content: /*
   * Copyright (C) 2017 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 androidx.leanback.leanbackshowcase.app.media;
  
  import android.graphics.Bitmap;
  import android.os.AsyncTask;
  import androidx.leanback.widget.PlaybackSeekDataProvider;
  import androidx.collection.LruCache;
  import android.util.Log;
  import android.util.SparseArray;
  
  import java.util.Iterator;
  import java.util.Map;
  
  /**
   *
   * Base class that implements PlaybackSeekDataProvider using AsyncTask.THREAD_POOL_EXECUTOR with
   * prefetching.
   */
  public abstract class PlaybackSeekAsyncDataProvider extends PlaybackSeekDataProvider {
  
      static final String TAG = "SeekAsyncProvider";
  
      long[] mSeekPositions;
      // mCache is for the bitmap requested by user
      final LruCache<Integer, Bitmap> mCache;
      // mPrefetchCache is for the bitmap not requested by user but prefetched by heuristic
      // estimation. We use a different LruCache so that items in mCache will not be evicted by
      // prefeteched items.
      final LruCache<Integer, Bitmap> mPrefetchCache;
      final SparseArray<LoadBitmapTask> mRequests = new SparseArray<>();
      int mLastRequestedIndex = -1;
  
      protected boolean isCancelled(Object task) {
          return ((AsyncTask) task).isCancelled();
      }
  
      protected abstract Bitmap doInBackground(Object task, int index, long position);
  
      class LoadBitmapTask extends AsyncTask<Object, Object, Bitmap> {
  
          int mIndex;
          ResultCallback mResultCallback;
  
          LoadBitmapTask(int index, ResultCallback callback) {
              mIndex = index;
              mResultCallback = callback;
          }
  
          @Override
          protected Bitmap doInBackground(Object[] params) {
              return PlaybackSeekAsyncDataProvider.this
                      .doInBackground(this, mIndex, mSeekPositions[mIndex]);
          }
  
          @Override
          protected void onPostExecute(Bitmap bitmap) {
              mRequests.remove(mIndex);
              Log.d(TAG, "thumb Loaded " + mIndex);
              if (mResultCallback != null) {
                  mCache.put(mIndex, bitmap);
                  mResultCallback.onThumbnailLoaded(bitmap, mIndex);
              } else {
                  mPrefetchCache.put(mIndex, bitmap);
              }
          }
  
      }
  
      public PlaybackSeekAsyncDataProvider() {
          this(16, 24);
      }
  
      public PlaybackSeekAsyncDataProvider(int cacheSize, int prefetchCacheSize) {
          mCache = new LruCache<Integer, Bitmap>(cacheSize);
          mPrefetchCache = new LruCache<Integer, Bitmap>(prefetchCacheSize);
      }
  
      public void setSeekPositions(long[] positions) {
          mSeekPositions = positions;
      }
  
      @Override
      public long[] getSeekPositions() {
          return mSeekPositions;
      }
  
      @Override
      public void getThumbnail(int index, ResultCallback callback) {
          Integer key = index;
          Bitmap bitmap = mCache.get(key);
          if (bitmap != null) {
              callback.onThumbnailLoaded(bitmap, index);
          } else {
              bitmap = mPrefetchCache.get(key);
              if (bitmap != null) {
                  mCache.put(key, bitmap);
                  mPrefetchCache.remove(key);
                  callback.onThumbnailLoaded(bitmap, index);
              } else {
                  LoadBitmapTask task = mRequests.get(index);
                  if (task == null || task.isCancelled()) {
                      // no normal task or prefetch for the position, create a new task
                      task = new LoadBitmapTask(index, callback);
                      mRequests.put(index, task);
                      task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
                  } else {
                      // update existing ResultCallback which might be normal task or prefetch
                      task.mResultCallback = callback;
                  }
              }
          }
          if (mLastRequestedIndex != index) {
              if (mLastRequestedIndex != -1) {
                  prefetch(mLastRequestedIndex, index > mLastRequestedIndex);
              }
              mLastRequestedIndex = index;
          }
      }
  
      protected void prefetch(int hintIndex, boolean forward) {
          for (Iterator<Map.Entry<Integer, Bitmap>> it =
                  mPrefetchCache.snapshot().entrySet().iterator(); it.hasNext(); ) {
              Map.Entry<Integer, Bitmap> entry = it.next();
              if (forward ? entry.getKey() < hintIndex : entry.getKey() > hintIndex) {
                  mPrefetchCache.remove(entry.getKey());
              }
          }
          int inc = forward ? 1 : -1;
          for (int i = hintIndex; (mRequests.size() + mPrefetchCache.size()
                  < mPrefetchCache.maxSize()) && (inc > 0 ? i < mSeekPositions.length : i >= 0);
                  i += inc) {
              Integer key = i;
              if (mCache.get(key) == null && mPrefetchCache.get(key) == null) {
                  LoadBitmapTask task = mRequests.get(i);
                  if (task == null) {
                      task = new LoadBitmapTask(key, null);
                      mRequests.put(i, task);
                      task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
                  }
              }
          }
      }
  
      @Override
      public void reset() {
          for (int i = 0; i < mRequests.size(); i++) {
              LoadBitmapTask task = mRequests.valueAt(i);
              task.cancel(true);
          }
          mRequests.clear();
          mCache.evictAll();
          mPrefetchCache.evictAll();
          mLastRequestedIndex = -1;
      }
  
      @Override
      public String toString() {
          StringBuilder b = new StringBuilder();
          b.append("Requests<");
          for (int i = 0; i < mRequests.size(); i++) {
              b.append(mRequests.keyAt(i));
              b.append(",");
          }
          b.append("> Cache<");
          for (Iterator<Integer> it = mCache.snapshot().keySet().iterator(); it.hasNext();) {
              Integer key = it.next();
              if (mCache.get(key) != null) {
                  b.append(key);
                  b.append(",");
              }
          }
          b.append(">");
          b.append("> PrefetchCache<");
          for (Iterator<Integer> it = mPrefetchCache.snapshot().keySet().iterator(); it.hasNext();) {
              Integer key = it.next();
              if (mPrefetchCache.get(key) != null) {
                  b.append(key);
                  b.append(",");
              }
          }
          b.append(">");
          return b.toString();
      }
  }
  