module Env.Parse
( Parser(..)
, VarF(..)
, parsePure
, Mod(..)
, prefixed
, var
, Var(..)
, defaultVar
, Reader
, str
, nonempty
, auto
, def
, helpDef
, flag
, switch
, Flag
, HasHelp
, help
) where
import Control.Applicative
import Control.Monad ((<=<))
import Data.Map (Map)
import qualified Data.Map as Map
#if __GLASGOW_HASKELL__ < 710
import Data.Monoid (Monoid(..))
#endif
import Data.String (IsString(..))
import Env.Free
import qualified Env.Error as Error
import Env.Val
parsePure :: Parser e b -> [(String, String)] -> Either [(String, e)] b
parsePure (Parser p) (Map.fromList -> env) =
toEither (runAlt go p)
where
go v = maybe id (\d x -> x <|> pure d) (varfDef v) (fromEither (readVar v env))
readVar :: VarF e a -> Map String String -> Either [(String, e)] a
readVar VarF {varfName, varfReader} =
mapLeft (pure . (\err -> (varfName, err))) . varfReader varfName
mapLeft :: (a -> b) -> Either a t -> Either b t
mapLeft f =
either (Left . f) Right
newtype Parser e a = Parser { unParser :: Alt (VarF e) a }
deriving (Functor)
instance Applicative (Parser e) where
pure = Parser . pure
Parser f <*> Parser x = Parser (f <*> x)
instance Alternative (Parser e) where
empty = Parser empty
Parser f <|> Parser x = Parser (f <|> x)
prefixed :: String -> Parser e a -> Parser e a
prefixed pre =
Parser . hoistAlt (\v -> v { varfName = pre ++ varfName v }) . unParser
data VarF e a = VarF
{ varfName :: String
, varfReader :: String -> Map String String -> Either e a
, varfHelp :: Maybe String
, varfDef :: Maybe a
, varfHelpDef :: Maybe String
} deriving (Functor)
type Reader e a = String -> Either e a
lookupVar :: Error.AsUnset e => String -> Map String String -> Either e String
lookupVar name =
maybe (Left Error.unset) Right . Map.lookup name
var :: Error.AsUnset e => Reader e a -> String -> Mod Var a -> Parser e a
var r n (Mod f) = Parser . liftAlt $ VarF
{ varfName = n
, varfReader = \name -> r <=< lookupVar name
, varfHelp = varHelp
, varfDef = varDef
, varfHelpDef = varHelpDef <*> varDef
}
where
Var { varHelp, varDef, varHelpDef } = f defaultVar
flag
:: forall e a. (Error.AsUnset e, Error.AsEmpty e)
=> a
-> a
-> String -> Mod Flag a -> Parser e a
flag f t n (Mod g) = Parser . liftAlt $ VarF
{ varfName = n
, varfReader = \name -> Right . either (const f) (const t) . (nonempty :: Reader e String) <=< lookupVar name
, varfHelp = flagHelp
, varfDef = Just f
, varfHelpDef = Nothing
}
where
Flag { flagHelp } = g defaultFlag
switch :: (Error.AsUnset e, Error.AsEmpty e) => String -> Mod Flag Bool -> Parser e Bool
switch = flag False True
str :: IsString s => Reader e s
str = Right . fromString
nonempty :: (Error.AsEmpty e, IsString s) => Reader e s
nonempty = fmap fromString . go where go [] = Left Error.empty; go xs = Right xs
auto :: (Error.AsUnread e, Read a) => Reader e a
auto = \s -> case reads s of [(v, "")] -> Right v; _ -> Left (Error.unread (show s))
newtype Mod t a = Mod (t a -> t a)
instance Monoid (Mod t a) where
mempty = Mod id
mappend (Mod f) (Mod g) = Mod (g . f)
data Var a = Var
{ varHelp :: Maybe String
, varHelpDef :: Maybe (a -> String)
, varDef :: Maybe a
}
defaultVar :: Var a
defaultVar = Var
{ varHelp = Nothing
, varDef = Nothing
, varHelpDef = Nothing
}
def :: a -> Mod Var a
def d = Mod (\v -> v { varDef = Just d })
data Flag a = Flag
{ flagHelp :: Maybe String
}
defaultFlag :: Flag a
defaultFlag = Flag { flagHelp = Nothing }
helpDef :: (a -> String) -> Mod Var a
helpDef d = Mod (\v -> v { varHelpDef = Just d })
class HasHelp t where
setHelp :: String -> t a -> t a
instance HasHelp Var where
setHelp h v = v { varHelp = Just h }
instance HasHelp Flag where
setHelp h v = v { flagHelp = Just h }
help :: HasHelp t => String -> Mod t a
help = Mod . setHelp