/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *     notice, this list of conditions and the following disclaimer in the
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 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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// FFTFrame implementation using FFmpeg's RDFT algorithm,
// suitable for use on Windows and Linux.

#include "wtf/build_config.h"

#if USE(WEBAUDIO_FFMPEG)

#include "platform/audio/FFTFrame.h"

#include "platform/audio/VectorMath.h"

extern "C" {
#include <libavcodec/avfft.h>
}

#include "wtf/MathExtras.h"

namespace blink {

#if ENABLE(ASSERT)
// Max FFT size for FFMPEG.  WebAudio currently only uses FFTs up to size 15
// (2^15 points).
const int kMaxFFTPow2Size = 16;
#endif

// Normal constructor: allocates for a given fftSize.
FFTFrame::FFTFrame(unsigned fftSize)
    : m_FFTSize(fftSize),
      m_log2FFTSize(static_cast<unsigned>(log2(fftSize))),
      m_realData(fftSize / 2),
      m_imagData(fftSize / 2),
      m_forwardContext(nullptr),
      m_inverseContext(nullptr),
      m_complexData(fftSize) {
  // We only allow power of two.
  ASSERT(1UL << m_log2FFTSize == m_FFTSize);

  m_forwardContext = contextForSize(fftSize, DFT_R2C);
  m_inverseContext = contextForSize(fftSize, IDFT_C2R);
}

// Creates a blank/empty frame (interpolate() must later be called).
FFTFrame::FFTFrame()
    : m_FFTSize(0),
      m_log2FFTSize(0),
      m_forwardContext(nullptr),
      m_inverseContext(nullptr) {}

// Copy constructor.
FFTFrame::FFTFrame(const FFTFrame& frame)
    : m_FFTSize(frame.m_FFTSize),
      m_log2FFTSize(frame.m_log2FFTSize),
      m_realData(frame.m_FFTSize / 2),
      m_imagData(frame.m_FFTSize / 2),
      m_forwardContext(nullptr),
      m_inverseContext(nullptr),
      m_complexData(frame.m_FFTSize) {
  m_forwardContext = contextForSize(m_FFTSize, DFT_R2C);
  m_inverseContext = contextForSize(m_FFTSize, IDFT_C2R);

  // Copy/setup frame data.
  unsigned nbytes = sizeof(float) * (m_FFTSize / 2);
  memcpy(realData(), frame.realData(), nbytes);
  memcpy(imagData(), frame.imagData(), nbytes);
}

void FFTFrame::initialize() {}

void FFTFrame::cleanup() {}

FFTFrame::~FFTFrame() {
  av_rdft_end(m_forwardContext);
  av_rdft_end(m_inverseContext);
}

void FFTFrame::doFFT(const float* data) {
  // Copy since processing is in-place.
  float* p = m_complexData.data();
  memcpy(p, data, sizeof(float) * m_FFTSize);

  // Compute Forward transform.
  av_rdft_calc(m_forwardContext, p);

  // De-interleave to separate real and complex arrays.
  int len = m_FFTSize / 2;

  float* real = m_realData.data();
  float* imag = m_imagData.data();
  for (int i = 0; i < len; ++i) {
    int baseComplexIndex = 2 * i;
    // m_realData[0] is the DC component and m_imagData[0] is the nyquist
    // component since the interleaved complex data is packed.
    real[i] = p[baseComplexIndex];
    imag[i] = p[baseComplexIndex + 1];
  }
}

void FFTFrame::doInverseFFT(float* data) {
  // Prepare interleaved data.
  float* interleavedData = getUpToDateComplexData();

  // Compute inverse transform.
  av_rdft_calc(m_inverseContext, interleavedData);

  // Scale so that a forward then inverse FFT yields exactly the original data.
  // For some reason av_rdft_calc above returns values that are half of what I
  // expect. Hence make the scale factor
  // twice as large to compensate for that.
  const float scale = 2.0 / m_FFTSize;
  VectorMath::vsmul(interleavedData, 1, &scale, data, 1, m_FFTSize);
}

float* FFTFrame::getUpToDateComplexData() {
  // FIXME: if we can't completely get rid of this method, SSE
  // optimization could be considered if it shows up hot on profiles.
  int len = m_FFTSize / 2;
  const float* real = m_realData.data();
  const float* imag = m_imagData.data();
  float* c = m_complexData.data();
  for (int i = 0; i < len; ++i) {
    int baseComplexIndex = 2 * i;
    c[baseComplexIndex] = real[i];
    c[baseComplexIndex + 1] = imag[i];
  }
  return const_cast<float*>(m_complexData.data());
}

RDFTContext* FFTFrame::contextForSize(unsigned fftSize, int trans) {
  // FIXME: This is non-optimal. Ideally, we'd like to share the contexts for
  // FFTFrames of the same size.  But FFmpeg's RDFT uses a scratch buffer
  // inside the context and so they are not thread-safe.  We could improve this
  // by sharing the FFTFrames on a per-thread basis.
  ASSERT(fftSize);
  int pow2size = static_cast<int>(log2(fftSize));
  ASSERT(pow2size < kMaxFFTPow2Size);

  RDFTContext* context = av_rdft_init(pow2size, (RDFTransformType)trans);
  return context;
}

}  // namespace blink

#endif  // USE(WEBAUDIO_FFMPEG)