{-# LANGUAGE OverloadedStrings #-}
module Data.CSS.Style.Importance (
        splitProperties, ImportanceSplitter(..)
    ) where

import Data.CSS.Syntax.Tokens
import Data.CSS.Style.Common

type Property = (Text, [Token])
splitProperties :: [Property] -> ([Property], [Property])
splitProperties (prop@(name, value):rest)
        | (Ident "important":Delim '!':value') <- reverse value =
            (unimportant, (name, reverse value'):important)
        | otherwise = (prop:unimportant, important)
    where (unimportant, important) = splitProperties rest
splitProperties [] = ([], [])

data ImportanceSplitter a = ImportanceSplitter a
instance RuleStore inner => RuleStore (ImportanceSplitter inner) where
    new = ImportanceSplitter new
    addStyleRule (ImportanceSplitter self) priority rule =
            ImportanceSplitter $ addStyleRule (
                addStyleRule self (negate priority) $ buildRule important
            ) priority $ buildRule unimportant
        where
            (important, unimportant) = splitProperties properties
            (StyleRule selector properties) = inner rule
            buildRule properties = rule {inner = StyleRule selector properties}
    lookupRules (ImportanceSplitter self) el = lookupRules self el