/*
 *  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.
 */

#include "video/adaptation/resource_adaptation_processor.h"

#include <algorithm>
#include <limits>
#include <memory>
#include <string>
#include <utility>

#include "absl/algorithm/container.h"
#include "absl/base/macros.h"
#include "api/task_queue/task_queue_base.h"
#include "api/video/video_source_interface.h"
#include "call/adaptation/resource.h"
#include "call/adaptation/video_source_restrictions.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/time_utils.h"

namespace webrtc {

const int kDefaultInputPixelsWidth = 176;
const int kDefaultInputPixelsHeight = 144;

namespace {

bool IsResolutionScalingEnabled(DegradationPreference degradation_preference) {
  return degradation_preference == DegradationPreference::MAINTAIN_FRAMERATE ||
         degradation_preference == DegradationPreference::BALANCED;
}

bool IsFramerateScalingEnabled(DegradationPreference degradation_preference) {
  return degradation_preference == DegradationPreference::MAINTAIN_RESOLUTION ||
         degradation_preference == DegradationPreference::BALANCED;
}

// Returns modified restrictions where any constraints that don't apply to the
// degradation preference are cleared.
VideoSourceRestrictions ApplyDegradationPreference(
    VideoSourceRestrictions source_restrictions,
    DegradationPreference degradation_preference) {
  switch (degradation_preference) {
    case DegradationPreference::BALANCED:
      break;
    case DegradationPreference::MAINTAIN_FRAMERATE:
      source_restrictions.set_max_frame_rate(absl::nullopt);
      break;
    case DegradationPreference::MAINTAIN_RESOLUTION:
      source_restrictions.set_max_pixels_per_frame(absl::nullopt);
      source_restrictions.set_target_pixels_per_frame(absl::nullopt);
      break;
    case DegradationPreference::DISABLED:
      source_restrictions.set_max_pixels_per_frame(absl::nullopt);
      source_restrictions.set_target_pixels_per_frame(absl::nullopt);
      source_restrictions.set_max_frame_rate(absl::nullopt);
  }
  return source_restrictions;
}

// Returns AdaptationCounters where constraints that don't apply to the
// degredation preference are cleared. This behaviour must reflect that of
// ApplyDegredationPreference for SourceRestrictions. Any to that method must
// also change this one.
AdaptationCounters ApplyDegradationPreference(
    AdaptationCounters counters,
    DegradationPreference degradation_preference) {
  switch (degradation_preference) {
    case DegradationPreference::BALANCED:
      break;
    case DegradationPreference::MAINTAIN_FRAMERATE:
      counters.fps_adaptations = 0;
      break;
    case DegradationPreference::MAINTAIN_RESOLUTION:
      counters.resolution_adaptations = 0;
      break;
    case DegradationPreference::DISABLED:
      counters.resolution_adaptations = 0;
      counters.fps_adaptations = 0;
      break;
    default:
      RTC_NOTREACHED();
  }
  return counters;
}

}  // namespace

class ResourceAdaptationProcessor::InitialFrameDropper {
 public:
  explicit InitialFrameDropper(QualityScalerResource* quality_scaler_resource)
      : quality_scaler_resource_(quality_scaler_resource),
        quality_scaler_settings_(QualityScalerSettings::ParseFromFieldTrials()),
        has_seen_first_bwe_drop_(false),
        set_start_bitrate_(DataRate::Zero()),
        set_start_bitrate_time_ms_(0),
        initial_framedrop_(0) {
    RTC_DCHECK(quality_scaler_resource_);
  }

  // Output signal.
  bool DropInitialFrames() const {
    return initial_framedrop_ < kMaxInitialFramedrop;
  }

