a generic, multi-source config interface

1 files changed, 38 insertions, 0 deletions

diff --git a/src/Conftrack/Value.hs b/src/Conftrack/Value.hs
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+++ b/src/Conftrack/Value.hs
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+{-# LANGUAGE DerivingStrategies #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+{-# LANGUAGE ImpredicativeTypes #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE AllowAmbiguousTypes #-}
+
+module Conftrack.Value (Value(..), ConfigError(..), Key(..), ConfigValue(..), Origin(..)) where
+
+import Data.Text(Text)
+import Data.List.NonEmpty (NonEmpty)
+
+data Value =
+  ConfigText Text
+  | ConfigInteger Integer
+  | ConfigOther Text Text
+  deriving Show
+
+newtype Key = Key (NonEmpty Text)
+  deriving newtype (Eq, Ord, Show)
+
+data ConfigError =
+  ParseError
+  | NotPresent
+  deriving Show
+
+class ConfigValue a where
+  fromConfig :: Value -> Either ConfigError a
+
+data Origin = Origin Key Text
+  deriving Show
+
+instance ConfigValue Text where
+  fromConfig (ConfigText a) = Right a
+  fromConfig _ = Left ParseError
+
+instance ConfigValue Integer where
+  fromConfig (ConfigInteger a) = Right a
+  fromConfig _ = Left ParseError