Prevented check_timeout calls when window is inactive or session has expired (#8074)

Author: mrafie1

Changelog.md

@@ -7,6 +7,7 @@
 ### 🚨 Breaking changes
 
 ### ✨ New features and improvements
+- Improved Session Timeout Logic: `check_timeout` polling paused when user is not focused on the MarkUs tab and polling stops after user session has timed out (#8074)
 - Migrated Groups Manager students and groups tables to use `react-table` v8 (#8068)
 - Decreased size of QR codes on scanned assessments and ignored whitespace in OCR of page labels (#8076)
 - Added automatic collection of scanned exam submissions once a paper's pages are all present and error-free (#8069)

app/assets/javascripts/check_timeout.js

@@ -1,9 +1,60 @@
 (function () {
+  let intervalId;
+  let sessionExpired = false;
+
   const domContentLoadedCB = () => {
-    setInterval(() => {
-      $.get(Routes.check_timeout_main_index_path());
+    startPolling();
+  };
+
+  const startPolling = () => {
+    if (intervalId) return;
+
+    intervalId = setInterval(() => {
+      checkTimeout();
     }, 120000);
   };
 
+  const stopPolling = () => {
+    clearInterval(intervalId);
+    intervalId = null;
+  };
+
+  const checkTimeout = () => {
+    fetch(Routes.check_timeout_main_index_path())
+      .then(response => {
+        if (response.status === 401) {
+          sessionExpired = true;
+          stopPolling();
+          return;
+        }
+
+        return response.json();
+      })
+      .then(data => {
+        if (!data) return;
+
+        if (data.time_remaining <= 300) {
+          timeout_imminent_modal.open();
+
+          $("#timeout-imminent-modal-close")
+            .off("click")
+            .on("click", function () {
+              refreshOrLogout();
+              timeout_imminent_modal.close();
+            });
+        }
+      });
+  };
+
   document.addEventListener("DOMContentLoaded", domContentLoadedCB);
+  document.addEventListener("visibilitychange", () => {
+    if (document.hidden) {
+      stopPolling();
+    } else {
+      checkTimeout();
+      if (!sessionExpired) {
+        startPolling();
+      }
+    }
+  });
 })();

app/controllers/main_controller.rb

@@ -123,7 +123,11 @@ def page_not_found
   end
 
   def check_timeout
-    head :ok unless check_imminent_expiry
+    if session_expired?
+      head :unauthorized
+    else
+      render json: { time_remaining: session_time_remaining }
+    end
   end
 
   def refresh_session

app/lib/session_handler.rb

@@ -148,9 +148,11 @@ def session_expired?
     Time.zone.parse(session[:timeout]) < Time.current
   end
 
-  def check_imminent_expiry
-    return false if remote_auth?
-    !session[:timeout].nil? && (Time.zone.parse(session[:timeout]) - Time.current) <= 5.minutes
+  def session_time_remaining
+    return 0 if remote_auth?
+    return 0 if session[:timeout].nil?
+
+    (Time.zone.parse(session[:timeout]) - Time.current).to_i
   end
 
   # Clear this current user's session set by this app