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{-# LANGUAGE OverloadedStrings #-}
module Data.HTML2CSS(
externalStyles, internalStyles,
cssPriorityAgent, cssPriorityUser, cssPriorityAuthor,
traverseStyles, traverseStyles', elToStylish
) where
import qualified Data.List as L
import qualified Data.Map as M
import qualified Data.Text as Txt
import qualified Text.XML as XML
import Data.CSS.Syntax.StyleSheet
import Data.CSS.Style
import Data.CSS.Syntax.Tokens (tokenize)
import Network.URI
---- Constants
cssPriorityAgent styles = styles {priority = 1}
cssPriorityUser styles = styles {priority = 2}
cssPriorityAuthor styles = styles {priority = 3}
---- Parsing
externalStyles :: PropertyParser s => QueryableStyleSheet s -> (M.Map XML.Name Txt.Text -> Bool) ->
XML.Element -> (URI -> IO Txt.Text) -> IO (QueryableStyleSheet s)
externalStyles stylesheet testMedia html loadURL = do
css <- externalStyles' testMedia html loadURL
return $ foldl parse (cssPriorityAuthor stylesheet) css
externalStyles' testMedia html loadURL = go $ linkedStyles' testMedia html
where -- TODO parallelise loads
go (link:links) = do
response <- loadURL $ link
rest <- go links
return $ response : rest
go [] = return []
linkedStyles' testMedia (XML.Element (XML.Name "link" _ _) attrs _)
| Just link <- "href" `M.lookup` attrs,
Just "stylesheet" <- "rel" `M.lookup` attrs,
testMedia attrs,
Just uri <- parseURIReference $ Txt.unpack link = [uri]
linkedStyles' testMedia (XML.Element _ _ children) =
concat [linkedStyles' testMedia el | XML.NodeElement el <- children]
internalStyles testMedia stylesheet html =
foldl parse (cssPriorityAuthor stylesheet) $ internalStyles' testMedia html
internalStyles' testMedia (XML.Element (XML.Name "style"_ _) attrs children)
| testMedia attrs = [strContent children]
internalStyles' testMedia (XML.Element _ _ children) =
concat [internalStyles' testMedia el | XML.NodeElement el <- children]
strContent :: [XML.Node] -> Txt.Text
strContent (XML.NodeContent text : rest) = text `Txt.append` strContent rest
-- We do want to read in comments for CSS, just not for display.
strContent (XML.NodeComment text : rest) = text `Txt.append` strContent rest
strContent (XML.NodeElement (XML.Element _ _ children):rest) =
strContent children `Txt.append` strContent rest
strContent (_:rest) = strContent rest
strContent [] = ""
---- Styling
traverseStyles :: PropertyParser s => (s -> [o] -> o) -> (s -> Txt.Text -> o) ->
QueryableStyleSheet s -> XML.Element -> o
traverseStyles = traverseStyles' Nothing temp Nothing
traverseStyles' parent parentStyle previous builder textBuilder stylesheet el@(
XML.Element _ attrs children
) = builder style $ traverseChildren Nothing children
where
stylishEl = elToStylish el parent previous
maybeEl = Just stylishEl
style = cascade stylesheet stylishEl overrides parentStyle
overrides | Just styleAttr <- "style" `M.lookup` attrs =
fst $ parseProperties' $ tokenize styleAttr
| otherwise = []
traverseChildren prev (XML.NodeContent txt:nodes) =
textBuilder style txt : traverseChildren prev nodes
traverseChildren prev (XML.NodeElement el:nodes) =
traverseStyles' maybeEl style prev builder textBuilder stylesheet el :
traverseChildren (Just $ elToStylish el maybeEl prev) nodes
traverseChildren prev (_:nodes) = traverseChildren prev nodes
traverseChildren _ [] = []
elToStylish (XML.Element (XML.Name name _ _) attrs _) parent previous =
ElementNode {
name = name,
attributes = L.sort [
Attribute (XML.nameLocalName name) (Txt.unpack value)
| (name, value) <- M.toList attrs
],
parent = parent,
previous = previous
}