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 com.google.android.exoplayer2.util;
  
  import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
  
  import android.os.Handler;
  import android.os.Looper;
  import androidx.annotation.GuardedBy;
  import androidx.annotation.Nullable;
  import com.google.errorprone.annotations.CanIgnoreReturnValue;
  import java.util.ArrayList;
  import java.util.List;
  
  /** The standard implementation of {@link HandlerWrapper}. */
  /* package */ final class SystemHandlerWrapper implements HandlerWrapper {
  
    private static final int MAX_POOL_SIZE = 50;
  
    @GuardedBy("messagePool")
    private static final List<SystemMessage> messagePool = new ArrayList<>(MAX_POOL_SIZE);
  
    private final android.os.Handler handler;
  
    public SystemHandlerWrapper(android.os.Handler handler) {
      this.handler = handler;
    }
  
    @Override
    public Looper getLooper() {
      return handler.getLooper();
    }
  
    @Override
    public boolean hasMessages(int what) {
      return handler.hasMessages(what);
    }
  
    @Override
    public Message obtainMessage(int what) {
      return obtainSystemMessage().setMessage(handler.obtainMessage(what), /* handler= */ this);
    }
  
    @Override
    public Message obtainMessage(int what, @Nullable Object obj) {
      return obtainSystemMessage().setMessage(handler.obtainMessage(what, obj), /* handler= */ this);
    }
  
    @Override
    public Message obtainMessage(int what, int arg1, int arg2) {
      return obtainSystemMessage()
          .setMessage(handler.obtainMessage(what, arg1, arg2), /* handler= */ this);
    }
  
    @Override
    public Message obtainMessage(int what, int arg1, int arg2, @Nullable Object obj) {
      return obtainSystemMessage()
          .setMessage(handler.obtainMessage(what, arg1, arg2, obj), /* handler= */ this);
    }
  
    @Override
    public boolean sendMessageAtFrontOfQueue(Message message) {
      return ((SystemMessage) message).sendAtFrontOfQueue(handler);
    }
  
    @Override
    public boolean sendEmptyMessage(int what) {
      return handler.sendEmptyMessage(what);
    }
  
    @Override
    public boolean sendEmptyMessageDelayed(int what, int delayMs) {
      return handler.sendEmptyMessageDelayed(what, delayMs);
    }
  
    @Override
    public boolean sendEmptyMessageAtTime(int what, long uptimeMs) {
      return handler.sendEmptyMessageAtTime(what, uptimeMs);
    }
  
    @Override
    public void removeMessages(int what) {
      handler.removeMessages(what);
    }
  
    @Override
    public void removeCallbacksAndMessages(@Nullable Object token) {
      handler.removeCallbacksAndMessages(token);
    }
  
    @Override
    public boolean post(Runnable runnable) {
      return handler.post(runnable);
    }
  
    @Override
    public boolean postDelayed(Runnable runnable, long delayMs) {
      return handler.postDelayed(runnable, delayMs);
    }
  
    @Override
    public boolean postAtFrontOfQueue(Runnable runnable) {
      return handler.postAtFrontOfQueue(runnable);
    }
  
    private static SystemMessage obtainSystemMessage() {
      synchronized (messagePool) {
        return messagePool.isEmpty()
            ? new SystemMessage()
            : messagePool.remove(messagePool.size() - 1);
      }
    }
  
    private static void recycleMessage(SystemMessage message) {
      synchronized (messagePool) {
        if (messagePool.size() < MAX_POOL_SIZE) {
          messagePool.add(message);
        }
      }
    }
  
    private static final class SystemMessage implements Message {
  
      @Nullable private android.os.Message message;
      @Nullable private SystemHandlerWrapper handler;
  
      @CanIgnoreReturnValue
      public SystemMessage setMessage(android.os.Message message, SystemHandlerWrapper handler) {
        this.message = message;
        this.handler = handler;
        return this;
      }
  
      public boolean sendAtFrontOfQueue(Handler handler) {
        boolean success = handler.sendMessageAtFrontOfQueue(checkNotNull(message));
        recycle();
        return success;
      }
  
      @Override
      public void sendToTarget() {
        checkNotNull(message).sendToTarget();
        recycle();
      }
  
      @Override
      public HandlerWrapper getTarget() {
        return checkNotNull(handler);
      }
  
      private void recycle() {
        message = null;
        handler = null;
        recycleMessage(this);
      }
    }
  }
  