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| -rw-r--r-- | src/Hakyll/Web/CompressCss.hs | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/src/Hakyll/Web/CompressCss.hs b/src/Hakyll/Web/CompressCss.hs new file mode 100644 index 0000000..cd03237 --- /dev/null +++ b/src/Hakyll/Web/CompressCss.hs @@ -0,0 +1,56 @@ +-- | 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 Text.Hakyll.Internal.CompressCss + ( compressCss + ) where + +import Data.Char (isSpace) +import Data.Maybe (listToMaybe) +import Data.List (isPrefixOf) +import Text.Regex.Posix ((=~~)) + +-- | A simple (but inefficient) regex replace funcion +-- +replaceAll :: String -- ^ Pattern + -> (String -> String) -- ^ Replacement (called on capture) + -> String -- ^ Source string + -> String -- ^ Result +replaceAll pattern f source = + case listToMaybe (source =~~ pattern) of + Nothing -> source + Just (o, l) -> + let (before, tmp) = splitAt o source + (capture, after) = splitAt l tmp + in before ++ f capture ++ replaceAll pattern f after + +-- | 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][ \t\n]*" (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' |