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

apps/api.lua

@@ -1,8 +1,6 @@
 local app = require("lapis").Application()
 local json_params = require("lapis.application").json_params
 
-local sse = require("lib.sse")
-
 local db = require("lapis.db")
 
 local html_escape = require("lapis.html").escape
@@ -10,33 +8,26 @@ local babycode = require("lib.babycode")
 
 local util = require("util")
 
-app:get("sse_thread_updates", "/thread-updates/:thread_id", function(self)
-  do
-    local thread = db.query("SELECT threads.id FROM threads WHERE threads.id = ?", self.params.thread_id)
-    if #thread == 0 then
-      return {status = 404, skip_render = true}
-    end
+app:post("api_get_thread_updates", "/thread-updates/:thread_id", json_params(function(self)
+  local thread = db.query("SELECT threads.id FROM threads WHERE threads.id = ?", self.params.thread_id)
+  if #thread == 0 then
+    return {json = {error = "no such thread"}, status = 404}
+  end
+  local target_time = self.params.since
+  if not target_time then
+    return {json = {error = "missing parameter 'since'"}, status = 400}
+  end
+  if not tonumber(target_time) then
+    return {json = {error = "parameter 'since' is not a number"}, status = 400}
   end
-  
-  local now = os.time()
-  local stream = sse:new()
-  
-  local thread_id = self.params.thread_id
   local new_posts_query = "SELECT id FROM posts WHERE thread_id = ? AND posts.created_at > ? ORDER BY posts.created_at ASC LIMIT 1"
-  
-  while stream.active do
-    stream:dispatch()
-    local new_post = db.query(new_posts_query, thread_id, now)
-    if #new_post > 0 then
-      local url = util.get_post_url(self, new_post[1].id)
-      stream:enqueue(url, "new_post_url")
-    end
-    
-    ngx.sleep(5)
+  local new_post = db.query(new_posts_query, self.params.thread_id, target_time)
+  if #new_post == 0 then
+    return {json = {status = "none"}, status = 200}
   end
-  
-  return {skip_render = true}
-end)
+  local url = util.get_post_url(self, new_post[1].id)
+  return {json = {status = "new_post", url = url}}
+end))
 
 app:post("babycode_preview", "/babycode-preview", json_params(function(self)
   local user = util.get_logged_in_user(self)

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();
 }

views/threads/thread.etlua

@@ -64,6 +64,6 @@
     </span>
   </div>
 </dialog>
-<input type="hidden" id="thread-subscribe-endpoint" value="<%= url_for("sse_thread_updates", {thread_id = thread.id}) %>">
+<input type="hidden" id="thread-subscribe-endpoint" value="<%= url_for("api_get_thread_updates", {thread_id = thread.id}, {since = os.time()}) %>">
 <% render("views.threads.new-post-notification") %>
-<script src="/static/js/thread.js"></script>
+<script src="/static/js/thread.js?v=1"></script>