Add nice, documented CLI parameters

app/Main.hs

@@ -1,19 +1,35 @@
+{-# LANGUAGE DataKinds          #-}
+{-# LANGUAGE DeriveGeneric      #-}
+{-# LANGUAGE FlexibleInstances  #-}
+{-# LANGUAGE OverloadedStrings  #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeOperators      #-}
+
 module Main where
 
 import           Lib
-import           System.Environment
+import           Options.Generic
 import           System.Random
 import           Text.Read
 
+data Parameters w =
+  Parameters
+    { width  :: w ::: Int <?> "Width of the board"
+    , length :: w ::: Int <?> "Length of the board"
+    , bombs  :: w ::: Int <?> "Number of bombs to be placed"
+    }
+  deriving (Generic)
+
+instance ParseRecord (Parameters Wrapped)
+
+deriving instance Show (Parameters Unwrapped)
+
 main :: IO ()
 main = do
-  args <- getArgs
-  let boardWidth = read (head args)
-      boardLength = read (args !! 1)
-      bombs = read (args !! 2)
+  (Parameters boardWidth boardLength bombsCount) <- unwrapRecord "Minesweeper"
   generator <- newStdGen
   gameStep . createBoard boardWidth boardLength $
-    generateRandomCoordinates (boardWidth - 1) (boardLength - 1) bombs generator
+    generateRandomCoordinates (boardWidth - 1) (boardLength - 1) bombsCount generator
 
 gameStep :: Board -> IO ()
 gameStep board = do
@@ -32,8 +48,8 @@ getCoordinates = do
   xString <- getLine
   yString <- getLine
   case (readMaybe xString, readMaybe yString) of
-    (Just x, Just y) -> return (x,y)
-    _ -> putStrLn "Invalid coordinates!" >> getCoordinates
+    (Just x, Just y) -> return (x, y)
+    _                -> putStrLn "Invalid coordinates!" >> getCoordinates
 
 gameLost :: Board -> IO ()
 gameLost board = do