Fix bug with NonEmpty, add support for Input and re-add option descriptions

lib/GEODE/Options.hs

 {-# LANGUAGE NamedFieldPuns #-}
 module GEODE.Options
-  ( Output(..)
-  , atLeastOne
+  ( Input(..)
+  , IOConfig(..)
+  , Output(..)
+  , input
+  , ioConfig
   , output ) where
 
-import Control.Applicative ((<|>), empty, many, optional)
-import Data.List.NonEmpty (NonEmpty(..), nonEmpty)
-import Data.Maybe (catMaybes)
+import Control.Applicative ((<|>))
+import Data.List.NonEmpty (NonEmpty(..))
 import Options.Applicative
-  ( Parser, flag', help, long, metavar, short
-  , strOption )
+  ( Parser, argument, flag', help, long, metavar, short, str, strOption, value )
+import Options.Applicative.Types (oneM, manyM, fromM)
+import Text.Printf (printf)
+
+data Input = StdIn | File FilePath
+
+input :: String -> Parser Input
+input stdinSemantics =
+  argument
+    (File <$> str)
+    ( value StdIn
+      <> metavar "INPUT_FILE"
+      <> help (printf "path of the file to process (%s)" stdinSemantics) )
 
 data Output = Metadata | TextRoot FilePath | XMLRoot FilePath
 
 output :: Parser Output
 output =
-    flag' Metadata ( long "metadata" <> short 'm')
-  <|> (TextRoot <$> strOption ( long "text-root" <> short 't'))
-  <|> (TextRoot <$> strOption ( long "xml-root" <> short 'x'))
+    flag' Metadata ( long "metadata"
+                     <> short 'm'
+                     <> help "Print metadata for splitted files on stdout" )
+  <|> (TextRoot <$> strOption
+        ( long "text-root"
+          <> short 't'
+          <> help "Root path where to output text files" ))
+  <|> (XMLRoot <$> strOption
+        ( long "xml-root"
+          <> short 'x'
+          <> help "Root path where to output XML files" ))
+
+data IOConfig = IOConfig
+  { from :: Input
+  , to :: NonEmpty Output }
 
-atLeastOne :: Parser a -> Parser (NonEmpty a)
-atLeastOne p = (:|) <$> p <*> many p
+ioConfig :: String -> Parser IOConfig
+ioConfig stdinSemantics = IOConfig
+  <$> input stdinSemantics
+  <*> some output
+  where
+    -- trick needed to avoid duplicated options in help message (occurring when
+    -- working directly at the Applicative level)
+    some p = fromM ((:|) <$> oneM p <*> manyM p)