestionsGatherer,
                        dictInfo.mProximityInfo);
                isInDict = dictInfo.mDictionary.isValidWord(text);
                if (!isInDict && Character.isUpperCase(text.codePointAt(0))) {
                    // If the first char is not uppercase, then the word is either all lower case,
                    // in which case we already tested it, or mixed case, in which case we don't
                    // want to test a lower-case version of it. Hence the test above.
                    // Also note that by isEmpty() test at the top of the method codePointAt(0) is
                    // guaranteed to be there.
                    final int len = text.codePointCount(0, text.length());
                    int capsCount = 1;
                    for (int i = 1; i < len; ++i) {
                        if (1 != capsCount && i != capsCount) break;
                        if (Character.isUpperCase(text.codePointAt(i))) ++capsCount;
                    }
                    // We know the first char is upper case. So we want to test if either everything
                    // else is lower case, or if everything else is upper case. If the string is
                    // exactly one char long, then we will arrive here with capsCount 0, and this is
                    // correct, too.
                    if (1 == capsCount || len == capsCount) {
                        isInDict = dictInfo.mDictionary.isValidWord(text.toLowerCase(mLocale));
                    }
                }
                if (!mDictionaryPool.offer(dictInfo)) {
                    Log.e(TAG, "Can't re-insert a dictionary into its pool");
                }
            } catch (InterruptedException e) {
                // I don't think this can happen.
                return EMPTY_SUGGESTIONS_INFO;
            }

            final String[] suggestions = suggestionsGatherer.getGatheredSuggestions();

            final int flags =
                    (isInDict ? SuggestionsInfo.RESULT_ATTR_IN_THE_DICTIONARY : 0)
                            | (null != suggestions
                                    ? SuggestionsInfo.RESULT_ATTR_LOOKS_LIKE_TYPO : 0);
            return new SuggestionsInfo(flags, suggestions);
        }
    }
}