    {-# LANGUAGE NoImplicitPrelude #-}
    {-# LANGUAGE OverloadedStrings #-}
    {-
    Copyright (C) 2011-2018 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) 2011-2018 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 Prelude
    import Codec.Compression.GZip as Gzip
    import Control.Applicative ((<|>))
    import Control.Monad.Except (throwError)
    import Control.Monad.Trans (lift)
    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 (escapeURIString)
    import System.FilePath (takeDirectory, takeExtension, (</>))
    import Text.HTML.TagSoup
    import Text.Pandoc.Class (PandocMonad (..), fetchItem, getInputFiles, report,
                              setInputFiles)
    import Text.Pandoc.Error
    import Text.Pandoc.Logging
    import Text.Pandoc.MIME (MimeType)
    import Text.Pandoc.Shared (isURI, 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 => [Tag String] -> m [Tag String]
    convertTags [] = return []
    convertTags (t@TagOpen{}:ts)
      | fromAttrib "data-external" t == "1" = (t:) <$> convertTags ts
    convertTags (t@(TagOpen tagname as):ts)
      | tagname `elem`
         ["img", "embed", "video", "input", "audio", "source", "track",
          "section"] = do
           as' <- mapM processAttribute as
           rest <- convertTags ts
           return $ TagOpen tagname as' : rest
      where processAttribute (x,y) =
               if x `elem` ["src", "data-src", "href", "poster", "data-background-image"]
                  then do
                    enc <- getDataURI (fromAttrib "type" t) y
                    return (x, enc)
                  else return (x,y)
    convertTags (t@(TagOpen "script" as):TagClose "script":ts) =
      case fromAttrib "src" t of
           []  -> (t:) <$> convertTags ts
           src    -> do
               let typeAttr = fromAttrib "type" t
               res <- getData typeAttr src
               rest <- convertTags 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 (t@(TagOpen "link" as):ts) =
      case fromAttrib "href" t of
           []  -> (t:) <$> convertTags ts
           src -> do
               res <- getData (fromAttrib "type" t) src
               case res of
                    Left dataUri -> do
                      rest <- convertTags ts
                      return $ TagOpen "link"
                         (("href",dataUri) : [(x,y) | (x,y) <- as, x /= "href"]) :
                         rest
                    Right (mime, bs)
                      | "text/css" `isPrefixOf` mime
                        && null (fromAttrib "media" t)
                        && not ("</" `B.isInfixOf` bs) -> do
                          rest <- convertTags $
                                     dropWhile (==TagClose "link") ts
                          return $
                           TagOpen "style" [("type", mime)]
                           : TagText (toString bs)
                           : TagClose "style"
                           : rest
                      | otherwise -> do
                          rest <- convertTags ts
                          return $ TagOpen "link"
                           (("href",makeDataURI (mime, bs)) :
                             [(x,y) | (x,y) <- as, x /= "href"]) : rest
    convertTags (t:ts) = (t:) <$> convertTags ts

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

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

    pCSSImport :: PandocMonad m
               => FilePath -> ParsecT ByteString () m ByteString
    pCSSImport d = P.try $ do
      P.string "@import"
      P.spaces
      res <- (pQuoted <|> pUrl) >>= handleCSSUrl d
      P.spaces
      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 =
      (B.pack <$> P.many1 (P.noneOf "u/ \n\r\t")) <|>
      (B.singleton <$> P.char 'u') <|>
      (B.singleton <$> P.char '/')

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

    pQuoted :: PandocMonad m
            => ParsecT ByteString () m (String, ByteString)
    pQuoted = P.try $ do
      quote <- P.oneOf "\"'"
      url <- P.manyTill P.anyChar (P.char quote)
      let fallback = B.pack ([quote] ++ trim url ++ [quote])
      return (url, fallback)

    pUrl :: PandocMonad m
         => ParsecT ByteString () m (String, ByteString)
    pUrl = 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 = B.pack ("url(" ++ maybe "" (:[]) quote ++ trim url ++
                                maybe "" (:[]) quote ++ ")")
      return (url, fallback)

    handleCSSUrl :: PandocMonad m
                 => FilePath -> (String, ByteString)
                 -> ParsecT ByteString () m
                      (Either ByteString (MimeType, ByteString))
    handleCSSUrl d (url, fallback) =
      case escapeURIString (/='|') (trim url) of
          '#':_ -> return $ Left fallback
          'd':'a':'t':'a':':':_ -> return $ Left fallback
          u ->  do let url' = if isURI u then u else d </> u
                   res <- lift $ getData "" 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 d raw
                                  else return raw
                          return $ Right (mt, b)

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

    getData :: PandocMonad m
            => MimeType -> String
            -> m (Either String (MimeType, ByteString))
    getData _ src@('d':'a':'t':'a':':':_) = return $ Left src-- already data: uri
    getData mimetype src = do
      let ext = map toLower $ takeExtension src
      (raw, respMime) <- fetchItem 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
      result <- if "text/css" `isPrefixOf` mime
                   then do
                     oldInputs <- getInputFiles
                     setInputFiles [src]
                     res <- cssURLs (takeDirectory src) raw'
                     setInputFiles oldInputs
                     return res
                   else return raw'
      return $ Right (mime, result)

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