/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef SINEWAVEGENERATOR_H_

#define SINEWAVEGENERATOR_H_

#include "MediaSegment.h"

namespace mozilla {

// generate 1k sine wave per second

class SineWaveGenerator

{

public:

  static const int bytesPerSample = 2;

  static const int millisecondsPerSecond = PR_MSEC_PER_SEC;

  explicit SineWaveGenerator(uint32_t aSampleRate, uint32_t aFrequency) :

    mTotalLength(aSampleRate / aFrequency),

    mReadLength(0) {

    // If we allow arbitrary frequencies, there's no guarantee we won't get rounded here

    // We could include an error term and adjust for it in generation; not worth the trouble

    //MOZ_ASSERT(mTotalLength * aFrequency == aSampleRate);

    mAudioBuffer = MakeUnique<int16_t[]>(mTotalLength);

    for (int i = 0; i < mTotalLength; i++) {

      // Set volume to -20db. It's from 32768.0 * 10^(-20/20) = 3276.8

      mAudioBuffer[i] = (3276.8f * sin(2 * M_PI * i / mTotalLength));

    }

  }

  // NOTE: only safely called from a single thread (MSG callback)

  void generate(int16_t* aBuffer, TrackTicks aLengthInSamples) {

    TrackTicks remaining = aLengthInSamples;

    while (remaining) {

      TrackTicks processSamples = 0;

      if (mTotalLength - mReadLength >= remaining) {

        processSamples = remaining;

      } else {

        processSamples = mTotalLength - mReadLength;

      }

      memcpy(aBuffer, &mAudioBuffer[mReadLength], processSamples * bytesPerSample);

      aBuffer += processSamples;

      mReadLength += processSamples;

      remaining -= processSamples;

      if (mReadLength == mTotalLength) {

        mReadLength = 0;

      }

    }

  }

private:

  UniquePtr<int16_t[]> mAudioBuffer;

  TrackTicks mTotalLength;

  TrackTicks mReadLength;

};

} // namespace mozilla

#endif /* SINEWAVEGENERATOR_H_ */