♻️ Create backend package (#643)

packages/backend/session.ts

@@ -0,0 +1,36 @@
+import { sealData, unsealData } from "iron-session";
+
+import { sessionConfig } from "./session-config";
+
+type UserSessionData = { id: string; isGuest: boolean };
+
+declare module "iron-session" {
+  export interface IronSessionData {
+    user: UserSessionData;
+  }
+}
+
+export const decryptToken = async <P = UserSessionData>(
+  token: string,
+): Promise<P | null> => {
+  const payload = await unsealData(token, {
+    password: sessionConfig.password,
+  });
+  if (Object.keys(payload).length === 0) {
+    return null;
+  }
+
+  return payload as P;
+};
+
+export const createToken = async <T = UserSessionData>(
+  payload: T,
+  options?: {
+    ttl?: number;
+  },
+) => {
+  return await sealData(payload, {
+    password: sessionConfig.password,
+    ttl: options?.ttl ?? 60 * 15, // 15 minutes
+  });
+};