{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE QuantifiedConstraints #-}
{-# LANGUAGE ImpredicativeTypes #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE AllowAmbiguousTypes #-}

module Conftrack.Source (ConfigSource(..), SomeSource(..)) where

import Conftrack.Value (Key, Value(..), ConfigError(..))

import Control.Monad.State (StateT (..))
import Data.Text (Text)


class ConfigSource s where
  type SourceState s
  fetchValue :: Key -> s -> StateT (SourceState s) IO (Either ConfigError (Value, Text))
  leftovers :: s -> StateT (SourceState s) IO (Maybe [Key])

data SomeSource = forall source. ConfigSource source
   => SomeSource (source, SourceState source)