{-# LANGUAGE LambdaCase #-}
module System.Environment.Guard
(
guardSet,
guardSet_,
guardExpected,
guardExpected_,
guardPredicate,
guardPredicate_,
)
where
import Control.Monad (void)
import Data.Char (toLower)
import System.Environment (lookupEnv)
guardSet :: String -> IO a -> IO (Maybe a)
guardSet :: forall a. [Char] -> IO a -> IO (Maybe a)
guardSet [Char]
var = [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
forall a. [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
guardPredicate [Char]
var (Bool -> [Char] -> Bool
forall a b. a -> b -> a
const Bool
True)
guardSet_ :: String -> IO a -> IO ()
guardSet_ :: forall a. [Char] -> IO a -> IO ()
guardSet_ [Char]
var = IO (Maybe a) -> IO ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (IO (Maybe a) -> IO ()) -> (IO a -> IO (Maybe a)) -> IO a -> IO ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [Char] -> IO a -> IO (Maybe a)
forall a. [Char] -> IO a -> IO (Maybe a)
guardSet [Char]
var
guardExpected :: String -> String -> IO a -> IO (Maybe a)
guardExpected :: forall a. [Char] -> [Char] -> IO a -> IO (Maybe a)
guardExpected [Char]
var [Char]
expected = [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
forall a. [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
guardPredicate [Char]
var ([Char] -> [Char] -> Bool
eqCaseInsensitive [Char]
expected)
guardExpected_ :: String -> String -> IO a -> IO ()
guardExpected_ :: forall a. [Char] -> [Char] -> IO a -> IO ()
guardExpected_ [Char]
var [Char]
expected = IO (Maybe a) -> IO ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (IO (Maybe a) -> IO ()) -> (IO a -> IO (Maybe a)) -> IO a -> IO ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [Char] -> [Char] -> IO a -> IO (Maybe a)
forall a. [Char] -> [Char] -> IO a -> IO (Maybe a)
guardExpected [Char]
var [Char]
expected
guardPredicate_ :: String -> (String -> Bool) -> IO a -> IO ()
guardPredicate_ :: forall a. [Char] -> ([Char] -> Bool) -> IO a -> IO ()
guardPredicate_ [Char]
var [Char] -> Bool
p = IO (Maybe a) -> IO ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (IO (Maybe a) -> IO ()) -> (IO a -> IO (Maybe a)) -> IO a -> IO ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
forall a. [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
guardPredicate [Char]
var [Char] -> Bool
p
guardPredicate :: String -> (String -> Bool) -> IO a -> IO (Maybe a)
guardPredicate :: forall a. [Char] -> ([Char] -> Bool) -> IO a -> IO (Maybe a)
guardPredicate [Char]
var [Char] -> Bool
p IO a
io =
[Char] -> IO (Maybe [Char])
lookupEnv [Char]
var
IO (Maybe [Char]) -> (Maybe [Char] -> IO (Maybe a)) -> IO (Maybe a)
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
Just [Char]
result | [Char] -> Bool
p [Char]
result -> a -> Maybe a
forall a. a -> Maybe a
Just (a -> Maybe a) -> IO a -> IO (Maybe a)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> IO a
io
Maybe [Char]
_ -> Maybe a -> IO (Maybe a)
forall (f :: * -> *) a. Applicative f => a -> f a
pure Maybe a
forall a. Maybe a
Nothing
eqCaseInsensitive :: String -> String -> Bool
eqCaseInsensitive :: [Char] -> [Char] -> Bool
eqCaseInsensitive [Char]
a [Char]
b = (Char -> Char) -> [Char] -> [Char]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Char -> Char
toLower [Char]
a [Char] -> [Char] -> Bool
forall a. Eq a => a -> a -> Bool
== (Char -> Char) -> [Char] -> [Char]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Char -> Char
toLower [Char]
b