pre/post method hooks in Lua for AOP

aspect.lua

--
-- dog
--
local dog = {}

function dog.new()
  return setmetatable({ name = 'dog' }, { __index = dog })
end
function dog:run()
  print("* " .. self.name .. " is running *")
end
function dog:sit(time)
  print("* " .. self.name .. " is sitting for " .. time .. " seconds *")
end

--
-- poodle
--
local poodle = setmetatable({}, { __index = dog })

function poodle.new()
  return setmetatable({ name = 'poodle' }, { __index = poodle })
end

--
-- doberman
--
local doberman = setmetatable({}, { __index = dog })

function doberman.new()
  return setmetatable({ name = 'doberman' }, { __index = doberman })
end

--
-- aspect
--
local aspect = { mt = {} }
aspect.mt.__index = aspect

-- syntactic sugar
function aspect.mt.__call(asp, t)
  return asp:apply(t)
end

function aspect.new(t)
  local instance = {}
  for k,v in pairs(t) do
    instance[k] = v
  end
  return setmetatable(instance, aspect.mt)
end

function aspect:apply(t)
  for k,v in pairs(self) do
    local tv = t[k]
    if type(tv) == 'function' then
      local asp = self[k]
      local prf
      local pof
      if asp.pre then
        prf = function(...)
          return tv(asp.pre(...))
        end
      else
        prf = tv
      end
      if asp.post then
        pof = function(...)
          return asp.post(prf(...))
        end
      else
        pof = prf
      end
      t[k] = pof
    end
  end
  return t
end

--
-- limping
--
local limping = aspect.new({
  run = {
    post = function()
      print("YELP!")
    end
  },
  sit = {
    pre = function(...)
      local instance = select(1, ...)
      local time     = select(2, ...)
      return instance, time * 50
    end
  }
})

--
-- main
--
local a = poodle.new()
local b = limping( doberman.new() )

a:run()
a:sit(10)
b:run()
b:sit(10)