  // Input signals.
  void SetStartBitrate(DataRate start_bitrate, int64_t now_ms) {
    set_start_bitrate_ = start_bitrate;
    set_start_bitrate_time_ms_ = now_ms;
  }

  void SetTargetBitrate(DataRate target_bitrate, int64_t now_ms) {
    if (set_start_bitrate_ > DataRate::Zero() && !has_seen_first_bwe_drop_ &&
        quality_scaler_resource_->is_started() &&
        quality_scaler_settings_.InitialBitrateIntervalMs() &&
        quality_scaler_settings_.InitialBitrateFactor()) {
      int64_t diff_ms = now_ms - set_start_bitrate_time_ms_;
      if (diff_ms <
              quality_scaler_settings_.InitialBitrateIntervalMs().value() &&
          (target_bitrate <
           (set_start_bitrate_ *
            quality_scaler_settings_.InitialBitrateFactor().value()))) {
        RTC_LOG(LS_INFO) << "Reset initial_framedrop_. Start bitrate: "
                         << set_start_bitrate_.bps()
                         << ", target bitrate: " << target_bitrate.bps();
        initial_framedrop_ = 0;
        has_seen_first_bwe_drop_ = true;
      }
    }
  }

  void OnFrameDroppedDueToSize() { ++initial_framedrop_; }

  void OnMaybeEncodeFrame() { initial_framedrop_ = kMaxInitialFramedrop; }

  void OnQualityScalerSettingsUpdated() {
    if (quality_scaler_resource_->is_started()) {
      // Restart frame drops due to size.
      initial_framedrop_ = 0;
    } else {
      // Quality scaling disabled so we shouldn't drop initial frames.
      initial_framedrop_ = kMaxInitialFramedrop;
    }
  }

 private:
  // The maximum number of frames to drop at beginning of stream to try and
  // achieve desired bitrate.
  static const int kMaxInitialFramedrop = 4;

  const QualityScalerResource* quality_scaler_resource_;
  const QualityScalerSettings quality_scaler_settings_;
  bool has_seen_first_bwe_drop_;
  DataRate set_start_bitrate_;
  int64_t set_start_bitrate_time_ms_;
  // Counts how many frames we've dropped in the initial framedrop phase.
  int initial_framedrop_;
};

ResourceAdaptationProcessor::ResourceAdaptationProcessor(
    Clock* clock,
    bool experiment_cpu_load_estimator,
    std::unique_ptr<OveruseFrameDetector> overuse_detector,
    VideoStreamEncoderObserver* encoder_stats_observer,
    ResourceAdaptationProcessorListener* adaptation_listener)
    : adaptation_listener_(adaptation_listener),
      clock_(clock),
      state_(State::kStopped),
      experiment_cpu_load_estimator_(experiment_cpu_load_estimator),
      has_input_video_(false),
      degradation_preference_(DegradationPreference::DISABLED),
      stream_adapter_(std::make_unique<VideoStreamAdapter>()),
      encode_usage_resource_(
          std::make_unique<EncodeUsageResource>(std::move(overuse_detector))),
      quality_scaler_resource_(std::make_unique<QualityScalerResource>()),
      initial_frame_dropper_(std::make_unique<InitialFrameDropper>(
          quality_scaler_resource_.get())),
      quality_scaling_experiment_enabled_(QualityScalingExperiment::Enabled()),
      last_input_frame_size_(absl::nullopt),
      target_frame_rate_(absl::nullopt),
      encoder_target_bitrate_bps_(absl::nullopt),
      quality_rampup_done_(false),
      quality_rampup_experiment_(QualityRampupExperiment::ParseSettings()),
      encoder_settings_(absl::nullopt),
      encoder_stats_observer_(encoder_stats_observer),
      active_counts_() {
  RTC_DCHECK(adaptation_listener_);
  RTC_DCHECK(encoder_stats_observer_);
  AddResource(encode_usage_resource_.get(),
              AdaptationObserverInterface::AdaptReason::kCpu);
  AddResource(quality_scaler_resource_.get(),
              AdaptationObserverInterface::AdaptReason::kQuality);
}

