const str screen_namespace = "/dev/screen/0";
const str mouse_namespace = "/dev/mouse/0";
const str terminal_namespace = "/dev/term/0";
const str new_line = "\n";
const byte WHITE = 255;

function main () {
  // open screen
  // use load immediate because it is a pointer to a string, not a value

  nat tmp_ptr = &screen_namespace;
  int mode = 0;
  plex screen = open(tmp_ptr, mode);

  nat screen_handle = screen.handle;
  str tmp_str = screen_handle as str;
  pln(tmp_str);

  nat width = screen.width;
  tmp_str = width as str;
  pln(tmp_str);

  nat buffer_size = screen.size;
  tmp_str = buffer_size as str;
  pln(tmp_str);

  nat screen_buffer = screen.buffer.ptr;
  tmp_str = screen_buffer as str;
  pln(tmp_str);

  // open mouse
  tmp_ptr = &mouse_namespace;
  plex mouse = open(tmp_ptr, mode);

  write(screen, screen_buffer, buffer_size); // redraw

  loop {
    // load mouse click data
    stat(mouse);

    byte left_down = mouse.left;

    if (left_down == 0) continue;

    nat x = mouse.x;
    nat y = mouse.y;

    // Compute start address: y*width + x
    nat pixel_pos = y * width;       // = y * width
    pixel_pos = x + pixel_pos; // += x
    pixel_pos = screen_buffer + pixel_pos; // += pixel_offset
    nat fat_ptr_size = 4; // need to add offset for fat pointer size
    pixel_pos = pixel_pos + fat_ptr_size;

    byte color = WHITE;
    store_absolute_8(pixel_pos, color); // draw color at screen [x,y]
    write(screen, screen_buffer, buffer_size); // redraw
  }
  exit(0);
}

function pln (str message) {
	nat term_ns = &terminal_namespace; // get terminal device
	int mode = 0;
	plex term = open(term_ns, mode);
	int msg_length = message.length;
	write(term, message, msg_length);
	str nl = &new_line;
	int nl_length = nl.length;
	write(term, nl, nl_length);
	return
}