cabal: Added http-conduit flag, which allows fetching https resources.

It also brings in a large number of dependencies (http-conduit and its
dependencies), which is why for now it is an optional flag.

Closes #820.

pandoc.cabal

@@ -224,6 +224,10 @@ Flag embed_data_files
   Description:   Embed data files in binary for relocatable executable.
   Default:       False
 
+Flag http-conduit
+  Description:   Enable downloading of resources over https.
+  Default:       True
+
 Library
   Build-Depends: base >= 4.2 && <5,
                  syb >= 0.1 && < 0.5,
@@ -262,6 +266,10 @@ Library
                  yaml >= 0.8.3 && < 0.9,
                  vector >= 0.10 && < 0.11,
                  hslua >= 0.3 && < 0.4
+  if flag(http-conduit)
+     Build-Depends: http-conduit >= 1.9 && < 1.10,
+                    http-types >= 0.8 && < 0.9
+     cpp-options:   -DHTTP_CONDUIT
   if flag(embed_data_files)
      cpp-options:   -DEMBED_DATA_FILES
      -- build-tools:   hsb2hs

src/Text/Pandoc/Shared.hs

@@ -89,7 +89,7 @@ import Data.Char ( toLower, isLower, isUpper, isAlpha,
                    isLetter, isDigit, isSpace )
 import Data.List ( find, isPrefixOf, intercalate )
 import qualified Data.Map as M
-import Network.URI ( escapeURIString, isAbsoluteURI, parseURI, unEscapeString )
+import Network.URI ( escapeURIString, isAbsoluteURI, unEscapeString )
 import System.Directory
 import Text.Pandoc.MIME (getMimeType)
 import System.FilePath ( (</>), takeExtension, dropExtension )
@@ -102,11 +102,9 @@ import Data.Time
 import System.IO (stderr)
 import Text.HTML.TagSoup (renderTagsOptions, RenderOptions(..), Tag(..),
          renderOptions)
-import qualified Data.ByteString as B
+import qualified Data.ByteString as BS
+import Data.ByteString.Lazy (toChunks)
 import qualified Data.ByteString.Char8 as B8
-import Network.HTTP (findHeader, rspBody,
-                     RequestMethod(..), HeaderName(..), mkRequest)
-import Network.Browser (browse, setAllowRedirects, setOutHandler, request)
 
 #ifdef EMBED_DATA_FILES
 import Text.Pandoc.Data (dataFiles)
@@ -114,6 +112,16 @@ import System.FilePath ( joinPath, splitDirectories )
 #else
 import Paths_pandoc (getDataFileName)
 #endif
+#ifdef HTTP_CONDUIT
+import Network.HTTP.Conduit (httpLbs, parseUrl, withManager,
+                             responseBody, responseHeaders)
+import Network.HTTP.Types.Header ( hContentType)
+#else
+import Network.URI (parseURI)
+import Network.HTTP (findHeader, rspBody,
+                     RequestMethod(..), HeaderName(..), mkRequest)
+import Network.Browser (browse, setAllowRedirects, setOutHandler, request)
+#endif
 
 --
 -- List processing
@@ -545,7 +553,7 @@ inDirectory path action = do
   setCurrentDirectory oldDir
   return result
 
-readDefaultDataFile :: FilePath -> IO B.ByteString
+readDefaultDataFile :: FilePath -> IO BS.ByteString
 readDefaultDataFile fname =
 #ifdef EMBED_DATA_FILES
   case lookup (makeCanonical fname) dataFiles of
@@ -558,17 +566,17 @@ readDefaultDataFile fname =
         go (_:as) ".." = as
         go as     x    = x : as
 #else
-  getDataFileName ("data" </> fname) >>= B.readFile
+  getDataFileName ("data" </> fname) >>= BS.readFile
 #endif
 
 -- | Read file from specified user data directory or, if not found there, from
 -- Cabal data directory.
-readDataFile :: Maybe FilePath -> FilePath -> IO B.ByteString
+readDataFile :: Maybe FilePath -> FilePath -> IO BS.ByteString
 readDataFile Nothing fname = readDefaultDataFile fname
 readDataFile (Just userDir) fname = do
   exists <- doesFileExist (userDir </> fname)
   if exists
-     then B.readFile (userDir </> fname)
+     then BS.readFile (userDir </> fname)
      else readDefaultDataFile fname
 
 -- | Same as 'readDataFile' but returns a String instead of a ByteString.
@@ -578,7 +586,7 @@ readDataFileUTF8 userDir fname =
 
 -- | Fetch an image or other item from the local filesystem or the net.
 -- Returns raw content and maybe mime type.
-fetchItem :: String -> String -> IO (B.ByteString, Maybe String)
+fetchItem :: String -> String -> IO (BS.ByteString, Maybe String)
 fetchItem sourceDir s =
   case s of
     _ | isAbsoluteURI s         -> openURL s
@@ -588,16 +596,23 @@ fetchItem sourceDir s =
                         ".gz" -> getMimeType $ dropExtension s
                         x     -> getMimeType x
           let f = sourceDir </> s
-          cont <- B.readFile f
+          cont <- BS.readFile f
           return (cont, mime)
 
 -- | Read from a URL and return raw data and maybe mime type.
-openURL :: String -> IO (B.ByteString, Maybe String)
+openURL :: String -> IO (BS.ByteString, Maybe String)
 openURL u
   | "data:" `isPrefixOf` u =
     let mime     = takeWhile (/=',') $ drop 5 u
         contents = B8.pack $ unEscapeString $ drop 1 $ dropWhile (/=',') u
     in  return (contents, Just mime)
+#ifdef HTTP_CONDUIT
+  | otherwise = do
+     req <- parseUrl u
+     resp <- withManager $ httpLbs req
+     return (BS.concat $ toChunks $ responseBody resp,
+             UTF8.toString `fmap` lookup hContentType (responseHeaders resp))
+#else
   | otherwise = getBodyAndMimeType `fmap` browse
               (do S.liftIO $ UTF8.hPutStrLn stderr $ "Fetching " ++ u ++ "..."
                   setOutHandler $ const (return ())
@@ -609,6 +624,7 @@ openURL u
                                                         uriString)
                                    Just v  -> mkRequest GET v
         u' = escapeURIString (/= '|') u  -- pipes are rejected by Network.URI
+#endif
 
 --
 -- Error reporting