{-# LANGUAGE GADTs, DataKinds, TypeOperators #-}

module Events.Spec
       ( interpret
       , Spec, Cmnd(..), Expr(..), Elem(..)
       ) where

import Events.Types
import Events.Spec.Types
import Events.Spec.Eval

import Control.Monad ((<=<))
import Control.Monad.IO.Class
import Control.Monad.State.Lazy

import Data.Monoid
import Data.Foldable
import Control.Lens

import Debug.Trace

type Spec m = Expr (Eval m) '[] Cmnd -- most significant last

data Cmnd = COverride Object
          | COccurs Bool
          | CNop
          deriving (Show)

interpret :: MonadIO m => Spec m -> Eval m ()
interpret = join . fmap interpretCmnd . evalExpr

interpretCmnd :: MonadIO m => Cmnd -> Eval m ()
interpretCmnd (COverride obj) = objPayload ?= obj
interpretCmnd (COccurs b)     = objOccurs .= b
interpretCmnd _               = return ()