nesemu/include/ppu.h

//
// Created by william on 12/30/23.
//

#include <stdbool.h>
#include <stddef.h>
#include "types.h"

#ifndef NESEMULATOR_PPU_H
#define NESEMULATOR_PPU_H

#define PPU_REGISTER_SIZE 0x8
#define PPU_VRAM_SIZE 0x4000
#define PPU_OAM_SIZE 0xff
#define PPU_RAM_BASE_ADDR 0x2000
#define PPU_RAM_MAX_ADDR 0x4000
#define PPU_RAM_BANK_SIZE 0x8
#define PPU_RAM_BANK_COUNT ((PPU_RAM_MAX_ADDR - PPU_RAM_BASE_ADDR) / PPU_RAM_BANK_SIZE)

#define PPU_REGISTER_CTRL 0x00
#define PPU_REGISTER_MASK 0x01
#define PPU_REGISTER_STATUS 0x02
#define PPU_REGISTER_OAM_ADDR 0x03
#define PPU_REGISTER_OAM_DATA 0x04
#define PPU_REGISTER_SCROLL 0x05
#define PPU_REGISTER_ADDR 0x06
#define PPU_REGISTER_DATA 0x07

#define PPU_CTRL_SCROLL_X 0x1
#define PPU_CTRL_SCROLL_Y 0x2
#define PPU_CTRL_BASE_NAMETABLE_ADDR 0x3
#define PPU_CTRL_VRAM_ADDR_INCREMENT 0x4
#define PPU_CTRL_SP_PATTERN_TABLE_ADDR 0x8
#define PPU_CTRL_BG_PATTERN_TABLE_ADDR 0x10
#define PPU_CTRL_SP_SIZE 0x20
#define PPU_CTRL_MODE_SELECT 0x40
#define PPU_CTRL_GEN_VBLANK_NMI 0x80

#define PPU_MASK_GREYSCALE 0x1
#define PPU_MASK_SHOW_BG_LEFT 0x2
#define PPU_MASK_SHOW_SP_LEFT 0x4
#define PPU_MASK_SHOW_BG 0x8
#define PPU_MASK_SHOW_SP 0x10
#define PPU_MASK_EMP_RED 0x20
#define PPU_MASK_EMP_GREEN 0x40
#define PPU_MASK_EMP_BLUE 0x80

#define PPU_STATUS_OPEN_BUS 0x1f
#define PPU_STATUS_SP_OVERFLOW 0x20
#define PPU_STATUS_SP_0_HIT 0x40
#define PPU_STATUS_VBLANK 0x80

#define PPU_MASK_NONE 0xff

#define PATTERN_TABLE_BYTES_SIZE 0x1000
#define NAMETABLE_BYTES_SIZE 0x0400
#define PALETTE_TABLE_BYTES_SIZE 0x0020

typedef struct ppu_memory {
    byte nametable_0[NAMETABLE_BYTES_SIZE];
    byte nametable_1[NAMETABLE_BYTES_SIZE];
    byte palette[PALETTE_TABLE_BYTES_SIZE];
} PPUMemory;

typedef struct ppu_tile_fetch {
    byte tile_id;
    byte attribute_table;
    byte pattern_table_tile_low;
    byte pattern_table_tile_high;
} PPUTileFetch;

#if DEBUG
typedef union {
    struct {
        byte tile_debugger: 1;
        byte tile_debugger_pattern_half: 2;
    } flags;
    byte flags_byte;
} PPUDebugFlags;
#endif

typedef struct ppu {
    PPUMemory memory;
    pixel pixels[256 * 240];

    byte registers[8];
    byte oam_dma_register;
    byte oam[PPU_OAM_SIZE];
    bool odd_frame;
    byte x_scroll;
    byte fine_x_scroll;
    byte y_scroll;
    byte x;
    bool w;

    byte ppu_addr_increment;
    address ppu_address;
    address temp_ppu_addr;
    address bg_pattern_table_addr;

    PPUTileFetch fetch;
    unsigned long frame;
    unsigned int scanline;
    unsigned int cycle;

#if DEBUG
    PPUDebugFlags debug;
#endif
} PPU;

PPU *ppu_get_state();

/**
 * Initializes the PPU, according to the power up state.
 * https://www.nesdev.org/wiki/PPU_power_up_state
 *
 * @param ppu
 */
void ppu_init();

/**
 * Cycles the PPU.
 *
 * @param ppu
 * @param ram
 */
void ppu_cycle();

/**
 * Read a flag from the PPU registers.
 *
 * @param reg The register index
 * @param mask The flag mask
 */
bool ppu_read_flag(size_t reg, byte mask);

byte ppu_read_reg(byte reg);

void ppu_write_reg(byte reg, byte data);

void ppu_write_oamaddr(byte data);

void ppu_write(address addr, byte data);

#endif //NESEMULATOR_PPU_H