drop the SSE, use client side fetch every 5s for thread updates

js/thread.js

@@ -37,8 +37,8 @@
     })
   }
   
-  let newPostSubscription = null;
-  
+  const threadEndpoint = document.getElementById("thread-subscribe-endpoint").value;
+  let now = Math.floor(new Date() / 1000);
   function hideNotification() {
     const notification = document.getElementById('new-post-notification');
     notification.classList.add('hidden');
@@ -50,35 +50,31 @@
     notification.classList.remove("hidden");
     
     document.getElementById("dismiss-new-post-button").onclick = () => {
+      now = Math.floor(new Date() / 1000);
       hideNotification();
-      reconnectSSE();
+      tryFetchUpdate();
     }
     
     document.getElementById("go-to-new-post-button").href = url;
     
     document.getElementById("unsub-new-post-button").onclick = () => {
-      hideNotification()
+      hideNotification();
     }
   }
-  
-  function reconnectSSE() {
-    if (newPostSubscription) newPostSubscription.close();
-    
-    const threadEndpoint = document.getElementById("thread-subscribe-endpoint").value;
-    newPostSubscription = new EventSource(threadEndpoint);
-    newPostSubscription.onerror = (e) => {
-      console.error(e);
-    };
-    newPostSubscription.addEventListener("new_post_url", (e) => {
-      showNewPostNotification(e.data);
-      newPostSubscription.close();
-    })
+
+  function tryFetchUpdate() {
+    if (!threadEndpoint) return;
+    const body = JSON.stringify({since: now});
+    fetch(threadEndpoint, {method: "POST", headers: {"Content-Type": "application/json"}, body: body})
+      .then(res => res.json())
+      .then(json => {
+        if (json.status === "none") {
+          setTimeout(tryFetchUpdate, 5000);
+        } else if (json.status === "new_post") {
+          showNewPostNotification(json.url);
+        }
+      })
+      .catch(error => console.log(error))
   }
-  window.addEventListener('beforeunload', () => {
-    if(newPostSubscription)
-    {
-      newPostSubscription.close();
-    }
-  });
-  reconnectSSE();
+  tryFetchUpdate();
 }