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

/**
 * Devices
 */
plex Terminal
  nat handle

plex Screen
  nat handle
  nat width
  nat height
  byte[] buffer

plex Mouse
  nat handle
  nat x
  nat y
  bool left
  bool right
  bool middle
  bool btn4
  nat size

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
  ptr screen = open(tmp_ptr, mode)

  nat screen_handle = screen.handle
  str tmp_str = nat_to_string(screen_handle)
  pln(tmp_str)

  nat width = screen.width
  tmp_str = nat_to_string(width)
  pln(tmp_str)

  nat buffer_size = screen.buffer
  tmp_str = nat_to_string(buffer_size)
  pln(tmp_str)

  nat offset_temp = 16
  nat screen_buffer = add_nat(screen, offset_temp)

  tmp_str = nat_to_string(screen_buffer)
  pln(tmp_str)

  // open mouse
  tmp_ptr = &mouse_namespace
  ptr mouse = open(tmp_ptr, mode)

  write(screen, screen_buffer, buffer_size) // redraw

  loop draw_loop
    // load mouse click data
    stat(mouse)

    byte left_down = mouse.left // load btn1 pressed

    jump_eq_nat(&draw_loop, left_down, mode) // mode is 0 which is an alias for false

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

    // Compute start address: y*width + x
    nat pixel_pos = mul_nat(y, width) 
    pixel_pos = add_nat(x, pixel_pos)
    pixel_pos = add_nat(screen_buffer, pixel_pos)
    nat fat_ptr_size = 4 // need to add offset for fat pointer size
    pixel_pos = add_nat(pixel_pos, fat_ptr_size)

    byte color = WHITE
    screen.buffer[pixel_pos] = color // draw color at screen [x,y]
    write(screen, screen_buffer, buffer_size) // redraw

    jump(&draw_loop)
  exit 0

function pln (str message)
	nat term_ns = &terminal_namespace // get terminal device
	int mode = 0
	ptr term = open(term_ns, mode)
	int msg_length = strlen(message)
	write(term, message, msg_length)
	str nl = &new_line
	int nl_length = strlen(nl)
	write(term, nl, nl_length)
	return