Move common html code to its own function

app/Main.hs

@@ -108,12 +108,7 @@ instance MimeRender PlainText BytesModel where
       ]
 
 instance MimeRender HTML BytesModel where
-  mimeRender _ model = renderHtml $ H.docTypeHtml $ do
-    H.head $ do
-      H.meta ! A.charset "utf-8"
-      H.title "utoy"
-      H.style $ H.toHtml $ Encoding.decodeUtf8 $(embedFile "static/utoy.css")
-    H.body $ do
+  mimeRender _ model = renderHtml $ documentWithBody $ do
     H.table $ for_ model.codepoints $ \(bytes, eiC) -> do
       H.tr $ do
         H.td $ H.pre $ H.toHtml $ unlines $ map unwords [map showByteHex bytes, map showByteBin bytes]
@@ -162,12 +157,7 @@ instance MimeRender PlainText CodepointsModel where
     ]
 
 instance MimeRender HTML CodepointsModel where
-  mimeRender _ model = renderHtml $ H.docTypeHtml $ do
-    H.head $ do
-      H.meta ! A.charset "utf-8"
-      H.title "utoy"
-      H.style $ H.toHtml $ Encoding.decodeUtf8 $(embedFile "static/utoy.css")
-    H.body $ do
+  mimeRender _ model = renderHtml $ documentWithBody $ do
     H.table $ for_ model.codepoints $ \(codepoint, eiC) ->
       H.tr $ do
         H.td $ H.code $ H.toHtml $ Text.pack $ printf "0x%X" codepoint
@@ -187,12 +177,7 @@ newtype TextModel = TextModel
   }
 
 instance MimeRender HTML TextModel where
-  mimeRender _ model = renderHtml $ H.docTypeHtml $ do
-    H.head $ do
-      H.meta ! A.charset "utf-8"
-      H.title "utoy"
-      H.style $ H.toHtml $ Encoding.decodeUtf8 $(embedFile "static/utoy.css")
-    H.body $ do
+  mimeRender _ model = renderHtml $ documentWithBody $ do
     H.table $ for_ (Text.unpack model.text) $ \c -> do
       H.tr $ do
         H.td $ H.input ! A.class_ "charbox" ! A.value (H.toValue [c])
@@ -221,6 +206,15 @@ orThrow (Right val) _ = pure val
 printfHtml :: PrintfArg a => String -> a -> H.Html
 printfHtml fmt = (H.toHtml :: String -> H.Html) . printf fmt
 
+documentWithBody :: H.Html -> H.Html
+documentWithBody body =
+  H.docTypeHtml $ do
+    H.head $ do
+      H.meta ! A.charset "utf-8"
+      H.title "utoy"
+      H.style $ H.toHtml $ Encoding.decodeUtf8 $(embedFile "static/utoy.css")
+    H.body body
+
 -- HTML routes
 
 data HTML