From 0c384514d88e58eeac0c62e5ec370ffbdc5ae202 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Wed, 11 Feb 2015 19:51:54 -0500
Subject: Parser: Allow internal chunk references

---
 src/Fragment.hs | 34 +++++++++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/Fragment.hs b/src/Fragment.hs
index 539d35a..4a12d5c 100644
--- a/src/Fragment.hs
+++ b/src/Fragment.hs
@@ -12,22 +12,34 @@ 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, see <http://www.gnu.org/licenses/>. -}
 
-module Fragment where
+module Fragment ( Fragment
+                , parseStdin
+                , parseFile) where
 
 import Data.Data (Data)
 import Data.Typeable (Typeable)
 import GHC.Generics (Generic)
 
-import Control.Applicative ((<$>), (<*>), pure)
+import Control.Applicative ((<$>), (<*>))
 import Control.Monad (void)
 import System.IO (hGetContents, stdin)
 import Text.Parsec
 import Text.Parsec.String
 
 data Fragment = Documentation String
-              | BlockCode String String
+              | BlockCode String [CodeOrReference]
               deriving (Eq, Show, Data, Typeable, Generic)
 
+data CodeOrReference = Code String
+                     | Reference String
+                     deriving (Eq, Show, Data, Typeable, Generic)
+
+parseStdin :: IO (Either ParseError [Fragment])
+parseStdin = parse literateFile "<stdin>" <$> hGetContents stdin
+
+parseFile :: FilePath -> IO (Either ParseError [Fragment])
+parseFile = parseFromFile literateFile
+
 literateFile :: Parser [Fragment]
 literateFile = many (blockCode <|> documentation)
 
@@ -39,10 +51,22 @@ documentation = do
 blockCode :: Parser Fragment
 blockCode = do
   void $ string "<<"
-  name <- manyTill anyChar (try $ string ">>=")
-  body <- manyTill anyChar (char '@')
+  name <- many1Till anyChar (try (string ">>=" <?> "start of code block"))
+  body <- many1Till (reference <|> code) (char '@')
   return $ BlockCode name body
 
+code :: Parser CodeOrReference
+code = do
+  body <- many1Till anyChar (lookAhead $ (void (char '@'))
+                                         <|> (void reference))
+  return $ Code body
+
+reference :: Parser CodeOrReference
+reference = do
+  void $ string "<<"
+  name <- many1Till anyChar (try $ string ">>")
+  return $ Reference name
+
 many1Till :: Stream s m t
              => ParsecT s u m a -> ParsecT s u m end -> ParsecT s u m [a]
 many1Till p end = (:) <$> p <*> manyTill p end
-- 
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