// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_GPU_CHROMEOS_OOP_VIDEO_DECODER_H_
#define MEDIA_GPU_CHROMEOS_OOP_VIDEO_DECODER_H_

#include "base/containers/lru_cache.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
#include "media/base/media_log.h"
#include "media/gpu/chromeos/video_decoder_pipeline.h"
#include "media/gpu/media_gpu_export.h"
#include "media/mojo/mojom/media_log.mojom.h"
#include "media/mojo/mojom/video_decoder.mojom.h"
#include "mojo/public/cpp/bindings/associated_receiver.h"
#include "mojo/public/cpp/bindings/receiver.h"
#include "mojo/public/cpp/bindings/remote.h"

#if BUILDFLAG(IS_CHROMEOS)
namespace chromeos {
class CdmContextForOOPVDImpl;
}  // namespace chromeos
#endif  // BUILDFLAG(IS_CHROMEOS)

namespace media {

class MediaLog;
class MojoDecoderBufferWriter;

// Proxy video decoder that connects with an out-of-process
// video decoder via Mojo. This class should be operated and
// destroyed on |decoder_task_runner_|.
//
// TODO(b/195769334): this class (or most of it) would be unnecessary if the
// MailboxVideoFrameConverter lived together with the remote decoder in the same
// process. Then, clients can communicate with that process without the GPU
// process acting as a proxy.
class OOPVideoDecoder : public VideoDecoderMixin,
                        public mojom::VideoDecoderClient,
                        public mojom::MediaLog {
 public:
  OOPVideoDecoder(const OOPVideoDecoder&) = delete;
  OOPVideoDecoder& operator=(const OOPVideoDecoder&) = delete;

  static std::unique_ptr<VideoDecoderMixin> Create(
      mojo::PendingRemote<mojom::VideoDecoder> pending_remote_decoder,
      std::unique_ptr<media::MediaLog> media_log,
      scoped_refptr<base::SequencedTaskRunner> decoder_task_runner,
      base::WeakPtr<VideoDecoderMixin::Client> client);

  // The first time this is called, |oop_video_decoder| will be used to query
  // the supported configurations of the out-of-process video decoder. When
  // those are obtained, they will be cached and |cb| will be called with a
  // PendingRemote that corresponds to the same pipe as |oop_video_decoder|.
  //
  // If a query is in progress, this method will store |cb|. |cb| will then be
  // called with |oop_video_decoder| once the query is done.
  //
  // If the supported configurations are already known, this method will
  // immediately call |cb|.
  //
  // Threading considerations: this method is thread- and sequence-safe. |cb|
  // will be called on the same sequence as the one NotifySupportKnown() is
  // called on.
  static void NotifySupportKnown(
      mojo::PendingRemote<mojom::VideoDecoder> oop_video_decoder,
      base::OnceCallback<void(mojo::PendingRemote<mojom::VideoDecoder>)> cb);

  // Returns the cached supported configurations of the out-of-process video
  // decoder if known (std::nullopt otherwise). This method is thread- and
  // sequence-safe.
  static std::optional<SupportedVideoDecoderConfigs> GetSupportedConfigs();

  // Resets the internal singleton state so that we can always run individual
  // tests as if they ran in dedicated processes.
  static void ResetGlobalStateForTesting();

  // VideoDecoderMixin implementation, VideoDecoder part.
  void Initialize(const VideoDecoderConfig& config,
                  bool low_delay,
                  CdmContext* cdm_context,
                  InitCB init_cb,
                  const PipelineOutputCB& output_cb,
                  const WaitingCB& waiting_cb) override;
  void Decode(scoped_refptr<DecoderBuffer> buffer, DecodeCB decode_cb) override;
  void Reset(base::OnceClosure reset_cb) override;
  bool NeedsBitstreamConversion() const override;
  bool CanReadWithoutStalling() const override;
  int GetMaxDecodeRequests() const override;
  VideoDecoderType GetDecoderType() const override;
  bool IsPlatformDecoder() const override;
  // VideoDecoderMixin implementation, specific part.
  void ApplyResolutionChange() override;
  bool NeedsTranscryption() override;

