Synnefo » snf-ganeti

  , wrap

  , trim

-- | Breaks a string in lines with length \<= maxWidth.

--

-- NOTE: The split is OK if:

--

-- * It doesn't break a word, i.e. the next line begins with space

--   (@isSpace . head $ rest@) or the current line ends with space

--   (@null revExtra@);

--

-- * It breaks a very big word that doesn't fit anyway (@null revLine@).

wrap :: Int      -- ^ maxWidth

     -> String   -- ^ string that needs wrapping

     -> [String] -- ^ string \"broken\" in lines

wrap maxWidth = filter (not . null) . map trim . wrap0

  where wrap0 :: String -> [String]

        wrap0 text

          | length text <= maxWidth = [text]

          | isSplitOK               = line : wrap0 rest

          | otherwise               = line' : wrap0 rest'

          where (line, rest) = splitAt maxWidth text

                (revExtra, revLine) = break isSpace . reverse $ line

                (line', rest') = (reverse revLine, reverse revExtra ++ rest)

                isSplitOK =

                  null revLine || null revExtra || startsWithSpace rest

                startsWithSpace (x:_) = isSpace x

                startsWithSpace _     = False

-- | Removes surrounding whitespace. Should only be used in small

-- strings.

trim :: String -> String

trim = reverse . dropWhile isSpace . reverse . dropWhile isSpace