/*
 *  Copyright (c) 2024 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/quality_convergence_controller.h"

#include <algorithm>
#include <memory>
#include <optional>

#include "api/field_trials_view.h"
#include "api/video/video_codec_type.h"
#include "rtc_base/checks.h"
#include "rtc_base/experiments/struct_parameters_parser.h"
#include "rtc_base/logging.h"
#include "video/quality_convergence_monitor.h"

namespace webrtc {
namespace {
// TODO(https://crbug.com/328598314): Remove default values once HW encoders
// correctly report the minimum QP value. These thresholds correspond to the
// default configurations used for the software encoders.
constexpr int kVp8DefaultStaticQpThreshold = 15;
constexpr int kVp9DefaultStaticQpThreshold = 32;
constexpr int kAv1DefaultStaticQpThreshold = 60;

struct StaticDetectionConfig {
  // Overrides the static QP threshold if set to a higher value than what is
  // reported by the encoder.
  std::optional<int> static_qp_threshold_override;
  std::unique_ptr<StructParametersParser> Parser();
};

std::unique_ptr<StructParametersParser> StaticDetectionConfig::Parser() {
  // The empty comments ensures that each pair is on a separate line.
  return StructParametersParser::Create("static_qp_threshold",
                                        &static_qp_threshold_override);
}

int GetDefaultStaticQpThreshold(VideoCodecType codec,
                                const FieldTrialsView& trials) {
  StaticDetectionConfig static_config;
  int default_static_qp_threhsold = 0;
  switch (codec) {
    case kVideoCodecVP8:
      default_static_qp_threhsold = kVp8DefaultStaticQpThreshold;
      static_config.Parser()->Parse(trials.Lookup("WebRTC-QCM-Static-VP8"));
      break;
    case kVideoCodecVP9:
      default_static_qp_threhsold = kVp9DefaultStaticQpThreshold;
      static_config.Parser()->Parse(trials.Lookup("WebRTC-QCM-Static-VP9"));
      break;
    case kVideoCodecAV1:
      default_static_qp_threhsold = kAv1DefaultStaticQpThreshold;
      static_config.Parser()->Parse(trials.Lookup("WebRTC-QCM-Static-AV1"));
      break;
    case kVideoCodecGeneric:
    case kVideoCodecH264:
    case kVideoCodecH265:
      // -1 will effectively disable the static QP threshold since QP values are
      // always >= 0.
      return -1;
  }

  if (static_config.static_qp_threshold_override.has_value()) {
    RTC_LOG(LS_INFO) << "static_qp_threshold_override: "
                     << *static_config.static_qp_threshold_override;
    return *static_config.static_qp_threshold_override;
  }

  return default_static_qp_threhsold;
}
}  // namespace

void QualityConvergenceController::Initialize(int number_of_layers,
                                              std::optional<int> encoder_min_qp,
                                              VideoCodecType codec,
                                              const FieldTrialsView& trials) {
  RTC_DCHECK(sequence_checker_.IsCurrent());
  RTC_CHECK(number_of_layers > 0);
  number_of_layers_ = number_of_layers;
  convergence_monitors_.clear();

  int qp_threshold = GetDefaultStaticQpThreshold(codec, trials);
  if (encoder_min_qp.has_value()) {
    qp_threshold = std::max(qp_threshold, *encoder_min_qp);
  }

  for (int i = 0; i < number_of_layers_; ++i) {
    convergence_monitors_.push_back(
        QualityConvergenceMonitor::Create(qp_threshold, codec, trials));
  }
  initialized_ = true;
}

bool QualityConvergenceController::AddSampleAndCheckTargetQuality(
    int layer_index,
    int qp,
    bool is_refresh_frame) {
  RTC_DCHECK(sequence_checker_.IsCurrent());
  RTC_CHECK(initialized_);
  if (layer_index < 0 || layer_index >= number_of_layers_) {
    return false;
  }

  // TODO(kron): Remove temporary check that verifies that the initialization is
  // working as expected. See https://crbug.com/359410061.
  RTC_DCHECK(number_of_layers_ ==
             static_cast<int>(convergence_monitors_.size()));
  if (number_of_layers_ != static_cast<int>(convergence_monitors_.size())) {
    return false;
  }

  convergence_monitors_[layer_index]->AddSample(qp, is_refresh_frame);
  return convergence_monitors_[layer_index]->AtTargetQuality();
}

}  // namespace webrtc