/*
 *  Copyright 2020 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef VIDEO_ADAPTATION_VIDEO_STREAM_ENCODER_RESOURCE_MANAGER_H_
#define VIDEO_ADAPTATION_VIDEO_STREAM_ENCODER_RESOURCE_MANAGER_H_

#include <atomic>
#include <map>
#include <memory>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>

#include "absl/types/optional.h"
#include "api/rtp_parameters.h"
#include "api/scoped_refptr.h"
#include "api/video/video_adaptation_counters.h"
#include "api/video/video_adaptation_reason.h"
#include "api/video/video_frame.h"
#include "api/video/video_source_interface.h"
#include "api/video/video_stream_encoder_observer.h"
#include "api/video_codecs/video_codec.h"
#include "api/video_codecs/video_encoder.h"
#include "api/video_codecs/video_encoder_config.h"
#include "call/adaptation/resource.h"
#include "call/adaptation/resource_adaptation_processor_interface.h"
#include "call/adaptation/video_stream_adapter.h"
#include "call/adaptation/video_stream_input_state_provider.h"
#include "rtc_base/critical_section.h"
#include "rtc_base/experiments/quality_rampup_experiment.h"
#include "rtc_base/experiments/quality_scaler_settings.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/task_queue.h"
#include "system_wrappers/include/clock.h"
#include "video/adaptation/encode_usage_resource.h"
#include "video/adaptation/overuse_frame_detector.h"
#include "video/adaptation/quality_scaler_resource.h"

namespace webrtc {

// The assumed input frame size if we have not yet received a frame.
// TODO(hbos): This is 144p - why are we assuming super low quality? Seems like
// a bad heuristic.
extern const int kDefaultInputPixelsWidth;
extern const int kDefaultInputPixelsHeight;

// Owns adaptation-related Resources pertaining to a single VideoStreamEncoder
// and passes on the relevant input from the encoder to the resources. The
// resources provide resource usage states to the ResourceAdaptationProcessor
// which is responsible for reconfiguring streams in order not to overuse
// resources.
//
// The manager is also involved with various mitigations not part of the
// ResourceAdaptationProcessor code such as the inital frame dropping.
class VideoStreamEncoderResourceManager
    : public ResourceAdaptationProcessorListener {
 public:
  VideoStreamEncoderResourceManager(
      VideoStreamInputStateProvider* input_state_provider,
      VideoStreamEncoderObserver* encoder_stats_observer,
      Clock* clock,
      bool experiment_cpu_load_estimator,
      std::unique_ptr<OveruseFrameDetector> overuse_detector);
  ~VideoStreamEncoderResourceManager() override;

  void Initialize(rtc::TaskQueue* encoder_queue,
                  rtc::TaskQueue* resource_adaptation_queue);
  void SetAdaptationProcessor(
      ResourceAdaptationProcessorInterface* adaptation_processor);

  // TODO(https://crbug.com/webrtc/11563): The degradation preference is a
  // setting of the Processor, it does not belong to the Manager - can we get
  // rid of this?
  void SetDegradationPreferences(DegradationPreference degradation_preference);
  DegradationPreference degradation_preference() const;

  // Starts the encode usage resource. The quality scaler resource is
  // automatically started on being configured.
  void StartEncodeUsageResource();
  // Stops the encode usage and quality scaler resources if not already stopped.
  void StopManagedResources();

  // Settings that affect the VideoStreamEncoder-specific resources.
  void SetEncoderSettings(EncoderSettings encoder_settings);
  void SetStartBitrate(DataRate start_bitrate);
  void SetTargetBitrate(DataRate target_bitrate);
  void SetEncoderRates(
      const VideoEncoder::RateControlParameters& encoder_rates);
  // TODO(https://crbug.com/webrtc/11338): This can be made private if we
  // configure on SetDegredationPreference and SetEncoderSettings.
  void ConfigureQualityScaler(const VideoEncoder::EncoderInfo& encoder_info);

  // Methods corresponding to different points in the encoding pipeline.
  void OnFrameDroppedDueToSize();
  void OnMaybeEncodeFrame();
  void OnEncodeStarted(const VideoFrame& cropped_frame,
                       int64_t time_when_first_seen_us);
  void OnEncodeCompleted(const EncodedImage& encoded_image,
                         int64_t time_sent_in_us,
                         absl::optional<int> encode_duration_us);
  void OnFrameDropped(EncodedImageCallback::DropReason reason);

  // Resources need to be mapped to an AdaptReason (kCpu or kQuality) in order
  // to be able to update |active_counts_|, which is used...
  // - Legacy getStats() purposes.
  // - Preventing adapting up in some circumstances (which may be questionable).
  // TODO(hbos): Can we get rid of this?
  void MapResourceToReason(rtc::scoped_refptr<Resource> resource,
                           VideoAdaptationReason reason);
  std::vector<rtc::scoped_refptr<Resource>> MappedResources() const;
  rtc::scoped_refptr<QualityScalerResource>
  quality_scaler_resource_for_testing();
  // If true, the VideoStreamEncoder should eexecute its logic to maybe drop
  // frames baseed on size and bitrate.
  bool DropInitialFrames() const;

