// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "build/build_config.h"

#if !BUILDFLAG(IS_MAC)

#include "base/compiler_specific.h"
#include "base/synchronization/lock.h"
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/audio/fft_frame.h"
#include "third_party/blink/renderer/platform/audio/hrtf_panner.h"
#include "third_party/blink/renderer/platform/audio/vector_math.h"
#include "third_party/blink/renderer/platform/wtf/math_extras.h"
#include "third_party/pffft/src/pffft.h"

namespace blink {

namespace {

// PFFFT supports real FFTs up to at least order 20 (1048576 samples), but we
// only go up to a max size of 32768, because we need at least an FFT size of
// 32768 for the convolver node.
constexpr unsigned kMaxFFTPow2Size = 15;

// PFFFT has a minimum real FFT order of 5 (32-point transforms).
constexpr unsigned kMinFFTPow2Size = 5;

// Thin wrapper around PFFFT_Setup so we can call the appropriate PFFFT
// routines to construct or release the PFFFT_Setup objects.
class FFTSetup {
 public:
  explicit FFTSetup(unsigned fft_size);
  ~FFTSetup();
  PFFFT_Setup* GetSetup() const { return setup_; }

 private:
  raw_ptr<PFFFT_Setup> setup_;
};

FFTSetup::FFTSetup(unsigned fft_size) {
  CHECK_LE(fft_size, 1U << kMaxFFTPow2Size);
  CHECK_GE(fft_size, 1U << kMinFFTPow2Size);

  // All FFTs we need are FFTs of real signals, and the inverse FFTs produce
  // real signals.  Hence |PFFFT_REAL|.
  setup_ = pffft_new_setup(fft_size, PFFFT_REAL);
  CHECK(setup_);
}

FFTSetup::~FFTSetup() {
  CHECK(setup_);

  pffft_destroy_setup(setup_.ExtractAsDangling());
}

HashMap<unsigned, std::unique_ptr<FFTSetup>>& FFTSetups() {
  // TODO(rtoy): Let this bake for a bit and then remove the assertions after
  // we're confident the first call is from the main thread.
  static bool first_call = true;

  // A HashMap to hold all of the possible FFT setups we need.  The setups are
  // initialized lazily.  The key is the fft size, and the value is the setup
  // data.
  using FFTHashMap = HashMap<unsigned, std::unique_ptr<FFTSetup>>;

  DEFINE_THREAD_SAFE_STATIC_LOCAL(FFTHashMap, fft_setups, ());

  if (first_call) {
    DEFINE_STATIC_LOCAL(base::Lock, setup_lock, ());

    // Make sure we construct the fft_setups vector below on the main thread.
    // Once constructed, we can access it from any thread.
    CHECK(IsMainThread());
    first_call = false;

    base::AutoLock locker(setup_lock);

    // Initialize the hash map with all the possible keys (FFT sizes), with a
    // value of nullptr because we want to initialize the setup data lazily. The
    // set of valid FFT sizes for PFFFT are of the form 2^k*3^m*5^n where k >=
    // 5, m >= 0, n >= 0.

    const unsigned kMaxConvolverFFTSize = FFTFrame::MaxFFTSize();

    for (unsigned n = 1; n <= kMaxConvolverFFTSize; n *= 5) {
      for (unsigned m = 1; m <= kMaxConvolverFFTSize / n; m *= 3) {
        for (unsigned k = FFTFrame::MinFFTSize();
             k <= kMaxConvolverFFTSize / (n * m); k *= 2) {
          unsigned size = k * m * n;
          if (size <= kMaxConvolverFFTSize && !fft_setups.Contains(size)) {
            fft_setups.insert(size, nullptr);
          }
        }
      }
    }

    // There should be 87 entries when we're done.
    CHECK_EQ(fft_setups.size(), 87u);
  }

  return fft_setups;
}

void InitializeFFTSetupForSize(wtf_size_t fft_size) {
  auto& setup = FFTSetups();

  CHECK(setup.Contains(fft_size));

  if (setup.find(fft_size)->value == nullptr) {
    DEFINE_STATIC_LOCAL(base::Lock, setup_lock, ());

