implemented decodeGemURL

src/Network/GemServ.hs

@@ -24,10 +24,11 @@ License along with this program.  If not, see
 
 -}
 
-{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE LambdaCase, OverloadedStrings, RecordWildCards #-}
 
 module Network.GemServ (
   encodeGemURL,
+  decodeGemURL,
   escapeString,
   unescapeString
 ) where
@@ -56,6 +57,49 @@ encodeGemURL url =
       Nothing -> ""
       Just q  -> '?' : escapeString q
 
+-- | Decodes a 'GemURL' from a 'String' (if possible)
+decodeGemURL :: String -> Maybe GemURL
+decodeGemURL str = do
+  let txt = T.pack str
+
+  noProt <- case T.splitOn "://" txt of
+    [prot, rest] -> if T.toLower prot == "gemini"
+      then Just rest
+      else Nothing
+    _ -> Nothing
+
+  noFrag <- case T.splitOn "#" noProt of
+    [x, _] -> Just x
+    [x]    -> Just x
+    _      -> Nothing
+
+  (noQuery, query) <- case T.splitOn "?" noFrag of
+    [nq, q] -> Just (nq, Just q)
+    [nq]    -> Just (nq, Nothing)
+    _       -> Nothing
+
+  gemQuery <- case query of
+    Just q  -> Just <$> unescapeString (T.unpack q)
+    Nothing -> Just Nothing
+
+  (auth, path) <- case T.splitOn "/" noQuery of
+    [a]     -> Just (a, [])
+    [a, ""] -> Just (a, [])
+    a:ps    -> Just (a, ps)
+    _       -> Nothing
+
+  gemPath  <- mapM (unescapeString . T.unpack) path
+
+  (host, gemPort) <- case T.splitOn ":" auth of
+    [h, p] -> case reads $ T.unpack p of
+      [(n, "")] -> Just (h, Just n)
+      _         -> Nothing
+    [h] -> Just (h, Nothing)
+    _   -> Nothing
+
+  let gemHost = T.unpack host
+  Just GemURL {..}
+
 -- | add required escape sequences to a string
 escapeString :: String -> String
 escapeString = concatMap