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{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE RankNTypes #-}
module Text.Markdown
( -- * Functions
markdown
-- * Settings
, MarkdownSettings
, defaultMarkdownSettings
, msXssProtect
, msStandaloneHtml
, msFencedHandlers
, msBlockCodeRenderer
, msLinkNewTab
, msBlankBeforeBlockquote
, msBlockFilter
, msAddHeadingId
, setNoFollowExternal
-- * Newtype
, Markdown (..)
-- * Fenced handlers
, FencedHandler (..)
, codeFencedHandler
, htmlFencedHandler
-- * Convenience re-exports
, def
) where
import Control.Arrow ((&&&))
import Text.Markdown.Inline
import Text.Markdown.Block
import Text.Markdown.Types
import Prelude hiding (sequence, takeWhile)
import Data.Char (isAlphaNum)
import Data.Default (Default (..))
import Data.List (intercalate, isInfixOf)
import Data.Maybe (isJust)
import Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL
import Text.Blaze (toValue)
import Text.Blaze.Html (ToMarkup (..), Html)
import Text.Blaze.Html.Renderer.Text (renderHtml)
import Data.Conduit
import qualified Data.Conduit.List as CL
import Data.Monoid (Monoid (mappend, mempty, mconcat), (<>))
import qualified Text.Blaze.Html5 as H
import qualified Text.Blaze.Html5.Attributes as HA
import Text.HTML.SanitizeXSS (sanitizeBalance)
import qualified Data.Map as Map
import Data.String (IsString)
import Data.Semigroup (Semigroup)
-- | A newtype wrapper providing a @ToHtml@ instance.
newtype Markdown = Markdown TL.Text
deriving(Eq, Ord, Monoid, Semigroup, IsString, Show)
instance ToMarkup Markdown where
toMarkup (Markdown t) = markdown def t
-- | Convert the given textual markdown content to HTML.
--
-- >>> :set -XOverloadedStrings
-- >>> import Text.Blaze.Html.Renderer.Text
-- >>> renderHtml $ markdown def "# Hello World!"
-- "<h1>Hello World!</h1>"
--
-- >>> renderHtml $ markdown def { msXssProtect = False } "<script>alert('evil')</script>"
-- "<script>alert('evil')</script>"
markdown :: MarkdownSettings -> TL.Text -> Html
markdown ms tl =
sanitize
$ runConduitPure
$ CL.sourceList blocksH
.| toHtmlB ms
.| CL.fold mappend mempty
where
sanitize
| msXssProtect ms = preEscapedToMarkup . sanitizeBalance . TL.toStrict . renderHtml
| otherwise = id
blocksH :: [Block Html]
blocksH = processBlocks blocks
blocks :: [Block Text]
blocks = runConduitPure
$ CL.sourceList (TL.toChunks tl)
.| toBlocks ms
.| CL.consume
processBlocks :: [Block Text] -> [Block Html]
processBlocks = map (fmap $ toHtmlI ms)
. msBlockFilter ms
. map (fmap $ intercalate [InlineHtml "<br>"])
. map (fmap $ map $ toInline refs)
. map toBlockLines
refs =
Map.unions $ map toRef blocks
where
toRef (BlockReference x y) = Map.singleton x y
toRef _ = Map.empty
data MState = NoState | InList ListType
toHtmlB :: Monad m => MarkdownSettings -> ConduitM (Block Html) Html m ()
toHtmlB ms =
loop NoState
where
loop state = await >>= maybe
(closeState state)
(\x -> do
state' <- getState state x
yield $ go x
loop state')
closeState NoState = return ()
closeState (InList Unordered) = yield $ escape "</ul>"
closeState (InList Ordered) = yield $ escape "</ol>"
getState NoState (BlockList ltype _) = do
yield $ escape $
case ltype of
Unordered -> "<ul>"
Ordered -> "<ol>"
return $ InList ltype
getState NoState _ = return NoState
getState state@(InList lt1) b@(BlockList lt2 _)
| lt1 == lt2 = return state
| otherwise = closeState state >> getState NoState b
getState state@(InList _) _ = closeState state >> return NoState
go (BlockPara h) = H.p h
go (BlockPlainText h) = h
go (BlockList _ (Left h)) = H.li h
go (BlockList _ (Right bs)) = H.li $ blocksToHtml bs
go (BlockHtml t) = escape t
go (BlockCode a b) = msBlockCodeRenderer ms a (id &&& toMarkup $ b)
go (BlockQuote bs) = H.blockquote $ blocksToHtml bs
go BlockRule = H.hr
go (BlockHeading level h)
| msAddHeadingId ms = wrap level H.! HA.id (clean h) $ h
| otherwise = wrap level h
where
wrap 1 = H.h1
wrap 2 = H.h2
wrap 3 = H.h3
wrap 4 = H.h4
wrap 5 = H.h5
wrap _ = H.h6
isValidChar c = isAlphaNum c || isInfixOf [c] "-_:."
clean = toValue . TL.filter isValidChar . (TL.replace " " "-") . TL.toLower . renderHtml
go BlockReference{} = return ()
blocksToHtml bs = runConduitPure $ mapM_ yield bs .| toHtmlB ms .| CL.fold mappend mempty
escape :: Text -> Html
escape = preEscapedToMarkup
toHtmlI :: MarkdownSettings -> [Inline] -> Html
toHtmlI ms is0
| msXssProtect ms = escape $ sanitizeBalance $ TL.toStrict $ renderHtml final
| otherwise = final
where
final = gos is0
gos = mconcat . map go
go (InlineText t) = toMarkup t
go (InlineItalic is) = H.i $ gos is
go (InlineBold is) = H.b $ gos is
go (InlineCode t) = H.code $ toMarkup t
go (InlineLink url mtitle content) =
H.a
H.! HA.href (H.toValue url)
H.!? (msLinkNewTab ms, HA.target "_blank")
H.!? (msNoFollowExternal ms && isExternalLink url, HA.rel "nofollow")
H.!? (isJust mtitle, HA.title $ maybe (error "impossible") H.toValue mtitle)
$ gos content
go (InlineImage url Nothing content) = H.img H.! HA.src (H.toValue url) H.! HA.alt (H.toValue content)
go (InlineImage url (Just title) content) = H.img H.! HA.src (H.toValue url) H.! HA.alt (H.toValue content) H.! HA.title (H.toValue title)
go (InlineHtml t) = escape t
go (InlineFootnoteRef x) = let ishown = TL.pack (show x)
in H.a H.! HA.href (H.toValue $ "#footnote-" <> ishown)
H.! HA.id (H.toValue $ "ref-" <> ishown) $ H.toHtml $ "[" <> ishown <> "]"
go (InlineFootnote x) = let ishown = TL.pack (show x)
in H.a H.! HA.href (H.toValue $ "#ref-" <> ishown)
H.! HA.id (H.toValue $ "footnote-" <> ishown) $ H.toHtml $ "[" <> ishown <> "]"
-- | For external links, add the rel="nofollow" attribute
--
-- @since 0.1.16
setNoFollowExternal :: MarkdownSettings -> MarkdownSettings
setNoFollowExternal ms = ms { msNoFollowExternal = True }
-- | Is the given URL an external link?
isExternalLink :: Text -> Bool
isExternalLink = T.isInfixOf "//"
|
