module Text.Hakyll.Util 
    ( trim,
      split,
      stripHTML
    ) where

import Data.Char
import Data.List

-- | Trim a string (drop spaces and tabs at both sides).
trim :: String -> String
trim = reverse . trim' . reverse . trim'
    where trim' = dropWhile isSpace

-- | Strip html tags.
stripHTML :: String -> String
stripHTML []  = []
stripHTML str = let (beforeTag, rest) = break (== '<') str
                    (_, afterTag)     = break (== '>') rest
                in beforeTag ++ (stripHTML $ tail' afterTag)
    -- We need a failsafe tail function.
    where tail' [] = []
          tail' xs = tail xs

-- | Split a list at a certain element.
split :: (Eq a) => a -> [a] -> [[a]]
split element = unfoldr splitOnce
    where splitOnce l = let r = break (== element) l
                        in case r of ([], []) -> Nothing
                                     (x, xs) -> if null xs
                                                    then Just (x, [])
                                                    else Just (x, tail xs)