local component_invoke = component.invoke
function boot_invoke(address, method, ...)
  local result = table.pack(pcall(component_invoke, address, method, ...))
  if not result[1] then
    return nil, result[2]
  else
    return table.unpack(result, 2, result.n)
  end
end

-- backwards compatibility, may remove later
local eeprom = component.list("eeprom")()
computer.getBootAddress = function()
  return boot_invoke(eeprom, "getData")
end
computer.setBootAddress = function(address)
  return boot_invoke(eeprom, "setData", address)
end

do
  local screen = component.list("screen")()
  local gpu = component.list("gpu")()
  if gpu and screen then
    boot_invoke(gpu, "bind", screen)
  end
end
local function tryLoadFrom(address)
  if component.type(address) == "filesystem" then
    local handle, reason = boot_invoke(address, "open", "/init.lua")
    if not handle then
      return nil, reason
    end
    local buffer = ""
    repeat
      local data, reason = boot_invoke(address, "read", handle, math.huge)
      if not data and reason then
        return nil, reason
      end
      buffer = buffer .. (data or "")
    until not data
    boot_invoke(address, "close", handle)
    return load(buffer, "=init")
  elseif component.type(address) == "tape_drive" then
    boot_invoke(address,"seek",-math.huge)
    local boottype = boot_invoke(address,"read",1)
    if boottype == "!" then
      local rl = tonumber(boot_invoke(address,"read",8))
      local buffer = boot_invoke(address,"read",rl)
      return load(buffer, "=init")
    end
  end
end

local bootdevs = {}
for address in component.list("filesystem") do
 bootdevs[#bootdevs+1] = address
end
for address in component.list("tape_drive") do
 bootdevs[#bootdevs+1] = address
end

do
 local gA,sA = component.list("gpu")(),component.list("screen")()
 if gA and sA then
  local gP,cy = component.proxy(gA),1
  gP.bind(sA)
  local sx, sy = gP.getResolution()
  gP.fill(1,1,sx,sy," ")
  local function wl(s)
   gP.set(1,cy,s)
   cy=cy+1
  end
  wl("SKS Enhanced BIOS v1")
  wl("Memory: "..tostring(computer.totalMemory()/1024).."K")
  wl(" ")
  for k,v in ipairs(bootdevs) do
   wl(tostring(k-1).." "..v.." "..component.type(v).." "..(component.invoke(v,"getLabel") or ""))
  end
  local timer = 5
  while computer.uptime() < timer do
   t,_,c = computer.pullSignal(0.5)
   if t == "key_down" and c > 47 and c < 58 then
    computer.setBootAddress(bootdevs[c-47])
    wl("Boot device set to "..bootdevs[c-47])
   elseif t == "key_down" and c == 32 then
    timer = timer + 10
   end
  end
 end
end

local init, reason
if computer.getBootAddress() then
  init, reason = tryLoadFrom(computer.getBootAddress())
end
if not init then
  computer.setBootAddress()
  for k,address in ipairs(bootdevs) do
    init, reason = tryLoadFrom(address)
    if init then
      computer.setBootAddress(address)
      break
    end
  end
end
if not init then
  error("no bootable medium found" .. (reason and (": " .. tostring(reason)) or ""), 0)
end
computer.beep(1000, 0.2)
init()