    // Make sure allocation of a new setup only occurs on the main thread so we
    // don't have a race condition with multiple threads trying to write to the
    // same element of the vector.
    CHECK(IsMainThread());

    auto fft_data = std::make_unique<FFTSetup>(fft_size);
    base::AutoLock locker(setup_lock);
    setup.find(fft_size)->value = std::move(fft_data);
  }
}

PFFFT_Setup* FFTSetupForSize(wtf_size_t fft_size) {
  auto& setup = FFTSetups();

  CHECK(setup.Contains(fft_size));
  CHECK(setup.find(fft_size)->value);

  return setup.find(fft_size)->value->GetSetup();
}

}  // namespace

void FFTFrame::PlatformConstruct() {
  CHECK_GE(fft_size_, MinFFTSize());
  CHECK_LE(fft_size_, MaxFFTSize());

  real_data_.Allocate(fft_size_ / 2);
  imag_data_.Allocate(fft_size_ / 2);
  complex_data_.Allocate(fft_size_);
  pffft_work_.Allocate(fft_size_);

  // Initialize the PFFFT_Setup object here so that it will be ready when we
  // compute FFTs.
  InitializeFFTSetupForSize(fft_size_);
}

unsigned FFTFrame::PlatformMinFFTSize() {
  return 1u << kMinFFTPow2Size;
}

unsigned FFTFrame::PlatformMaxFFTSize() {
  return 1u << kMaxFFTPow2Size;
}

void FFTFrame::PlatformInitialize(float sample_rate) {
  // Initialize the vector now so it's ready for use when we construct
  // FFTFrames.
  FFTSetups();

  // Determine the order of the convolvers used by the HRTF kernel.  Allocate
  // FFT setups for that size and for half that size.  The HRTF kernel uses half
  // size for analysis FFTs.
  //
  // TODO(rtoy): Try to come up with some way so that |Initialize()| doesn't
  // need to know about how the HRTF panner uses FFTs.
  unsigned hrtf_fft_size =
      static_cast<unsigned>(HRTFPanner::FftSizeForSampleRate(sample_rate));

  CHECK_GT(hrtf_fft_size, 1U << kMinFFTPow2Size);
  CHECK_LE(hrtf_fft_size, 1U << kMaxFFTPow2Size);

  InitializeFFTSetupForSize(hrtf_fft_size);
  InitializeFFTSetupForSize(hrtf_fft_size / 2);
}

void FFTFrame::PlatformCleanup() {
  for (auto& setup : FFTSetups()) {
    setup.value.reset();
  }
}

void FFTFrame::PlatformDoFFT(base::span<const float> data_span) {
  DCHECK_EQ(pffft_work_.size(), fft_size_);

  PFFFT_Setup* setup = FFTSetupForSize(fft_size_);
  DCHECK(setup);

  pffft_transform_ordered(setup, data_span.data(), complex_data_.Data(),
                          pffft_work_.Data(), PFFFT_FORWARD);

  unsigned len = fft_size_ / 2;

  // Split FFT data into real and imaginary arrays.  PFFFT transform already
  // uses the desired format; we just need to split out the real and imaginary
  // parts.
  for (unsigned k = 0; k < len; ++k) {
    int index = 2 * k;
    real_data_[k] = complex_data_[index];
    imag_data_[k] = complex_data_[index + 1];
  }
}

void FFTFrame::PlatformDoInverseFFT(base::span<float> data_span) {
  DCHECK_EQ(complex_data_.size(), fft_size_);

  unsigned len = fft_size_ / 2;

  // Pack the real and imaginary data into the complex array format.  PFFFT
  // already uses the desired format; we just need to pack the parts together.
  for (unsigned k = 0; k < len; ++k) {
    int index = 2 * k;
    complex_data_[index] = real_data_[k];
    complex_data_[index + 1] = imag_data_[k];
  }

  PFFFT_Setup* setup = FFTSetupForSize(fft_size_);
  DCHECK(setup);

  pffft_transform_ordered(setup, complex_data_.Data(), data_span.data(),
                          pffft_work_.Data(), PFFFT_BACKWARD);

  // The inverse transform needs to be scaled because PFFFT doesn't.
  float scale = 1.0 / fft_size_;
  vector_math::Vsmul(data_span, scale, data_span, fft_size_);
}

}  // namespace blink

#endif  // !BUILDFLAG(IS_MAC)