using Posix;

public class FramebufferDemo {
    private const int WIDTH = 720;
    private const int HEIGHT = 720;
    private const int BPP = 4; // BGRA = 4 bytes per pixel
    
    private int fb_fd;
    private uint8[] framebuffer;
    
    public FramebufferDemo() {
        // Open framebuffer device
        fb_fd = Posix.open("/dev/fb0", Posix.O_RDWR);
        if (fb_fd < 0) {
            GLib.stderr.printf("Error: Cannot open framebuffer device /dev/fb0\n");
            GLib.stderr.printf("Make sure you have permissions (try running with sudo)\n");
            return;
        }
        
        // Allocate framebuffer memory
        framebuffer = new uint8[WIDTH * HEIGHT * BPP];
        
        GLib.stdout.printf("Framebuffer opened successfully\n");
        GLib.stdout.printf("Resolution: %dx%d, Format: BGRA\n", WIDTH, HEIGHT);
    }
    
    ~FramebufferDemo() {
        if (fb_fd >= 0) {
            Posix.close(fb_fd);
        }
    }
    
    // Set a pixel at (x, y) with BGRA color
    public void set_pixel(int x, int y, uint8 b, uint8 g, uint8 r, uint8 a) {
        if (x < 0 || x >= WIDTH || y < 0 || y >= HEIGHT) {
            return;
        }
        
        int offset = (y * WIDTH + x) * BPP;
        framebuffer[offset + 0] = b; // Blue
        framebuffer[offset + 1] = g; // Green
        framebuffer[offset + 2] = r; // Red
        framebuffer[offset + 3] = a; // Alpha
    }
    
    // Fill entire screen with a color
    public void fill_screen(uint8 b, uint8 g, uint8 r, uint8 a) {
        for (int y = 0; y < HEIGHT; y++) {
            for (int x = 0; x < WIDTH; x++) {
                set_pixel(x, y, b, g, r, a);
            }
        }
    }
    
    // Draw a rectangle
    public void draw_rectangle(int x, int y, int w, int h, uint8 b, uint8 g, uint8 r, uint8 a) {
        for (int dy = 0; dy < h; dy++) {
            for (int dx = 0; dx < w; dx++) {
                set_pixel(x + dx, y + dy, b, g, r, a);
            }
        }
    }
    
    // Draw a circle
    public void draw_circle(int cx, int cy, int radius, uint8 b, uint8 g, uint8 r, uint8 a) {
        for (int y = -radius; y <= radius; y++) {
            for (int x = -radius; x <= radius; x++) {
                if (x * x + y * y <= radius * radius) {
                    set_pixel(cx + x, cy + y, b, g, r, a);
                }
            }
        }
    }
    
    // Update the framebuffer (write to /dev/fb0)
    public void update() {
        if (fb_fd < 0) {
            GLib.stderr.printf("Error: Framebuffer not opened\n");
            return;
        }
        
        // Seek to beginning of framebuffer
        Posix.lseek(fb_fd, 0, Posix.SEEK_SET);
        
        // Write framebuffer data
        ssize_t written = Posix.write(fb_fd, framebuffer, framebuffer.length);
        if (written < 0) {
            GLib.stderr.printf("Error writing to framebuffer\n");
        }
    }
    
    public bool is_open() {
        return fb_fd >= 0;
    }
    
    public static int main(string[] args) {
        var fb = new FramebufferDemo();
        
        if (!fb.is_open()) {
            return 1;
        }
        
        GLib.stdout.printf("Drawing demo graphics...\n");
        
        // Fill screen with black
        fb.fill_screen(0, 0, 0, 255);
        
        // Draw a red rectangle
        fb.draw_rectangle(100, 100, 200, 150, 0, 0, 255, 255);
        
        // Draw a green circle
        fb.draw_circle(500, 200, 80, 0, 255, 0, 255);
        
        // Draw a blue rectangle
        fb.draw_rectangle(200, 400, 300, 100, 255, 0, 0, 255);
        
        // Draw a yellow circle
        fb.draw_circle(360, 360, 100, 0, 255, 255, 255);
        
        // Update the framebuffer
        fb.update();
        
        GLib.stdout.printf("Graphics drawn! Press Enter to clear and exit...\n");
        GLib.stdin.read_line();
        
        // Clear screen before exit
        fb.fill_screen(0, 0, 0, 255);
        fb.update();
        
        GLib.stdout.printf("Done!\n");
        return 0;
    }
}