  // mojom::VideoDecoderClient implementation.
  void OnVideoFrameDecoded(
      const scoped_refptr<VideoFrame>& frame,
      bool can_read_without_stalling,
      const std::optional<base::UnguessableToken>& release_token) final;
  void OnWaiting(WaitingReason reason) final;
  void RequestOverlayInfo() final;

  // mojom::MediaLog implementation.
  void AddLogRecord(const MediaLogRecord& event) final;

  FrameResource* GetOriginalFrame(const base::UnguessableToken& tracking_token);

 private:
  OOPVideoDecoder(
      std::unique_ptr<media::MediaLog> media_log,
      scoped_refptr<base::SequencedTaskRunner> decoder_task_runner,
      base::WeakPtr<VideoDecoderMixin::Client> client,
      mojo::PendingRemote<mojom::VideoDecoder> pending_remote_decoder);
  ~OOPVideoDecoder() override;

  void OnInitializeDone(const DecoderStatus& status,
                        bool needs_bitstream_conversion,
                        int32_t max_decode_requests,
                        VideoDecoderType decoder_type,
                        bool needs_transcryption);

  void OnDecodeDone(uint64_t decode_id,
                    bool is_flush_cb,
                    const DecoderStatus& status);
  void DeferDecodeCallback(DecodeCB decode_cb, const DecoderStatus& status);
  void CallDeferredDecodeCallback(DecodeCB decode_cb,
                                  const DecoderStatus& status);
  bool HasPendingDecodeCallbacks() const;

  void OnResetDone();
  void CallResetCallback();

  void Stop();

  void ReleaseVideoFrame(const base::UnguessableToken& release_token);

  InitCB init_cb_ GUARDED_BY_CONTEXT(sequence_checker_);
  PipelineOutputCB output_cb_ GUARDED_BY_CONTEXT(sequence_checker_);
  WaitingCB waiting_cb_ GUARDED_BY_CONTEXT(sequence_checker_);
  uint64_t decode_counter_ GUARDED_BY_CONTEXT(sequence_checker_) = 0;

  // |pending_decodes_| tracks the decode requests that have been sent to the
  // remote decoder. We use std::map to ensure that iterating through
  // |pending_decodes_| is done in the order in which Decode() is called.
  std::map<uint64_t, DecodeCB> pending_decodes_
      GUARDED_BY_CONTEXT(sequence_checker_);

  // |num_deferred_decode_cbs_| tracks how many decode callbacks are in the
  // queue as tasks waiting to be executed. This does not include decode
  // callbacks awaiting a reply from the remote decoder.
  uint64_t num_deferred_decode_cbs_ GUARDED_BY_CONTEXT(sequence_checker_) = 0;

  bool is_flushing_ GUARDED_BY_CONTEXT(sequence_checker_) = false;

  // |fake_timestamp_to_real_timestamp_cache_| allows us to associate Decode()
  // calls with decoded frames. On each non-flush Decode() call, we generate a
  // fake timestamp (tracked in |current_fake_timestamp_|) and we map that to
  // the DecoderBuffer's timestamp. When a decoded frame is received, we look up
  // its timestamp in |fake_timestamp_to_real_timestamp_cache_| and update it to
  // the real timestamp. This logic allows us to do a couple of things:
  //
  // 1) Not trust the timestamps that come from the remote decoder (the trust
  //    model is that the remote decoder is untrusted).
  //
  // 2) Guarantee the following requirement mandated by the
  //    VideoDecoder::Decode() API: "If |buffer| is an EOS buffer then the
  //    decoder must be flushed, i.e. |output_cb| must be called for each frame
  //    pending in the queue and |decode_cb| must be called after that." We can
  //    do this by clearing the cache when a flush has been reported to be
  //    completed by the remote decoder.
  //
  // 3) Guarantee the following requirement mandated by the
  //    VideoDecoder::Reset() API: "All pending Decode() requests will be
  //    finished or aborted before |closure| is called."
  base::TimeDelta current_fake_timestamp_
      GUARDED_BY_CONTEXT(sequence_checker_) = base::Microseconds(0u);
  base::LRUCache<base::TimeDelta, base::TimeDelta>
      fake_timestamp_to_real_timestamp_cache_
          GUARDED_BY_CONTEXT(sequence_checker_);

