Lua-automato

help = [[
Reference:
Using is pretty easy:
 Foo = require 'auto'

Creating the table with optional fields load/update/unload
 local t = {a = 10, b = 20}
 function t:load(x, y)
  self.x, self.y = x, y
 end
 function t:unload()
  self.x, self.y = self.a, self.b
 end

Creating another table
 local c = {}
 function c:load()
  Foo:set('t')
 end
 function c:unload()
  print('c exit')
 end

 Foo:new('t', t)
 Foo:new('c', c)
 Foo:set('t', 256, 128)
 -- t.x, t.y = 256, 128
 Foo:set('c')
 --> print 'c exit'
 -- t.x = t.a = 10, t.y = t.b = 20
]]

local automato = {}

local error = error
local function err(v, s)
    if not v then error(s, 2) end
end

setmetatable(automato,
    {__call =
        function(self)
            self.__index = self
            return setmetatable({states = {current = {}}}, self)
        end
    }
)

-- creating new state, (string )name using for set/get,
-- t contains any table with any parameters, but
-- fields load, update and unload must be a functions
--
function automato:new(name, t)
    err(type(name) == 'string', 'arg #1: statename string expected, got '..type(name))
    if t.load then err(type(t.load) == 'function', 'arg #2: load function expected, got '..type(t.load)) end
    if t.update then err(type(t.update) == 'function', 'arg #3: update function expected, got '..type(t.update)) end
    if t.unload then err(type(t.unload) == 'function', 'arg #4: unload function expected, got '..type(t.unload)) end
    self.states[name] = t
end

-- set state with any args
function automato:set(name, ...)
    err(self.states[name], 'State "'..name..'" does not exists', 3)
    if self.states.current.unload then self.states.current.unload(self.states.current) end
    self.states.current = self.states[name]
    if self.states.current.load then self.states.current.load(self.states.current, ...) end
end

-- return state with name or current [if nil]
function automato:get(name)
    return self.states.current[name] and self.states.current.name or self.states.current
end

-- update state with any args
function automato:update(...)
    if self.states.current.update then self.states.current.update(self.states.current, ...) end
end

return automato, help