luabad

local inputlabels = {"A", "B", "Select", "Start", "Right", "Left", "Up", "Down"}

function get_lcd_status()
    memory.usememorydomain("System Bus")
    return memory.readbyte(0xFF40)
end

function determine_lcd_status()
	return bit.band(get_lcd_status(), 0x80)
end

function getinputbyte()
  if not movie.isloaded() then
    return 0
  end

  local t = movie.getinput(emu.framecount())
  local b = 0

  for i = 0, 7 do
    if t[inputlabels[i + 1]] then
      b = b + bit.lshift(1, i)
    end
  end

  return b
end

function tryinput(file)
	local input = getinputbyte()
	file:write(string.char(input))
    lastinput = input
end

local demo = io.open("bgb.dem", "wb")
local lastinput = -1

function lcdbad()
	if determine_lcd_status() ~= 0 then
	tryinput(demo)
	end
end

local vblank = 0x0040

while emu.framecount() <= movie.length() do
	event.onmemoryexecute(lcdbad, vblank)
	emu.frameadvance()
end

demo:close()

client.pause()