{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE FlexibleContexts #-}
module Module.Environment (
      Environment(..)
    , HasEnvironment
    , empty
    , register
    , reorder
  ) where

import Context (Path)
import Control.Monad.State (MonadState, modify)
import Data.Map (Map)
import qualified Data.Map as Map (empty, insert)
import Priority (Queue)
import qualified Priority (empty)

data Environment a = Environment {
      modules :: Map Path a
    , queue :: Queue Path
  }

type HasEnvironment a = MonadState (Environment a)

register :: HasEnvironment a m => Path -> a -> m ()
register path module_ = modify $ \moduleSpace -> moduleSpace {
    modules = Map.insert path module_ (modules moduleSpace)
  }

reorder :: HasEnvironment a m => (Queue Path -> Queue Path) -> m ()
reorder f = modify $ \moduleSpace -> moduleSpace {
    queue = f (queue moduleSpace)
  }

empty :: Environment a
empty = Environment {
      modules = Map.empty
    , queue = Priority.empty
  }