src/Text/Hakyll/CompressCSS.hs · hakyll

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hakyll/src/Text/Hakyll/CompressCSS.hs

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1-- | Module used for CSS compression. The compression is currently in a simple

2-- state, but would typically reduce the number of bytes by about 25%.

3module Text.Hakyll.CompressCSS

4 ( compressCSS

5 ) where

7import Data.List (isPrefixOf)

9import Text.Hakyll.Regex (substituteRegex)

11-- | Compress CSS to speed up your site.

12compressCSS :: String -> String

13compressCSS = compressSeparators

14 . stripComments

15 . compressWhitespace

17-- | Compresses certain forms of separators.

18compressSeparators :: String -> String

19compressSeparators = substituteRegex "; *}" "}"

20 . substituteRegex " *([{};:]) *" "\\1"

21 . substituteRegex ";;*" ";"

23-- | Compresses all whitespace.

24compressWhitespace :: String -> String

25compressWhitespace = substituteRegex "[ \t\n][ \t\n]*" " "

27-- | Function that strips CSS comments away.

28stripComments :: String -> String

29stripComments [] = []

30stripComments str

31 | isPrefixOf "/*" str = stripComments $ eatComments $ drop 2 str

32 | otherwise = head str : stripComments (tail str)

33 where

34 eatComments str' | null str' = []

35 | isPrefixOf "*/" str' = drop 2 str'

36 | otherwise = eatComments $ tail str'