/*
* Copyright (C) 2016 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.internal.inputmethod;
import com.android.internal.annotations.VisibleForTesting;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.icu.util.ULocale;
import android.os.LocaleList;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
public final class LocaleUtils {
@VisibleForTesting
public interface LocaleExtractor<T> {
@Nullable
Locale get(@Nullable T source);
}
/**
* Calculates a matching score for the single desired locale.
*
* @see LocaleUtils#calculateMatchingScore(ULocale, LocaleList, byte[])
*
* @param supported The locale supported by IME subtype.
* @param desired The locale preferred by user.
* @return A score based on the locale matching for the default subtype enabling.
*/
@IntRange(from=1, to=3)
private static byte calculateMatchingSubScore(@NonNull final ULocale supported,
@NonNull final ULocale desired) {
// Assuming supported/desired is fully expanded.
if (supported.equals(desired)) {
return 3; // Exact match.
}
// Skip language matching since it was already done in calculateMatchingScore.
final String supportedScript = supported.getScript();
if (supportedScript.isEmpty() || !supportedScript.equals(desired.getScript())) {
// TODO: Need subscript matching. For example, Hanb should match with Bopo.
return 1;
}
final String supportedCountry = supported.getCountry();
if (supportedCountry.isEmpty() || !supportedCountry.equals(desired.getCountry())) {
return 2;
}
// Ignore others e.g. variants, extensions.
return 3;
}
/**
* Calculates a matching score for the desired locale list.
*
* <p>The supported locale gets a matching score of 3 if all language, script and country of the
* supported locale matches with the desired locale. The supported locale gets a matching
* score of 2 if the language and script of the supported locale matches with the desired
* locale. The supported locale gets a matching score of 1 if only language of the supported
* locale matches with the desired locale. The supported locale gets a matching score of 0 if
* the language of the supported locale doesn't match with the desired locale.</p>
*
* @param supported The locale supported by IME subtyle.
* @param desired The locale list preferred by user. Typically system locale list.
* @param out The output buffer to be stored the individual score for the desired language list.
* The length of {@code out} must be same as the length of {@code desired} language list.
* @return {@code false} if supported locale doesn't match with any desired locale list.
* Otherwise {@code true}.
*/
private static boolean calculateMatchingScore(@NonNull final ULocale supported,
@NonNull final LocaleList desired, @NonNull byte[] out) {
if (desired.isEmpty()) {
return false;
}
boolean allZeros = true;
final int N = desired.size();
for (int i = 0; i < N; ++i) {
final Locale locale = desired.get(i);
if (!locale.getLanguage().equals(supported.getLanguage())) {
// TODO: cache the result of addLikelySubtags if it is slow.
out[i] = 0;
} else {
out[i] = calculateMatchingSubScore(
supported, ULocale.addLikelySubtags(ULocale.forLocale(locale)));
if (allZeros && out[i] != 0) {
allZeros = false;
}
}
}
return !allZeros;
}
private static final class ScoreEntry implements Comparable<ScoreEntry> {
public int mIndex = -1;
@NonNull public final byte[] mScore; // matching score of the i-th system languages.
ScoreEntry(@NonNull byte[] score, int index) {
mScore = new byte[score.length];
set(score, index);
}
private void set(@NonNull byte[] score, int index) {
for (int i = 0; i < mScore.length; ++i) {
mScore[i] = score[i];
}
mIndex = index;
}
/**
* Update score and index if the given score is better than this.
*/
public void updateIfBetter(@NonNull byte[] score, int index) {
if (compare(mScore, score) == -1) { // mScore < score
set(score, index);
}
}
/**
* Provides comaprison for bytes[].
*
* <p> Comparison does as follows. If the first value of {@code left} is larger than the
* first value of {@code right}, {@code left} is large than {@code right}. If the first
* value of {@code left} is less than the first value of {@code right}, {@code left} is less
* than {@code right}. If the first value of {@code left} and the first value of
* {@code right} is equal, do the same comparison to the next value. Finally if all values
* in {@code left} and {@code right} are equal, {@code left} and {@code right} is equal.</p>
*
* @param left The length must be equal to {@code right}.
* @param right The length must be equal to {@code left}.
* @return 1 if {@code left} is larger than {@code right}. -1 if {@code left} is less than
* {@code right}. 0 if {@code left} and {@code right} is equal.
*/
@IntRange(from=-1, to=1)
private static int compare(@NonNull byte[] left, @NonNull byte[] right) {
for (int i = 0; i < left.length; ++i) {
if (left[i] > right[i]) {
return 1;
} else if (left[i] < right[i]) {
return -1;
}
}
return 0;
}
@Override
public int compareTo(final ScoreEntry other) {
return -1 * compare(mScore, other.mScore); // Order by descending order.
}
}
/**
* Filters the given items based on language preferences.
*
* <p>For each language found in {@code preferredLanguages}, this method tries to copy at most
* one best-match item from {@code source} to {@code dest}. For example, if
* {@code "en-GB", "ja", "en-AU", "fr-CA", "en-IN"} is specified to {@code preferredLanguages},
* this method tries to copy at most one English locale, at most one Japanese, and at most one
* French locale from {@code source} to {@code dest}. Here the best matching English locale
* will be searched from {@code source} based on matching score. For the score design, see
* {@link LocaleUtils#calculateMatchingScore(ULocale, LocaleList, byte[])}</p>
*
* @param sources Source items to be filtered.
* @param extractor Type converter from the source items to {@link Locale} object.
* @param preferredLanguages Ordered list of locales with which the input items will be
* filtered.
* @param dest Destination into which the filtered items will be added.
* @param <T> Type of the data items.
*/
@VisibleForTesting
public static <T> void filterByLanguage(
@NonNull List<T> sources,
@NonNull LocaleExtractor<T> extractor,
@NonNull LocaleList preferredLanguages,
@NonNull ArrayList<T> dest) {
final HashMap<String, ScoreEntry> scoreboard = new HashMap<>();
final byte[] score = new byte[preferredLanguages.size()];
final int sourceSize = sources.size();
for (int i = 0; i < sourceSize; ++i) {
final Locale locale = extractor.get(sources.get(i));
if (locale == null ||
!calculateMatchingScore(ULocale.addLikelySubtags(ULocale.forLocale(locale)),
preferredLanguages, score)) {
continue;
}
final String lang = locale.getLanguage();
final ScoreEntry bestScore = scoreboard.get(lang);
if (bestScore == null) {
scoreboard.put(lang, new ScoreEntry(score, i));
} else {
bestScore.updateIfBetter(score, i);
}
}
final ScoreEntry[] result = scoreboard.values().toArray(new ScoreEntry[scoreboard.size()]);
Arrays.sort(result);
for (final ScoreEntry entry : result) {
dest.add(sources.get(entry.mIndex));
}
}
}