Flatten the main function

This should make it a bit easier to read while hopefully making it
easier to change in the future.

Use pattern matching to see if the user wants to the see the usage
instructions, this allows us to make use of one `case` expression
instead of a `case` expression and an `if` expression.

Do configuration reification pointfree style while using lenses.

app/Main.hs

@@ -20,15 +20,15 @@ import           Control.Monad.Log                        ( defaultBatchingOptio
 import           Control.Monad.Reader                     ( runReaderT )
 import           Control.Monad.Trans                      ( liftIO )
 import           Data.FileEmbed                           ( embedDir )
+import           Data.Foldable                            ( traverse_ )
 import           Data.IORef                               ( IORef
                                                           , readIORef
                                                           )
 import           Data.Time.Format                         ( defaultTimeLocale
                                                           , formatTime
                                                           , iso8601DateFormat
                                                           )
-import           Lens.Micro.Platform                      ( (<&>)
-                                                          , set
+import           Lens.Micro.Platform                      ( set
                                                           , view
                                                           )
 import           Network.HTTP.Client.TLS                  ( newTlsManager )
@@ -64,53 +64,52 @@ opts =
            "Update interval"
   ]
 
+usage :: IO ()
+usage = putStrLn $ usageInfo "mat-chalmers [OPTION...]" opts
+
 main :: IO ()
 main =
-  getArgs
-    <&> getOpt Permute opts
-    >>= \case
-          (_     , _    , _ : _) -> usage
-          (_     , _ : _, _    ) -> usage
-          (!confs, _    , _    ) -> do
-            let config = foldl (flip id) defaultConfig confs
-            if view cHelp config
-              then usage
-              else do
-                upd                      <- newMVar () -- putMVar when to update
-                mgr                      <- newTlsManager
-                (viewRef, refreshAction) <- runLoggingT
-                  (runReaderT refresh (ClientContext config mgr))
-                  print
+  (reifyConfig . getOpt Permute opts <$> getArgs)
+  >>= \case
+        (_                  , _    , _ : _) -> usage
+        (_                  , _ : _, _    ) -> usage
+        (Config{_cHelp=True}, _    , _    ) -> usage
+        (config,              _    , _    ) -> do
+          upd                      <- newMVar () -- putMVar when to update
+          mgr                      <- newTlsManager
+          (viewRef, refreshAction) <- runLoggingT
+            (runReaderT refresh (ClientContext config mgr))
+            print
+
+          -- In the list there are three items running concurrently:
+          -- 1. Timer that sends a signal to the updater when it's time to update
+          -- 2. Webserver that serves the menus to the user
+          -- 3. Updater that fetches new data from the restaurants
+          Async.runConcurrently $ traverse_ Async.Concurrently
+            [ timer
+            , webserver config viewRef upd
+            , updater
+            ]
+ where
+   timer = forever $ tryPutMVar upd () >> threadDelay (view cInterval config)
 
-                Async.concurrently_
-                  (Async.concurrently_
-                    -- timer
-                    (forever $ tryPutMVar upd () >> threadDelay (view cInterval config))
-                    -- webserver
-                    (serve config viewRef upd))
-                  -- updater
-                  (forever
-                    $ withFDHandler defaultBatchingOptions stdout 1.0 80
-                    $ \logCallback ->
-                        runReaderT (refreshAction upd) (ClientContext config mgr)
-                          `runLoggingT` ( logCallback
-                                        . renderWithTimestamp
-                                            (formatTime
-                                              defaultTimeLocale
-                                              (iso8601DateFormat
-                                                (Just "%H:%M:%S")
-                                              )
-                                            )
-                                            id
-                                        ))
-  where usage = putStrLn $ usageInfo "mat-chalmers [OPTION...]" opts
+   updater =
+     forever
+       $ withFDHandler defaultBatchingOptions stdout 1.0 80
+       $ \logCallback ->
+           runLoggingT
+           (runReaderT (refreshAction upd) (ClientContext config mgr))
+           (logCallback . renderWithTimestamp (
+             formatTime defaultTimeLocale (iso8601DateFormat (Just "%H:%M:%S")))
+             id
+           )
 
-serve
+webserver
   :: Config
   -> IORef View -- ^ View model
   -> MVar () -- ^ Update signal
   -> IO ()
-serve conf viewRef upd = scotty (view cPort conf) $ do
+webserver conf viewRef upd = scotty (view cPort conf) $ do
   middleware logStdout
   middleware (static $(embedDir "static"))
   get "/"  ((html . render) =<< liftIO (readIORef viewRef))

src/Config.hs

@@ -4,6 +4,7 @@
 
 module Config where
 
+import           Data.Foldable                            ( foldl' )
 import           Lens.Micro.Platform
 
 -- | Configuration record
@@ -18,3 +19,16 @@ makeLenses ''Config
 
 defaultConfig :: Config
 defaultConfig = Config False 14 (1000000 * 60 * 30) 5007
+
+-- | Create a Config we can touch
+--
+-- Yes, this function implementation is overly cute. It uses a lens to update
+-- the first field of the tuple by using defaultConfig as first argument to
+-- every function in the list. The brain needs to turn inside out a couple of
+-- times before it makes sense, so if you're in a hurry, look at the types.
+--
+-- TODO: Feel free to bikeshed the function name.
+reifyConfig
+  :: ([Config -> Config], [String], [String])
+  -> (Config,             [String], [String])
+reifyConfig  = (& _1 %~ foldl' (flip id) defaultConfig)