  base::OnceClosure reset_cb_ GUARDED_BY_CONTEXT(sequence_checker_);

  mojo::AssociatedReceiver<mojom::VideoDecoderClient> client_receiver_
      GUARDED_BY_CONTEXT(sequence_checker_){this};

  mojo::Receiver<mojom::MediaLog> media_log_receiver_
      GUARDED_BY_CONTEXT(sequence_checker_){this};

#if BUILDFLAG(IS_CHROMEOS)
  std::unique_ptr<chromeos::CdmContextForOOPVDImpl> cdm_context_for_oopvd_
      GUARDED_BY_CONTEXT(sequence_checker_);
  std::unique_ptr<mojo::Receiver<mojom::CdmContextForOOPVD>>
      cdm_context_for_oopvd_receiver_ GUARDED_BY_CONTEXT(sequence_checker_);
#endif  // BUILDFLAG(IS_CHROMEOS)
  bool initialized_for_protected_content_
      GUARDED_BY_CONTEXT(sequence_checker_) = false;

  bool needs_bitstream_conversion_ GUARDED_BY_CONTEXT(sequence_checker_) =
      false;

  int32_t max_decode_requests_ GUARDED_BY_CONTEXT(sequence_checker_) = 8u;

  VideoDecoderType remote_decoder_type_ GUARDED_BY_CONTEXT(sequence_checker_) =
      VideoDecoderType::kUnknown;

  mojo::Remote<mojom::VideoDecoder> remote_decoder_
      GUARDED_BY_CONTEXT(sequence_checker_);
  bool has_error_ GUARDED_BY_CONTEXT(sequence_checker_) = false;

  mojo::Remote<mojom::VideoFrameHandleReleaser>
      video_frame_handle_releaser_remote_ GUARDED_BY_CONTEXT(sequence_checker_);

  std::unique_ptr<MojoDecoderBufferWriter> mojo_decoder_buffer_writer_
      GUARDED_BY_CONTEXT(sequence_checker_);

  bool can_read_without_stalling_ GUARDED_BY_CONTEXT(sequence_checker_) = false;

  // This is to indicate we should perform transcryption before sending the data
  // to the video decoder utility process.
  bool needs_transcryption_ GUARDED_BY_CONTEXT(sequence_checker_) = false;

  // |received_token_to_decoded_frame_map_| and
  // |generated_token_to_decoded_frame_map_| are maps that allow us to recycle
  // buffers safely. In the absence of them, the MailboxVideoFrameConverter
  // would create a SharedImage for every single incoming frame, and it would
  // destroy the SharedImage every time the client returns the decoded frame. To
  // avoid this churn, every time we get a decoded frame from the remote
  // decoder, we check if we already know about the underlying buffer by looking
  // it up in |received_token_to_decoded_frame_map_|. If we do, we re-use it for
  // the next stage in the pipeline. If we don't know about it, we insert it in
  // |received_token_to_decoded_frame_map_|.
  base::flat_map<base::UnguessableToken, scoped_refptr<FrameResource>>
      received_token_to_decoded_frame_map_
          GUARDED_BY_CONTEXT(sequence_checker_);
  base::flat_map<base::UnguessableToken,
                 raw_ptr<FrameResource, CtnExperimental>>
      generated_token_to_decoded_frame_map_
          GUARDED_BY_CONTEXT(sequence_checker_);

  SEQUENCE_CHECKER(sequence_checker_);

  base::WeakPtrFactory<OOPVideoDecoder> weak_this_factory_
      GUARDED_BY_CONTEXT(sequence_checker_);
};

}  // namespace media

#endif  // MEDIA_GPU_CHROMEOS_OOP_VIDEO_DECODER_H_