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.launcher3.dynamicui;
  
  import android.annotation.TargetApi;
  import android.app.WallpaperManager;
  import android.app.job.JobInfo;
  import android.app.job.JobScheduler;
  import android.content.ComponentName;
  import android.content.Context;
  import android.content.SharedPreferences;
  import android.graphics.Color;
  import android.os.Build;
  import android.support.v4.graphics.ColorUtils;
  import android.support.v7.graphics.Palette;
  
  import com.android.launcher3.Utilities;
  import com.android.launcher3.config.FeatureFlags;
  
  import java.util.List;
  
  /**
   * Contains helper fields and methods related to extracting colors from the wallpaper.
   */
  public class ExtractionUtils {
      public static final String EXTRACTED_COLORS_PREFERENCE_KEY = "pref_extractedColors";
      public static final String WALLPAPER_ID_PREFERENCE_KEY = "pref_wallpaperId";
  
      private static final float MIN_CONTRAST_RATIO = 2f;
  
      /**
       * Extract colors in the :wallpaper-chooser process, if the wallpaper id has changed.
       * When the new colors are saved in the LauncherProvider,
       * Launcher will be notified in Launcher#onSettingsChanged(String, String).
       */
      public static void startColorExtractionServiceIfNecessary(final Context context) {
          if (FeatureFlags.LAUNCHER3_GRADIENT_ALL_APPS) {
              return;
          }
          // Run on a background thread, since the service is asynchronous anyway.
          Utilities.THREAD_POOL_EXECUTOR.execute(new Runnable() {
              @Override
              public void run() {
                  if (hasWallpaperIdChanged(context)) {
                      startColorExtractionService(context);
                  }
              }
          });
      }
  
      /** Starts the {@link ColorExtractionService} without checking the wallpaper id */
      public static void startColorExtractionService(Context context) {
          if (FeatureFlags.LAUNCHER3_GRADIENT_ALL_APPS) {
              return;
          }
          JobScheduler jobScheduler = (JobScheduler) context.getSystemService(
                  Context.JOB_SCHEDULER_SERVICE);
          jobScheduler.schedule(new JobInfo.Builder(Utilities.COLOR_EXTRACTION_JOB_ID,
                  new ComponentName(context, ColorExtractionService.class))
                  .setMinimumLatency(0).build());
      }
  
      private static boolean hasWallpaperIdChanged(Context context) {
          if (!Utilities.ATLEAST_NOUGAT) {
              // TODO: update an id in sharedprefs in onWallpaperChanged broadcast, and read it here.
              return false;
          }
          final SharedPreferences sharedPrefs = Utilities.getPrefs(context);
          int wallpaperId = getWallpaperId(WallpaperManager.getInstance(context));
          int savedWallpaperId = sharedPrefs.getInt(ExtractionUtils.WALLPAPER_ID_PREFERENCE_KEY, -1);
          return wallpaperId != savedWallpaperId;
      }
  
      @TargetApi(Build.VERSION_CODES.N)
      public static int getWallpaperId(WallpaperManager wallpaperManager) {
          return Utilities.ATLEAST_NOUGAT ?
                  wallpaperManager.getWallpaperId(WallpaperManager.FLAG_SYSTEM) : -1;
      }
  
      public static boolean isSuperLight(Palette p) {
          return !isLegibleOnWallpaper(Color.WHITE, p.getSwatches());
      }
  
      public static boolean isSuperDark(Palette p) {
          return !isLegibleOnWallpaper(Color.BLACK, p.getSwatches());
      }
  
      /**
       * Given a color, returns true if that color is legible on
       * the given wallpaper color swatches, else returns false.
       */
      private static boolean isLegibleOnWallpaper(int color, List<Palette.Swatch> wallpaperSwatches) {
          int legiblePopulation = 0;
          int illegiblePopulation = 0;
          for (Palette.Swatch swatch : wallpaperSwatches) {
              if (isLegible(color, swatch.getRgb())) {
                  legiblePopulation += swatch.getPopulation();
              } else {
                  illegiblePopulation += swatch.getPopulation();
              }
          }
          return legiblePopulation > illegiblePopulation;
      }
  
      /** @return Whether the foreground color is legible on the background color. */
      private static boolean isLegible(int foreground, int background) {
          background = ColorUtils.setAlphaComponent(background, 255);
          return ColorUtils.calculateContrast(foreground, background) >= MIN_CONTRAST_RATIO;
      }
  
  }
  