com.zz.langchecker.LangChecker.java Source code

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Here is the source code for com.zz.langchecker.LangChecker.java

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/*
 *
 *     Copyright 2013-2014 https://github.com/blizznets authors
 *
 *    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.zz.langchecker;

import com.google.common.base.Charsets;
import com.google.common.base.Optional;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.io.Resources;
import java.io.IOException;
import java.util.Map;
import java.util.Set;

final class LangChecker {
    final Map<Lang, Set<String>> nonexistent2gram;
    final Map<Lang, Set<String>> nonexistent3gram;
    final Map<Lang, Set<String>> nonexistentFirst4gram;
    final Map<Lang, Set<String>> nonexistent4gram;

    public LangChecker(Map<Lang, Set<String>> nonexistent2gram, Map<Lang, Set<String>> nonexistent3gram,
            Map<Lang, Set<String>> nonexistentFirst4gram, Map<Lang, Set<String>> nonexistent4gram) {
        this.nonexistent2gram = nonexistent2gram;
        this.nonexistent3gram = nonexistent3gram;
        this.nonexistentFirst4gram = nonexistentFirst4gram;
        this.nonexistent4gram = nonexistent4gram;
    }

    public static LangChecker create() {
        return new LangChecker(
                ImmutableMap.of(Lang.EN, readVocabulary("nonexistent2gram-en.txt"), Lang.RU,
                        readVocabulary("nonexistent2gram-ru.txt")),
                ImmutableMap.of(Lang.EN, readVocabulary("nonexistent3gram-en.txt"), Lang.RU,
                        readVocabulary("nonexistent3gram-ru.txt")),
                ImmutableMap.of(Lang.EN, readVocabulary("nonexistentFirst4gram-en.txt"), Lang.RU,
                        readVocabulary("nonexistentFirst4gram-ru.txt")),
                ImmutableMap.of(Lang.EN, readVocabulary("nonexistent4gram-en.txt"), Lang.RU,
                        readVocabulary("nonexistent4gram-ru.txt")));
    }

    public boolean check(Lang lang, String word) {
        int length = word.length();

        if (!Characters.hasVowel(lang, word)) {
            return false;
        }

        if (length >= 6) {
            Optional<String> firstConsonant6gram = firstNgram(lang, word, 6, false);
            if (firstConsonant6gram.isPresent()) {
                return false;
            }
        }

        if (length >= 4) {
            if (nonexistentFirst4gram.get(lang).contains(word.substring(0, 4))) {
                return false;
            }
        }

        if (length >= 3) {
            Optional<String> firstVowel3gram = firstNgram(lang, word, 3, true);
            if (firstVowel3gram.isPresent() && nonexistent3gram.get(lang).contains(firstVowel3gram.get())) {
                return false;
            }
        }

        if (length >= 4) {
            Optional<String> firstConsonant4gram = firstNgram(lang, word, 4, false);
            if (firstConsonant4gram.isPresent() && nonexistent4gram.get(lang).contains(firstConsonant4gram.get())) {
                return false;
            }
        }

        Set<String> nonexistent2grams = nonexistent2gram.get(lang);
        if (length >= 2) {
            if (nonexistent2grams.contains("*" + word.substring(0, 2))
                    || nonexistent2grams.contains(word.substring(length - 2) + "*")) {
                return false;
            }
        }

        if (length >= 4) {
            for (int i = 1; i < length - 2; i++) {
                if (nonexistent2grams.contains(word.substring(i, i + 2))) {
                    return false;
                }
            }
        }

        return true;
    }

    static Optional<String> firstNgram(Lang lang, String word, int n, boolean vowel) {
        char[] chars = word.toCharArray();
        for (int begin = 0, end = n; end <= word.length(); begin++, end++) {
            boolean check = true;
            for (int i = begin; i < end; i++) {
                if (vowel && !Characters.isVowel(lang, chars[i])
                        || !vowel && !Characters.isConsonant(lang, chars[i])) {
                    check = false;
                    break;
                }
            }
            if (check) {
                return Optional.of(word.substring(begin, end));
            }
        }

        return Optional.absent();
    }

    private static Set<String> readVocabulary(String name) {
        try {
            return ImmutableSet.copyOf(
                    Resources.asCharSource(LangChecker.class.getResource(name), Charsets.UTF_8).readLines());
        } catch (IOException e) {
            throw Throwables.propagate(e);
        }
    }
}