ResourceAdaptationProcessor::~ResourceAdaptationProcessor() {
  RTC_DCHECK_EQ(state_, State::kStopped);
}

void ResourceAdaptationProcessor::StartResourceAdaptation(
    ResourceAdaptationProcessorListener* adaptation_listener) {
  RTC_DCHECK_EQ(state_, State::kStopped);
  RTC_DCHECK(encoder_settings_.has_value());
  // TODO(https://crbug.com/webrtc/11222): Rethink when the adaptation listener
  // should be passed in and why. If resources are separated from modules then
  // those resources may be started or stopped separately from the module.
  RTC_DCHECK_EQ(adaptation_listener, adaptation_listener_);
  encode_usage_resource_->StartCheckForOveruse(GetCpuOveruseOptions());
  for (auto& resource_and_reason : resources_) {
    resource_and_reason.resource->RegisterListener(this);
  }
  state_ = State::kStarted;
}

void ResourceAdaptationProcessor::StopResourceAdaptation() {
  encode_usage_resource_->StopCheckForOveruse();
  quality_scaler_resource_->StopCheckForOveruse();
  for (auto& resource_and_reason : resources_) {
    resource_and_reason.resource->UnregisterListener(this);
  }
  state_ = State::kStopped;
}

void ResourceAdaptationProcessor::AddResource(Resource* resource) {
  return AddResource(resource, AdaptationObserverInterface::AdaptReason::kCpu);
}

void ResourceAdaptationProcessor::AddResource(
    Resource* resource,
    AdaptationObserverInterface::AdaptReason reason) {
  RTC_DCHECK(resource);
  RTC_DCHECK(absl::c_find_if(resources_,
                             [resource](const ResourceAndReason& r) {
                               return r.resource == resource;
                             }) == resources_.end())
      << "Resource " << resource->name() << " already was inserted";
  resources_.emplace_back(resource, reason);
}

void ResourceAdaptationProcessor::SetHasInputVideo(bool has_input_video) {
  // While false, OnResourceUnderuse() and OnResourceOveruse() are NO-OPS.
  has_input_video_ = has_input_video;
}

void ResourceAdaptationProcessor::SetDegradationPreference(
    DegradationPreference degradation_preference) {
  degradation_preference_ = degradation_preference;
  if (stream_adapter_->SetDegradationPreference(degradation_preference) ==
      VideoStreamAdapter::SetDegradationPreferenceResult::
          kRestrictionsCleared) {
    active_counts_.fill(AdaptationCounters());
  }
  MaybeUpdateVideoSourceRestrictions();
}

void ResourceAdaptationProcessor::SetEncoderSettings(
    EncoderSettings encoder_settings) {
  encoder_settings_ = std::move(encoder_settings);

  quality_rampup_experiment_.SetMaxBitrate(
      LastInputFrameSizeOrDefault(),
      encoder_settings_->video_codec().maxBitrate);
  MaybeUpdateTargetFrameRate();
}

void ResourceAdaptationProcessor::SetStartBitrate(DataRate start_bitrate) {
  if (!start_bitrate.IsZero())
    encoder_target_bitrate_bps_ = start_bitrate.bps();
  initial_frame_dropper_->SetStartBitrate(start_bitrate,
                                          clock_->TimeInMicroseconds());
}

void ResourceAdaptationProcessor::SetTargetBitrate(DataRate target_bitrate) {
  if (!target_bitrate.IsZero())
    encoder_target_bitrate_bps_ = target_bitrate.bps();
  initial_frame_dropper_->SetTargetBitrate(target_bitrate,
                                           clock_->TimeInMilliseconds());
}

void ResourceAdaptationProcessor::SetEncoderRates(
    const VideoEncoder::RateControlParameters& encoder_rates) {
  encoder_rates_ = encoder_rates;
}

void ResourceAdaptationProcessor::ResetVideoSourceRestrictions() {
  stream_adapter_->ClearRestrictions();
  active_counts_.fill(AdaptationCounters());
  MaybeUpdateVideoSourceRestrictions();
}

void ResourceAdaptationProcessor::OnFrame(const VideoFrame& frame) {
  last_input_frame_size_ = frame.size();
}

