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--------------------------------------------------------------------------------
-- | Module used for CSS compression. The compression is currently in a simple
-- state, but would typically reduce the number of bytes by about 25%.
module Hakyll.Web.CompressCss
( compressCssCompiler
, compressCss
) where
--------------------------------------------------------------------------------
import Control.Applicative ((<$>))
import Data.Char (isSpace)
import Data.List (isPrefixOf)
--------------------------------------------------------------------------------
import Hakyll.Core.Compiler
import Hakyll.Core.Item
import Hakyll.Core.Util.String
--------------------------------------------------------------------------------
-- | Compiler form of 'compressCss'
compressCssCompiler :: Compiler (Item String)
compressCssCompiler = fmap compressCss <$> getResourceString
--------------------------------------------------------------------------------
-- | Compress CSS to speed up your site.
compressCss :: String -> String
compressCss = compressSeparators . stripComments . compressWhitespace
--------------------------------------------------------------------------------
-- | Compresses certain forms of separators.
compressSeparators :: String -> String
compressSeparators =
replaceAll "; *}" (const "}") .
replaceAll " *([{};:]) *" (take 1 . dropWhile isSpace) .
replaceAll ";+" (const ";")
--------------------------------------------------------------------------------
-- | Compresses all whitespace.
compressWhitespace :: String -> String
compressWhitespace = replaceAll "[ \t\n\r]+" (const " ")
--------------------------------------------------------------------------------
-- | Function that strips CSS comments away.
stripComments :: String -> String
stripComments [] = []
stripComments str
| isPrefixOf "/*" str = stripComments $ eatComments $ drop 2 str
| otherwise = head str : stripComments (drop 1 str)
where
eatComments str'
| null str' = []
| isPrefixOf "*/" str' = drop 2 str'
| otherwise = eatComments $ drop 1 str'
|
