#include <assert.h>

#include <SDL.h>

#include <stdbool.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

extern char DEBUG;

extern unsigned long long COUNTDOWN;

typedef struct {

unsigned char memory[64 * 1024];

// Pair orderings are important because you can use these in pairs: AF, BC, DE, HL.

// This assumes little-endian architecture since A should be most significant when reading AF.

unsigned char F;

unsigned char A;

unsigned char C;

unsigned char B;

unsigned char E;

unsigned char D;

unsigned char L;

unsigned char H;

unsigned short SP;

unsigned short PC;

int set_ime_after_n_instructions;

int unset_ime_after_n_instructions;

bool IME;

bool halted;

bool halt_di_bug;

unsigned long long global_simulated_ticks; // In CPU clock ticks.

int ticks_to_next_instruction;

SDL_Window* window;

SDL_Surface* window_surface;

} Gameboy;

#define REG_JOYP (0xFF00)

#define REG_SB (0xFF01)

#define REG_SC (0xFF02)

#define REG_DIV (0xFF04)

#define REG_TIMA (0xFF05)

#define REG_TMA (0xFF06)

#define REG_TAC (0xFF07)

#define REG_IF (0xFF0F)

#define REG_NR10 (0xFF10)

#define REG_NR11 (0xFF11)

#define REG_NR12 (0xFF12)

#define REG_NR14 (0xFF14)

#define REG_NR21 (0xFF16)

#define REG_NR22 (0xFF17)

#define REG_NR24 (0xFF19)

#define REG_NR30 (0xFF1A)

#define REG_NR31 (0xFF1B)

#define REG_NR32 (0xFF1C)

#define REG_NR33 (0xFF1E)

#define REG_NR41 (0xFF20)

#define REG_NR42 (0xFF21)

#define REG_NR43 (0xFF22)

#define REG_NR44 (0xFF23)

#define REG_NR50 (0xFF24)

#define REG_NR51 (0xFF25)

#define REG_NR52 (0xFF26)

#define REG_LCDC (0xFF40)

#define REG_STAT (0xFF41)

#define REG_SCY (0xFF42)

#define REG_SCX (0xFF43)

#define REG_LY (0xFF44)

#define REG_LYC (0xFF45)

#define REG_DMA (0xFF46)

#define REG_BGP (0xFF47)

#define REG_OBP0 (0xFF48)

#define REG_OBP1 (0xFF49)

#define REG_WY (0xFF4A)

#define REG_WX (0xFF4B)

#define REG_IE (0xFFFF)

#define CPU_AF_REF(c) ((unsigned short*)&(c)->F)

#define CPU_BC_REF(c) ((unsigned short*)&(c)->C)

#define CPU_DE_REF(c) ((unsigned short*)&(c)->E)

#define CPU_HL_REF(c) ((unsigned short*)&(c)->L)

#define CPU_AF(c) (*CPU_AF_REF(c))

#define CPU_BC(c) (*CPU_BC_REF(c))

#define CPU_DE(c) (*CPU_DE_REF(c))

#define CPU_HL(c) (*CPU_HL_REF(c))

#define BIT(v, index) (((v) >> (index)) & 1)

#define CPU_FLAG_Z(f) BIT((f), 7)

#define CPU_FLAG_N(f) BIT((f), 6)

#define CPU_FLAG_H(f) BIT((f), 5)

#define CPU_FLAG_C(f) BIT((f), 4)

#define CPU_F(z, n, h, c) ((z) << 7 | (n) << 6 | (h) << 5 | (c) << 4)

#define SET_BIT(v, index) ((v) | (1 << (index)))

#define UNSET_BIT(v, index) ((v) & ~(1 << (index)))

int gameboy_execute_instruction(Gameboy* gb);

void gameboy_read_mem(Gameboy* gb, unsigned short address, unsigned char* output, int len);

void gameboy_write_mem(Gameboy* gb, unsigned short address, unsigned char* data, int len);

#define GB_SCREEN_WIDTH (160)

#define GB_SCREEN_HEIGHT (144)

typedef struct {

unsigned char yplusheight;

unsigned char xpluswidth;

unsigned char tile;

unsigned char attributes;

} sprite;

#define VIDEO_OAM_OBJ_PRIORITY(f) BIT((f), 7)

#define VIDEO_OAM_Y_FLIP(f) BIT((f), 6)

#define VIDEO_OAM_X_FLIP(f) BIT((f), 5)

#define VIDEO_OAM_PALETTE_NUMBER(f) BIT((f), 4)

#define VIDEO_OAM_NUM_SPRITES (40)

#define VIDEO_TILE_0(gb, t) (gb->memory[0x8800 + ((char)t + 128) * 16])

#define VIDEO_TILE_1(gb, t) (gb->memory[0x8000 + (t) * 16])

#define VIDEO_BG_MAP(gb, map, x, y) (gb->memory[((map) ? 0x9c00 : 0x9800) + (y) * 32 + (x)])