/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim:set ts=2 sw=2 sts=2 et cindent: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef AllocationPolicy_h_

#define AllocationPolicy_h_

#include "MediaInfo.h"

#include "PlatformDecoderModule.h"

#include "TimeUnits.h"

#include "mozilla/MozPromise.h"

#include "mozilla/StaticMutex.h"

#include "mozilla/ReentrantMonitor.h"

#include <queue>

namespace mozilla {

/**

 * This is a singleton which controls the number of decoders that can be

 * created concurrently. Before calling PDMFactory::CreateDecoder(), Alloc()

 * must be called to get a token object as a permission to create a decoder.

 * The token should stay alive until Shutdown() is called on the decoder.

 * The destructor of the token will restore the decoder count so it is available

 * for next calls of Alloc().

 */

class GlobalAllocPolicy

{

public:

  class Token

  {

    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(Token)

  protected:

    virtual ~Token() {}

  };

  using Promise = MozPromise<RefPtr<Token>, bool, true>;

  // Acquire a token for decoder creation. Thread-safe.

  RefPtr<Promise> Alloc();

  // Called by ClearOnShutdown() to delete the singleton.

  void operator=(decltype(nullptr));

  // Get the singleton for the given track type. Thread-safe.

  static GlobalAllocPolicy& Instance(TrackInfo::TrackType aTrack);

private:

  class AutoDeallocToken;

  using PromisePrivate = Promise::Private;

  GlobalAllocPolicy();

  ~GlobalAllocPolicy();

  // Called by the destructor of TokenImpl to restore the decoder limit.

  void Dealloc();

  // Decrement the decoder limit and resolve a promise if available.

  void ResolvePromise(ReentrantMonitorAutoEnter& aProofOfLock);

  // Protect access to Instance().

  static StaticMutex sMutex;

  ReentrantMonitor mMonitor;

  // The number of decoders available for creation.

  int mDecoderLimit;

  // Requests to acquire tokens.

  std::queue<RefPtr<PromisePrivate>> mPromises;

};

class AllocationWrapper : public MediaDataDecoder

{

  using Token = GlobalAllocPolicy::Token;

public:

  AllocationWrapper(already_AddRefed<MediaDataDecoder> aDecoder,

                    already_AddRefed<Token> aToken);

  ~AllocationWrapper();

  RefPtr<InitPromise> Init() override { return mDecoder->Init(); }

  RefPtr<DecodePromise> Decode(MediaRawData* aSample) override

  {

    return mDecoder->Decode(aSample);

  }

  RefPtr<DecodePromise> Drain() override { return mDecoder->Drain(); }

  RefPtr<FlushPromise> Flush() override { return mDecoder->Flush(); }

  bool IsHardwareAccelerated(nsACString& aFailureReason) const override

  {

    return mDecoder->IsHardwareAccelerated(aFailureReason);

  }

  nsCString GetDescriptionName() const override

  {

    return mDecoder->GetDescriptionName();

  }

  void SetSeekThreshold(const media::TimeUnit& aTime) override

  {

    mDecoder->SetSeekThreshold(aTime);

  }

  bool SupportDecoderRecycling() const override

  {

    return mDecoder->SupportDecoderRecycling();

  }

  RefPtr<ShutdownPromise> Shutdown() override;

  typedef MozPromise<RefPtr<MediaDataDecoder>,

                     MediaResult,

                     /* IsExclusive = */ true>

    AllocateDecoderPromise;

  // Will create a decoder has soon as one can be created according to the

  // GlobalAllocPolicy.

  // Warning: all aParams members must be valid until the promise has been

  // resolved, as some contains raw pointers to objects.

  static RefPtr<AllocateDecoderPromise> CreateDecoder(

    const CreateDecoderParams& aParams);

private:

  RefPtr<MediaDataDecoder> mDecoder;

  RefPtr<Token> mToken;

};

} // namespace mozilla

#endif