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+{- portable environment variables
+ -
+ - Copyright 2013 Joey Hess <joey@kitenet.net>
+ -
+ - License: BSD-2-clause
+ -}
+
+{-# LANGUAGE CPP #-}
+
+module Utility.Env where
+
+#ifdef mingw32_HOST_OS
+import Utility.Exception
+import Control.Applicative
+import Data.Maybe
+import qualified System.Environment as E
+#else
+import qualified System.Posix.Env as PE
+#endif
+
+getEnv :: String -> IO (Maybe String)
+#ifndef mingw32_HOST_OS
+getEnv = PE.getEnv
+#else
+getEnv = catchMaybeIO . E.getEnv
+#endif
+
+getEnvDefault :: String -> String -> IO String
+#ifndef mingw32_HOST_OS
+getEnvDefault = PE.getEnvDefault
+#else
+getEnvDefault var fallback = fromMaybe fallback <$> getEnv var
+#endif
+
+getEnvironment :: IO [(String, String)]
+#ifndef mingw32_HOST_OS
+getEnvironment = PE.getEnvironment
+#else
+getEnvironment = E.getEnvironment
+#endif
+
+{- Returns True if it could successfully set the environment variable.
+ -
+ - There is, apparently, no way to do this in Windows. Instead,
+ - environment varuables must be provided when running a new process. -}
+setEnv :: String -> String -> Bool -> IO Bool
+#ifndef mingw32_HOST_OS
+setEnv var val overwrite = do
+ PE.setEnv var val overwrite
+ return True
+#else
+setEnv _ _ _ = return False
+#endif
+
+{- Returns True if it could successfully unset the environment variable. -}
+unsetEnv :: String -> IO Bool
+#ifndef mingw32_HOST_OS
+unsetEnv var = do
+ PE.unsetEnv var
+ return True
+#else
+unsetEnv _ = return False
+#endif
+
+{- Adds the environment variable to the input environment. If already
+ - present in the list, removes the old value.
+ -
+ - This does not really belong here, but Data.AssocList is for some reason
+ - buried inside hxt.
+ -}
+addEntry :: Eq k => k -> v -> [(k, v)] -> [(k, v)]
+addEntry k v l = ( (k,v) : ) $! delEntry k l
+
+addEntries :: Eq k => [(k, v)] -> [(k, v)] -> [(k, v)]
+addEntries = foldr (.) id . map (uncurry addEntry) . reverse
+
+delEntry :: Eq k => k -> [(k, v)] -> [(k, v)]
+delEntry _ [] = []
+delEntry k (x@(k1,_) : rest)
+ | k == k1 = rest
+ | otherwise = ( x : ) $! delEntry k rest