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{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE QuantifiedConstraints #-}
{-# LANGUAGE ImpredicativeTypes #-}
{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE RecordWildCards #-}
module Conftrack
( Config(..)
, Warning(..)
, runFetchConfig
, readValue
, readOptionalValue
, readRequiredValue
, readNested
, SomeSource
, ConfigError(..)
, Key(..)
, Value(..)
, configKeysOf
) where
import Conftrack.Value (ConfigError(..), ConfigValue(..), Key (..), Origin(..), Value(..), KeyPart, prefixedWith)
import Conftrack.Source (SomeSource (..), ConfigSource (..))
import Prelude hiding (unzip)
import Control.Monad.State (StateT (..))
import Data.Functor ((<&>))
import Data.List.NonEmpty (NonEmpty, unzip)
import qualified Data.List.NonEmpty as NonEmpty
import Control.Monad (forM, (>=>))
import Data.Either (isRight)
import Data.Text (Text)
import qualified Data.Text as T
import Data.Maybe (isJust, mapMaybe)
class Config a where
readConfig :: Fetch a
data FetcherState = FetcherState
{ fetcherSources :: [SomeSource]
, fetcherPrefix :: [KeyPart]
, fetcherOrigins :: [Origin]
, fetcherWarnings :: [Warning]
, fetcherErrors :: [ConfigError]
}
newtype Fetch a = Fetch (FetcherState -> IO (a, FetcherState))
deriving (Functor)
newtype Warning = Warning Text
deriving Show
instance Applicative Fetch where
pure a = Fetch (\s -> pure (a, s))
liftA2 f (Fetch m) (Fetch n) = Fetch $ \s -> do
(a, s2) <- m s
(b, s3) <- n s2
pure (f a b, s3)
runFetchConfig :: forall a. Config a => NonEmpty SomeSource -> IO (Either [ConfigError] (a, [Origin], [Warning]))
runFetchConfig sources = do
let (Fetch m) = readConfig @a
(result, FetcherState sources2 _ origins warnings errors) <- m (FetcherState (NonEmpty.toList sources) [] [] [] [])
unusedWarnings <- collectUnused sources2
if null errors
then pure $ Right (result, origins, unusedWarnings <> warnings)
else pure $ Left errors
configKeysOf :: forall a. Config a => IO [Key]
configKeysOf = do
let (Fetch m) = readConfig @a
(_, FetcherState _ _ origins warnings errors) <- m (FetcherState [] [] [] [] [])
let keys = mapMaybe (\case {(NotPresent key) -> Just key; _ -> Nothing }) errors
pure keys
readOptionalValue :: ConfigValue a => Key -> Fetch (Maybe a)
readOptionalValue bareKey = Fetch $ \s1@FetcherState{..} -> do
let key = bareKey `prefixedWith` fetcherPrefix
stuff <- firstMatchInSources key fetcherSources
let (maybeValues, sources) = unzip stuff
let values = maybeValues <&> \case
Right (val, text) -> fromConfig val <&> (\val -> (val, Origin key text))
Left e -> Left e
val <- case fmap (\(Right a) -> a) $ filter isRight values of
[] -> pure (Nothing, Origin key "default value")
(value, origin):_ -> pure (Just value, origin)
pure (fst val, s1 { fetcherSources = sources, fetcherOrigins = snd val : fetcherOrigins })
readRequiredValue :: ConfigValue a => Key -> Fetch a
readRequiredValue key =
let
Fetch m = readOptionalValue key
in
Fetch (m >=> (\(a, s) -> case a of
Nothing ->
let
dummy = error "A nonexisting config value was evaluated. This is a bug."
in
pure (dummy, s { fetcherErrors = NotPresent (key `prefixedWith` fetcherPrefix s) : fetcherErrors s })
Just v -> pure (v, s)))
readValue :: forall a. ConfigValue a => a -> Key -> Fetch a
readValue defaultValue key =
let
Fetch m = readOptionalValue @a key
in
Fetch (m >=> (\(a, s) -> case a of
Just val -> pure (val, s)
Nothing -> do
pure (defaultValue, s { fetcherOrigins = Origin (key `prefixedWith` fetcherPrefix s) "default value" : fetcherOrigins s })))
firstMatchInSources :: Key -> [SomeSource] -> IO [(Either ConfigError (Value, Text), SomeSource)]
firstMatchInSources _ [] = pure []
firstMatchInSources key (SomeSource (source, sourceState):sources) = do
(eitherValue, newState) <- runStateT (fetchValue key source) sourceState
case eitherValue of
Left _ -> do
firstMatchInSources key sources
<&> (\a -> (eitherValue, SomeSource (source, newState)) : a)
Right _ ->
pure $ (eitherValue, SomeSource (source, newState)) : fmap (Left Shadowed ,) sources
readNested :: forall a. Config a => Key -> Fetch a
readNested (Key prefix') = Fetch $ \s1 -> do
let (Fetch nested) = readConfig @a
(config, s2) <- nested (s1 { fetcherPrefix = fetcherPrefix s1 <> NonEmpty.toList prefix' })
pure (config, s2 { fetcherPrefix = fetcherPrefix s1 })
collectUnused :: [SomeSource] -> IO [Warning]
collectUnused sources = do
forM sources (\(SomeSource (source, sourceState)) ->
runStateT (leftovers source) sourceState <&> fst)
<&> fmap (\(Just a) -> Warning $ "Unused Keys " <> T.pack (show a))
. filter (\(Just a) -> not (null a))
. filter isJust
|
