feat: Slack notification on new user signup

.beads/last-touched

@@ -1 +1 @@
-perception-8c0
+perception-s9t.1

firebase.json

@@ -1,4 +1,8 @@
 {
+  "functions": {
+    "source": "functions",
+    "runtime": "nodejs22"
+  },
   "hosting": {
     "public": "dashboard/dist",
     "ignore": [

functions/.gitignore

@@ -0,0 +1 @@
+node_modules/

functions/index.js

@@ -0,0 +1,59 @@
+const { logger } = require("firebase-functions");
+
+/**
+ * Notify Slack when a new user signs up.
+ *
+ * Uses the v1 Auth onCreate trigger which fires on every
+ * Firebase Auth signup event.
+ */
+
+const functions = require("firebase-functions");
+
+/** Mask email for logging: "user@example.com" → "us***@example.com" */
+function maskEmail(email) {
+  if (!email) return "no email";
+  const [local, domain] = email.split("@");
+  if (!domain) return "***";
+  const visible = local.slice(0, 2);
+  return `${visible}***@${domain}`;
+}
+
+exports.onNewUser = functions
+  .runWith({ secrets: ["SLACK_WEBHOOK_URL"] })
+  .auth.user()
+  .onCreate(async (user) => {
+    const webhookUrl = process.env.SLACK_WEBHOOK_URL;
+    if (!webhookUrl) {
+      logger.error("SLACK_WEBHOOK_URL secret not configured");
+      return;
+    }
+
+    const createdAt = user.metadata.creationTime || new Date().toISOString();
+    const maskedEmail = maskEmail(user.email);
+    const shortUid = user.uid.slice(0, 8);
+
+    const payload = JSON.stringify({
+      text: [
+        ":new: *New Perception user signup*",
+        `*Email:* ${maskedEmail}`,
+        `*UID:* \`${shortUid}...\``,
+        `*Provider:* ${user.providerData?.[0]?.providerId || "email"}`,
+        `*Time:* ${createdAt}`,
+      ].join("\n"),
+    });
+
+    const response = await fetch(webhookUrl, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: payload,
+      signal: AbortSignal.timeout(10000),
+    });
+
+    if (!response.ok) {
+      const body = await response.text();
+      logger.error(`Slack webhook failed: ${response.status} ${body}`);
+      throw new Error(`Slack webhook failed: ${response.status}`);
+    }
+
+    logger.info(`Slack notified for new user: ${maskedEmail}`);
+  });

functions/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "perception-functions",
+  "description": "Firebase Cloud Functions for Perception",
+  "engines": {
+    "node": "22"
+  },
+  "main": "index.js",
+  "dependencies": {
+    "firebase-admin": "^12.7.0",
+    "firebase-functions": "^6.3.0"
+  }
+}