session-stuff.ts

// root.tsx
import { getUserSession, requireUser, logout } from "~/session";

export function loader({ request }) {
  // use case: know if the user is logged in, no redirect to /login
  let userSession = await getUserSession(request);
  let isAuthenticated = userSession.has("userId");
  return { isAuthenticated };
}

// dashboard.tsx
export function loader({ request }) {
  // use case: redirect to login if they aren't logged in
  let userId = await requireUser(request);
  return db.jokes.findWhere({ userId });
}

// logout.tsx
export function action({ request }) {
  // use case: redirect to login if they aren't logged in
  return logout(request);
}

// login.tsx
export function action({ request }) {
  let data = await request.formData();
  let email = data.get("email");
  let password = data.get("password");

  if (typeof email !== "string" || typeof password !== "string") {
    return "Both email and password are required";
  }

  // do additional validation
  let userId = users.findOne({ where: { email } });
  // compare password hashes
  // if it matches?
  return createUserSession(userId, "/dashboard");
}
```

```tsx
// session.ts
import { redirect } from "remix";

let { getSession, commitSession, destroySession } = createCookieSessionStorage({
  cookie: {
    // browser handles expiration
    expires: "...",
  },
});

export function getUserSession(request) {
  return getSession(request.headers.get("Cookie"));
}

export function requireUser(request) {
  let session = getSession(request.headers.get("Cookie"));
  if (!session.has("userId")) {
    throw redirect("/login");
  }
  let userId = session.get("userId");
  invariant(userId, "expected userId on session");
  return userId;
}

export function logout(request) {
  let session = getSession(request.headers.get("Cookie"));
  return redirect("/login", { headers: await destroySession(session) });
}

export function createUserSession(userId, redirectTo) {
  let session = getSession();
  session.set("userId", userId);
  return redirect(redirect, {
    headers: { cookie: await commitSession(session) },
  });
}