Mesen/Core/Mapper35.h

#pragma once
#include "stdafx.h"
#include "BaseMapper.h"
#include "CPU.h"
#include "PPU.h"

class Mapper35 : public BaseMapper
{
private:
	uint8_t _irqCounter;
	bool _irqEnabled;
	uint32_t _cyclesDown;
	uint32_t _lastCycle;

protected:
	virtual uint16_t GetPRGPageSize() { return 0x2000; }
	virtual uint16_t GetCHRPageSize() { return 0x0400; }

	void InitMapper()
	{
		_irqEnabled = false;
		_irqCounter = 0;
		_cyclesDown = 0;
		_lastCycle = 0;

		SelectPRGPage(3, -1);
	}

	void StreamState(bool saving)
	{
		BaseMapper::StreamState(saving);
		Stream(_irqCounter, _irqEnabled, _cyclesDown, _lastCycle);
	}

	void WriteRegister(uint16_t addr, uint8_t value)
	{
		switch(addr & 0xF007) {
			case 0x8000: case 0x8001: case 0x8002: case 0x8003:
				SelectPRGPage(addr & 0x03, value);
				break;

			case 0x9000: case 0x9001: case 0x9002: case 0x9003:
			case 0x9004: case 0x9005: case 0x9006: case 0x9007:
				SelectCHRPage(addr & 0x07, value);
				break;

			case 0xC002: 
				_irqEnabled = false;
				CPU::ClearIRQSource(IRQSource::External);
				break;

			case 0xC003: _irqEnabled = true; break;
			case 0xC005: _irqCounter = value; break;
			
			case 0xD001:
				SetMirroringType(value & 0x01 ? MirroringType::Horizontal : MirroringType::Vertical);
				break;
		}
	}
	
	virtual void NotifyVRAMAddressChange(uint16_t addr)
	{
		//MMC3-style A12 IRQ counter
		uint32_t cycle = PPU::GetFrameCycle();

		if((addr & 0x1000) == 0) {
			if(_cyclesDown == 0) {
				_cyclesDown = 1;
			} else {
				if(_lastCycle > cycle) {
					//We changed frames
					_cyclesDown += (89342 - _lastCycle) + cycle;
				} else {
					_cyclesDown += (cycle - _lastCycle);
				}
			}
		} else if(addr & 0x1000) {
			if(_cyclesDown > 8) {
				if(_irqEnabled) {
					_irqCounter--;
					if(_irqCounter == 0) {
						_irqEnabled = false;
						CPU::SetIRQSource(IRQSource::External);
					}
				}
			}
			_cyclesDown = 0;
		}
		_lastCycle = cycle;
	}

};