rewrite parsePage to use only ByteStrings

src/TemplatePage.hs

@@ -11,15 +11,14 @@ module TemplatePage (
 
 import GHC.Generics (Generic)
 import qualified Data.ByteString as BS
-import qualified Data.ByteString.Lazy as LBS
-import qualified Data.ByteString.UTF8 as BS.UTF8
+import qualified Data.ByteString.Char8 as BS.Char8
 import Data.ByteString (ByteString)
-import Data.List.Split (splitOn)
 import qualified Data.Aeson as JSON
 import Data.Aeson ((.:))
 import Data.Aeson.Types (FromJSON)
 import qualified Data.Map as Map
 import Data.Map (Map)
+import Data.Bool (bool)
 
 newtype PageContext = PageContext { ctxPageviews :: Map String Int }
 
@@ -36,25 +35,21 @@ buildPage context template = BS.concat $ map handlePart template
         handlePart (PTComputed p) = p context
 
 parsePage :: ByteString -> PageTemplate
-parsePage = parseSplit . splitOn "\\\\\\\\$" . BS.UTF8.toString
-  where parseSplit :: [String] -> [PageTemplatePart]
-        parseSplit [] = []
-        parseSplit [part] = [PTString $ BS.UTF8.fromString part]
-        parseSplit (first:rest) = PTString (BS.UTF8.fromString first) : concatMap parseSegment rest
-
-        parseSegment :: String -> [PageTemplatePart]
-        parseSegment segment =
-          let (numStr, next) = break (== '$') segment
-              (templatePart, rawPart) = splitAt (read numStr) (drop 1 next)
-           in [parseTemplate $ BS.UTF8.fromString templatePart, PTString $ BS.UTF8.fromString rawPart]
+parsePage = parsePage' . BS.breakSubstring "\\\\\\\\$"
+  where parsePage' :: (ByteString, ByteString) -> PageTemplate
+        parsePage' (prematch, match)
+          | BS.null match = [PTString prematch]
+          | otherwise = let (lenStr, rest) = BS.breakSubstring "{" $ BS.drop 5 match
+                            (templateStr, rest') = case BS.Char8.readInt lenStr of
+                                                     Just (len, _) -> BS.splitAt len rest
+                                                     Nothing -> (BS.empty, rest)
+                            parsed = parseTemplate templateStr : parsePage rest'
+                         in bool (PTString prematch : parsed) parsed $ BS.null prematch
 
         parseTemplate :: ByteString -> PageTemplatePart
-        parseTemplate = parseTemplate' . JSON.decode . LBS.fromStrict
-        --parseTemplate v = PTString $ BS.UTF8.fromString $ "[-" ++ BS.UTF8.toString v ++ "-]"
-
-        parseTemplate' :: Maybe JsonTemplate -> PageTemplatePart
-        parseTemplate' Nothing = PTString "{parse error}"
-        parseTemplate' (Just jt) = PTComputed $ jsonTemplateFn jt
+        parseTemplate template = case JSON.decode $ BS.fromStrict template of
+                                   Nothing -> PTString $ BS.concat ["{parse error on `", template, "` }"]
+                                   Just json -> PTComputed $ jsonTemplateFn json
 
 newtype JsonTemplate = TViewCount { jtPage :: String } deriving (Generic, Show)
 
@@ -66,6 +61,6 @@ instance FromJSON JsonTemplate where
 
 jsonTemplateFn :: JsonTemplate -> (PageContext -> ByteString)
 jsonTemplateFn TViewCount { jtPage = page } PageContext { ctxPageviews = pageviews }
-  = BS.UTF8.fromString $ viewStr $ Map.lookup page pageviews
+  = BS.Char8.pack $ viewStr $ Map.lookup page pageviews
   where viewStr Nothing = "{unk}"
         viewStr (Just viewcount) = show viewcount