local serial = require "serialization"
local minitel = require "minitel"
local event = require "event"
local rpc = {}
_G.rpcf = {}
rpc.port = 111

local function setacl(self, fname, host)
 self[fname] = self[fname] or {}
 self[fname][host] = true
end
-- function rpc.allow(fn, host) -- string string -- -- Enable the allow list for function *fname* and add *host* to it.
-- function rpc.deny(fn, host) -- string string -- -- Enable the deny list for function *fname* and add *host* to it.
rpc.allow = setmetatable({},{__call=setacl})
rpc.deny = setmetatable({},{__call=setacl})

local function isPermitted(host,fn)
 if rpc.allow[fn] then
  return rpc.allow[fn][host] or false
 end
 if rpc.deny[fn] and rpc.deny[fn][host] then
  return false
 end
 return true
end

local function rpcexec(_, from, port, data)
 if port ~= rpc.port then return false end
 os.spawn(function()
  local rpcrq = serial.unserialize(data) or {}
  if rpcf[rpcrq[1]] and isPermitted(from,rpcrq[1]) then
   os.setenv("RPC_CLIENT",from)
   minitel.send(from,port,serial.serialize({rpcrq[2],pcall(rpcf[rpcrq[1]],table.unpack(rpcrq,3))}))
  elseif type(rpcrq[2]) == "string" then
   minitel.send(from,port,serial.serialize({rpcrq[2],false,"function unavailable"}))
 end
 end,"rpc worker for "..tostring(from))
end
function rpcf.list()
 local rt = {}
 for k,v in pairs(rpcf) do
  rt[#rt+1] = k
 end
 return rt
end

function rpc.call(hostname,fn,...) -- string string -- boolean -- Calls exported function *fn* on host *hostname*, with parameters *...*, returning whatever the function returns, or false.
 if hostname == "localhost" then
  return rpcf[fn](...)
 end
 local rv = minitel.genPacketID()
 minitel.rsend(hostname,rpc.port,serial.serialize({fn,rv,...}),true)
 local st = computer.uptime()
 local rt = {}
 repeat
  local _, from, port, data = event.pull(30, "net_msg", hostname, rpc.port)
  rt = serial.unserialize(tostring(data)) or {}
 until (type(rt) == "table" and rt[1] == rv) or computer.uptime() > st + 30
 if rt[1] == rv then
  if rt[2] then
   return table.unpack(rt,3)
  end
  error(rt[3])
 end
 error("timed out")
end
function rpc.proxy(hostname,filter) -- string string -- table -- Returns a component.proxy()-like table from the functions on *hostname* with names matching *filter*.
 filter=(filter or "").."(.+)"
 local fnames = rpc.call(hostname,"list")
 if not fnames then return false end
 local rt = {}
 for k,v in pairs(fnames) do
  fv = v:match(filter)
  if fv then
   rt[fv] = function(...)
    return rpc.call(hostname,v,...)
   end
  end
 end
 return rt
end
function rpc.register(name,fn) -- string function -- -- Registers a function to be exported by the RPC library.
 local rpcrunning = false
 for k,v in pairs(os.tasks()) do
  if os.taskInfo(v).name == "rpc daemon" then
   rpcrunning = true
  end
 end
 if not rpcrunning then
  os.spawn(function()
   while true do
    pcall(rpcexec,event.pull("net_msg"))
   end
  end,"rpc daemon")
 end
 rpcf[name] = fn
end

function rpc.unregister(name) -- string -- -- Removes a function from the RPC function registry, clearing any ACL rules.
 rpcf[name] = nil
 rpc.allow[name] = nil
 rpc.deny[name] = nil
end

return rpc