Implement wordWrap and paginate

src/HCat/Internal.hs

@@ -1,6 +1,9 @@
 -- | Internal module in order to facilitate testability.
 module HCat.Internal where
 
+import Data.Text (Text)
+import Data.Text qualified as T
+
 -- | @parseArgs@ takes a list of strings and returns a single FilePath if there was exactly one element.
 --
 -- >>> parseArgs ["foo"]
@@ -28,3 +31,39 @@ chunksOf n xs@(_ : _)
   | otherwise =
       let (chunk, rest) = splitAt n xs
        in chunk : chunksOf n rest
+
+-- | @wordWrap@ splits the given Text if it is longer than the given margin.
+--
+-- >>> :set -XOverloadedStrings
+-- >>> wordWrap 3 "abcdef"
+-- ["abc","def"]
+--
+-- >>> wordWrap 3 "abc"
+-- ["abc"]
+--
+-- >>> wordWrap 3 "ab"
+-- ["ab"]
+wordWrap :: Int -> Text -> [Text]
+wordWrap n text
+  | n > 0 && T.length text > n =
+      let (line, rest) = T.splitAt n text
+       in line : wordWrap n rest
+  | otherwise = pure text
+
+data ScreenDimensions = ScreenDimensions
+  { screenRows :: Int
+  , screenColumns :: Int
+  }
+  deriving (Show)
+
+-- | @paginate@ transforms a given piece of Text into pages of lines that fit
+-- onto the screen.
+--
+-- >>> paginate ScreenDimensions{screenRows = 2, screenColumns = 2} "foo bar baz"
+-- ["fo\no \n","ba\nr \n","ba\nz\n"]
+paginate :: ScreenDimensions -> Text -> Pages
+paginate (ScreenDimensions rows cols) =
+  fmap T.unlines . chunksOf rows . concatMap (wordWrap cols) . T.lines
+
+type Pages = [Page]
+type Page = Text