Like Reauth

local AM = luajava.bindClass("com.theincgi.advancedMacros.AdvancedMacros")
local mc = AM:getMinecraft()
local session = (mc.getSession or mc.func_110432_I)(mc)
local username = (session.getUsername or session.func_111285_a)(session)
log( "Username is &a&B"..username )



local mcProxy = (mc.getProxy or mc.func_110437_J)(mc)

local YggAuthServ = luajava.bindClass("com.mojang.authlib.yggdrasil.YggdrasilAuthenticationService")
local UUID = luajava.bindClass("java.util.UUID")
local Agent = luajava.bindClass("com.mojang.authlib.Agent")
local ReflectionHelper = luajava.bindClass("net.minecraftforge.fml.relauncher.ReflectionHelper")
local randomUUID = UUID:randomUUID():toString()
local UUIDTypeAdapter = luajava.bindClass("com.mojang.util.UUIDTypeAdapter")
--local YggUserAuth =
--local YggSessServ

local yas = luajava.new(YggAuthServ, mcProxy, randomUUID )
local yua = yas:createUserAuthentication( Agent.MINECRAFT )
local ymss = yas:createMinecraftSessionService()

local function setSession( s ) --TODO check
  local sessionField = ReflectionHelper:findField(
    mc.getClass(), "session", "S", "field_71449_j"
  )
  sessionField.setAccessable(true)
  sessionField.set(mc, s )
end

local function loginOnline(user, pass)
  disconnect()
  yua:setUsername(user)
  yua:setPassword(pass) pass = nil
  a, b = pcall( yua.logIn, yua )
  if a then
    toast("Login","Success!")
    setSession( luajava.new(Session,
      yua:getSelectedProfile():getName(),
      UUIDTypeAdapter:fromUUID( yua:getSelectedProfile():getId() ),
      yua:getAuthenticatedToken(),
      yua:getUserType():getName()
    ))
    toast("Login","Session set!")
  else
    toast("Login","Fail'd")
  end
end

local function loginOffline(username)
  disconnect()
  local tmp = "OfflinePlayer:"..username --TODO FIX
  local uuid = UUID:fromString( tmp )
  toast("UUID", uuid)
  setSession( luajava.new(Session,
      username,
      uuid:toString() ,
      "invalid",
      "legacy"
    ))
    toast("Login","Offline done")
end

loginOffline("NotMyAccount")