void ResourceAdaptationProcessor::OnFrameDroppedDueToSize() {
  AdaptationCounters counters_before = stream_adapter_->adaptation_counters();
  OnResourceOveruse(AdaptationObserverInterface::AdaptReason::kQuality);
  if (degradation_preference() == DegradationPreference::BALANCED &&
      stream_adapter_->adaptation_counters().fps_adaptations >
          counters_before.fps_adaptations) {
    // Adapt framerate in same step as resolution.
    OnResourceOveruse(AdaptationObserverInterface::AdaptReason::kQuality);
  }
  if (stream_adapter_->adaptation_counters().resolution_adaptations >
      counters_before.resolution_adaptations) {
    encoder_stats_observer_->OnInitialQualityResolutionAdaptDown();
  }
  initial_frame_dropper_->OnFrameDroppedDueToSize();
}

void ResourceAdaptationProcessor::OnEncodeStarted(
    const VideoFrame& cropped_frame,
    int64_t time_when_first_seen_us) {
  encode_usage_resource_->OnEncodeStarted(cropped_frame,
                                          time_when_first_seen_us);
}

void ResourceAdaptationProcessor::OnEncodeCompleted(
    const EncodedImage& encoded_image,
    int64_t time_sent_in_us,
    absl::optional<int> encode_duration_us) {
  // Inform |encode_usage_resource_| of the encode completed event.
  uint32_t timestamp = encoded_image.Timestamp();
  int64_t capture_time_us =
      encoded_image.capture_time_ms_ * rtc::kNumMicrosecsPerMillisec;
  encode_usage_resource_->OnEncodeCompleted(
      timestamp, time_sent_in_us, capture_time_us, encode_duration_us);
  // Inform |quality_scaler_resource_| of the encode completed event.
  quality_scaler_resource_->OnEncodeCompleted(encoded_image, time_sent_in_us);
}

void ResourceAdaptationProcessor::OnFrameDropped(
    EncodedImageCallback::DropReason reason) {
  quality_scaler_resource_->OnFrameDropped(reason);
}

bool ResourceAdaptationProcessor::DropInitialFrames() const {
  return initial_frame_dropper_->DropInitialFrames();
}

void ResourceAdaptationProcessor::OnMaybeEncodeFrame() {
  initial_frame_dropper_->OnMaybeEncodeFrame();
  MaybePerformQualityRampupExperiment();
}

void ResourceAdaptationProcessor::UpdateQualityScalerSettings(
    absl::optional<VideoEncoder::QpThresholds> qp_thresholds) {
  if (qp_thresholds.has_value()) {
    quality_scaler_resource_->StopCheckForOveruse();
    quality_scaler_resource_->StartCheckForOveruse(qp_thresholds.value());
  } else {
    quality_scaler_resource_->StopCheckForOveruse();
  }
  initial_frame_dropper_->OnQualityScalerSettingsUpdated();
}

void ResourceAdaptationProcessor::ConfigureQualityScaler(
    const VideoEncoder::EncoderInfo& encoder_info) {
  const auto scaling_settings = encoder_info.scaling_settings;
  const bool quality_scaling_allowed =
      IsResolutionScalingEnabled(degradation_preference_) &&
      scaling_settings.thresholds;

  // TODO(https://crbug.com/webrtc/11222): Should this move to
  // QualityScalerResource?
  if (quality_scaling_allowed) {
    if (!quality_scaler_resource_->is_started()) {
      // Quality scaler has not already been configured.

      // Use experimental thresholds if available.
      absl::optional<VideoEncoder::QpThresholds> experimental_thresholds;
      if (quality_scaling_experiment_enabled_) {
        experimental_thresholds = QualityScalingExperiment::GetQpThresholds(
            GetVideoCodecTypeOrGeneric(encoder_settings_));
      }
      UpdateQualityScalerSettings(experimental_thresholds
                                      ? *experimental_thresholds
                                      : *(scaling_settings.thresholds));
    }
  } else {
    UpdateQualityScalerSettings(absl::nullopt);
  }

