/*
 *  Copyright (c) 2017 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 "modules/audio_processing/aec3/erle_estimator.h"

#include <algorithm>
#include <numeric>

#include "rtc_base/numerics/safe_minmax.h"

namespace webrtc {

ErleEstimator::ErleEstimator(float min_erle,
                             float max_erle_lf,
                             float max_erle_hf)
    : min_erle_(min_erle),
      max_erle_lf_(max_erle_lf),
      max_erle_hf_(max_erle_hf) {
  erle_.fill(min_erle_);
  erle_onsets_.fill(min_erle_);
  hold_counters_.fill(0);
  coming_onset_.fill(true);
  erle_time_domain_ = min_erle_;
  hold_counter_time_domain_ = 0;
}

ErleEstimator::~ErleEstimator() = default;

void ErleEstimator::Update(rtc::ArrayView<const float> render_spectrum,
                           rtc::ArrayView<const float> capture_spectrum,
                           rtc::ArrayView<const float> subtractor_spectrum) {
  RTC_DCHECK_EQ(kFftLengthBy2Plus1, render_spectrum.size());
  RTC_DCHECK_EQ(kFftLengthBy2Plus1, capture_spectrum.size());
  RTC_DCHECK_EQ(kFftLengthBy2Plus1, subtractor_spectrum.size());
  const auto& X2 = render_spectrum;
  const auto& Y2 = capture_spectrum;
  const auto& E2 = subtractor_spectrum;

  // Corresponds of WGN of power -46 dBFS.
  constexpr float kX2Min = 44015068.0f;
  constexpr int kOnsetSizeBlocks = 4;
  constexpr int kErleHold = 100;
  constexpr int kErleOnsetHold = kErleHold + kOnsetSizeBlocks;

  auto erle_band_update = [](float erle_band, float new_erle, float alpha_inc,
                             float alpha_dec, float min_erle, float max_erle) {
    float alpha = new_erle > erle_band ? alpha_inc : alpha_dec;
    float erle_band_out = erle_band;
    erle_band_out = erle_band + alpha * (new_erle - erle_band);
    erle_band_out = rtc::SafeClamp(erle_band_out, min_erle, max_erle);
    return erle_band_out;
  };

  // Update the estimates in a clamped minimum statistics manner.
  auto erle_update = [&](size_t start, size_t stop, float max_erle) {
    for (size_t k = start; k < stop; ++k) {
      if (X2[k] > kX2Min && E2[k] > 0.f) {
        const float new_erle = Y2[k] / E2[k];

        if (coming_onset_[k - 1]) {
          hold_counters_[k - 1] = kErleOnsetHold;
          coming_onset_[k - 1] = false;
        }
        if (hold_counters_[k - 1] > kErleHold) {
          erle_onsets_[k] = erle_band_update(erle_onsets_[k], new_erle, 0.05f,
                                             0.1f, min_erle_, max_erle);
        } else {
          hold_counters_[k - 1] = kErleHold;
        }
        erle_[k] = erle_band_update(erle_[k], new_erle, 0.01f, 0.02f, min_erle_,
                                    max_erle);
      }
    }
  };

  constexpr size_t kFftLengthBy4 = kFftLengthBy2 / 2;
  erle_update(1, kFftLengthBy4, max_erle_lf_);
  erle_update(kFftLengthBy4, kFftLengthBy2, max_erle_hf_);

  for (size_t k = 0; k < hold_counters_.size(); ++k) {
    hold_counters_[k]--;
    if (hold_counters_[k] <= 0) {
      coming_onset_[k] = true;
      if (erle_[k + 1] > erle_onsets_[k + 1]) {
        erle_[k + 1] = std::max(erle_onsets_[k + 1], 0.97f * erle_[k + 1]);
        RTC_DCHECK_LE(min_erle_, erle_[k + 1]);
      }
    }
  }

  erle_[0] = erle_[1];
  erle_[kFftLengthBy2] = erle_[kFftLengthBy2 - 1];

  // Compute ERLE over all frequency bins.
  const float X2_sum = std::accumulate(X2.begin(), X2.end(), 0.0f);
  const float E2_sum = std::accumulate(E2.begin(), E2.end(), 0.0f);
  if (X2_sum > kX2Min * X2.size() && E2_sum > 0.f) {
    const float Y2_sum = std::accumulate(Y2.begin(), Y2.end(), 0.0f);
    const float new_erle = Y2_sum / E2_sum;
    if (new_erle > erle_time_domain_) {
      hold_counter_time_domain_ = kErleHold;
      erle_time_domain_ += 0.1f * (new_erle - erle_time_domain_);
      erle_time_domain_ =
          rtc::SafeClamp(erle_time_domain_, min_erle_, max_erle_lf_);
    }
  }
  --hold_counter_time_domain_;
  erle_time_domain_ = (hold_counter_time_domain_ > 0)
                        ? erle_time_domain_
                        : std::max(min_erle_, 0.97f * erle_time_domain_);
}

}  // namespace webrtc