  // ResourceAdaptationProcessorListener implementation.
  // Updates |video_source_restrictions_| and |active_counts_|.
  void OnVideoSourceRestrictionsUpdated(
      VideoSourceRestrictions restrictions,
      const VideoAdaptationCounters& adaptation_counters,
      rtc::scoped_refptr<Resource> reason) override;

  // For reasons of adaptation and statistics, we not only count the total
  // number of adaptations, but we also count the number of adaptations per
  // reason.
  // This method takes the new total number of adaptations and allocates that to
  // the "active" count - number of adaptations for the current reason.
  // The "other" count is the number of adaptations for the other reason.
  // This must be called for each adaptation step made.
  static void OnAdaptationCountChanged(
      const VideoAdaptationCounters& adaptation_count,
      VideoAdaptationCounters* active_count,
      VideoAdaptationCounters* other_active);

 private:
  class InitialFrameDropper;

  VideoAdaptationReason GetReasonFromResource(
      rtc::scoped_refptr<Resource> resource) const;

  CpuOveruseOptions GetCpuOveruseOptions() const;
  int LastInputFrameSizeOrDefault() const;

  // Calculates an up-to-date value of the target frame rate and informs the
  // |encode_usage_resource_| of the new value.
  void MaybeUpdateTargetFrameRate();

  // Use nullopt to disable quality scaling.
  void UpdateQualityScalerSettings(
      absl::optional<VideoEncoder::QpThresholds> qp_thresholds);

  void UpdateAdaptationStats(const VideoAdaptationCounters& total_counts,
                             VideoAdaptationReason reason);
  void UpdateStatsAdaptationSettings() const;

  // Checks to see if we should execute the quality rampup experiment. The
  // experiment resets all video restrictions at the start of the call in the
  // case the bandwidth estimate is high enough.
  // TODO(https://crbug.com/webrtc/11222) Move experiment details into an inner
  // class.
  void MaybePerformQualityRampupExperiment();

  void ResetActiveCounts();
  std::string ActiveCountsToString() const;

  // TODO(hbos): Consider moving all of the manager's resources into separate
  // files for testability.

  // Does not trigger adaptations, only prevents adapting up based on
  // |active_counts_|.
  class PreventAdaptUpDueToActiveCounts final
      : public rtc::RefCountedObject<Resource> {
   public:
    explicit PreventAdaptUpDueToActiveCounts(
        VideoStreamEncoderResourceManager* manager);
    ~PreventAdaptUpDueToActiveCounts() override = default;

    void SetAdaptationProcessor(
        ResourceAdaptationProcessorInterface* adaptation_processor);

    // Resource overrides.
    std::string name() const override {
      return "PreventAdaptUpDueToActiveCounts";
    }
    bool IsAdaptationUpAllowed(
        const VideoStreamInputState& input_state,
        const VideoSourceRestrictions& restrictions_before,
        const VideoSourceRestrictions& restrictions_after,
        rtc::scoped_refptr<Resource> reason_resource) const override;

   private:
    // The |manager_| must be alive as long as this resource is added to the
    // ResourceAdaptationProcessor, i.e. when IsAdaptationUpAllowed() is called.
    VideoStreamEncoderResourceManager* const manager_;
    ResourceAdaptationProcessorInterface* adaptation_processor_
        RTC_GUARDED_BY(resource_adaptation_queue());
  };

  // Does not trigger adaptations, only prevents adapting up resolution.
  class PreventIncreaseResolutionDueToBitrateResource final
      : public rtc::RefCountedObject<Resource> {
   public:
    explicit PreventIncreaseResolutionDueToBitrateResource(
        VideoStreamEncoderResourceManager* manager);
    ~PreventIncreaseResolutionDueToBitrateResource() override = default;

    void OnEncoderSettingsUpdated(
        absl::optional<EncoderSettings> encoder_settings);
    void OnEncoderTargetBitrateUpdated(
        absl::optional<uint32_t> encoder_target_bitrate_bps);

    // Resource overrides.
    std::string name() const override {
      return "PreventIncreaseResolutionDueToBitrateResource";
    }
    bool IsAdaptationUpAllowed(
        const VideoStreamInputState& input_state,
        const VideoSourceRestrictions& restrictions_before,
        const VideoSourceRestrictions& restrictions_after,
        rtc::scoped_refptr<Resource> reason_resource) const override;

   private:
    // The |manager_| must be alive as long as this resource is added to the
    // ResourceAdaptationProcessor, i.e. when IsAdaptationUpAllowed() is called.
    VideoStreamEncoderResourceManager* const manager_;
    absl::optional<EncoderSettings> encoder_settings_
        RTC_GUARDED_BY(resource_adaptation_queue());
    absl::optional<uint32_t> encoder_target_bitrate_bps_
        RTC_GUARDED_BY(resource_adaptation_queue());
  };

