local gpus,screens,ttyn,pids = {}, {}, 0, {}
local basepid = nil
local shell = require "shell"
local vtansi = require "vtansi"
local function scan()
 local w,di = pcall(computer.getDeviceInfo)
 if w then
  for a,t in pairs(component.list()) do
   if t == "gpu" then
    gpus[a] = gpus[a] or {false, tonumber(di[a].capacity)}
   elseif t == "screen" then
    screens[a] = screens[a] or {false, tonumber(di[a].capacity)}
   end
  end
 else
  dprint("no getDevInfo")
  for a,t in pairs(component.list()) do
   if t == "gpu" then
    gpus[a] = gpus[a] or {false, 8000}
   elseif t == "screen" then
    screens[a] = screens[a] or {false, 8000}
   end
  end
 end
end
local function nextScreen(n)
 local rt = {}
 for k,v in pairs(screens) do
  if not v[1] then
   rt[v[2]] = rt[v[2]] or k
  end
 end
 return rt[n] or rt[8000] or rt[2000] or rt[600]
end

local function spawnShell(fin,fout)
 io.input(fin)
 io.output(fout):setvbuf("no")
 print(_OSVERSION.." - "..tostring(math.floor(computer.totalMemory()/1024)).."K RAM")
 return os.spawn(shell.interactive, "shell: "..tostring(fin))
end

local function allocate()
 for k,v in pairs(gpus) do
  dprint(k)
  local sA = nextScreen(v[2])
  if v[1] == false and sA then
   local r,w = vtansi.vtsession(k,sA)
   devfs.register("tty"..tostring(ttyn), function() return r,w,function() end end)
   gpus[k][1] = true
   screens[sA][1] = true
   pids["tty"..tostring(ttyn)] = {-1}
   ttyn = ttyn + 1
  end
 end
end

function start()
basepid = os.spawn(function()
scan()
allocate()
dprint("screens ready")
while true do
 coroutine.yield()
 for k,v in pairs(pids) do
  if not os.taskInfo(v[1]) then
   dprint("Spawning new shell for "..k)
   pids[k][1] = spawnShell(v[2] or "/dev/"..k, v[3] or "/dev/"..k)
   pids[k][2], pids[k][3] = pids[k][2] or io.input(), pids[k][3] or io.output()
  end
 end
end
end,"getty")
return basepid
end
function stop()
 os.kill(basepid)
 basepid = nil
end