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 init, reason
if computer.getBootAddress() then
  init, reason = tryLoadFrom(computer.getBootAddress())
end
if not init then
  computer.setBootAddress()
  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
  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()