add search, chat, and feedback analytics with dashboard

lib/analytics/client.ts

@@ -0,0 +1,42 @@
+/**
+ * Browser helpers for docs feedback. The visitor id is an anonymous random id kept in
+ * localStorage so a person can change their vote; nothing else identifies them.
+ */
+const VisitorKey = 'pg-visitor-id';
+
+export function randomId() {
+  if (typeof crypto !== 'undefined' && 'randomUUID' in crypto) return crypto.randomUUID();
+  return `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 12)}`;
+}
+
+let fallbackVisitorId: string | undefined;
+
+export function getVisitorId() {
+  try {
+    let id = localStorage.getItem(VisitorKey);
+    if (!id) {
+      id = randomId();
+      localStorage.setItem(VisitorKey, id);
+    }
+    return id;
+  } catch {
+    // storage unavailable (private mode): one id per page load
+    return (fallbackVisitorId ??= randomId());
+  }
+}
+
+export type Vote = -1 | 0 | 1;
+
+/** fire-and-forget; analytics must never break the page */
+export function sendEvent(url: string, body: Record<string, unknown>) {
+  void fetch(url, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ ...body, visitorId: getVisitorId() }),
+    keepalive: true,
+  }).catch(() => undefined);
+}
+
+export function sendFeedback(kind: 'page' | 'message', body: Record<string, unknown>) {
+  sendEvent(`/api/feedback/${kind}`, body);
+}