dropLine :: Int -> [Word] -> Line
dropLine len [] = []
dropLine len (w:ws)
  | len >= length w = dropLine newlen ws
  | otherwise = (w:ws)
  where newlen = len - (length w)

joinLine :: Line -> String
joinLine [] = []
joinLine (x:xs) = (x ++ " ") ++ joinLine xs


appendSpaceToWord :: Word -> Word
appendSpaceToWord w = w ++ " "

appendSpaceToFirstElementOfLine :: Word -> (Int, Line) -> (Int, Line)
appendSpaceToFirstElementOfLine x (n, xs) = (n, (appendSpaceToWord x):xs)

joinLineN :: (Int, Line) -> (Int, Line)
joinLineN (n, []) = (n, [])
joinLineN (0, xs) = (0, xs)
joinLineN (n, (x:xs))
  | (wordLength x) < n = (fst result, snd result)
  | otherwise = (n, (x:xs))
  where result = appendSpaceToFirstElementOfLine x (joinLineN (left, xs))
        wordLength x = length x
        left = n - wordLength x

lineLength :: Line -> Int
lineLength line = Prelude.sum [length x | x <- line]

joinLineA :: Int -> Line -> Line
joinLineA 0 xs = xs
joinLineA _ [] = []
joinLineA n xs
  | n > 0 = joinLineA (fst result) (snd result)
  | otherwise = snd result
  where
    result = joinLineN (n, xs)




joinLines :: [Line] -> String
joinLines [] = []
joinLines (x:xs) = (line ++ "\n") ++ joinLines xs
  where line = joinLine x


-- Splitting into lines.

splitLines :: [Word] -> [Line]
splitLines [] = []
splitLines ws
  = getLine lineLen ws
         : splitLines (dropLine lineLen ws)

-- To fill a text string into lines, we write

fill :: String -> [Line]
fill = splitLines . splitWords