Custom monad

src/API.hs

@@ -17,6 +17,7 @@ import Servant
 import Servant.HTML.Lucid (HTML)
 import Lucid (HtmlT, ToHtml(..))
 import qualified Lucid.Html5 as H
+import Types
 
 data Index = Index
 
@@ -39,5 +40,5 @@ instance ToHtml Index where
 
 type API = Get '[HTML] Index
 
-handler :: ServerT API Handler
+handler :: ServerT API AppM
 handler = return Index

src/Main.hs

@@ -2,9 +2,10 @@ module Main where
 
 import Server (server)
 import Network.Wai.Handler.Warp (run)
+import Types
 
 defaultMain :: IO ()
-defaultMain = run 8080 server
+defaultMain = run 8080 (server App)
 
 main :: IO ()
 main = defaultMain

src/Server.hs

@@ -13,15 +13,18 @@ module Server where
 
 import qualified API as API
 import Servant
+import Types
+import ClassyPrelude hiding (Handler)
+import Control.Monad.Logger
+import Control.Monad.Except
 
 type API = API.API :<|> "static" :> Raw
 
-handler :: ServerT API Handler
-handler = API.handler :<|> serveDirectoryFileServer "static"
 
-
-server :: Application
-server = serve api handler
+server :: App -> Application
+server app = serve api (enter server' API.handler :<|> serveDirectoryFileServer "static")
   where
+    server' :: AppM :~> Servant.Handler
+    server' = NT (Handler . ExceptT . try . (`runReaderT` app) . (runFileLoggingT "logs/server.log"))
     api :: Proxy API
     api = Proxy

src/Types.hs

@@ -0,0 +1,9 @@
+{-# Language NoImplicitPrelude #-}
+module Types where
+
+import ClassyPrelude
+import Control.Monad.Logger
+
+data App = App
+
+type AppM = LoggingT (ReaderT App IO)