Custom argument parsing for sha ranges and file paths

src/Arguments.hs

@@ -1,25 +1,40 @@
-module Arguments (Arguments(..), args) where
+module Arguments (Arguments(..), ExtraArg(..), args, filePathsFromArgs, maybeShasFromArgs) where
 
 import Data.Functor.Both
-import qualified Prelude as P
+import Data.Monoid
 import Prelude
 import qualified Renderer as R
 
+data ExtraArg = ShaPair (Both (Maybe String)) | FileArg FilePath deriving (Show)
+
 -- | The command line arguments to the application.
-data Arguments = Arguments {
-  format :: R.Format,
-  maybeShas :: Both (Maybe P.String),
-  maybeTimeout :: Maybe Float,
-  output :: Maybe FilePath,
-  noIndex :: Bool,
-  filepaths :: [FilePath] }
-  deriving (Show)
+data Arguments = Arguments
+  { format :: R.Format
+  , maybeTimeout :: Maybe Float
+  , output :: Maybe FilePath
+  , noIndex :: Bool
+  , extraArgs :: [ExtraArg]
+  } deriving (Show)
 
 args :: String -> String -> [String] -> R.Format -> Arguments
-args sha1 sha2 filePaths format = Arguments { format = format
-                                            , maybeShas = Just <$> both sha1 sha2
-                                            , filepaths = filePaths
-                                            , maybeTimeout = Just 10.0
-                                            , output = Nothing
-                                            , noIndex = False
-                                            }
+args sha1 sha2 filePaths format = Arguments
+  { format = format
+  , maybeTimeout = Just 10.0
+  , output = Nothing
+  , noIndex = False
+  , extraArgs = [ShaPair (Just <$> both sha1 sha2)] <> (FileArg <$> filePaths)
+  }
+
+filePathsFromArgs :: Arguments -> [FilePath]
+filePathsFromArgs Arguments{..} = go extraArgs
+  where
+    go [] = []
+    go (FileArg x:xs) = x : go xs
+    go (_:xs) = go xs
+
+maybeShasFromArgs :: Arguments -> Both (Maybe String)
+maybeShasFromArgs Arguments{..} = go extraArgs
+  where
+    go [] = both Nothing Nothing
+    go (ShaPair x:_) = x
+    go (_:xs) = go xs