local component = require "component"
local sides = require "sides"

local tA = {...}

if #tA < 3 then
 io.stderr:write("usage: addalias <address> <side> <hostname>")
 return
end

local alines = {}

local f = io.open("/etc/talias","rb")
if f then
 for line in f:lines() do
  local lt = {}
  for word in line:gmatch("%S+") do
   lt[#lt+1] = word
  end
  alines[string.format("%s\t%s",table.remove(lt,1), table.remove(lt,1))] = lt
 end
 f:close()
end

local addr = component.get(tA[1])
local side = tonumber(tA[2]) or sides[tA[2]]
local aname = string.format("%s\t%s",addr,side)
alines[aname] = alines[aname] or {}
alines[aname][#alines[aname]+1] = tA[3]

local f = io.open("/etc/talias","wb")
for k,v in pairs(alines) do
 f:write(k)
 for _,w in ipairs(v) do
  f:write("\t"..w)
 end
 f:write("\n")
end
f:close()