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{-# LANGUAGE OverloadedStrings #-}
-- | Evaluates !important.
-- INTERNAL MODULE.
module Data.CSS.Style.Importance (
ImportanceSplitter(..)
) where
import Data.CSS.Syntax.Tokens
import Data.CSS.Style.Common
type Property = (Text, [Token])
splitProperties :: [Property] -> ([Property], [Property])
splitProperties (prop@(key, value):rest)
| (Ident "important":Delim '!':value') <- reverse value =
(unimportant, (key, reverse value'):important)
| otherwise = (prop:unimportant, important)
where (unimportant, important) = splitProperties rest
splitProperties [] = ([], [])
--- NOTE: Prorities are defined with lower numbers being more important,
--- so negate to be consistant with other priority sources.
--- This API decision started out being accidental, but I find it more intuitive.
-- | Evaluates "!important" by splitting all `StyleRule'` in two.
data ImportanceSplitter a = ImportanceSplitter a
instance RuleStore inner => RuleStore (ImportanceSplitter inner) where
new = ImportanceSplitter new
addStyleRule (ImportanceSplitter self) priority rule =
ImportanceSplitter $ addStyleRule (
addStyleRule self (map negate priority) $ buildRule unimportant
) priority $ buildRule important
where
(unimportant, important) = splitProperties props
(StyleRule sel props psuedo) = inner rule
buildRule x = rule {inner = StyleRule sel x psuedo}
lookupRules (ImportanceSplitter self) el = lookupRules self el