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{-# LANGUAGE OverloadedStrings #-}
{-
Copyright (C) 2011-2017 John MacFarlane <jgm@berkeley.edu>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

{- |
   Module      : Text.Pandoc.SelfContained
   Copyright   : Copyright (C) 2011-2017 John MacFarlane
   License     : GNU GPL, version 2 or above

   Maintainer  : John MacFarlane <jgm@berkeley.edu>
   Stability   : alpha
   Portability : portable

Functions for converting an HTML file into one that can be viewed
offline, by incorporating linked images, CSS, and scripts into
the HTML using data URIs.
-}
module Text.Pandoc.SelfContained ( makeDataURI, makeSelfContained ) where
import Codec.Compression.GZip as Gzip
import Control.Applicative ((<|>))
import Control.Monad.Except (throwError)
import Control.Monad.Trans (lift)
import Data.Monoid ((<>))
import Data.ByteString (ByteString)
import Data.ByteString.Base64
import qualified Data.ByteString.Char8 as B
import qualified Data.ByteString.Lazy as L
import Data.Char (isAlphaNum, isAscii, toLower)
import Data.List (isPrefixOf)
import Network.URI (URI (..), escapeURIString, isURI, parseURI)
import System.FilePath (takeDirectory, takeExtension, (</>))
import Text.HTML.TagSoup
import Text.Pandoc.Class (PandocMonad (..), fetchItem, report)
import Text.Pandoc.Error
import Text.Pandoc.Logging
import Text.Pandoc.MIME (MimeType)
import Text.Pandoc.Options (WriterOptions (..))
import Text.Pandoc.Shared (renderTags', trim)
import Text.Pandoc.UTF8 (toString)
import Text.Parsec (ParsecT, runParserT)
import qualified Text.Parsec as P

isOk :: Char -> Bool
isOk c = isAscii c && isAlphaNum c

makeDataURI :: (MimeType, ByteString) -> String
makeDataURI (mime, raw) =
  if textual
     then "data:" ++ mime' ++ "," ++ escapeURIString isOk (toString raw)
     else "data:" ++ mime' ++ ";base64," ++ toString (encode raw)
  where textual = "text/" `Data.List.isPrefixOf` mime
        mime' = if textual && ';' `notElem` mime
                   then mime ++ ";charset=utf-8"
                   else mime  -- mime type already has charset

convertTags :: PandocMonad m => Maybe String -> [Tag String] -> m [Tag String]
convertTags _ [] = return []
convertTags sourceURL (t@TagOpen{}:ts)
  | fromAttrib "data-external" t == "1" = (t:) <$> convertTags sourceURL ts
convertTags sourceURL (t@(TagOpen tagname as):ts)
  | tagname `elem`
     ["img", "embed", "video", "input", "audio", "source", "track"] = do
       as' <- mapM processAttribute as
       rest <- convertTags sourceURL ts
       return $ TagOpen tagname as' : rest
  where processAttribute (x,y) =
           if x == "src" || x == "data-src" || x == "href" || x == "poster"
              then do
                enc <- getDataURI sourceURL (fromAttrib "type" t) y
                return (x, enc)
              else return (x,y)
convertTags sourceURL (t@(TagOpen "script" as):TagClose "script":ts) =
  case fromAttrib "src" t of
       []  -> (t:) <$> convertTags sourceURL ts
       src    -> do
           let typeAttr = fromAttrib "type" t
           res <- getData sourceURL typeAttr src
           rest <- convertTags sourceURL ts
           case res of
                Left dataUri -> return $ TagOpen "script"
                     (("src",dataUri) : [(x,y) | (x,y) <- as, x /= "src"]) :
                     TagClose "script" : rest
                Right (mime, bs)
                  | ("text/javascript" `isPrefixOf` mime ||
                     "application/javascript" `isPrefixOf` mime ||
                     "application/x-javascript" `isPrefixOf` mime) &&
                     not ("</script" `B.isInfixOf` bs) ->
                     return $
                       TagOpen "script" [("type", typeAttr)|not (null typeAttr)]
                       : TagText (toString bs)
                       : TagClose "script"
                       : rest
                  | otherwise ->
                       return  $ TagOpen "script"
                         (("src",makeDataURI (mime, bs)) :
                          [(x,y) | (x,y) <- as, x /= "src"]) :
                        TagClose "script" : rest
convertTags sourceURL (t@(TagOpen "link" as):ts) =
  case fromAttrib "href" t of
       []  -> (t:) <$> convertTags sourceURL ts
       src -> do
           res <- getData sourceURL (fromAttrib "type" t) src
           case res of
                Left dataUri -> do
                  rest <- convertTags sourceURL ts
                  return $ TagOpen "link"
                     (("href",dataUri) : [(x,y) | (x,y) <- as, x /= "href"]) :
                     rest
                Right (mime, bs)
                  | "text/css" `isPrefixOf` mime
                    && not ("</" `B.isInfixOf` bs) -> do
                      rest <- convertTags sourceURL $
                                 dropWhile (==TagClose "link") ts
                      return $
                       TagOpen "style" [("type", mime)]
                       : TagText (toString bs)
                       : TagClose "style"
                       : rest
                  | otherwise -> do
                      rest <- convertTags sourceURL ts
                      return $ TagOpen "link"
                       (("href",makeDataURI (mime, bs)) :
                         [(x,y) | (x,y) <- as, x /= "href"]) : rest
convertTags sourceURL (t:ts) = (t:) <$> convertTags sourceURL ts

