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

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

  ptr tmp_ptr $0 = &screen_namespace
  int mode $1 = 0
  ptr screen $2 = open tmp_ptr mode 

  nat screen_handle $3 = @memory.u32[screen + 4]
  str tmp_str $4 = nat_to_string screen_handle 
  pln(tmp_str)

  nat width $5 = @memory.u32[screen + 8]
  tmp_str = nat_to_string width 
  pln(tmp_str)

  nat buffer_size $6 = @memory.u32[screen + 12]
  tmp_str = nat_to_string buffer_size 
  pln(tmp_str)

  nat offset_temp $7 = 16
  ptr 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 $8 = open tmp_ptr mode

  write screen screen_buffer buffer_size // redraw

  loop draw_loop
    // load mouse click data
    stat mouse

    bool left_down $9 = @memory.u8[mouse + 16] // load btn1 pressed

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

    nat x $10 = @memory.u32[mouse + 8]
    nat y $11 = @memory.u32[mouse + 12]

    // Compute start address: y*width + x
    nat pixel_pos $12 = mul_nat y width 
    pixel_pos = add_nat x pixel_pos
    pixel_pos = add_nat screen_buffer pixel_pos
    nat fat_ptr_size $13 = 4 // need to add offset for fat pointer size
    pixel_pos = add_nat pixel_pos fat_ptr_size

    byte color $14 = @memory.u8[ &WHITE ]
    @memory.u8[pixel_pos] = color // draw color at screen [xy]
    write screen screen_buffer buffer_size // redraw

    jump &draw_loop
  exit 0

function pln (str message $0)
	nat term_ns $1 = &terminal_namespace // get terminal device
	int mode $2 = 0
	ptr term $3 = open term_ns mode
	int msg_length $4 = strlen message
	write term message msg_length
	str nl $5 = &new_line
	int nl_length $6 = strlen nl
	write term nl nl_length
	return