feat(System.Environment): implement module allowing to read environme…

…nt variables

src/System/Environment.purs

@@ -0,0 +1,21 @@
+module System.Environment (readEnvString, readEnvInt) where
+
+import Control.Applicative (pure)
+import Control.Monad (bind, (>>=))
+import Data.Function (identity, ($))
+import Data.Maybe (Maybe(..), maybe)
+import Effect (Effect)
+import Node.Process (lookupEnv)
+import Simple.JSON (readJSON_)
+
+readEnvString :: String -> String -> Effect String
+readEnvString variable defaultValue = do
+ maybeValue <- lookupEnv variable
+ pure $ maybe defaultValue identity maybeValue
+
+readEnvInt :: String -> Int -> Effect Int
+readEnvInt variable defaultValue = do
+ maybeValue <- lookupEnv variable
+ case (maybeValue >>= readJSON_ :: Maybe Int) of
+ Nothing -> pure defaultValue
+ (Just value) -> pure value