Track visitor activity presence

public/widget.js

@@ -7,6 +7,7 @@
   const session = loadSession();
   const allowedImageTypes = new Set(["image/jpeg", "image/png", "image/webp", "image/gif", "image/avif"]);
   const maxAttachmentBytes = 3_000_000;
+  let lastActivityAt = Date.now();
 
   fetch(`${apiBase}/api/widget/config?siteKey=${encodeURIComponent(siteKey)}`)
     .then((res) => res.json())
@@ -164,10 +165,14 @@
     });
 
     rememberPage();
+    trackVisitorActivity(root);
     pingVisitor();
     setInterval(pingVisitor, 25_000);
     document.addEventListener("visibilitychange", () => {
-      if (!document.hidden) pingVisitor();
+      if (!document.hidden) {
+        noteActivity();
+        pingVisitor();
+      }
     });
     if (session.conversationId) {
       loadExistingConversation(messages).finally(() => connectEvents(messages, typing, panel, launcher, settings));
@@ -340,6 +345,7 @@
       currentUrl: location.href,
       referrer: document.referrer,
       browsingHistory: rememberPage(),
+      lastActivityAt: new Date(lastActivityAt).toISOString(),
       language: navigator.language,
       timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
       device: {
@@ -354,6 +360,20 @@
     postJson(`${apiBase}/api/widget/visitors/ping`, withVisitorContext({})).catch(() => {});
   }
 
+  function trackVisitorActivity(root) {
+    const passive = { passive: true, capture: true };
+    for (const eventName of ["pointerdown", "keydown", "mousemove", "touchstart", "scroll"]) {
+      document.addEventListener(eventName, noteActivity, passive);
+      root.addEventListener(eventName, noteActivity, passive);
+    }
+  }
+
+  function noteActivity() {
+    const now = Date.now();
+    if (now - lastActivityAt < 1_000) return;
+    lastActivityAt = now;
+  }
+
   function showFormError(root, message) {
     const note = root.querySelector(".mf-note");
     note.textContent = message;