gbemu/include/ppu.h

#pragma once

#include <common.h>

static const int LINES_PER_FRAME = 154;
static const int TICKS_PER_LINE = 456;
static const int YRES = 144;
static const int XRES = 160;

bool window_visible();

typedef enum {
    FS_TILE,
    FS_DATA0,
    FS_DATA1,
    FS_IDLE,
    FS_PUSH
} fetch_state;

typedef struct _fifo_entry {
    struct _fifo_entry *next;
    u32 value;
} fifo_entry;

typedef struct {
    fifo_entry *head;
    fifo_entry *tail;
    u32 size;  //32 bit color
} fifo;

typedef struct {
    fetch_state cur_fetch_state;
    fifo pixel_fifo;
    u8 line_x;
    u8 pushed_x;
    u8 fetch_x;
    u8 bgw_fetch_data[3];
    u8 fetch_entry_data[6]; //oam data
    u8 map_y;
    u8 map_x;
    u8 tile_y;
    u8 fifo_x;
    u8 lo_scroll_x; 
} pixel_fifo_context;

typedef struct {
    u8 y;
    u8 x;
    u8 tile;

    u8 f_cgb_pn : 3;
    u8 f_cgb_vram_bank : 1;
    u8 f_pn : 1;
    u8 f_x_flip : 1;
    u8 f_y_flip : 1;
    u8 f_bgp : 1;
} oam_entry;

typedef struct _oam_line_entry {
    oam_entry entry;
    struct _oam_line_entry *next;
} oam_line_entry;

typedef struct {
    oam_entry oam_ram[40];
    u8 vram[0x2000];

    u8 line_sprite_count; // 0 to 10 sprites
    oam_line_entry *line_sprites; //linked list of sprites
    oam_line_entry line_entry_array[10]; //memory to use for list
    
    u8 fetched_entry_count;
    oam_entry fetched_entries[3]; //entries fetched during pipeline
    u8 window_line;

    pixel_fifo_context pfc;

    u32 current_frame;
    u32 line_ticks;
    u32 *video_buffer;

    bool rendering_window;
    u32 target_frame_time;
    bool paused;
    bool frame;
    bool debug;
} ppu_context;

void ppu_init();
void ppu_tick();

void ppu_oam_write(u16 address, u8 value);
u8 ppu_oam_read(u16 address);

void ppu_vram_write(u16 address, u8 value);
u8 ppu_vram_read(u16 address);

ppu_context *ppu_get_context();