  // Set the qp-thresholds to the balanced settings if balanced mode.
  if (degradation_preference_ == DegradationPreference::BALANCED &&
      quality_scaler_resource_->is_started()) {
    absl::optional<VideoEncoder::QpThresholds> thresholds =
        stream_adapter_->balanced_settings().GetQpThresholds(
            GetVideoCodecTypeOrGeneric(encoder_settings_),
            LastInputFrameSizeOrDefault());
    if (thresholds) {
      quality_scaler_resource_->SetQpThresholds(*thresholds);
    }
  }

  encoder_stats_observer_->OnAdaptationChanged(
      VideoStreamEncoderObserver::AdaptationReason::kNone,
      GetActiveCounts(AdaptationObserverInterface::AdaptReason::kCpu),
      GetActiveCounts(AdaptationObserverInterface::AdaptReason::kQuality));
}

ResourceListenerResponse
ResourceAdaptationProcessor::OnResourceUsageStateMeasured(
    const Resource& resource) {
  const auto& registered_resource =
      absl::c_find_if(resources_, [&resource](const ResourceAndReason& r) {
        return r.resource == &resource;
      });
  RTC_DCHECK(registered_resource != resources_.end())
      << resource.name() << " not found.";

  const AdaptationObserverInterface::AdaptReason reason =
      registered_resource->reason;
  switch (resource.usage_state()) {
    case ResourceUsageState::kOveruse:
      return OnResourceOveruse(reason);
    case ResourceUsageState::kStable:
      // Do nothing.
      //
      // This module has two resources: |encoude_usage_resource_| and
      // |quality_scaler_resource_|. A smarter adaptation module might not
      // attempt to adapt up unless ALL resources were underused, but this
      // module acts on each resource's measurement in isolation - without
      // taking the current usage of any other resource into account.
      return ResourceListenerResponse::kNothing;
    case ResourceUsageState::kUnderuse:
      OnResourceUnderuse(reason);
      return ResourceListenerResponse::kNothing;
  }
}

void ResourceAdaptationProcessor::OnResourceUnderuse(
    AdaptationObserverInterface::AdaptReason reason) {
  // We can't adapt up if we're already at the highest setting.
  // Note that this only includes counts relevant to the current degradation
  // preference. e.g. we previously adapted resolution, now prefer adpating fps,
  // only count the fps adaptations and not the previous resolution adaptations.
  //
  // TODO(https://crbug.com/webrtc/11394): Checking the counts for reason should
  // be replaced with checking the overuse state of all resources. This is
  // effectively trying to infer if the the Resource specified by |reason| is OK
  // with adapting up by looking at active counters. If the relevant Resources
  // simply told us this directly we wouldn't have to depend on stats counters
  // to abort GetAdaptUpTarget().
  int num_downgrades = ApplyDegradationPreference(active_counts_[reason],
                                                  degradation_preference_)
                           .Total();
  RTC_DCHECK_GE(num_downgrades, 0);
  if (num_downgrades == 0)
    return;
  // Current video input states used by VideoStreamAdapter.
  const VideoStreamAdapter::VideoInputMode input_mode = GetVideoInputMode();
  const int input_pixels = LastInputFrameSizeOrDefault();
  const int input_fps = encoder_stats_observer_->GetInputFrameRate();
  // Should we adapt, if so to what target?
  absl::optional<VideoStreamAdapter::AdaptationTarget> target =
      stream_adapter_->GetAdaptUpTarget(encoder_settings_,
                                        encoder_target_bitrate_bps_, input_mode,
                                        input_pixels, input_fps, reason);
  if (!target.has_value())
    return;
  // Apply target.
  stream_adapter_->ApplyAdaptationTarget(target.value(), encoder_settings_,
                                         input_mode, input_pixels, input_fps);
  // Update VideoSourceRestrictions based on adaptation. This also informs the
  // |adaptation_listener_|.
  MaybeUpdateVideoSourceRestrictions();
  // Stats and logging.
  UpdateAdaptationStats(reason);
  RTC_LOG(LS_INFO) << ActiveCountsToString();
}