cssURLs :: PandocMonad m
        => Maybe String -> FilePath -> ByteString -> m ByteString
cssURLs sourceURL d orig = do
  res <- runParserT (parseCSSUrls sourceURL d) () "css" orig
  case res of
       Left e    -> do
         report $ CouldNotParseCSS (show e)
         return orig
       Right bs  -> return bs

parseCSSUrls :: PandocMonad m
             => Maybe String -> FilePath -> ParsecT ByteString () m ByteString
parseCSSUrls sourceURL d = B.concat <$> P.many
    (pCSSWhite <|> pCSSComment <|> pCSSImport sourceURL d <|>
     pCSSUrl sourceURL d <|> pCSSOther)

pCSSImport :: PandocMonad m => Maybe String -> FilePath
           -> ParsecT ByteString () m ByteString
pCSSImport sourceURL d = P.try $ do
  P.string "@import"
  P.spaces
  res <- pCSSUrl' sourceURL d
  P.spaces
  P.optional $ P.char ';' >> P.spaces
  case res of
       Left b       -> return $ B.pack "@import " <> b
       Right (_, b) -> return b

-- Note: some whitespace in CSS is significant, so we can't collapse it!
pCSSWhite :: PandocMonad m => ParsecT ByteString () m ByteString
pCSSWhite = B.singleton <$> P.space <* P.spaces

pCSSComment :: PandocMonad m => ParsecT ByteString () m ByteString
pCSSComment = P.try $ do
  P.string "/*"
  P.manyTill P.anyChar (P.try (P.string "*/"))
  return B.empty

pCSSOther :: PandocMonad m => ParsecT ByteString () m ByteString
pCSSOther = do
  (B.pack <$> P.many1 (P.noneOf "u/ \n\r\t")) <|>
    (B.singleton <$> P.char 'u') <|>
    (B.singleton <$> P.char '/')

pCSSUrl :: PandocMonad m
        => Maybe String -> FilePath -> ParsecT ByteString () m ByteString
pCSSUrl sourceURL d = P.try $ do
  res <- pCSSUrl' sourceURL d
  case res of
       Left b -> return b
       Right (mt,b) -> do
         let enc = makeDataURI (mt, b)
         return (B.pack $ "url(" ++ enc ++ ")")

pCSSUrl' :: PandocMonad m
         => Maybe String -> FilePath
         -> ParsecT ByteString () m (Either ByteString (MimeType, ByteString))
pCSSUrl' sourceURL d = P.try $ do
  P.string "url("
  P.spaces
  quote <- P.option Nothing (Just <$> P.oneOf "\"'")
  url <- P.manyTill P.anyChar (maybe (P.lookAhead (P.char ')')) P.char quote)
  P.spaces
  P.char ')'
  let fallback = Left $
          B.pack ("url(" ++ maybe "" (:[]) quote ++ trim url ++
                            maybe "" (:[]) quote ++ ")")
  -- pipes are used in URLs provided by Google Code fonts
  -- but parseURI doesn't like them, so we escape them:
  case escapeURIString (/='|') (trim url) of
      '#':_ -> return fallback
      'd':'a':'t':'a':':':_ -> return fallback
      u ->  do let url' = if isURI u then u else d </> u
               res <- lift $ getData sourceURL "" url'
               case res of
                    Left uri -> return $ Left (B.pack $ "url(" ++ uri ++ ")")
                    Right (mt, raw) -> do
                      -- note that the downloaded CSS may
                      -- itself contain url(...).
                      b <- if "text/css" `isPrefixOf` mt
                              then cssURLs sourceURL d raw
                              else return raw
                      return $ Right (mt, b)

getDataURI :: PandocMonad m => Maybe String -> MimeType -> String -> m String
getDataURI sourceURL mimetype src = do
  res <- getData sourceURL mimetype src
  case res of
       Left uri -> return uri
       Right x  -> return $ makeDataURI x

getData :: PandocMonad m
        => Maybe String -> MimeType -> String
        -> m (Either String (MimeType, ByteString))
getData _ _ src@('d':'a':'t':'a':':':_) = return $ Left src-- already data: uri
getData sourceURL mimetype src = do
  let ext = map toLower $ takeExtension src
  (raw, respMime) <- fetchItem sourceURL src
  let raw' = if ext == ".gz"
                then B.concat $ L.toChunks $ Gzip.decompress $ L.fromChunks
                      $ [raw]
                else raw
  mime <- case (mimetype, respMime) of
                  ("",Nothing) -> throwError $ PandocSomeError
                         $ "Could not determine mime type for `" ++ src ++ "'"
                  (x, Nothing) -> return x
                  (_, Just x ) -> return x
  let cssSourceURL = case parseURI src of
                          Just u
                            | uriScheme u `elem` ["http:","https:"] ->
                                Just $ show u{ uriPath = "",
                                               uriQuery = "",
                                               uriFragment = "" }
                          _ -> Nothing
  result <- if "text/css" `isPrefixOf` mime
               then cssURLs cssSourceURL (takeDirectory src) raw'
               else return raw'
  return $ Right (mime, result)



-- | Convert HTML into self-contained HTML, incorporating images,
-- scripts, and CSS using data: URIs.
makeSelfContained :: PandocMonad m => WriterOptions -> String -> m String
makeSelfContained opts inp = do
  let tags = parseTags inp
  out' <- convertTags (writerSourceURL opts) tags
  return $ renderTags' out'