content: /*
   * 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.server.inputmethod;
  
  import android.annotation.IntRange;
  import android.annotation.NonNull;
  import android.annotation.Nullable;
  import android.icu.util.ULocale;
  import android.os.LocaleList;
  import android.text.TextUtils;
  import android.util.ArrayMap;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Locale;
  
  final class LocaleUtils {
      public interface LocaleExtractor<T> {
          @Nullable
          Locale get(@Nullable T source);
      }
  
      /**
       * Calculates a matching score for the single desired locale.
       *
       * @see LocaleUtils#filterByLanguage(List, LocaleExtractor, LocaleList, ArrayList)
       *
       * @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;
      }
  
      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 preferredLocales}, 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 preferredLocales},
       * 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#calculateMatchingSubScore(ULocale, ULocale)}</p>
       *
       * @param sources Source items to be filtered.
       * @param extractor Type converter from the source items to {@link Locale} object.
       * @param preferredLocales 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.
       */
      public static <T> void filterByLanguage(
              @NonNull List<T> sources,
              @NonNull LocaleExtractor<T> extractor,
              @NonNull LocaleList preferredLocales,
              @NonNull ArrayList<T> dest) {
          if (preferredLocales.isEmpty()) {
              return;
          }
  
          final int numPreferredLocales = preferredLocales.size();
          final ArrayMap<String, ScoreEntry> scoreboard = new ArrayMap<>();
          final byte[] score = new byte[numPreferredLocales];
          final ULocale[] preferredULocaleCache = new ULocale[numPreferredLocales];
  
          final int sourceSize = sources.size();
          for (int i = 0; i < sourceSize; ++i) {
              final Locale locale = extractor.get(sources.get(i));
              if (locale == null) {
                  continue;
              }
  
              boolean canSkip = true;
              for (int j = 0; j < numPreferredLocales; ++j) {
                  final Locale preferredLocale = preferredLocales.get(j);
                  if (!TextUtils.equals(locale.getLanguage(), preferredLocale.getLanguage())) {
                      score[j] = 0;
                      continue;
                  }
                  if (preferredULocaleCache[j] == null) {
                      preferredULocaleCache[j] = ULocale.addLikelySubtags(
                              ULocale.forLocale(preferredLocale));
                  }
                  score[j] = calculateMatchingSubScore(
                          preferredULocaleCache[j],
                          ULocale.addLikelySubtags(ULocale.forLocale(locale)));
                  if (canSkip && score[j] != 0) {
                      canSkip = false;
                  }
              }
              if (canSkip) {
                  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 int numEntries = scoreboard.size();
          final ScoreEntry[] result = new ScoreEntry[numEntries];
          for (int i = 0; i < numEntries; ++i) {
              result[i] = scoreboard.valueAt(i);
          }
          Arrays.sort(result);
          for (final ScoreEntry entry : result) {
              dest.add(sources.get(entry.mIndex));
          }
      }
  }
  