local component, error, math, select = component, error, math, select
local cl, ci, ct = component.list, component.invoke, component.type

local function bail(msg, ...)
	if select('#', ...) > 0 then
		msg = msg:format(...)
	end
	return error(msg, 0)
end
local function unique(addr1, addr2, what)
	if addr1 and addr2 then
		return bail('multiple %s: %s, %s', what, addr1, addr2)
	end
	return addr1 or addr2 or bail('no %s', what)
end

local eeprom
for addr in cl('eeprom') do eeprom = unique(eeprom, addr, 'eeproms') end
eeprom = unique(eeprom, nil, 'eeprom')

local data = ci(eeprom, 'getData')
local bootfs, bootpath
if data == '' then
	for fs in cl('filesystem') do
		if ci(fs, 'exists', '/init.lua') then
			bootfs = unique(bootfs, fs, 'bootable filesystems')
			bootpath = '/init.lua'
		end
	end
	bootfs = unique(bootfs, nil, 'bootable filesystem')
else
	local split = data:find(':')
	if split then
		bootfs, bootpath = data:sub(1, split - 1), data:sub(split + 1)
	else
		bootfs, bootpath = data, '/init.lua'
	end
	local ty, err = ct(bootfs)
	if not ty then bail('bootfs %s absent', bootfs) end
	if ty ~= 'filesystem' then bail('bootfs %s is a %s', bootfs, ty) end
end

--polyfill {get,set}BootAddress like openloader does
--lua bios says these are for "backwards compatibility", but neither [lua bios, openloader] provide
--other ways to find the boot filesystem and both [openos, plan9k] call getBootAddress during boot
function computer.getBootAddress()
	return bootfs
end
function computer.setBootAddress(addr)
	return ci(eeprom, 'setData', addr)
end

local fd, err = ci(bootfs, 'open', bootpath)
if not fd then bail('open %s:%s failed: %s', bootfs:sub(1, 8), bootpath, err) end
local code = ''
local lots = math.maxinteger or math.huge --read as much as possible
repeat
	local chunk, err = ci(bootfs, 'read', fd, lots)
	if err then bail('read %s:%s failed: %s', bootfs:sub(1, 8), bootpath, err) end
	code = code .. (chunk or '')
until not chunk
ci(bootfs, 'close', fd)
local fn = assert(load(code, '@' .. bootpath))
return fn(bootfs, bootpath)