Mesen-X/Core/EPSGAudio.h

#pragma once
#include "stdafx.h"
#include "Snapshotable.h"
#include "APU.h"
#include "BaseExpansionAudio.h"
#include "SSGAudio.h"
#include "Console.h"

#include <array>
#include "ym3438.h"

using EPSGSSGAudio = SSGAudio<AudioChannel::EPSG_L, AudioChannel::EPSG_R>;

class EPSGAudio : public EPSGSSGAudio
{
private:
	ym3438_t _chip;

	int16_t _lastOutputs[2];
	int16_t _currentOutputs[2];

	double _clock;

	static constexpr uint8_t cycleCount = 24;

	struct InputEntry
	{
		uint8_t addr = 0;
		uint8_t data = 0;
		uint8_t cycle = 0;
		uint8_t wrote = 0;
	};

	static constexpr uint8_t INPUT_BUFFER_SIZE = cycleCount;
	using InputBuffer = std::array<InputEntry, INPUT_BUFFER_SIZE>;
	InputBuffer _inputBuffer;

	void UpdateOutputLevel()
	{
		int16_t summedOutput = 0;
		for (size_t x = 0; x < 2; x++)
		{
			_console->GetApu()->AddExpansionAudioDelta(x == 0 ? AudioChannel::EPSG_L : AudioChannel::EPSG_R, _currentOutputs[x] - _lastOutputs[x]);
			_lastOutputs[x] = _currentOutputs[x];
		}
	}

	uint8_t GetCurrentCycle() const
	{
		return static_cast<uint8_t>(std::floor(_clock)) % cycleCount;
	}

	void WriteToChip(uint8_t a, uint8_t d)
	{
		const auto cycle = GetCurrentCycle();

		if (_inputBuffer[cycle].wrote)
		{
			std::cout << "EPSG CHIP DOUBLE WRITE" << std::endl;
		}

		_inputBuffer[cycle] = {
			a,
			d,
			cycle,
			true
		};
	}

	uint32_t getClockFrequency()
	{
		return _console->GetSettings()->GetEPSGClockFrequency() / 6;
	}

protected:
	void StreamState(bool saving) override
	{
		EPSGSSGAudio::StreamState(saving);

		ArrayInfo<int16_t> lastOutputs{ _lastOutputs, 2 };
		ArrayInfo<int16_t> currentOutputs{ _currentOutputs, 2 };
		ArrayInfo<InputBuffer> inputBuffer{ &_inputBuffer };
		ValueInfo<ym3438_t> chip{ &_chip };
		ValueInfo<double> clock { &_clock };
		Stream(lastOutputs, currentOutputs, inputBuffer, chip, clock);
	}

	void ClockAudio() override
	{
		EPSGSSGAudio::ClockAudio();

		_clock += getClockFrequency() / (double)_console->GetCpu()->GetClockRate(_console->GetModel());

		while (_clock >= cycleCount)
		{
			for (uint8_t x = 0; x < 2; x++)
			{
				_currentOutputs[x] = 0;
			}

			for (uint8_t cycle = 0; cycle < cycleCount; cycle++)
			{
				_clock--;

				int16_t samples[2];
				OPN2_Clock(&_chip, samples);

				for (uint8_t x = 0; x < 2; x++)
				{
					_currentOutputs[x] += samples[x];
				}

				auto& input = _inputBuffer[cycle];
				if(input.wrote)
				{
					input.wrote = false;

					OPN2_Write(&_chip, input.addr, input.data);
				}
			}

			for (uint8_t x = 0; x < 2; x++)
			{
				_currentOutputs[x] /= 12;
			}

			UpdateOutputLevel();
		}
	}

	virtual uint32_t GetSSGClockFrequency()
	{
		return EPSGSSGAudio::GetSSGClockFrequency() * (_console->GetSettings()->GetEPSGClockFrequency() / 3579545.0 );
	}

public:
	EPSGAudio(shared_ptr<Console> console) : EPSGSSGAudio(console)
	{
		memset(_lastOutputs, 0, sizeof(_lastOutputs));
		memset(_currentOutputs, 0, sizeof(_currentOutputs));
		_inputBuffer = {};

		_clock = 0;

		OPN2_Reset(&_chip);
		OPN2_SetChipType(0);
	}

	void WriteRegister(uint16_t addr, uint8_t value)
	{
		EPSGSSGAudio::WriteRegister(addr, value);

		switch(addr) {
			case 0xC000:
			case 0xE000:
			case 0xC002:
			case 0xE002:

				const uint8_t a0 = (addr & 0xF000) == 0xE000;
				const uint8_t a1 = !!(addr & 0xF);

				WriteToChip(a0 | (a1 << 1), value);

				break;
		}
	}
};