#include "shorthand.h"
#include "bd-font.c"

//
// Memory sections.
//

// Defines for the different memory sections in the GBA.
#define MEM_SROM  0x00000000
#define MEM_EW    0x02000000
#define MEM_IW    0x03000000
#define MEM_IO    0x04000000
#define MEM_PAL   0x05000000
#define MEM_VRAM  0x06000000
#define MEM_OAM   0x07000000
#define MEM_PAK   0x08000000
#define MEM_CART  0x0E000000

//
// Display modes.
//

// Display modes.
#define DISP_MODE_0 0x0000
#define DISP_MODE_1 0x0001
#define DISP_MODE_2 0x0002
#define DISP_MODE_3 0x0003
#define DISP_MODE_4 0x0004
#define DISP_MODE_5 0x0005

// Layers.
#define DISP_BG0 0x0100
#define DISP_BG1 0x0200
#define DISP_BG2 0x0400
#define DISP_BG3 0x0800
#define DISP_OBJ 0x1000

static inline void
set_display_mode(u16 value) {
    *((vu32*)(MEM_IO + 0x0000)) = value;
}

// Screen settings.
#define SCREEN_WIDTH 240
#define SCREEN_HEIGHT 160

// The GBA in mode 3 expects rbg15 colors in the VRAM, where each component
// (RGB) have a 0--31 range. For example, pure red would be rgb15(31, 0, 0).
typedef u16 Color;

// We can treat the screen as a HxW matrix. With the following macro we can
// write a pixel to the screen at the (x, y) position using:
//
//     FRAMEBUFFER[y][x] = color;
//
typedef Color Scanline[SCREEN_WIDTH];
#define FRAMEBUFFER ((Scanline*)MEM_VRAM)

//
// Colors.
//

static inline Color
rgb15(u32 red, u32 green, u32 blue ) {
    return (blue << 10) | (green << 5) | red;
}

// Using bd-font, an 8x8 bitmap font.
static inline void
put_char(int x, int y, Color clr, u8 chr) {
    for (size_t i = 0; i < 8; ++i) {
        for (size_t j = 0; j < 8; ++j) {
            if ((font[chr][i] >> (7 - j)) & 0x1) {
                FRAMEBUFFER[y + i][x + j] = clr;
            }
        }
    }
}

static inline void
put_line(int x, int y, Color clr, char *msg) {
    int count = 0;
    while (*msg) {
        put_char(x + count, y, clr, *msg++);
        count += 8;
    }
}

//
// Main functions.
//

int main(void) {
    set_display_mode(DISP_MODE_3 | DISP_BG2);

    while(true) {
        put_line(16,  20 + 16, rgb15(28, 0, 0), "Hello world from the GBA!");
        put_line(16,  20 + 32, rgb15(0, 28, 28), "Using my little 8x8 bd-font");
        put_line(16,  20 + 64, rgb15(16, 0, 28), "Isn't that neat? :D");
    };

    return 0;
}