Allow light-bg and no-color modes for executable

app/Main.hs

@@ -26,10 +26,56 @@ module Main where
 import Data.Text (unpack)
 import qualified Data.Text.IO as T
 import qualified Data.Text.Lazy.IO as LT
-import Text.Pretty.Simple (pString)
+import Options.Applicative 
+       ( Parser, ReadM, execParser, fullDesc, help, helper, info, long
+       , option, progDesc, readerError, short, showDefaultWith, str, value, (<**>))
+import Data.Monoid ((<>))
+import Text.Pretty.Simple 
+       ( pStringOpt, OutputOptions
+       , defaultOutputOptionsDarkBg
+       , defaultOutputOptionsLightBg
+       , defaultOutputOptionsNoColor
+       )
+
+data Color = DarkBg
+           | LightBg
+           | NoColor
+
+newtype Args = Args { color :: Color }
+
+colorReader :: ReadM Color
+colorReader = do
+  string <- str
+  case string of
+    "dark-bg"  -> pure DarkBg
+    "light-bg" -> pure LightBg
+    "no-color" -> pure NoColor
+    x          -> readerError $ "Could not parse " <> x <> " as a color."
+
+args :: Parser Args
+args = Args
+    <$> option colorReader
+        ( long "color"
+       <> short 'c'
+       <> help "Select printing color. Available options: dark-bg (default), light-bg, no-color."
+       <> showDefaultWith (\_ -> "dark-bg")
+       <> value DarkBg
+        )
 
 main :: IO ()
 main = do
+  args' <- execParser opts
   input <- T.getContents
-  let output = pString $ unpack input
+  let printOpt = getPrintOpt $ color args'
+      output = pStringOpt printOpt $ unpack input
   LT.putStr output
+  where
+    opts = info (args <**> helper)
+      ( fullDesc
+     <> progDesc "Format Haskell data types with indentation and highlighting"
+      )
+
+    getPrintOpt :: Color -> OutputOptions
+    getPrintOpt DarkBg  = defaultOutputOptionsDarkBg
+    getPrintOpt LightBg = defaultOutputOptionsLightBg
+    getPrintOpt NoColor = defaultOutputOptionsNoColor

pretty-simple.cabal

@@ -51,6 +51,7 @@ executable pretty-simple
   build-depends:       base
                      , pretty-simple
                      , text
+                     , optparse-applicative
   default-language:    Haskell2010
   ghc-options:         -Wall -threaded -rtsopts -with-rtsopts=-N