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{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE QuantifiedConstraints #-}
{-# LANGUAGE ImpredicativeTypes #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE OverloadedStrings #-}
-- | A trivial source reading from a @Map Key Value@, only useful as a demonstration or for tests.
module Conftrack.Source.Trivial where
import Conftrack.Value (Key, Value(..), ConfigError(..))
import Conftrack.Source (SomeSource(..), ConfigSource (..))
import Control.Monad.State (get, modify, MonadState (..))
import Data.Map.Strict (Map)
import qualified Data.Map.Strict as M
import Data.Function ((&))
import qualified Data.Text as T
newtype Trivial = Trivial (Map Key Value)
mkTrivialSource :: [(Key, Value)] -> SomeSource
mkTrivialSource pairs = SomeSource (source, [])
where source = Trivial (M.fromList pairs)
instance ConfigSource Trivial where
type SourceState Trivial = [Key]
fetchValue key (Trivial tree) = do
case M.lookup key tree of
Nothing -> pure $ Left (NotPresent key)
Just val -> do
modify (key :)
pure $ Right (val, "Trivial source with keys "<> T.pack (show (M.keys tree)))
leftovers (Trivial tree) = do
used <- get
M.keys tree
& filter (`notElem` used)
& Just
& pure
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