#pragma once

#include <cstdint>
#include <queue>


class NES;


const unsigned int VRAM_SIZE = 2048u;
const unsigned int PALETTE_SIZE = 8u;
const unsigned int OAM_SIZE = 256u;
const unsigned int VIDEO_WIDTH = 256u;
const unsigned int VIDEO_HEIGHT = 240u;
const unsigned int TOTAL_SCANLINES = 262u;
const unsigned int TOTAL_DOTS = 341u;


class PPU
{
public:
	PPU();
	enum Register
	{
		PPUCTRL = 0x00,
		PPUMASK = 0x01,
		PPUSTATUS = 0x02,
		OAMADDR = 0x03,
		OAMDATA = 0x04,
		PPUSCROLL = 0x05,
		PPUADDR = 0x06,
		PPUDATA = 0x07,
	};

	void Tick();
	void WriteRegister(Register reg, uint8_t value);
	uint8_t ReadRegister(Register reg);

	void WriteMemory(uint16_t address, uint8_t value);
	uint8_t ReadMemory(uint16_t address);

private:
	friend class NES;

	void FetchNT();
	void FetchAT();
	void FetchPTLow();
	void FetchPTHigh();
	void SetVBlank();
	void SetTileX();
	void SetTileY();
	void LoadBackground();
	void Draw();
	void IncrementTileX();
	void IncrementTileY();
	void ClearFlags();

	enum Event
	{
		FETCH_NT = 0x1,
		FETCH_AT = 0x2,
		FETCH_PT_LOW = 0x4,
		FETCH_PT_HIGH = 0x8,
		LOAD_BACKGROUND = 0x10,
		SHIFT_BACKGROUND = 0x20,
		SET_VBLANK = 0x40,
		SET_TILE_X = 0x80,
		SET_TILE_Y = 0x100,
		DRAW = 0x200,
		INCREMENT_TILE_X = 0x400,
		INCREMENT_TILE_Y = 0x800,
		CLEAR_FLAGS = 0x1000
	};

	struct PpuCtrl
	{
		void SetByte(uint8_t byte);

		uint16_t nametableBaseAddr;
		uint8_t vramAddrIncrement;
		uint8_t spritePatternTableAddr;
		uint8_t bgPatternTableAddr;
		uint8_t spriteSize;
		uint8_t masterSlaveSelect;
		uint8_t nmiEnable;
	};

	struct PpuMask
	{
		void SetByte(uint8_t byte);

		uint8_t grayscale;
		uint8_t showBackgroundLeft;
		uint8_t showSpritesLeft;
		uint8_t showBackground;
		uint8_t showSprites;
		uint8_t redEmphasis;
		uint8_t greenEmphasis;
		uint8_t blueEmphasis;
	};

	struct PpuStatus
	{
		uint8_t GetByte();

		uint8_t vblankStarted;
		uint8_t sprite0Hit;
		uint8_t spriteOverflow;
		uint8_t previousLsb;
	};

	struct Address
	{
		uint16_t GetValue();
		void SetValue(uint16_t value);

		uint8_t scrollFineY;
		uint8_t nametableX;
		uint8_t nametableY;
		uint8_t scrollCoarseX;
		uint8_t scrollCoarseY;
	};

	// External Registersgg
	PpuCtrl regPPUCTRL{}; // $2000, W
	PpuMask regPPUMASK{}; // $2001, W
	PpuStatus regPPUSTATUS{}; // $2002, R
	uint8_t regOAMADDR{}; // $2003, W
	uint8_t oldByte{};

	// Internal Registers
	Address currentAddress{};
	Address tempAddress{};
	uint8_t scrollFineX{};
	bool firstWrite{true};

	// Timing tracking
	uint32_t events[TOTAL_SCANLINES][TOTAL_DOTS]{};
	uint16_t currentCycle{};
	uint16_t currentScanline{};

	// Memory
	uint8_t ram[VRAM_SIZE]{};
	uint8_t palette[PALETTE_SIZE][4]{};
	uint8_t oam[OAM_SIZE]{};
	uint32_t video[VIDEO_WIDTH * VIDEO_HEIGHT]{};

	uint64_t frameNumber{};

	// Shift registers and latches
	uint16_t patternTableHighShift{};
	uint16_t patternTableLowShift{};
	uint8_t atShiftLow{};
	uint8_t atShiftHigh{};
	uint8_t nametableLatch{};
	uint8_t attributeTableLatch{};
	uint8_t attribute;
	uint8_t patternTableLowLatch{};
	uint8_t patternTableHighLatch{};


	NES* nes;
	void ShiftBG();
};