{-# LANGUAGE ViewPatterns, OverloadedStrings, FlexibleContexts #-}

module Utils
       ( showEntity
       , apply, apply'
       , entities
       ) where

import Data.Text (Text)
import qualified Data.Text as Text

import Data.PQueue.Prio.Max (MaxPQueue)
import qualified Data.PQueue.Prio.Max as MaxPQueue

import Data.Monoid (Monoid(..), (<>))

import Control.Monad.State.Class
import Control.Monad.Writer.Class

import Data.Set (Set)
import qualified Data.Set as Set

import Types

showEntity :: Entity -> Text
showEntity (Entity name number)
  | (Just (show -> n)) <- number = name <> " № " <> Text.pack n
  | otherwise = name

apply' :: (MonadState Sequence m, MonadWriter History m) => Alteration -> m ()
apply' alteration = do
  (newSt, hist) <- apply alteration <$> get
  tell hist
  put newSt

apply :: Alteration -> Sequence -> (Sequence, History)
apply alteration seq = undefined

entities :: MonadState Sequence m => m (Set Entity)
entities = Set.fromList . MaxPQueue.keys <$> get