feat: add SSE client JS for live recipe reload on detail and index pages

src/Roux/Html.hs

@@ -329,6 +329,39 @@ searchJs =
         , "})();"
         ]
 
+-- ---------------------------------------------------------------------------
+-- SSE live-reload scripts
+-- ---------------------------------------------------------------------------
+
+-- | Inline JavaScript for SSE live-reload on the recipe detail page.
+sseRecipeJs :: Text
+sseRecipeJs =
+    T.unlines
+        [ "(function(){"
+        , "'use strict';"
+        , "if (!window.EventSource) return;"
+        , "var el = document.getElementById('roux-current-recipe');"
+        , "if (!el) return;"
+        , "var currentRecipe = el.textContent;"
+        , "var es = new EventSource('/events');"
+        , "es.addEventListener('recipe-changed', function(e) {"
+        , "  if (e.data === currentRecipe) location.reload();"
+        , "});"
+        , "})();"
+        ]
+
+-- | Inline JavaScript for SSE live-reload on the index page.
+sseIndexJs :: Text
+sseIndexJs =
+    T.unlines
+        [ "(function(){"
+        , "'use strict';"
+        , "if (!window.EventSource) return;"
+        , "var es = new EventSource('/events');"
+        , "es.addEventListener('recipe-changed', function() { location.reload(); });"
+        , "})();"
+        ]
+
 -- | Render the recipe index page -- shell with embedded JSON + JS rendering.
 indexPage :: SortMode -> [Idx.RecipeInfo] -> ByteString
 indexPage _mode recipes =
@@ -356,6 +389,8 @@ indexPage _mode recipes =
             H.toHtml (decodeUtf8 (LB.toStrict (Fleece.encode (Fleece.encoder (FC.list Idx.recipeSearchEntrySchema)) (Prelude.map Idx.toSearchEntry (filterBad recipes)))))
         -- Inline JS
         H.script ! A.type_ "text/javascript" $ H.preEscapedText searchJs
+        -- Inline JS for SSE live-reload
+        H.script ! A.type_ "text/javascript" $ H.preEscapedText sseIndexJs
   where
     filterOk = filter (isRight . Idx.riRecipe)
     filterBad = filter (isLeft . Idx.riRecipe)
@@ -368,9 +403,19 @@ recipePage info =
                 H.nav $ H.ul $ H.li $ H.a ! A.href "/" $ "← Back"
                 H.h2 "Parse Error"
                 H.p $ H.toHtml (Idx.riTitle info <> ": " <> T.pack err)
+                hiddenRecipeSpan info
+                sseScript
         Right recipe ->
-            page (titleText recipe) $
+            page (titleText recipe) $ do
                 renderRecipe recipe
+                hiddenRecipeSpan info
+                sseScript
+  where
+    hiddenRecipeSpan rInfo =
+        H.span ! A.id "roux-current-recipe" ! A.style "display: none;" $
+            H.toHtml (T.pack (Idx.riFilename rInfo))
+    sseScript =
+        H.script ! A.type_ "text/javascript" $ H.preEscapedText sseRecipeJs
 
 -- | Render the body of a recipe page (no page shell).
 renderRecipe :: Recipe -> Html