| /* |
| * Copyright (C) 2014 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.utils; |
| |
| import java.util.Arrays; |
| import java.util.regex.Pattern; |
| |
| import com.android.inputmethod.latin.Constants; |
| import com.android.inputmethod.latin.NgramContext; |
| import com.android.inputmethod.latin.NgramContext.WordInfo; |
| import com.android.inputmethod.latin.settings.SpacingAndPunctuations; |
| |
| public final class NgramContextUtils { |
| private NgramContextUtils() { |
| // Intentional empty constructor for utility class. |
| } |
| |
| private static final Pattern SPACE_REGEX = Pattern.compile("\\s+"); |
| // Get context information from nth word before the cursor. n = 1 retrieves the words |
| // immediately before the cursor, n = 2 retrieves the words before that, and so on. This splits |
| // on whitespace only. |
| // Also, it won't return words that end in a separator (if the nth word before the cursor |
| // ends in a separator, it returns information representing beginning-of-sentence). |
| // Example (when Constants.MAX_PREV_WORD_COUNT_FOR_N_GRAM is 2): |
| // (n = 1) "abc def|" -> abc, def |
| // (n = 1) "abc def |" -> abc, def |
| // (n = 1) "abc 'def|" -> empty, 'def |
| // (n = 1) "abc def. |" -> beginning-of-sentence |
| // (n = 1) "abc def . |" -> beginning-of-sentence |
| // (n = 2) "abc def|" -> beginning-of-sentence, abc |
| // (n = 2) "abc def |" -> beginning-of-sentence, abc |
| // (n = 2) "abc 'def|" -> empty. The context is different from "abc def", but we cannot |
| // represent this situation using NgramContext. See TODO in the method. |
| // TODO: The next example's result should be "abc, def". This have to be fixed before we |
| // retrieve the prior context of Beginning-of-Sentence. |
| // (n = 2) "abc def. |" -> beginning-of-sentence, abc |
| // (n = 2) "abc def . |" -> abc, def |
| // (n = 2) "abc|" -> beginning-of-sentence |
| // (n = 2) "abc |" -> beginning-of-sentence |
| // (n = 2) "abc. def|" -> beginning-of-sentence |
| public static NgramContext getNgramContextFromNthPreviousWord(final CharSequence prev, |
| final SpacingAndPunctuations spacingAndPunctuations, final int n) { |
| if (prev == null) return NgramContext.EMPTY_PREV_WORDS_INFO; |
| final String[] w = SPACE_REGEX.split(prev); |
| final WordInfo[] prevWordsInfo = new WordInfo[Constants.MAX_PREV_WORD_COUNT_FOR_N_GRAM]; |
| Arrays.fill(prevWordsInfo, WordInfo.EMPTY_WORD_INFO); |
| for (int i = 0; i < prevWordsInfo.length; i++) { |
| final int focusedWordIndex = w.length - n - i; |
| // Referring to the word after the focused word. |
| if ((focusedWordIndex + 1) >= 0 && (focusedWordIndex + 1) < w.length) { |
| final String wordFollowingTheNthPrevWord = w[focusedWordIndex + 1]; |
| if (!wordFollowingTheNthPrevWord.isEmpty()) { |
| final char firstChar = wordFollowingTheNthPrevWord.charAt(0); |
| if (spacingAndPunctuations.isWordConnector(firstChar)) { |
| // The word following the focused word is starting with a word connector. |
| // TODO: Return meaningful context for this case. |
| break; |
| } |
| } |
| } |
| // If we can't find (n + i) words, the context is beginning-of-sentence. |
| if (focusedWordIndex < 0) { |
| prevWordsInfo[i] = WordInfo.BEGINNING_OF_SENTENCE_WORD_INFO; |
| break; |
| } |
| final String focusedWord = w[focusedWordIndex]; |
| // If the word is, the context is beginning-of-sentence. |
| final int length = focusedWord.length(); |
| if (length <= 0) { |
| prevWordsInfo[i] = WordInfo.BEGINNING_OF_SENTENCE_WORD_INFO; |
| break; |
| } |
| // If ends in a sentence separator, the context is beginning-of-sentence. |
| final char lastChar = focusedWord.charAt(length - 1); |
| if (spacingAndPunctuations.isSentenceSeparator(lastChar)) { |
| prevWordsInfo[i] = WordInfo.BEGINNING_OF_SENTENCE_WORD_INFO; |
| break; |
| } |
| // If ends in a word separator or connector, the context is unclear. |
| // TODO: Return meaningful context for this case. |
| if (spacingAndPunctuations.isWordSeparator(lastChar) |
| || spacingAndPunctuations.isWordConnector(lastChar)) { |
| break; |
| } |
| prevWordsInfo[i] = new WordInfo(focusedWord); |
| } |
| return new NgramContext(prevWordsInfo); |
| } |
| } |