  // Does not trigger adaptations, only prevents adapting up in BALANCED.
  class PreventAdaptUpInBalancedResource final
      : public rtc::RefCountedObject<Resource> {
   public:
    explicit PreventAdaptUpInBalancedResource(
        VideoStreamEncoderResourceManager* manager);
    ~PreventAdaptUpInBalancedResource() override = default;

    void SetAdaptationProcessor(
        ResourceAdaptationProcessorInterface* adaptation_processor);
    void OnEncoderTargetBitrateUpdated(
        absl::optional<uint32_t> encoder_target_bitrate_bps);

    // Resource overrides.
    std::string name() const override {
      return "PreventAdaptUpInBalancedResource";
    }
    bool IsAdaptationUpAllowed(
        const VideoStreamInputState& input_state,
        const VideoSourceRestrictions& restrictions_before,
        const VideoSourceRestrictions& restrictions_after,
        rtc::scoped_refptr<Resource> reason_resource) const override;

   private:
    // The |manager_| must be alive as long as this resource is added to the
    // ResourceAdaptationProcessor, i.e. when IsAdaptationUpAllowed() is called.
    VideoStreamEncoderResourceManager* const manager_;
    ResourceAdaptationProcessorInterface* adaptation_processor_
        RTC_GUARDED_BY(resource_adaptation_queue());
    absl::optional<uint32_t> encoder_target_bitrate_bps_
        RTC_GUARDED_BY(resource_adaptation_queue());
  };

  const rtc::scoped_refptr<PreventAdaptUpDueToActiveCounts>
      prevent_adapt_up_due_to_active_counts_;
  const rtc::scoped_refptr<PreventIncreaseResolutionDueToBitrateResource>
      prevent_increase_resolution_due_to_bitrate_resource_;
  const rtc::scoped_refptr<PreventAdaptUpInBalancedResource>
      prevent_adapt_up_in_balanced_resource_;
  const rtc::scoped_refptr<EncodeUsageResource> encode_usage_resource_;
  const rtc::scoped_refptr<QualityScalerResource> quality_scaler_resource_;

  rtc::TaskQueue* encoder_queue_;
  rtc::TaskQueue* resource_adaptation_queue_;
  VideoStreamInputStateProvider* const input_state_provider_
      RTC_GUARDED_BY(encoder_queue_);
  ResourceAdaptationProcessorInterface* adaptation_processor_
      RTC_GUARDED_BY(resource_adaptation_queue_);
  // Thread-safe.
  VideoStreamEncoderObserver* const encoder_stats_observer_;

  DegradationPreference degradation_preference_ RTC_GUARDED_BY(encoder_queue_);
  VideoSourceRestrictions video_source_restrictions_
      RTC_GUARDED_BY(encoder_queue_);

  const BalancedDegradationSettings balanced_settings_;
  Clock* clock_ RTC_GUARDED_BY(encoder_queue_);
  const bool experiment_cpu_load_estimator_ RTC_GUARDED_BY(encoder_queue_);
  const std::unique_ptr<InitialFrameDropper> initial_frame_dropper_
      RTC_GUARDED_BY(encoder_queue_);
  const bool quality_scaling_experiment_enabled_ RTC_GUARDED_BY(encoder_queue_);
  absl::optional<uint32_t> encoder_target_bitrate_bps_
      RTC_GUARDED_BY(encoder_queue_);
  absl::optional<VideoEncoder::RateControlParameters> encoder_rates_
      RTC_GUARDED_BY(encoder_queue_);
  // Used on both the encoder queue and resource adaptation queue.
  std::atomic<bool> quality_rampup_done_;
  QualityRampupExperiment quality_rampup_experiment_
      RTC_GUARDED_BY(encoder_queue_);
  absl::optional<EncoderSettings> encoder_settings_
      RTC_GUARDED_BY(encoder_queue_);

  // Ties a resource to a reason for statistical reporting. This AdaptReason is
  // also used by this module to make decisions about how to adapt up/down.
  struct ResourceAndReason {
    ResourceAndReason(rtc::scoped_refptr<Resource> resource,
                      VideoAdaptationReason reason)
        : resource(resource), reason(reason) {}
    virtual ~ResourceAndReason() = default;

    const rtc::scoped_refptr<Resource> resource;
    const VideoAdaptationReason reason;
  };
  rtc::CriticalSection resource_lock_;
  std::vector<ResourceAndReason> resources_ RTC_GUARDED_BY(&resource_lock_);
  // One AdaptationCounter for each reason, tracking the number of times we have
  // adapted for each reason. The sum of active_counts_ MUST always equal the
  // total adaptation provided by the VideoSourceRestrictions.
  // TODO(https://crbug.com/webrtc/11542): When we have an adaptation queue,
  // guard the activec counts by it instead. The |encoder_stats_observer_| is
  // thread-safe anyway, and active counts are used by
  // PreventAdaptUpDueToActiveCounts to make decisions.
  std::unordered_map<VideoAdaptationReason, VideoAdaptationCounters>
      active_counts_ RTC_GUARDED_BY(resource_adaptation_queue_);
};

}  // namespace webrtc

#endif  // VIDEO_ADAPTATION_VIDEO_STREAM_ENCODER_RESOURCE_MANAGER_H_