Add 'doctest' as a cabal test

We provide a simple wrapper that executes `doctest` on our `src`
directory. This allows us to run all doctests during a regular `cabal
test` run.

src/HCat/Internal.hs

@@ -4,6 +4,8 @@ module HCat.Internal where
 import Data.Text (Text)
 import Data.Text qualified as T
 
+import System.IO
+import System.Info qualified as SysInfo
 import System.Process qualified as P
 
 -- | @parseArgs@ takes a list of strings and returns a single FilePath if there was exactly one element.
@@ -70,7 +72,28 @@ paginate (ScreenDimensions rows cols) =
 type Pages = [Page]
 type Page = Text
 
-getScreenDimensions :: IO ScreenDimensions
+getTerminalSize :: IO ScreenDimensions
-getScreenDimensions = ScreenDimensions <$> tput "lines" <*> tput "cols"
+getTerminalSize = case SysInfo.os of
+  "linux" -> tputScreenDimensions
+  "darwin" -> tputScreenDimensions
+  _ -> pure $ defaultScreenDimensions{screenRows = 25, screenColumns = 80}
+
+defaultScreenDimensions :: ScreenDimensions
+defaultScreenDimensions = ScreenDimensions{screenRows = 25, screenColumns = 80}
+
+tputScreenDimensions :: IO ScreenDimensions
+tputScreenDimensions = ScreenDimensions <$> tput "lines" <*> tput "cols"
  where
   tput cmd = read <$> P.readProcess "tput" [cmd] ""
+
+data UserCommand = NextPage | Quit deriving (Show)
+
+getUserCommand :: IO UserCommand
+getUserCommand = do
+  hSetBuffering stdin NoBuffering
+  hSetEcho stdin False
+  input <- getChar
+  case input of
+    ' ' -> pure NextPage
+    'q' -> pure Quit
+    _ -> getUserCommand