add verbose flag

make-pages/Main.hs

@@ -1,14 +1,24 @@
 module Main (main) where
 
 import qualified Data.ByteString.Lazy as ByteString
+import Data.ByteString.Lazy (ByteString)
 import qualified Data.YAML as YAML
 import qualified Data.Text.Lazy.IO as Text
 import qualified Options.Applicative as Opt
+import System.IO (hPrint, stderr)
 import Text.Printf (printf)
 import Control.Applicative
+import Control.Monad
 import SinglePage
 
 data Options =
+    Options {
+      verbose :: Bool,
+      mode    :: ModeOptions
+    }
+  deriving Show
+
+data ModeOptions =
     SinglePage {
       file        :: FilePath,
       includeNsfw :: Bool,
@@ -23,9 +33,13 @@ data Options =
   deriving Show
 
 optionsParser :: Opt.ParserInfo Options
-optionsParser =
-  (Opt.hsubparser (single <> gallery) <**> Opt.helper) `Opt.info` mainInfo
- where
+optionsParser = globalOpts `Opt.info` mainInfo where
+  globalOpts = Options <$> verboseOpt <*> subcommands <**> Opt.helper
+  verboseOpt = Opt.switch $
+    Opt.short 'v' <> Opt.long "verbose" <>
+    Opt.help "print extra stuff to stderr"
+  subcommands = Opt.hsubparser (single <> gallery)
+
   single = Opt.command "single" $ singleOpts `Opt.info` singleInfo
   singleOpts = SinglePage <$> fileArg <*> nsfwSwitchS <*> outputOpt <*> copyOpt
   fileArg = Opt.strArgument $
@@ -55,24 +69,32 @@ optionsParser =
 
 
 main :: IO ()
-main = main2 =<< Opt.execParser optionsParser
+main = do
+  opts <- Opt.execParser optionsParser
+  printVerbose opts opts
+  main2 opts
 
 main2 :: Options -> IO ()
-main2 s@(SinglePage {file, includeNsfw, output}) = do
-  print s
-  page <- make includeNsfw <$> readYAML file
+main2 (Options {mode = SinglePage {file, includeNsfw, output}}) = do
+  info <- readYAML file
+  print info
+  let page = make includeNsfw info
   case output of
     Nothing  -> Text.putStr page
     Just out -> Text.writeFile out page
 
-main2 g@(GalleryPage {}) = do
-  print g
+main2 (Options {mode = GalleryPage {}}) = do
   error "surprise! this doesn't exist yet"
 
 
+printVerbose :: Show a => Options -> a -> IO ()
+printVerbose (Options {verbose}) x = when verbose $ hPrint stderr x
+
 readYAML :: YAML.FromYAML a => FilePath -> IO a
-readYAML file = do
-  txt <- ByteString.readFile file
+readYAML file = ByteString.readFile file >>= decode1Must file
+
+decode1Must :: YAML.FromYAML a => FilePath -> ByteString -> IO a
+decode1Must file txt =
   case YAML.decode1 txt of
     Right val -> pure val
     Left (YAML.Pos {posLine, posColumn}, err) ->