ResourceListenerResponse ResourceAdaptationProcessor::OnResourceOveruse(
    AdaptationObserverInterface::AdaptReason reason) {
  if (!has_input_video_)
    return ResourceListenerResponse::kQualityScalerShouldIncreaseFrequency;
  // Current video input states used by VideoStreamAdapter.
  const VideoStreamAdapter::VideoInputMode input_mode = GetVideoInputMode();
  const int input_pixels = LastInputFrameSizeOrDefault();
  const int input_fps = encoder_stats_observer_->GetInputFrameRate();
  // Should we adapt, if so to what target?
  absl::optional<VideoStreamAdapter::AdaptationTarget> target =
      stream_adapter_->GetAdaptDownTarget(encoder_settings_, input_mode,
                                          input_pixels, input_fps,
                                          encoder_stats_observer_);
  if (!target.has_value())
    return ResourceListenerResponse::kNothing;
  // Apply target.
  ResourceListenerResponse response = stream_adapter_->ApplyAdaptationTarget(
      target.value(), encoder_settings_, input_mode, input_pixels, input_fps);
  // Update VideoSourceRestrictions based on adaptation. This also informs the
  // |adaptation_listener_|.
  MaybeUpdateVideoSourceRestrictions();
  // Stats and logging.
  UpdateAdaptationStats(reason);
  RTC_LOG(INFO) << ActiveCountsToString();
  return response;
}

// TODO(pbos): Lower these thresholds (to closer to 100%) when we handle
// pipelining encoders better (multiple input frames before something comes
// out). This should effectively turn off CPU adaptations for systems that
// remotely cope with the load right now.
CpuOveruseOptions ResourceAdaptationProcessor::GetCpuOveruseOptions() const {
  // This is already ensured by the only caller of this method:
  // StartResourceAdaptation().
  RTC_DCHECK(encoder_settings_.has_value());
  CpuOveruseOptions options;
  // Hardware accelerated encoders are assumed to be pipelined; give them
  // additional overuse time.
  if (encoder_settings_->encoder_info().is_hardware_accelerated) {
    options.low_encode_usage_threshold_percent = 150;
    options.high_encode_usage_threshold_percent = 200;
  }
  if (experiment_cpu_load_estimator_) {
    options.filter_time_ms = 5 * rtc::kNumMillisecsPerSec;
  }
  return options;
}

int ResourceAdaptationProcessor::LastInputFrameSizeOrDefault() const {
  // The dependency on this hardcoded resolution is inherited from old code,
  // which used this resolution as a stand-in for not knowing the resolution
  // yet.
  // TODO(hbos): Can we simply DCHECK has_value() before usage instead? Having a
  // DCHECK passed all the tests but adding it does change the requirements of
  // this class (= not being allowed to call OnResourceUnderuse() or
  // OnResourceOveruse() before OnFrame()) and deserves a standalone CL.
  return last_input_frame_size_.value_or(kDefaultInputPixelsWidth *
                                         kDefaultInputPixelsHeight);
}

void ResourceAdaptationProcessor::MaybeUpdateVideoSourceRestrictions() {
  VideoSourceRestrictions new_restrictions = ApplyDegradationPreference(
      stream_adapter_->source_restrictions(), degradation_preference_);
  if (video_source_restrictions_ != new_restrictions) {
    video_source_restrictions_ = std::move(new_restrictions);
    adaptation_listener_->OnVideoSourceRestrictionsUpdated(
        video_source_restrictions_);
    MaybeUpdateTargetFrameRate();
  }
}

void ResourceAdaptationProcessor::MaybeUpdateTargetFrameRate() {
  absl::optional<double> codec_max_frame_rate =
      encoder_settings_.has_value()
          ? absl::optional<double>(
                encoder_settings_->video_codec().maxFramerate)
          : absl::nullopt;
  // The current target framerate is the maximum frame rate as specified by
  // the current codec configuration or any limit imposed by the adaptation
  // module. This is used to make sure overuse detection doesn't needlessly
  // trigger in low and/or variable framerate scenarios.
  absl::optional<double> target_frame_rate =
      ApplyDegradationPreference(stream_adapter_->source_restrictions(),
                                 degradation_preference_)
          .max_frame_rate();
  if (!target_frame_rate.has_value() ||
      (codec_max_frame_rate.has_value() &&
       codec_max_frame_rate.value() < target_frame_rate.value())) {
    target_frame_rate = codec_max_frame_rate;
  }
  encode_usage_resource_->SetTargetFrameRate(target_frame_rate);
}

void ResourceAdaptationProcessor::OnAdaptationCountChanged(
    const AdaptationCounters& adaptation_count,
    AdaptationCounters* active_count,
    AdaptationCounters* other_active) {
  RTC_DCHECK(active_count);
  RTC_DCHECK(other_active);
  const int active_total = active_count->Total();
  const int other_total = other_active->Total();
  const AdaptationCounters prev_total = *active_count + *other_active;
  const AdaptationCounters delta = adaptation_count - prev_total;

