fix getText endpoint

Author: jruehlow

service/src/Handler/Text.hs

@@ -15,70 +15,33 @@ import System.Random (randomRIO)
 
 getRandomParagraph :: Text -> Text -> Int -> Handler (Entity TextParagraph)
 getRandomParagraph era source book = do
-  res <-
-    runDB $
-      rawSql
-        "SELECT MIN(id), MAX(id) \
-        \FROM text_paragraph      \
-        \WHERE era    = ?         \
-        \  AND source = ?         \
-        \  AND book   = ?"
-        [ toPersistValue era,
-          toPersistValue source,
-          toPersistValue book
-        ]
-  pair <- case res of
-    [(Single mMinId, Single mMaxId)] ->
-      let minId = fromMaybe (error "no rows") mMinId
-          maxId = fromMaybe minId mMaxId
-       in return (minId, maxId)
-    _ -> notFound
-  let (minId, maxId) = pair
-  rnd <- liftIO $ randomRIO (minId, maxId)
-  let baseFilters =
+  let filters =
         [ TextParagraphEra ==. era,
           TextParagraphSource ==. source,
           TextParagraphBook ==. book
         ]
-  mEnt <-
-    runDB $
-      selectFirst
-        (baseFilters ++ [TextParagraphId >=. toSqlKey rnd])
-        [Asc TextParagraphId]
-  case mEnt of
-    Just ent -> return ent
-    Nothing -> do
-      mEnt2 <-
-        runDB $
-          selectFirst
-            baseFilters
-            [Asc TextParagraphId]
-      maybe notFound return mEnt2
+  total <- runDB $ count filters
+  when (total == 0) notFound
+
+  idx <- liftIO $ randomRIO (0, total - 1)
+
+  results <- runDB $ selectList filters [OffsetBy idx, LimitTo 1]
+  case results of
+    [ent] -> return ent
+    _ -> error "No paragraph found for this era."
 
 getRandomNewText :: Text -> Handler (Entity TextParagraph)
 getRandomNewText era = do
-  App {appMinMaxByEra = cacheRef} <- getYesod
-  cache <- liftIO $ readIORef cacheRef
-  case Map.lookup era cache of
-    Nothing -> notFound
-    Just (minId, maxId) -> do
-      rnd <- liftIO $ randomRIO (minId, maxId)
-      mEnt <-
-        runDB $
-          selectFirst
-            [ TextParagraphEra ==. era,
-              TextParagraphId >=. toSqlKey rnd
-            ]
-            [Asc TextParagraphId]
-      case mEnt of
-        Just ent -> return ent
-        Nothing -> do
-          mEnt2 <-
-            runDB $
-              selectFirst
-                [TextParagraphEra ==. era]
-                [Asc TextParagraphId]
-          maybe notFound return mEnt2
+  let filters = [TextParagraphEra ==. era]
+  total <- runDB $ count filters
+  when (total == 0) notFound
+
+  idx <- liftIO $ randomRIO (0, total - 1)
+
+  results <- runDB $ selectList filters [OffsetBy idx, LimitTo 1]
+  case results of
+    [ent] -> return ent
+    _ -> error "No paragraph found for this era."
 
 getCustomText :: UserId -> Text -> Handler ByteString
 getCustomText userId filename = do