From 70c43cb7f1db503080485bbf133a95c5b4d2d86c Mon Sep 17 00:00:00 2001
From: Sam Truzjan <pxqr.sta@gmail.com>
Date: Sun, 29 Sep 2013 08:28:35 +0400
Subject: Hide internals from main API

---
 src/Data/BEncode/Internal.hs | 126 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 src/Data/BEncode/Internal.hs

(limited to 'src/Data/BEncode/Internal.hs')

diff --git a/src/Data/BEncode/Internal.hs b/src/Data/BEncode/Internal.hs
new file mode 100644
index 0000000..7ea61c0
--- /dev/null
+++ b/src/Data/BEncode/Internal.hs
@@ -0,0 +1,126 @@
+module Data.BEncode.Internal
+       ( decode
+       , encode
+       , ppBEncode
+       ) where
+
+import Control.Applicative
+import           Data.Attoparsec.ByteString.Char8 (Parser)
+import qualified Data.Attoparsec.ByteString.Char8 as P
+import           Data.ByteString as B
+import qualified Data.ByteString.Lazy as Lazy
+import qualified Data.ByteString.Lazy.Builder as B
+import qualified Data.ByteString.Lazy.Builder.ASCII as B
+import           Data.ByteString.Internal as B (c2w, w2c)
+import Data.Foldable
+import Data.List as L
+import Data.Monoid
+import Text.PrettyPrint hiding ((<>))
+
+import Data.BEncode.Types
+import Data.BEncode.BDict as BD
+
+
+{--------------------------------------------------------------------
+-- Serialization
+--------------------------------------------------------------------}
+
+-- | BEncode format encoder according to specification.
+builder :: BValue -> B.Builder
+builder = go
+    where
+      go (BInteger i) = B.word8 (c2w 'i') <>
+                        B.integerDec i <>
+                        B.word8 (c2w 'e')
+      go (BString  s) = buildString s
+      go (BList    l) = B.word8 (c2w 'l') <>
+                        foldMap go l <>
+                        B.word8 (c2w 'e')
+      go (BDict    d) = B.word8 (c2w 'd') <>
+                        bifoldMap mkKV d <>
+                        B.word8 (c2w 'e')
+          where
+            mkKV k v = buildString k <> go v
+
+      buildString s = B.intDec (B.length s) <>
+                      B.word8 (c2w ':') <>
+                      B.byteString s
+      {-# INLINE buildString #-}
+
+-- | Convert bencoded value to raw bytestring according to the
+-- specification.
+encode :: BValue -> Lazy.ByteString
+encode = B.toLazyByteString . builder
+
+{--------------------------------------------------------------------
+-- Deserialization
+--------------------------------------------------------------------}
+
+-- TODO try to replace peekChar with something else
+-- | BEncode format parser according to specification.
+parser :: Parser BValue
+parser = valueP
+  where
+    valueP = do
+      mc <- P.peekChar
+      case mc of
+        Nothing -> fail "end of input"
+        Just c  ->
+            case c of
+              -- if we have digit it always should be string length
+              di | di <= '9' -> BString <$> stringP
+              'i' -> P.anyChar *> ((BInteger <$> integerP)  <* P.anyChar)
+              'l' -> P.anyChar *> ((BList    <$> listBodyP) <* P.anyChar)
+              'd' -> P.anyChar *>  (BDict    <$> dictBodyP) <* P.anyChar
+              t   -> fail ("bencode unknown tag: " ++ [t])
+
+    dictBodyP :: Parser BDict
+    dictBodyP = Cons <$> stringP <*> valueP <*> dictBodyP
+            <|> pure Nil
+
+    listBodyP = do
+      c <- P.peekChar
+      case c of
+        Just 'e' -> return []
+        _        -> (:) <$> valueP <*> listBodyP
+
+    stringP :: Parser ByteString
+    stringP = do
+      n <- P.decimal :: Parser Int
+      P.char ':'
+      P.take n
+    {-# INLINE stringP #-}
+
+    integerP :: Parser Integer
+    integerP = do
+      c <- P.peekChar
+      case c of
+        Just '-' -> do
+          P.anyChar
+          negate <$> P.decimal
+        _        ->  P.decimal
+    {-# INLINE integerP #-}
+
+-- | Try to convert raw bytestring to bencoded value according to
+-- specification.
+decode :: ByteString -> Either String BValue
+decode = P.parseOnly parser
+
+{--------------------------------------------------------------------
+  Pretty Printing
+--------------------------------------------------------------------}
+
+ppBS :: ByteString -> Doc
+ppBS = text . L.map w2c . B.unpack
+
+-- | Convert to easily readable JSON-like document. Typically used for
+-- debugging purposes.
+ppBEncode :: BValue -> Doc
+ppBEncode (BInteger i) = int $ fromIntegral i
+ppBEncode (BString  s) = ppBS s
+ppBEncode (BList    l)
+    = brackets $ hsep $ punctuate comma $ L.map ppBEncode l
+ppBEncode (BDict    d)
+    = braces $ vcat $ punctuate comma $ L.map ppKV $ BD.toAscList d
+  where
+    ppKV (k, v) = ppBS k <+> colon <+> ppBEncode v
-- 
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