  RTC_DCHECK_EQ(
      std::abs(delta.resolution_adaptations) + std::abs(delta.fps_adaptations),
      1)
      << "Adaptation took more than one step!";

  if (delta.resolution_adaptations > 0) {
    ++active_count->resolution_adaptations;
  } else if (delta.resolution_adaptations < 0) {
    if (active_count->resolution_adaptations == 0) {
      RTC_DCHECK_GT(active_count->fps_adaptations, 0) << "No downgrades left";
      RTC_DCHECK_GT(other_active->resolution_adaptations, 0)
          << "No resolution adaptation to borrow from";
      // Lend an fps adaptation to other and take one resolution adaptation.
      --active_count->fps_adaptations;
      ++other_active->fps_adaptations;
      --other_active->resolution_adaptations;
    } else {
      --active_count->resolution_adaptations;
    }
  }
  if (delta.fps_adaptations > 0) {
    ++active_count->fps_adaptations;
  } else if (delta.fps_adaptations < 0) {
    if (active_count->fps_adaptations == 0) {
      RTC_DCHECK_GT(active_count->resolution_adaptations, 0)
          << "No downgrades left";
      RTC_DCHECK_GT(other_active->fps_adaptations, 0)
          << "No fps adaptation to borrow from";
      // Lend a resolution adaptation to other and take one fps adaptation.
      --active_count->resolution_adaptations;
      ++other_active->resolution_adaptations;
      --other_active->fps_adaptations;
    } else {
      --active_count->fps_adaptations;
    }
  }

  RTC_DCHECK(*active_count + *other_active == adaptation_count);
  RTC_DCHECK_EQ(other_active->Total(), other_total);
  RTC_DCHECK_EQ(active_count->Total(), active_total + delta.Total());
  RTC_DCHECK_GE(active_count->resolution_adaptations, 0);
  RTC_DCHECK_GE(active_count->fps_adaptations, 0);
  RTC_DCHECK_GE(other_active->resolution_adaptations, 0);
  RTC_DCHECK_GE(other_active->fps_adaptations, 0);
}

// TODO(nisse): Delete, once AdaptReason and AdaptationReason are merged.
void ResourceAdaptationProcessor::UpdateAdaptationStats(
    AdaptationObserverInterface::AdaptReason reason) {
  // Update active counts
  AdaptationCounters& active_count = active_counts_[reason];
  AdaptationCounters& other_active = active_counts_[(reason + 1) % 2];
  const AdaptationCounters total_counts =
      stream_adapter_->adaptation_counters();

  OnAdaptationCountChanged(total_counts, &active_count, &other_active);

  switch (reason) {
    case AdaptationObserverInterface::AdaptReason::kCpu:
      encoder_stats_observer_->OnAdaptationChanged(
          VideoStreamEncoderObserver::AdaptationReason::kCpu,
          GetActiveCounts(AdaptationObserverInterface::AdaptReason::kCpu),
          GetActiveCounts(AdaptationObserverInterface::AdaptReason::kQuality));
      break;
    case AdaptationObserverInterface::AdaptReason::kQuality:
      encoder_stats_observer_->OnAdaptationChanged(
          VideoStreamEncoderObserver::AdaptationReason::kQuality,
          GetActiveCounts(AdaptationObserverInterface::AdaptReason::kCpu),
          GetActiveCounts(AdaptationObserverInterface::AdaptReason::kQuality));
      break;
  }
}

