Refactor graphImageResponse to use Temporary Files

CHANGELOG.md

@@ -18,6 +18,7 @@
 - Added test cases for the saveGraphJSON function in `Controllers/Graph`
 - Added test cases for the getGraphJSON function in `Controllers/Graph`
 - Fix unused variable from `Graph.js`, formatting in `Container.js` and `GraphDropdown.js`, and eslint config
+- Refactor `graphImageResponse` in `Controllers/Graph` to use temporary files
 
 ## [0.7.2] - 2025-12-10
 

app/Controllers/Graph.hs

@@ -6,17 +6,19 @@ import Data.Maybe (fromMaybe)
 import Happstack.Server (Response, ServerPart, look, lookBS, lookText', ok, toResponse)
 import MasterTemplate (masterTemplate)
 import Scripts (graphScripts)
+import System.IO (hClose)
+import System.IO.Temp (withSystemTempFile)
 import Text.Blaze ((!))
 import qualified Text.Blaze.Html5 as H
 import qualified Text.Blaze.Html5.Attributes as A
 
 import Config (runDb)
 import Database.Persist.Sqlite (Entity, SelectOpt (Asc), SqlPersistM, selectList, (==.))
 import Database.Tables as Tables (EntityField (GraphDynamic, GraphTitle), Graph, SvgJSON, Text)
-import Export.GetImages (getActiveGraphImage)
+import Export.GetImages (writeActiveGraphImage)
 import Models.Graph (getGraph, insertGraph)
 import Util.Happstack (createJSONResponse)
-import Util.Helpers (returnImageData)
+import Util.Helpers (readImageData)
 
 graphResponse :: ServerPart Response
 graphResponse =
@@ -51,8 +53,12 @@ getGraphJSON = do
 graphImageResponse :: ServerPart Response
 graphImageResponse = do
     graphInfo <- look "JsonLocalStorageObj"
-    (svgFilename, imageFilename) <- liftIO $ getActiveGraphImage graphInfo
-    liftIO $ returnImageData svgFilename imageFilename
+    liftIO $ withSystemTempFile "graph.svg" $ \svgPath svgHandle -> do
+        hClose svgHandle
+        withSystemTempFile "graph.png" $ \pngPath pngHandle -> do
+            hClose pngHandle
+            writeActiveGraphImage graphInfo svgPath pngPath
+            readImageData pngPath
 
 -- | Inserts SVG graph data into Texts, Shapes, and Paths tables
 saveGraphJSON :: ServerPart Response

app/Export/GetImages.hs

@@ -7,7 +7,7 @@ Defines functions for creating images from graphs and timetables, most
 functions return the name of the created svg and png files after creation.
 -}
 module Export.GetImages
-    (getActiveGraphImage, getTimetableImage, randomName, getActiveTimetable) where
+    (getActiveGraphImage, getTimetableImage, randomName, getActiveTimetable, writeActiveGraphImage) where
 
 import Config (runDb)
 import Data.Aeson (decode)
@@ -24,16 +24,22 @@ import Models.Meeting (getMeetingTime)
 import Svg.Generator
 import System.Random (genWord32, newStdGen)
 
-
--- | If there is an active graph available, an image of that graph is created,
--- otherwise the Computer Science graph is created as a default.
--- Either way, the resulting graph's .svg and .png names are returned.
-getActiveGraphImage :: String -> IO (String, String)
-getActiveGraphImage graphInfo = do
+-- | If there is an active graph available, an image of the active graph is written,
+-- otherwise the Computer Science graph is written as a default.
+writeActiveGraphImage :: String -> FilePath -> FilePath -> IO ()
+writeActiveGraphImage graphInfo svgPath pngPath = do
     let graphInfoMap = fromMaybe M.empty $ decode $ fromStrict $ BC.pack graphInfo :: M.Map T.Text T.Text
         graphName = fromMaybe "Computer-Science" $ M.lookup "active-graph" graphInfoMap
-    getGraphImage graphName graphInfoMap
+    getGraphImage graphName graphInfoMap svgPath pngPath
 
+-- | Creates an image of the graph given info and returns resulting graph's .svg and .png names.
+getActiveGraphImage :: String -> IO (String, String)
+getActiveGraphImage graphInfo = do
+    rand <- randomName
+    let svgFilename = rand ++ ".svg"
+        imageFilename = rand ++ ".png"
+    writeActiveGraphImage graphInfo svgFilename imageFilename
+    return (svgFilename, imageFilename)
 
 -- | If there are selected lectures available, an timetable image of
 -- those lectures in specified session is created.
@@ -107,16 +113,11 @@ generateTimetableImg schedule courseSession = do
     createImageFile svgFilename imageFilename
     return (svgFilename, imageFilename)
 
--- | Creates an image, and returns the name of the svg used to create the
--- image and the name of the image
-getGraphImage :: T.Text -> M.Map T.Text T.Text -> IO (String, String)
-getGraphImage graphName courseMap = do
-    rand <- randomName
-    let svgFilename = rand ++ ".svg"
-        imageFilename = rand ++ ".png"
-    buildSVG graphName courseMap svgFilename True
-    createImageFile svgFilename imageFilename
-    return (svgFilename, imageFilename)
+-- | Creates an image, given file paths to the svg and image to write to
+getGraphImage :: T.Text -> M.Map T.Text T.Text -> FilePath -> FilePath -> IO ()
+getGraphImage graphName courseMap svgPath pngPath = do
+    buildSVG graphName courseMap svgPath True
+    createImageFile svgPath pngPath
 
 -- | Creates an image, and returns the name of the svg used to create the
 -- image and the name of the image

app/Util/Helpers.hs

@@ -3,7 +3,7 @@
     Description : Contains general-use helper functions.
 -}
 module Util.Helpers
-    (safeHead, returnImageData) where
+    (safeHead, readImageData, returnImageData) where
 
 import qualified Data.ByteString as BS (readFile)
 import qualified Data.ByteString.Base64 as BEnc (encode)
@@ -16,12 +16,18 @@ safeHead :: a -> [a] -> a
 safeHead listHead [] = listHead
 safeHead _ (listHead:_) = listHead
 
+-- | Reads the data in an image file and returns the data as a response.
+readImageData :: String -> IO Response
+readImageData imageFileName = do
+    imageData <- BS.readFile imageFileName
+    let encodedData = BEnc.encode imageData
+    return $ toResponse encodedData
+
 -- | Creates and converts an SVG file to an image file, deletes them both and
 -- returns the image data as a response.
 returnImageData :: String -> String -> IO Response
 returnImageData svgFilename imageFilename = do
-    imageData <- BS.readFile imageFilename
+    response <- readImageData imageFilename
     _ <- removeFile imageFilename
     _ <- removeFile svgFilename
-    let encodedData = BEnc.encode imageData
-    return $ toResponse encodedData
+    return response

courseography.cabal

@@ -94,6 +94,7 @@ library
     split,
     system-filepath,
     tagsoup,
+    temporary,
     text,
     time,
     tls,
@@ -271,6 +272,7 @@ executable courseography
     stylish-haskell,
     system-filepath,
     tagsoup,
+    temporary,
     text,
     time,
     tls,