#include "../syscall.h"
#include "../drivers/vga.h"
#include <stdint.h>

enum {
    FRAME_SIZE = VGA_GRAPHICS_WIDTH * VGA_GRAPHICS_HEIGHT,
    BLOCK_WIDTH = 270,
    BLOCK_HEIGHT = 100,
    BLOCK_X = 10,
    BLOCK_Y = 0,
};

// Non-zero initializer keeps the framebuffer in the program image, which this
// loader maps more reliably than a large BSS object.
static uint8_t frame[FRAME_SIZE] = { 1 };

static uint32_t time_ms(void) {
    return (uint32_t)syscall(SYS_time_ms, 0);
}

static void clear_frame(uint8_t color) {
    for (uint32_t i = 0; i < FRAME_SIZE; i++) {
        frame[i] = color;
    }
}

static void put_pixel(int x, int y, uint8_t color) {
    if (x < 0 || x >= VGA_GRAPHICS_WIDTH || y < 0 || y >= VGA_GRAPHICS_HEIGHT) {
        return;
    }
    frame[y * VGA_GRAPHICS_WIDTH + x] = color;
}

static void draw_demo(void) {
    clear_frame(0x01);

    for (int y = 0; y < BLOCK_HEIGHT; y++) {
        for (int x = 0; x < BLOCK_WIDTH; x++) {
            int screen_x = BLOCK_X + x;
            int screen_y = BLOCK_Y + y;
            uint8_t color = (uint8_t)((x + 2 * y) & 0x3f);

            if (x < 3 || y < 3 || x >= BLOCK_WIDTH - 3 || y >= BLOCK_HEIGHT - 3) {
                color = 0x3f;
            }
            put_pixel(screen_x, screen_y, color);
        }
    }
}

int main(void) {
    syscall(SYS_switch_to_graphics, 0);
    draw_demo();
    syscall(SYS_swap_frame, (uintptr_t)frame);

    uint32_t start = time_ms();
    while ((uint32_t)(time_ms() - start) < 2000) {
    }

    return 0;
}