VideoStreamEncoderObserver::AdaptationSteps
ResourceAdaptationProcessor::GetActiveCounts(
    AdaptationObserverInterface::AdaptReason reason) {
  // TODO(https://crbug.com/webrtc/11392) Ideally this shuold be moved out of
  // this class and into the encoder_stats_observer_.
  const AdaptationCounters counters = active_counts_[reason];

  VideoStreamEncoderObserver::AdaptationSteps counts =
      VideoStreamEncoderObserver::AdaptationSteps();
  counts.num_resolution_reductions = counters.resolution_adaptations;
  counts.num_framerate_reductions = counters.fps_adaptations;
  switch (reason) {
    case AdaptationObserverInterface::AdaptReason::kCpu:
      if (!IsFramerateScalingEnabled(degradation_preference_))
        counts.num_framerate_reductions = absl::nullopt;
      if (!IsResolutionScalingEnabled(degradation_preference_))
        counts.num_resolution_reductions = absl::nullopt;
      break;
    case AdaptationObserverInterface::AdaptReason::kQuality:
      if (!IsFramerateScalingEnabled(degradation_preference_) ||
          !quality_scaler_resource_->is_started()) {
        counts.num_framerate_reductions = absl::nullopt;
      }
      if (!IsResolutionScalingEnabled(degradation_preference_) ||
          !quality_scaler_resource_->is_started()) {
        counts.num_resolution_reductions = absl::nullopt;
      }
      break;
  }
  return counts;
}

VideoStreamAdapter::VideoInputMode
ResourceAdaptationProcessor::GetVideoInputMode() const {
  if (!has_input_video_)
    return VideoStreamAdapter::VideoInputMode::kNoVideo;
  return (encoder_settings_.has_value() &&
          encoder_settings_->encoder_config().content_type ==
              VideoEncoderConfig::ContentType::kScreen)
             ? VideoStreamAdapter::VideoInputMode::kScreenshareVideo
             : VideoStreamAdapter::VideoInputMode::kNormalVideo;
}

void ResourceAdaptationProcessor::MaybePerformQualityRampupExperiment() {
  if (!quality_scaler_resource_->is_started())
    return;

  if (quality_rampup_done_)
    return;

  int64_t now_ms = clock_->TimeInMilliseconds();
  uint32_t bw_kbps = encoder_rates_.has_value()
                         ? encoder_rates_.value().bandwidth_allocation.kbps()
                         : 0;

  bool try_quality_rampup = false;
  if (quality_rampup_experiment_.BwHigh(now_ms, bw_kbps)) {
    // Verify that encoder is at max bitrate and the QP is low.
    if (encoder_settings_ &&
        encoder_target_bitrate_bps_.value_or(0) ==
            encoder_settings_->video_codec().maxBitrate * 1000 &&
        quality_scaler_resource_->QpFastFilterLow()) {
      try_quality_rampup = true;
    }
  }
  // TODO(https://crbug.com/webrtc/11392): See if we can rely on the total
  // counts or the stats, and not the active counts.
  const AdaptationCounters& qp_counts =
      std::get<AdaptationObserverInterface::kQuality>(active_counts_);
  const AdaptationCounters& cpu_counts =
      std::get<AdaptationObserverInterface::kCpu>(active_counts_);
  if (try_quality_rampup && qp_counts.resolution_adaptations > 0 &&
      cpu_counts.Total() == 0) {
    RTC_LOG(LS_INFO) << "Reset quality limitations.";
    ResetVideoSourceRestrictions();
    quality_rampup_done_ = true;
  }
}

std::string ResourceAdaptationProcessor::ActiveCountsToString() const {
  rtc::StringBuilder ss;

  ss << "Downgrade counts: fps: {";
  for (size_t reason = 0; reason < active_counts_.size(); ++reason) {
    ss << (reason ? " cpu" : "quality") << ":";
    ss << active_counts_[reason].fps_adaptations;
  }
  ss << "}, resolution {";
  for (size_t reason = 0; reason < active_counts_.size(); ++reason) {
    ss << (reason ? " cpu" : "quality") << ":";
    ss << active_counts_[reason].resolution_adaptations;
  }
  ss << "}";

  return ss.Release();
}
}  // namespace webrtc