feat: session replay

* wip

* wip

* wip

* wip

* final fixes

* comments

* fix

apps/api/src/utils/ids.ts

@@ -0,0 +1,158 @@
+import crypto from 'node:crypto';
+import { generateDeviceId } from '@openpanel/common/server';
+import { getSafeJson } from '@openpanel/json';
+import { getRedisCache } from '@openpanel/redis';
+
+export async function getDeviceId({
+  projectId,
+  ip,
+  ua,
+  salts,
+  overrideDeviceId,
+}: {
+  projectId: string;
+  ip: string;
+  ua: string | undefined;
+  salts: { current: string; previous: string };
+  overrideDeviceId?: string;
+}) {
+  if (overrideDeviceId) {
+    return { deviceId: overrideDeviceId, sessionId: '' };
+  }
+
+  if (!ua) {
+    return { deviceId: '', sessionId: '' };
+  }
+
+  const currentDeviceId = generateDeviceId({
+    salt: salts.current,
+    origin: projectId,
+    ip,
+    ua,
+  });
+  const previousDeviceId = generateDeviceId({
+    salt: salts.previous,
+    origin: projectId,
+    ip,
+    ua,
+  });
+
+  return await getDeviceIdFromSession({
+    projectId,
+    currentDeviceId,
+    previousDeviceId,
+  });
+}
+
+async function getDeviceIdFromSession({
+  projectId,
+  currentDeviceId,
+  previousDeviceId,
+}: {
+  projectId: string;
+  currentDeviceId: string;
+  previousDeviceId: string;
+}) {
+  try {
+    const multi = getRedisCache().multi();
+    multi.hget(
+      `bull:sessions:sessionEnd:${projectId}:${currentDeviceId}`,
+      'data'
+    );
+    multi.hget(
+      `bull:sessions:sessionEnd:${projectId}:${previousDeviceId}`,
+      'data'
+    );
+    const res = await multi.exec();
+    if (res?.[0]?.[1]) {
+      const data = getSafeJson<{ payload: { sessionId: string } }>(
+        (res?.[0]?.[1] as string) ?? ''
+      );
+      if (data) {
+        const sessionId = data.payload.sessionId;
+        return { deviceId: currentDeviceId, sessionId };
+      }
+    }
+    if (res?.[1]?.[1]) {
+      const data = getSafeJson<{ payload: { sessionId: string } }>(
+        (res?.[1]?.[1] as string) ?? ''
+      );
+      if (data) {
+        const sessionId = data.payload.sessionId;
+        return { deviceId: previousDeviceId, sessionId };
+      }
+    }
+  } catch (error) {
+    console.error('Error getting session end GET /track/device-id', error);
+  }
+
+  return {
+    deviceId: currentDeviceId,
+    sessionId: getSessionId({
+      projectId,
+      deviceId: currentDeviceId,
+      graceMs: 5 * 1000,
+      windowMs: 1000 * 60 * 30,
+    }),
+  };
+}
+
+/**
+ * Deterministic session id for (projectId, deviceId) within a time window,
+ * with a grace period at the *start* of each window to avoid boundary splits.
+ *
+ * - windowMs: 30 minutes by default
+ * - graceMs: 1 minute by default (events in first minute of a bucket map to previous bucket)
+ * - Output: base64url, 128-bit (16 bytes) truncated from SHA-256
+ */
+function getSessionId(params: {
+  projectId: string;
+  deviceId: string;
+  eventMs?: number; // use event timestamp; defaults to Date.now()
+  windowMs?: number; // default 5 min
+  graceMs?: number; // default 1 min
+  bytes?: number; // default 16 (128-bit). You can set 24 or 32 for longer ids.
+}): string {
+  const {
+    projectId,
+    deviceId,
+    eventMs = Date.now(),
+    windowMs = 5 * 60 * 1000,
+    graceMs = 60 * 1000,
+    bytes = 16,
+  } = params;
+
+  if (!projectId) {
+    throw new Error('projectId is required');
+  }
+  if (!deviceId) {
+    throw new Error('deviceId is required');
+  }
+  if (windowMs <= 0) {
+    throw new Error('windowMs must be > 0');
+  }
+  if (graceMs < 0 || graceMs >= windowMs) {
+    throw new Error('graceMs must be >= 0 and < windowMs');
+  }
+  if (bytes < 8 || bytes > 32) {
+    throw new Error('bytes must be between 8 and 32');
+  }
+
+  const bucket = Math.floor(eventMs / windowMs);
+  const offset = eventMs - bucket * windowMs;
+
+  // Grace at the start of the bucket: stick to the previous bucket.
+  const chosenBucket = offset < graceMs ? bucket - 1 : bucket;
+
+  const input = `sess:v1:${projectId}:${deviceId}:${chosenBucket}`;
+
+  const digest = crypto.createHash('sha256').update(input).digest();
+  const truncated = digest.subarray(0, bytes);
+
+  // base64url
+  return truncated
+    .toString('base64')
+    .replace(/\+/g, '-')
+    .replace(/\//g, '_')
+    .replace(/=+$/g, '');
+}