Proxy object that wraps another object and delegates everything

proxy.lua

local Proxy = {}

function Proxy:new(wrapped)
   local instance = { __wrapped = wrapped }
   setmetatable(instance, self)
   return instance
end

function Proxy.__index(instance, attrname)
   local attr = instance.__wrapped[attrname]
   if type(attr) ~= 'function' then
      return attr
   else
      function wrapper(...)
         local t = {...}
         if select('#', ...) >= 1 and t[1] == instance then
            -- method call
            return attr(instance.__wrapped, unpack(t, 2))
         else
            -- function call
            return attr(...)
         end
      end
      -- cache and return wrapper function
      instance[attrname] = wrapper
      return wrapper
   end
end

return Proxy