Apply max-age header to bust PDF cache at midnight

Also update stylish-haskell config

app/Main.hs

@@ -1,6 +1,6 @@
-{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE OverloadedRecordDot #-}
-{-# LANGUAGE OverloadedStrings   #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 module Main (main) where
 
@@ -29,6 +29,7 @@ import Text.Blaze.Html.Renderer.Utf8 (renderHtml)
 import Text.Blaze.Html5 ((!))
 import Text.Printf (printf)
 
+import qualified Data.ByteString.Char8 as BS8
 import qualified Data.Text as Text
 import qualified Database.PostgreSQL.Opium as Opium
 import Network.Wai (responseFile)
@@ -37,7 +38,7 @@ import qualified Text.Blaze.Html5 as H
 import qualified Text.Blaze.Html5.Attributes as A
 
 import Yore.DB (DayFile (..))
-import Yore.Time (addYears, getCurrentDay)
+import Yore.Time (addYears, getCurrentDay, getSecondsUntilMidnight)
 
 import qualified Yore.DB as DB
 
@@ -68,7 +69,7 @@ server connPool = rootR :<|> todayR :<|> apiTodayR
     rootR = todayR 0
 
     todayR issue = do
-      dateThen <- liftIO $ get100YearsAgo
+      dateThen <- liftIO get100YearsAgo
       Right count <- liftIO $ withResource connPool $ DB.getNumberOfIssues dateThen
       Right dayFile <- liftIO $ withResource connPool $ DB.getDayFileByIssue dateThen issue
       pure $ RootModel dateThen dayFile issue count
@@ -79,8 +80,15 @@ server connPool = rootR :<|> todayR :<|> apiTodayR
         res <- withResource connPool $ DB.getDayFileByIssue dateThen issue
         dayFile <- either throwIO pure res
         let fullPath = "download" </> dayFile.relative_path
+        secondsUntilMidnight <- getSecondsUntilMidnight
 
-        respond $ responseFile status200 [("content-type", "application/pdf")] fullPath Nothing
+        respond $ responseFile
+          status200
+          [ ("content-type", "application/pdf")
+          , ("cache-control", BS8.pack $ printf "public, max-age=%d" secondsUntilMidnight)
+          ]
+          fullPath
+          Nothing
 
 data RootModel = RootModel Day DB.DayFile Int Int